Category Archives: Materials

Your food may soon come wrapped in self-cleaning, biodegradable plastic inspired by the lotus

Researchers are developing a self-cleaning, eco-friendly bioplastic by taking inspiration from the lotus leaf.

Image via Wikimedia.

Plastic waste is one of the most widespread types of pollution on the planet, with particles of this material permeating soil, water, and the atmosphere. The main drivers of this issue are single-use plastics combined with inadequate recycling capacity. Since plastic is very chemically-stable, it doesn’t break down in the wild, leading to rapid build-ups.plastic

In a bid to help address this issue, researchers at the RMIT University in Melbourne, Australia, have developed a self-cleaning bioplastic that degrades rapidly once it comes into contact with soils. The team envisions their material being used in packaging for fresh foods and takeaway. Since it is compostable (breaks down naturally), swapping regular plastic for this new bioplastic in these applications would lead to tremendous environmental benefits, as food packaging is one of the main applications for single-use plastic.


Plastic waste is one of our biggest environmental challenges but the alternatives we develop need to be both eco-friendly and cost-effective, to have a chance of widespread use,” says RMIT PhD researcher Mehran Ghasemlou, lead author of a duo of papers describing the material.

“We designed this new bioplastic with large-scale fabrication in mind, ensuring it was simple to make and could easily be integrated with industrial manufacturing processes.”

Ghasemlou explains that nature is full of ingenious designs and solutions to a variety of problems researchers are trying to solve, and we can draw on this wealth of natural expertise when designing new, high-performance materials that can serve a variety of roles. The new bioplastic is one example of this.

During the development process, the team replicated the “phenomenally water-repellent structure of lotus leaves” into their material to ensure it has excellent hygienic properties. Lotus leaves are covered in tiny pillars, all covered in a layer of wax. This prevents water droplets from adhering to their surface, instead simply rolling off as gravity or wind pulls at them. As they slide off, these droplets carry away any particles from the leaves, keeping them clean.

Image credits Mehran Ghasemlou et al., (2022), ACS Publ.

The surface of the new material is imprinted with a pattern similar to that on lotus leaves. A protective layer of silicon-based organic polymer (PDMS) is then applied. The bioplastic itself is made from starch and cellulose, cheap and widely-available materials in use in a great number of applications today; this means that the logistics needed to create the bioplastic are already well-developed, making it much easier for commercial actors to use the material.

Its manufacturing process requires only simple equipment and requires no high temperatures. Such a process can be carried out cheaply and many areas of the world have the technical capability for it. The team is confident that these traits will help with getting production of the bioplastic rolling en masse.

These materials also promote biodegradability and are non-toxic, meaning that the bioplastic can be used as compost after serving its purpose and actually support natural environments instead of polluting them.

It also offers good physical properties such as strength, making it a suitable replacement for current plastics in a wide range of consumer applications. Due to its biodegradable nature, short-lived items such as single-use containers would be most suited for this bioplastic.

Most compostable or biodegradable plastics today need to undergo industrial processes and be exposed to high temperatures to break down, the team explains. Their bioplastic, however, requires no such intervention — it breaks down naturally and quickly in soils.

“There are big differences between plant-based materials — just because something is made from green ingredients doesn’t mean it will easily degrade,” Ghasemlou said. “We carefully selected our raw materials for compostability and this is reflected in the results from our soil studies, where we can see our bioplastic rapidly breaks down simply with exposure to the bacteria and bugs in soil.”

“Our ultimate aim is to deliver packaging that could be added to your backyard compost or thrown into a green bin alongside other organic waste, so that food waste can be composted together with the container it came in, to help prevent food contamination of recycling.”

The papers “Biodegradation of novel bioplastics made of starch, polyhydroxyurethanes and cellulose nanocrystals in soil environment” and “Robust and Eco-Friendly Superhydrophobic Starch Nanohybrid Materials with Engineered Lotus Leaf Mimetic Multiscale Hierarchical Structures” have been published in the journals Science of The Total Environment and ACS Applied Materials & Interfaces, respectively.

China builds the world’s first artificial moon

Chinese scientists have built an ‘artificial moon’ possessing lunar-like gravity to help them prepare astronauts for future exploration missions. The structure uses a powerful magnetic field to produce the celestial landscape — an approach inspired by experiments once used to levitate a frog.

The key component is a vacuum chamber that houses an artificial moon measuring 60cm (about 2 feet) in diameter. Image credits: Li Ruilin, China University of Mining and Technology

Preparing to colonize the moon

Simulating low gravity on Earth is a complex process. Current techniques require either flying a plane that enters a free fall and then climbs back up again or jumping off a drop tower — but these both last mere minutes. With the new invention, the magnetic field can be switched on or off as needed, producing no gravity, lunar gravity, or earth-level gravity instantly. It is also strong enough to magnetize and levitate other objects against the gravitational force for as long as needed.

All of this means that scientists will be able to test equipment in the extreme simulated environment to prevent costly mistakes. This is beneficial as problems can arise in missions due to the lack of atmosphere on the moon, meaning the temperature changes quickly and dramatically. And in low gravity, rocks and dust may behave in a completely different way than on Earth – as they are more loosely bound to each other.

Engineers from the China University of Mining and Technology built the facility (which they plan to launch in the coming months) in the eastern city of Xuzhou, in Jiangsu province. A vacuum chamber, containing no air, houses a mini “moon” measuring 60cm (about 2 feet) in diameter at its heart. The artificial landscape consists of rocks and dust as light as those found on the lunar surface-where gravity is about one-sixth as powerful as that on Earth–due to powerful magnets that levitate the room above the ground. They plan to test a host of technologies whose primary purpose is to perform tasks and build structures on the surface of the Earth’s only natural satellite.

Group leader Li Ruilin from the China University of Mining and Technology says it’s the “first of its kind in the world” that will take lunar simulation to a whole new level. Adding that their artificial moon makes gravity “disappear.” For “as long as you want,” he adds.

In an interview with the South China Morning Post, the team explains that some experiments take just a few seconds, such as an impact test. Meanwhile, others like creep testing (where the amount a material deforms under stress is measured) can take several days.

Li said astronauts could also use it to determine whether 3D printing structures on the surface is possible rather than deploying heavy equipment they can’t use on the mission. He continues:

“Some experiments conducted in the simulated environment can also give us some important clues, such as where to look for water trapped under the surface.”

It could also help assess whether a permanent human settlement could be built there, including issues like how well the surface traps heat.

From amphibians to artificial celestial bodies

The group explains that the idea originates from Russian-born UK-based physicist Andre Geim’s experiments which saw him levitate a frog with a magnet – that gained him a satirical Ig Nobel Prize in 2000, which celebrates science that “first makes people laugh, and then think.” Geim also won a Nobel Prize in Physics in 2010 for his work on graphene.

The foundation of his work involves a phenomenon known as diamagnetic levitation, where scientists apply an external magnetic force to any material. In turn, this field induces a weak repulsion between the object and the magnets, causing it to drift away from them and ‘float’ in midair.

For this to happen, the magnetic force must be strong enough to ‘magnetize’ the atoms that make up a material. Essentially, the atoms inside the object (or frog) acts as tiny magnets, subject to the magnetic force existing around them. If the magnet is powerful enough, it will change the direction of the electrons revolving around the atom’s nuclei, allowing them to produce a magnetic field to repulse the magnets.

Diamagnetic levitation of a tiny horse. Image credits: Pieter Kuiper / Wiki Commons.

Different substances on Earth have varying degrees of diamagnetism which affect their ability to levitate under a magnetic field; adding a vacuum, as was done here, allowed the researchers to produce an isolated chamber that mimics a microgravity environment.

However, simulating the harsh lunar environment was no easy task as the magnetic force needed is so strong it could tear apart components such as superconducting wires. It also affected the many metallic parts necessary for the vacuum chamber, which do not function properly near a powerful magnet.

To counteract this, the team came up with several technical innovations, including simulating lunar dust that could float a lot easier in the magnetic field and replacing steel with aluminum in many of the critical components.

The new space race

This breakthrough signals China’s intent to take first place in the international space race. That includes its lunar exploration program (named after the mythical moon goddess Chang’e), whose recent missions include landing a rover on the dark side of the moon in 2019 and 2020 that saw rock samples brought back to Earth for the first time in over 40 years.

Next, China wants to establish a joint lunar research base with Russia, which could start as soon as 2027.  

The new simulator will help China better prepare for its future space missions. For instance, the Chang’e 5 mission returned with far fewer rock samples than planned in December 2020, as the drill hit unexpected resistance. Previous missions led by Russia and the US have also had related issues.

Experiments conducted on a smaller prototype simulator suggested drill resistance on the moon could be much higher than predicted by purely computational models, according to a study by the Xuzhou team published in the Journal of China University of Mining and Technology. The authors hope this paper will enable space engineers across the globe (and in the future, the moon) to alter their equipment before launching multi-billion dollar missions.

The team is adamant that the facility will be open to researchers worldwide, and that includes Geim. “We definitely welcome Professor Geim to come and share more great ideas with us,” Li said.

What is stainless steel?

Today, iron is the most widely-used metal. It’s durable, versatile, and abundant in the Earth’s crust (making it cheap). However, in its pure form, iron is very susceptible to oxygen — it rusts rapidly. Stainless steel provides a solution to this problem.

Image via Pixabay.

The world as we know it wouldn’t be possible without stainless steel. It’s a material that combines strength, flexibility, and durability at an affordable cost. This alloy makes an appearance in everything, from high-rises and high-performance cars to spoons and baby monitors. To quite a large extent, our world is built on stainless steel. So let’s learn more about it.

What is stainless steel?

‘Stainless steel’ is a generic, umbrella term, that denotes a wide range of metal alloys — cocktails of metals — based on iron. Like all other types of steel, it also contains carbon.

It has excellent resistance to corrosion (oxidation or rusting), is relatively non-reactive with most chemicals, has high durability, and good hygienic properties. It sees wide use today in products ranging from cutlery to medical devices to construction materials.

Aesthetically, stainless steel is a lustrous, silvery metal, that can take a very high polish. From a practical point of view, stainless steel is a strong and highly resilient material; its exact properties depend on the composition of the alloy, but it can be tailored to suit a wide range of needs, having the potential to be highly flexible, resistant to scratching, mechanically tough, or any other property needed in a certain application. It can be recycled practically forever, as its recovery rate during recycling is close to 100%

Although it is more difficult and expensive to produce than iron metal, stainless steel has practically replaced iron in all except the most specialized cases due to the advantages it holds over the un-alloyed metal. Almost all ‘iron’ products you’ve encountered in your life were made from stainless steel.

What is stainless steel made of?

Molten metal pouring from ladle. Image credits Goodwin Steel Castings / Flickr.

Stainless steel differs from other types of steel through the addition of a handful of elements to the mix. The exact elements added vary with alloy type but, as a rule of thumb, stainless steels contain chromium (Cr), in quantities ranging from 10.5 to 30% by weight.

Chromium is what gives these alloys their high resistance to corrosion. As it interacts with corrosive agents in the air, chromium forms a passive layer — a ‘film’ of chromium oxide — on the metal’s surface which protects the alloy. Oxygen and moisture cannot penetrate this film, so it protects the iron throughout the body of the steel from rusting.

Other elements that are added to stainless steel include non-metals such as sulphur, silicon, or nitrogen, metals such as nickel, aluminium, copper, or more exotic metals such as selenium, niobium, and molybdenum. Although the exact composition of the alloy is decided based on its desired properties — each element added in, and their proportion, changes the characteristics of the alloy — some of the most commonly-seen extra elements in stainless steel alloys are nickel and nitrogen. These improve its hardiness and ability to resist corrosion in certain conditions, but also increase its price per pound.

There are currently over 100 types (known as ‘grades’) of stainless steel being produced and used, each with its own ISO number, many of them for specialized applications. The most common five types are known as ‘austenitic’, ‘ferritic’, ‘martensitic’, ‘duplex’, and ‘precipitation hardening’ steels.

  • Austenitic stainless steels are the most widely used grade. They have very good resistance to corrosion and heat, offering good mechanical properties over a wide range of temperatures. It’s used in household goods, industrial applications, in construction, and in decorations.
  • Ferritic stainless steels have lower mechanical resitance — they resemble mild steels in strength — but are better able to resist corrosion, heat, and are harder to crack. Any washing machine or boiler you have at home are probably made of ferritic steel.
  • Martensitic stainless steels are much harder and stronger than their peers, but they’re not as able to withstand corrosion. This is the type of steel that makes high-grade knives, and is also used for turbine blades.
  • Duplex stainless steel is a mixture of austenitic and ferritic steels, and their properties are, similarly, a middle-ground between these two grades. As a rule of thumb, it is used in applications where both strength and flexibility are required, and corrosion resistance is a plus; shipbuilding is a prime example.
  • Precipitation hardening stainless steels are a subclass of alloys, somewhere in the overlap between martensitic and austenitic steels. They offer the best mechanical properties of the lot (they have very high material strength), due to the addition of elements such as aluminium, copper, and niobium.

What is stainless steel used for?

Stainless steel facade. Image credits Dean Moriarty.

With a material as versatile as stainless steel, it’s hard to cover all its uses in any detail. Suffice to say, it’s used in virtually all goods and applications where strength, flexibility, good looks, and hygiene are required, for relatively low cost, and weight is not a huge concern.

Household goods and appliances make heavy use of stainless steel, especially kitchenware or other products meant to come into contact with water. Knives and cutlery, home appliances such as washing machines, bathroom fixtures, piping, cookware make use of stainless steel due to its resistance to corrosion, its good looks, ease of washing, and high durability. Various grades of stainless steel are used depending on the intended role and usage of each product.

Medical tools also make ample use of stainless steel. Things like surgical and dental instruments, scissors, trays, and a wide range of other medical-use objects are made from this alloy. Here, it is the chemical inertness and corrosion resistance of stainless steel that is most important. Medical devices also contain stainless steel, in particular structural elements and coverings, due to their strength and ease of cleaning. Medical implants, such as those used in knee or hip replacement surgery, are also made of stainless steel.

Stainless steel is also used in the construction of vehicles, mostly ships, trains, and cars. Aircraft manufacturers tend to prefer aluminium alloys, as they are more lightweight. That being said, stainless steel is essential in the production of aircraft frames and various structural elements of the landing gear. For all vehicles, however, stainless steel combines good mechanical properties with high longevity (due to its resistance to corrosion), making for durable and long-lived parts.

Construction and architecture are two further domains that love stainless steel. The combination of strength and high chemical inertness makes this alloy ideal for structural elements in buildings such as skyscrapers, or in exposed elements, such as fire escapes or service ladders.

Jewelry manufacturers also employ stainless steel in their products, where it’s preferred due to its hypoallergnic properties (it doesn’t trigger metal allergies).

Stainless steel, today, is an indispensible alloy. Our societies depend heavily on it, using it in everything from tiny knicknacks around the house to the mightiest skyscraper. Its unique combination of strength, longevity, and relatively low cost makes it so that, most likely, stainless steel won’t be replaced anytime soon.

Damascus steel: the forgotten metal used to forge some of the world’s most amazing blades

Persian shamshir / saif, 17th century, Damascus steel. Credit: Met Museum.

When the first Crusaders reached the Middle East in the 11th century, they were in for a shocking surprise. It wasn’t just the scorching heat, unfamiliar territory, and foreign culture that threw them off guard, but also a novel deadly weapon: sabers made from Damascus steel.

Damascus steel is incredibly strong but malleable at the same time. It’s easily recognizable due to the watery dark patterns, called “damask”, that form on the surface of the metal. When Damascus steel is hammered into a blade, its edge can stay sharp for years even after clashing through many battles.

Prized for its distinctive wavy surface, linked by poets to ant tracks or rippling water, the Damascene sword was a weapon of the highest quality. But despite their best efforts, Europeans could never replicate Damascus steel to a tee, as its manufacturing method was kept a closely guarded state secret by Middle Eastern armorers.

Reforging Damascus steel

Sword (yatagan) (detail); Ottoman, Turkey; 18th – 19th century; ivory and Damascus steel. Credit: Qatar Museums.

Although the recipe for Damascus steel has been lost over the ages and we’ll probably never be able to replicate it exactly, modern analytical methods allow us to infer some of the material’s most important properties. Damascus steel’s number one requirement, for instance, is a very high carbon content.

Modern steel contains about 1% carbon, which increases the hardness and strength of the alloy. Damascus steel contains between 1% and 2% carbon, according to an analysis conducted by metallurgists at Stanford University in the 1980s.

Another key requirement was forging and hammering at a relatively low temperature of about 920 degrees Celsius (1,700 degrees Fahrenheit). After the blade is shaped, the steel is again reheated to the same temperature, then rapidly cooled by quenching it in a fluid.

It was during this quenching process that some armorers in Persia believed the blade acquired its magical properties. Legend had it that the finest Damascus blades were quenched in “dragon blood”, according to the Encyclopedia of the Sword.

What form this dragon blood took is anyone’s guess. One Pakistani man sent a letter to the Arms and Armor Division of the Metropolitan Museum of Art in New York claiming that the Damascus sword held in his family for many generations was quenched by its Afghan blacksmiths in the urine of a donkey, goat, or even a redheaded boy.

Sword (shamshir) (detail); Safavid, Iran; 18th century; ivory and Damascus steel. Credit: Qatar Museums.

One written account from Turkey dating from eight centuries ago stressed that the Damascus sword had to be heated until it glowed “like the sun rising in the desert”. After the blade is cooled until it gains the color of royal purple, it then has to be thrust “into the body of a muscular slave” so that his vitality and strength are transferred to the sword. Oddly specific.

While these anecdotes cannot be trusted for their veracity, outrageous as they may sound, it is possible that some of these outlandish quenching techniques may have genuinely contributed to the blade’s quality. For instance, by adding nitrogen to the alloy.

However, the most important component of Damascus steel — and the reason why we’ll probably never replicate a true Damascus sword — is “wootz”, a special type of steel that used to be made in India.

Wootz, which first began production more than 2,300 years ago, is an ultra-high grade carbon steel, containing between 1% and 2% carbon. Excavations in India and Sri Lanka suggest that it was fabricated inside a crucible, a container that can be used in very hot temperatures required to melt steel. In 300 B.C., when the first Wootz steel was cast, the crucible was likely made of clay. Inside the crucible, iron was melted with charcoal with no oxygen. Under these reducing atmospheric conditions, the steel absorbed the carbon from charcoal.

When Europeans started descending onto the Indian subcontinent in great numbers in the 19th century, some scientists from England attempted to replicate the wootz manufacturing method in order to understand how steel with such extraordinary strength was made with ancient tools. In the process, they found that the high carbon content was a key requirement.

But it wasn’t until the 20th-century that scientists learned about another property of Wootz steel. Steel with such a high carbon content can become “superplastic”, which allows it to be formed into complex shapes.

According to Encyclopedia of the Sword by Nick Evangelista, a batch of wootz steel was heated until molten then bundled into sheets that were yet again heated and hammered into the rough shape of a sword. Forging the material alters the crystalline structure into the familiar waving or watered pattern that Damascus steel is known for. 

After culling, the blade was filed, ground, polished, and finely decorated. The most prized Damascus swords were the ones with a series of bars crossing the blade, known as “Mohamet’s Ladder”. These fine blades were often decorated with gold or silver.

Unfortunately, the technique for making wootz was lost in the 1700s. With the source material gone, so were the Damascus swords, whose production was already exceptionally rare by the 15th century.

Despite a great deal of research and effort to reverse engineer Damascus blades, no one has been able to cast a material that is close to the ancient quality. That’s despite what you might find on Amazon. Those are Damascus sword ripoffs made from pattern-welded steel that has been merely etched with acid in order to mimic the watery light/dark patterns.

New ‘super jelly’ is soft, but strong enough to withstand the weight of a few cars

It’s not easy being soft and strong at the same time — unless you’re the new hydrogel developed at the University of Cambridge. This is the first soft material that has such a huge degree of resistance to compression, the authors report.

Image credits Zehuan Huang.

A new material developed by researchers at the University of Cambridge looks like a squishy gel normally, but like an ultra-hard, shatterproof glass when compressed — despite being 80% water. Its secret lies in the non-water portion of the material; this consists of a polymer network with elements held together by “reversible interactions”. As these interactions turn on and off, the properties of the materials shift.

The so-dubbed ‘super jelly’ could be employed for a wide range of applications where both strength and softness are needed such as bioelectronics, cartilage replacement in medicine, or in flexible robots.

Hardy hydrogel

“In order to make materials with the mechanical properties we want, we use crosslinkers, where two molecules are joined through a chemical bond,” said Dr. Zehuan Huang from the Yusuf Hamied Department of Chemistry, the study’s first author.

“We use reversible crosslinkers to make soft and stretchy hydrogels, but making a hard and compressible hydrogel is difficult and designing a material with these properties is completely counterintuitive.”

The macroscopic properties of any substance arise from its microscopic properties — its molecular structure and the way its molecules interact. Because of the way hydrogels are structured, it’s exceedingly rare to see such a substance show both flexibility and strength.

The team’s secret lay in the use of molecules known as cucurbiturils. These are barrel-shaped molecules that the team used as ‘handcuffs’ to hold other polymers together (a practice known as ‘crosslinking’). This holds two ‘guest molecules’ inside the cavity it forms, which were designed to preferentially reside inside the cucurbituril molecule. Because the polymers are linked so tightly, the overall material has a very high resistance to compression (there isn’t much free space at the molecular level for compression to take place).

The alterations the team made to the guest molecules also slows down the internal dynamics of the material considerably, they report. This gives the hydrogel overall properties ranging between rubber-like and glass-like states. According to their experiments, the gel can withstand pressures of up to 100 MPa (14,503 pounds per square inch). An average car, for comparison, weighs 2,871 pounds.

“The way the hydrogel can withstand compression was surprising, it wasn’t like anything we’ve seen in hydrogels,” said co-author Dr. Jade McCune, also from the Department of Chemistry. “We also found that the compressive strength could be easily controlled through simply changing the chemical structure of the guest molecule inside the handcuff.”

“People have spent years making rubber-like hydrogels, but that’s just half of the picture,” said Scherman. “We’ve revisited traditional polymer physics and created a new class of materials that span the whole range of material properties from rubber-like to glass-like, completing the full picture.”

The authors say that, as far as they know, this is the first time a glass-like hydrogel has been developed. They tested the material by using it to build a real-time pressure sensor to monitor human motions.

They’re now working on further developing their glass-like hydrogel for various biomedical and bioelectronic applications.

The paper “Highly compressible glass-like supramolecular polymer networks” has been published in the journal Nature Materials.

Why transparent solar cells could replace windows in the near future

No matter how sustainable, eco-friendly, and clean sources of energy they are, conventional solar panels require a large setup area and heavy initial investment. Due to these limitations, it’s hard to introduce them in urban areas (especially neighborhoods with lots of apartment blocks or shops). But thanks to the work of ingenious engineers at the University of Michigan, that may soon no longer be the case.

The researchers have created transparent solar panels which they claim could be used as power generating windows in our homes, buildings, and even rented apartments.

Image credits: Djim Loic/Unsplash

If these transparent panels are indeed capable of generating electricity cost-efficiently, the days of regular windows may be passing as we speak. Soon, we could have access to cheap solar energy regardless of where we live — and to make it even better, we could be rid of those horrific power cuts that happen every once in a while because, with transparent glass-like solar panels, every house and every tall skyscraper will be able to generate its own power independently.

An overview of the transparent solar panels

In order to generate power from sunlight, solar cells embedded on a solar panel are required to absorb radiation from the sun. Therefore, they cannot allow sunlight to completely pass through them (in the way that a glass window can). So at first, the idea of transparent solar panels might seem preposterous and completely illogical because a transparent panel should be unable to absorb radiation. 

But that’s not necessarily the case, researchers have found. In fact, that’s not the case at all.

Professor R. Lunt at MSU showing the transparent luminescent solar concentrator. Image credits: Michigan State University

The solar panels created by engineers at the University of Michigan consist of transparent luminescent solar concentrators (TLSC). Composed of cyanine, the TLSC is capable of selectively absorbing invisible solar radiation including infrared and UV lights, and letting the rest of the visible rays pass through them. So in other words, these devices are transparent to the human eye (very much like a window) but still absorb a fraction of the solar light which they can then convert into electricity. It’s a relatively new technology, only first developed in 2013, but it’s already seeing some impressive developments.

Panels equipped with TLSC can be molded in the form of thin transparent sheets that can be used further to create windows, smartphone screens, car roofs, etc. Unlike, traditional panels, transparent solar panels do not use silicone; instead they consist of a zinc oxide layer covered with a carbon-based IC-SAM layer and a fullerene layer. The IC-SAM and fullerene layers not only increase the efficiency of the panel but also prevent the radiation-absorbing regions of the solar cells from breaking down.

Surprisingly, the researchers at Michigan State University (MSU) also claim that their transparent solar panels can last for 30 years, making them more durable than most regular solar panels. Basically, you could fit your windows with these transparent solar cells and get free electricity without much hassle for decades. Unsurprisingly, this prospect has a lot of people excited.

According to Professor Richard Lunt (who headed the transparent solar cell experiment at MSU), “highly transparent solar cells represent the wave of the future for new solar applications”. He further adds that these devices in the future can provide a similar electricity-generation potential as rooftop solar systems plus, they can also equip our buildings, automobiles, and gadgets with self-charging abilities.

“That is what we are working towards,” he said. “Traditional solar applications have been actively researched for over five decades, yet we have only been working on these highly transparent solar cells for about five years. Ultimately, this technology offers a promising route to inexpensive, widespread solar adoption on small and large surfaces that were previously inaccessible.”

Recent developments in the field of transparent solar cell technology

Apart from the research work conducted by Professor Richard Lunt and his team at MSU, there are some other research groups and companies working on developing advanced solar-powered glass windows. Earlier this year, a team from ITMO University in Russia developed a cheaper method of producing transparent solar cells. The researchers found a way to produce transparent solar panels much cheaper than ever before.

“Regular thin-film solar cells have a non-transparent metal back contact that allows them to trap more light. Transparent solar cells use a light-permeating back electrode. In that case, some of the photons are inevitably lost when passing through, thus reducing the devices’ performance. Besides, producing a back electrode with the right properties can be quite expensive,” says Pavel Voroshilov, a researcher at ITMO University’s Faculty of Physics and Engineering.

“For our experiments, we took a solar cell based on small molecules and attached nanotubes to it. Next, we doped nanotubes using an ion gate. We also processed the transport layer, which is responsible for allowing a charge from the active layer to successfully reach the electrode. We were able to do this without vacuum chambers and working in ambient conditions. All we had to do was dribble some ionic liquid and apply a slight voltage in order to create the necessary properties,” adds co-author Pavel Voroshilov.

Image credits: Kenrick Baksh/Unsplash

PHYSEE, a technology company from the Netherlands has successfully installed their solar energy-based “PowerWindow” in a 300 square feet area of a bank building in The Netherlands. Though at present, the transparent PowerWindows are not efficient enough to meet the energy demands of the whole building, PHYSEE claims that with some more effort, soon they will be able to increase the feasibility and power generation capacity of their solar windows.   

California-based Ubiquitous Energy is also working on a “ClearView Power” system that aims to create a solar coating that can turn the glass used in windows into transparent solar panels. This solar coating will allow transparent glass windows to absorb high-energy infrared radiations, the company claims to have achieved an efficiency of 9.8% with ClearView solar cells during their initial tests.

In September 2021, the Nippon Sheet Glass (NSG) Corporation facility located in Chiba City became Japan’s first solar window-equipped building. The transparent solar panels installed by NSG in their facility are developed by Ubiquitous Energy.  Recently, as a part of their association with Morgan Creek Ventures, Ubiquitous Energy has also installed transparent solar windows on Boulder Commons II, an under-construction commercial building in Colorado.

All these exciting developments indicate that sooner or later, we also might be able to install transparent power-generating solar windows in our homes. Such a small change in the way we produce energy, on a global scale could turn out to be a great step towards living in a more energy-efficient world.

Not there just yet

If this almost sounds too good to be true, well sort of is. The efficiency of these fully transparent solar panels is around 1%, though the technology has the potential to reach around 10% efficiency — this is compared to the 15% we already have for conventional solar panels (some efficient ones can reach 22% or even a bit higher).

So the efficiency isn’t quite there yet to make transparent solar cells efficient yet, but it may get there in the not-too-distant future. Furthermore, the appeal of this system is that it can be deployed on a small scale, in areas where regular solar panels are not possible. They don’t have to replace regular solar panels, they just have to complement them.

When you think about it, solar energy wasn’t regarded as competitive up to about a decade ago — and a recent report found that now, it’s the cheapest form of electricity available so far in human history. Although transparent solar cells haven’t been truly used yet, we’ve seen how fast this type of technology can develop, and the prospects are there for great results.

The mere idea that we may soon be able to power our buildings through our windows shows how far we’ve come. An energy revolution is in sight, and we’d be wise to take it seriously.

Scientists make eco-knives from hardened wood that slice through steak

Wood might be the last material you’d think of to use in cutting tools, but researchers employed a novel method that processes wood into knives sharp enough to easily slice steak. In fact, these wooden knives are nearly three times sharper than a stainless steel dinner table knife.

The knife is made from processed wood that is 23 times harder than natural wood and up to three times sharper than a stainless-steel dinner table knife. Credit: Bo Chen.

Most kitchen knives are either made of steel or ceramic, both of which require high temperatures of up to a few thousand degrees Celsius to forge. Wood, on the other hand, is sustainable and far less energy-intensive to process.

“A wood knife could be a promising sustainable alternative for a stainless-steel dinner table knife, with even better performance,” Teng Li, senior author of the study and a materials scientist at the University of Maryland, told ZME Science.

Wood is one of the oldest materials in human history, having been used for tens of thousands of years in virtually all areas of life, from construction and furniture to energy production. Wood can be turned, planed, finely carved, bent, and woven. When burned in the absence of oxygen, it turns to coal, a fuel still used by millions for cooking and heating.

However, natural wood has its limits. When processed into furniture or construction materials, wood tends to rebound after shaping. Seeking to make wood more versatile, Li and colleagues devised a new processing method that keeps the advantageous properties of the material while removing those that may hamper wood’s ability to act as a cutting tool.

Wood is super strong thanks to cellulose, which has a higher ratio of strength to density than ceramics, most metals, and polymers. However, cellulose only makes up to 50% of the wood, the rest consisting of lignin and hemicellulose.

Using a two-step process, the scientists first delignify the wood by boiling it at 100° Celsius in a bath of chemicals. Typically, wood is very rigid, but once the binding lignin is gone, the material becomes soft and flexible. In the second step, the now squishy wood is hot pressed to densify and remove the excess water.

Finally, after the processed material is carved into the desired shape, a mineral oil coating is applied so that the wooden knife doesn’t go dull (cellulose likes water a bit too much for a cutting knife).

Besides knives, the researchers also fashioned their processed wood into nails, which proved as sharp and sturdy as conventional steel nails. But unlike their metal counterparts, the wooden nails don’t rust. In one demonstration, the researchers hammered together three boards without any damage to the wooden nails.

It was obvious from these demonstrations that the researchers had made a super strong material — and they soon found out why. When viewing treated samples under the lens of a high-resolution microscope, the scientists found the processed wood had much fewer voids and pits, which are common defects in natural wood.

“When we found that the processed wood can be 23 times harder than natural wood, we were excited and wondered what such hardened wood could be used for. The brainstorming we enjoyed led to two potential demonstrations, wood knives and nails, which could be a sustainable alternative for the steel and plastic dinner table knives and steel nails. Cutting a medium-well done steak with our wood knife easily was fun and satisfying,” Li said.

For now, these are just demonstrations of the technology at the lab scale. However, the researchers believe they can scale the process so that sharp wooden knives could be sold at a cost that is competitive with conventional steel knives. “This will take some time and extra research and development efforts. But this is definitely worth doing,” Li added.

“The wood knife and nails are just two demonstrations of the hardened wood. Hard and strong materials are widely used in our daily life. There exist fertile opportunities to use hardened wood as a potential replacement of current cutlery and construction materials, such as steel and ceramics,” Li said.

“There are more than 3 trillion mature trees on earth, per a recent study published in Nature. This translates to more than 400 trees for each of us in the world. Trees are renewable and wood is sustainable. Our existing use of wood barely touches its full potential. There are fertile opportunities for us to use widely available materials in nature toward a sustainable future.”

The findings were reported in the journal Matter.

Could machine learning help us develop next-generation materials? These researchers believe so

In the past few years, 3D printing has seen a massive growth in popularity — and it’s not just for toys and trinkets anymore. Scientists and engineers are 3D printing everything from boats to bridges to nuclear plants components. But as 3D printing becomes a more and more integral part of modern engineering, it’s also important to develop new innovative materials.

To cut down on the time and resources required to develop these new materials, researchers at MIT have used machine learning to help them find new materials with the desired characteristics (like toughness and strength).

Image in public domain.

Materials development is still very much a manual process, says Mike Foshey, a mechanical engineer and project manager in the Computational Design and Fabrication Group (CDFG) of the Computer Science and Artificial Intelligence Laboratory (CSAIL), and co-lead author of the paper.

“A chemist goes into a lab, mixes ingredients by hand, makes samples, tests them, and comes to a final formulation. But rather than having a chemist who can only do a couple of iterations over a span of days, our system can do hundreds of iterations over the same time span,” says Foshey.

In the new process, a scientist selects some ingredients, inputs their chemical compositions into the algorithm, and defines what mechanical properties he wants the new material to have. Then, instead of having the researcher do trial-and-error themselves, the algorithm increases and decreases the amounts of these properties and checks how each version would affect the material’s properties and make it most similar to what is desired.

Then, the researcher would actually create the material in the way recommended by the algorithm and test it. Streamlining this development process not only saves a lot of time and effort but also has a positive environmental impact by reducing the amount of chemical waste. In addition, the algorithm could find some combinations that may escape human intuition.

“We think, for a number of applications, this would outperform the conventional method because you can rely more heavily on the optimization algorithm to find the optimal solution. You wouldn’t need an expert chemist on hand to preselect the material formulations,” Foshey says.

The team trialed the system by asking it to optimize formulations for a 3D-printing ink that only hardens when exposed to ultraviolet light. They found six chemicals that could be used in the mix and asked the algorithm to find the best material that can be made from those six chemicals, in terms of toughness, stiffness, and strength.

This was a particularly challenging task because the properties can be contradictory — the strongest material may not be the toughest or the stiffest. However, the team was impressed to see just how many different materials the algorithm suggested — and how good the properties of these materials were. Ultimately, the material zoomed in on 12 top-performing materials that had optimal tradeoffs between the desired properties.

To encourage other researchers to use it, the researchers have also created a free, open-source materials optimization platform called AutoOED that incorporates the algorithm. AutoOED is a full software package that encourages exploration and allows researchers to optimize the process.

Researchers expect algorithm-driven material development to become more and more important over the next few years. Overall, the approach promises great improvements over the old-fashioned way of doing things.

“This has broad applications across materials science in general. For instance, if you wanted to design new types of batteries that were higher efficiency and lower cost, you could use a system like this to do it. Or if you wanted to optimize paint for a car that performed well and was environmentally friendly, this system could do that, too,” Foshey concludes.

Journal Reference: Timothy Erps, Accelerated Discovery of 3D Printing Materials Using Data-Driven Multi-Objective Optimization, Science Advances (2021). DOI: 10.1126/

The next innovative material for clothes? How about muscles

We wear clothes made from unusual things all the time — you even start to wonder what a “normal” material would be. From plant fibers to plastic to stuff produced by worms, there’s no shortage of raw materials that can be used to make clothes. But researchers are constantly looking for others, with potentially even better properties.

An unusual idea is muscles — or muscle fibers, to be more precise. It sounds a bit odd, but according to a new study, it could be more resilient than Kevlar, at a price that is competitive with other materials? Oh, and it’s also more eco-friendly, and no animals are harmed in the process.

Would you wear clothes made from synthetic muscle protein? Image credit: Washington University in St. Louis.

Cheap, durable, scalable

A belt made from muscle sounds like something straight out of a horror movie, but thanks to the work of researchers at Washington University in St. Louis, it may become real in the not too distant future. The team used microbes to polymerize proteins which were then spun into fibers (somewhat like how silkworms produce silk, but using microbes instead of worms).

The microbes can be engineered to tweak the properties of the protein, and in this case, researchers designed fibers that can endure a lot of energy before breaking.

“Its production can be cheap and scalable. It may enable many applications that people had previously thought about, but with natural muscle fibers,” said Fuzhong Zhang, professor in the Department of Energy, Environmental & Chemical Engineering, and one of the study authors.

No actual animal tissues are needed for the process. Instead, the process starts from a protein called titin, which grants muscles passive elasticity. Adult humans have about 0.5 kg of titin in their bodies.

Titin was desirable because of its molecular size. “It’s the largest known protein in nature,” said Cameron Sargent, a Ph.D. student in the Division of Biological and Biomedical Sciences and a first author on the paper. This makes it very resilient but raises some challenges in producing it.

Surprisingly doable

As weird as it may sound, the idea is not new. In fact, researchers have been toying with the idea of using muscle protein as fibers for a long time — but gathering them from animals is unethical and challenging in many ways. So they looked for another idea.

“We wondered, ‘Why don’t we just directly make synthetic muscles?'” Zhang said. “But we’re not going to harvest them from animals, we’ll use microbes to do it.”

Getting bacteria to produce large proteins is very hard. So instead, the researchers engineered bacteria to piece together smaller parts of the protein into an ultra-sturdy structure. They ended up with a protein with a high molecular weight and about 50 times larger than the average bacterial protein. Then, they used a wet-spinning process, converting the proteins into fibers about 10 times thinner than a human hair.

They opted for a fiber that is especially strong, but the process could be tweaked for any desired property. You could make clothes that are softer or dry quicker, the process can be scaled in any desired direction.

“The beauty of the system is that it’s really a platform that can be applied anywhere,” Sargent said. “We can take proteins from different natural contexts, then put them into this platform for polymerization and create larger, longer proteins for various material applications with a greater sustainability.”

Furthermore, because the fibers are almost indistinguishable from natural muscle, they can also be used in medical procedures, for instance for sutures and stitching up wounds. Unlike other synthetic polymers, this is also biodegradable and less polluting to the environment.

“By harnessing the biosynthetic power of microbes, this work has produced a novel high-performance material that recaptures not only the most desirable mechanical properties of natural muscle fibers (i.e., high damping capacity and rapid mechanical recovery) but also high strength and toughness, higher even than that of many manmade and natural high-performance fiber,” the researchers conclude.

So, would you wear clothes made from muscle?

The research has been published in Nature Communications.

Batman cloak-like chainmail switches from flexible to tough on command


Researchers at Caltech and JPL have devised a new smart material that can instantly morph from fluid and flexible to tough and rigid. The material’s configuration is inspired by chainmail armors and could potentially prove useful in exoskeletons, casts for broken limbs, and robotics.

This modern chainmail sounds mighty similar to Batman’s cloak, which drapes behind the superhero at rest but stiffens into a glider when he needs to make a fast escape. However, unlike the DC movies, the technology was initially inspired by the physics of vacuum-packed coffee.

Coffee inspiration

 “Think about coffee in a vacuum-sealed bag. When still packed, it is solid, via a process we call ‘jamming’. But as soon as you open the package, the coffee grounds are no longer jammed against each other and you can pour them as though they were a fluid,” Chiara Daraio, a professor of mechanical engineering and applied physics at Caltech, explained.

While individual coffee grounds or sand particles only jam when compressed, sheets of linked rings can jam together under both compression and tension. Starting from this idea, Daraio and colleagues experimented with a number of different configurations of linked particles and tested each using both computer simulations and 3-D printing.

Testing the impact resistance of the material when unjammed (soft). Credit: Caltech.
Testing the impact resistance of the material when jammed (rigid). Credit: Caltech.

Although it doesn’t lead to the stiffest configuration, the researchers settled on an octagonal shape of the chainmail links. The best stiffness effect is achieved with circular rings and squares, which is actually the design used in ancient armors. However, these configurations are also much heavier due to the denser stacking of the links. The octagonal configuration is the most optimal one in terms of both stiffness and lighter weight.

The chainmail is made from linked octahedrons. Credit: Catech.

During one demonstration, 3-D printed polymer chainmail was compressed using a vacuum chamber or by dropping weight to control the jamming of the material. The vacuum-locked chainmail remarkably supported a load more than 50 times its weight.

When stiffened the chainmail can support 40 times its own weight. Credit: Caltech.

“Granular materials are a beautiful example of complex systems, where simple interactions at a grain scale can lead to complex behavior structurally. In this chain mail application, the ability to carry tensile loads at the grain scale is a game changer. It’s like having a string that can carry compressive loads. The ability to simulate such complex behavior opens the door to extraordinary structural design and performance,” says José E. Andrade, the George W. Housner Professor of Civil and Mechanical Engineering and Caltech’s resident expert in the modeling of granular materials.

The modern chainmail fabrics have potential applications in smart wearable clothing. “When unjammed, they are lightweight, compliant, and comfortable to wear; after the jamming transition, they become a supportive and protective layer on the wearer’s body,” says Wang, now an assistant professor at Nanyang Technological University in Singapore.

In parallel, the researchers are working on a new design consisting of strips of polymers that shrink on command when heat is present. These strips could be woven into the chainmail to create objects like bridges that fold down flat when required. The two materials joining together could use prove highly useful when incorporated into robots that can morph into different shapes and configurations.

The first ever 3D-printed steel bridge opens in Amsterdam

Queen Maxima of the Netherlands inaugurated the bridge. Image credit: Imperial.

The 12-meter long structure was developed by engineers at Imperial College London, in partnership with the Dutch Company MX3D. It was created by robotic arms using welding torches to deposit the structure of the bridge layer by layer. The construction took over four years, using about 4,500 kilograms of stainless steel. 

“A 3D-printed metal structure large and strong enough to handle pedestrian traffic has never been constructed before,” Imperial co-contributor Professor Leroy Gardner, who was involved in the research, said in a statement. “We have tested and simulated the structure and its components throughout the printing process and upon its completion.”

The bridge will be used by pedestrians to cross the capital’s Oudezijds Achterburgwal canal. Its performance will be regularly monitored by the researchers at Imperial College, who set up a network of sensors in different parts of the bridge. The data will also be made available to other researchers worldwide who also want to contribute to the study.

The researchers will insert the data into a “digital twin” of the bridge, a computerized version that will imitate the physical bridge in real-time as the sensor data comes in. The performance of the physical bridge will be tested against the twin and this will help answer questions about the long-term behavior of the 3D-printed steel and its use in future projects. 

“For over four years we have been working from the micrometre scale, studying the printed microstructure up to the meter scale, with load testing on the completed bridge,” co-contributor Craig Buchanan said in a statement. “This challenging work has been carried out in our testing laboratories at Imperial, and during the construction process on site in Amsterdam.”

Mark Girolami at the University of Cambridge, who worked on the digital model of the bridge, told New Scientist that investigations into bridge failures often reveal deterioration that was missed. Now, with constant data coming from the bridge, they may be able to detect these failures before they do any damage, he added. 

Image credit: Imperial

3D printing has been consistently making headlines over the past few years, slowly becoming a reality for us commoners. Companies are building houses either fully on 3D or with most of their elements made out of a printer. In Mexico, the world’s first 3D printed neighborhood is already moving forward, while Germany’s first 3D residential building is under construction.

But it’s not just housing, it can be almost anything. With the COVID-19 pandemic, researchers discovered they could print face shields and ventilator parts much faster and cheaper than with regular methods. A 3D printer even built a miniature heart, using a patient’s own cells, as well as human cartilage.

A set of research papers were published by Imperial academics during the construction and testing of the bridge. One was published in September 2020 in the Journal of Construction Steel Research, another one in July 2020 in the journal Materials & Design, and a third one in February 2019 in the journal Engineering Structures

Can AI helps us discover new, innovative materials?

In their never-ending quest for better materials, researchers have found an unexpected ally — one that can scour through giant datasets with ease and compute how materials will behave at various temperatures and pressures. This ally, commonly known as Artificial Intelligence (or AI) could usher in a new age of material science.

Computing materials

Here’s the thing with materials: you have a lot of things that can be put together to obtain new materials with exciting properties, but it takes time, money, and effort. So instead, what researchers do before actually making a new material is creating a model of it on a computer.

The current prediction methods work well, and they’ve become quite standard — but it also takes a lot of computation power. Oftentimes, these simulations need supercomputers and can use up a lot of resources, which many researchers and companies just don’t have access to.

“You would typically have to run tons of physics-based simulations to solve that problem,” says Mark Messner, principal mechanical engineer at the U.S. Department of Energy’s (DOE) Argonne National Laboratory.

So instead, Messner and colleagues looked for a shortcut. That shortcut came in the form of AI that uncovers patterns in massive datasets (something which neural networks are particularly good at) and then simulates what happens to the material in extreme conditions using much less processing power. If it works, it’s much more efficient and fast than existing methods… but does it work?

In a new study, Messner and his team say it does.

AI, sort this out

In their new study, they computed the properties of a material 2,000 times faster than the standard modeling approach, and many of the necessary calculations could be performed on a common laptop. The team used a convolutional neural network — a relatively simple class of deep neural networks, most commonly applied to analyze images — to recognize a material’s structural properties.

“My idea was that a material’s structure is no different than a 3D image,” he said. “It makes sense that the 3D version of this neural network will do a good job of recognizing the structure’s properties—just like a neural network learns that an image is a cat or something else,” Messner said.

To put the approach to the test, Messner first designed a square with bricks, somewhat similar to how an image is built from pixels. He then took random samples of that design and used a simulation to create two million data points, which linked the design structure to physical properties like density and stiffness. These two million data points were fed into the neural network, and then the network was trained to look for the desired properties. Lastly, he used a different type of AI (a genetic algorithm, commonly used for optimization) to find an overall structure that would match the desired properties.

This simulation shows the steps that neural networks and genetic algorithms take to find an overall structure that matches specific material properties. Credit: Image by Argonne National Laboratory.

With this approach, the AI method found the right structure in 0.00075 seconds, compared to 0.207 seconds, which would have been the standard physics-based model. If the same ratio can be maintained for more complex computation, the approach could make it much easier for labs and companies with fewer resources to enter the material-making arena.

The potential is especially great in the field of renewable energy, where materials must withstand high temperatures, pressures, and corrosion, and must last decades. Another promising avenue is 3D printing materials — making a structure layer by layer allows for more flexibility than traditional measures, and if you can tell the machine exactly what you want it to produce.

“You would give the structure—determined by a neural network—to someone with a 3D printer and they would print it off with the properties you want,” he said. “We are not quite there yet, but that’s the hope.”

Messner and the team are even working on designing a molten salt nuclear reactor, which uses molten salt as a coolant and can operate at pressures far lower than existing nuclear reactors — but researchers first need to ensure that the stainless steel needed for the reactor will behave well under extreme conditions for decades.

The future of mechanical engineering looks bright. With ever-increasing computing power, 3D printing, and smarter algorithms, engineers can finely tune materials and produce the innovative materials industries need to thrive.

The study has been published in the Journal of Mechanical Design.

Eco-friendly geometry: smart pasta can halve packaging waste at no extra cost

Pasta comes in a variety of shapes and sizes — from the plain and simple to all sorts of quirky spirals. But for the most part, they have one thing in common: they’re not using space very effectively. But a new study may change that.

Researchers from Carnegie Mellon University have found a way to change that, designing new types of pasta that use less packaging and are easier to transport, reducing both transportation emissions and packaging plastic.

Unconventional pasta shapes use up less space but spring to life in water. Image credits: Morphing Matter Lab. Carnegie Mellon University.

Pasta is big business. In 2019, nearly 16 million tons of pasta were produced in the world — up from 7 million tons produced 20 years ago. That adds up to billions of packets that are transported, stored, and ultimately discarded across the world.

Since pasta often has such odd shape, pasta packages often end with a lot of wasted space, which also has to be transported and stored. Using less space means less trucks driving across states and less plastic.

Carnegie Mellon University’s Morphing Matter Lab director Lining Yao had an idea on how that could be reduced — with a bit of help from an old friend: geometry.

“By tuning the grooving pattern, we can achieve both zero (e.g., helices) and nonzero (e.g., saddles) Gaussian curvature geometries,” the study reads. It then goes on to translate what this means. “This mechanism allows us to demonstrate approaches that could improve the efficiency of certain food manufacturing processes and facilitate the sustainable packaging of food, for instance, by creating morphing pasta that can be flat-packed to reduce the air space in the packaging.”

They started out with a computer simulation to see how different shapes would achieve the goal. They tried various designs, including helixes, saddles, twists, and even boxes. After they settled on a few efficient shapes, they put it to the boiler test — quite literally.

Flat-packed pasta before and after boiling. Image credits: Morphing Matter Lab. Carnegie Mellon University.

Speaking to Inverse, Yao says wasted space could be reduced by 60% by flat-packing pasta — and that’s just the start of it. The method could also be used for things like wagashi or gelatin products. The method could also be used to design more complex and fancy shapes for special occasions. In dry form, a piece of pasta could look like a disc, but when boiled, it could become a rose flower.

Credits: Carnegie Mellon University..

However, there are limitations to study. Flour dough is known to be a complex material. It can have different proportions of water, starch, gluten, fiber, and fat. Flour dough also has variable, nonlinear properties, which makes it hard to anticipate how different types of pasta would behave — this was just a proof of concept.

Researchers recommend more quantitative models of assessment to see how different materials with complicated groove shapes and patterns would behave.

The study was published in Science.

Citrus fruit stands poised to make transparent wood more sustainable, stronger, and more transparent

Transparent wood is getting a citrusy update that’s poised to make it more sustainable, hardier, and even more transparent.

A piece of the new transparent wood. Image credits Céline Montanari.

First developed five years ago by researchers at the KTH Royal Institute of Technology, transparent wood is definitely an interesting material. It has many of the characteristics of regular wood (and, indeed, starts out life as such) but it’s generally stronger, more resilient, transparent, and an ok medium to store thermal energy (heat) in.

Now, new research reports how this material can be further improved with a little help from citrus-derived compounds.

Needs some lemon

“The new limonene acrylate it is made from renewable citrus, such as peel waste that can be recycled from the orange juice industry,” says Céline Montanari, a Ph.D. student at the KTH Royal Institute of Technology and lead author of the study.

The process of making transparent wood involves chemically stripping lignin out of wood. Lignin is a natural polymer that plants such as trees use to give their tissues mechanical strength, but it’s also the main light-absorbing compound in there. The empty spaces left over after all this lignin has been removed are later filled in with another transparent compound to restore the material’s strength while allowing light to pass through.

At first, fossil-based polymers (such as synthetic resins) were used for this role. The new paper reports on an alternative to these polymers: limonene acrylate. This is a monomer (individual building blocks of polymers) produced from limonene, which is, in turn, available in the oils found in citrus fruits.

Transparent wood created using the new approach offers much improved optical properties — a “90% optical transmittance” through a plate 1.2 mm thick and a haze of only 30% — the team explains. Unlike other similar composites developed over the last 5 years, transparent wood produced using limonene acrylate is strong enough (and intended to be used) for structural use such as girders or beams. It’s also more sustainable than previous incarnations of the material.

“Replacing the fossil-based polymers has been one of the challenges we have had in making sustainable transparent wood,” Professor Lars Berglund, the head of the KTH’s Department of Fibre and Polymer Technology and corresponding author of the study.

The material requires no solvents to produce, and all the compounds used in the process are derived from biological raw materials. The novel way this material interacts with light further opens new possibilities in fields such as wood nanotechnology, he adds.

“We have looked at where the light goes, and what happens when it hits the cellulose,” Berglund says. “Some of the light goes straight through the wood, and makes the material transparent. Some of the light is refracted and scattered at different angles and gives pleasant effects in lighting applications.”

The team is now hard at work exploring some of these potential applications.

The paper “High Performance, Fully Bio‐Based, and Optically Transparent Wood Biocomposites” has been published in the journal Advanced Science.

Watch a 3D printer produce an entire boat

Using a massive 3D printer, the University of Maine built the world’s largest 3D-printed boat. Here it is — it took more than three and a half days, but you can see it in half a minute.

The team set three world records in the process: world’s largest 3D printer, largest solid 3D-printed object, and largest 3D-printed boat. But the researchers didn’t build the boat for quirks and records — they built it to see if wood and plastic could work together for 3D printing.

If wood can be integrated into large-scale 3D printing, it could serve as a possible replacement for metal, becoming a more sustainable alternative. Normally, when building large things, you want metal because it’s so strong and rigid. But biobased materials like wood could offer similar parameters at a fraction of a cost.

“Maine is the most forested state in the nation, and now we have a 3D printer big enough to make use of this bountiful resource,” said Maine Senator Angus King, who attended the boat’s unveiling.

The 25-foot patrol boat is now tested with a wind machine and wave basin at an offshore facility, and if the approach is confirmed, it could mark a turning point for 3D-printed materials.

The key element that allows traditional 3D-printing polymers to “play nice” with wood is something called cellulose nanofibers, or CNF. CNF consists of tiny fibers that can be integrated with thermoplastic to make the resulting material much stronger. Cellulose nanofiber is lightweight, durable, and has thermal expansion parameters on par with glass. It’s also sustainable and has a low environmental impact. It’s not surprising that teams are looking to incorporate it.

“The UMaine Composites Center received $500,000 from the Maine Technology Institute (MTI) to form a technology cluster to help Maine boatbuilders explore how large-scale 3D printing using economical, wood-filled plastics can provide the industry with a competitive advantage,” says a UMaine news release. “The cluster brings together the expertise of UMaine researchers and marine industry leaders to further develop and commercialize 3D printing to benefit boatbuilders in the state. By 3D printing plastics with 50% wood, boat molds and parts can be produced much faster and are more economical than today’s traditional methods.”

This is also a stepping stone for other, even more ambitious projects. 3D printing is entering a golden stage, and finding ways to incorporate sustainable materials with the desired properties into larger designs is already a major field of research. The University of Maine recently secured $2.8 million in funding from the U.S. Department of Energy to develop a more eco-friendly method of 3D printing wind turbine blade molds, using the same printing system.  

Simple seaweed could be used to heal human wounds with bio-ink

Throughout history, societies have enjoyed the nutritional and medical virtues of seaweed. But a group of scientists found another interesting use for algae: healing wounds in humans through bioprinting.

Seaweed keeps on surprising us with further virtues
Image credit: Flickr / Peter Castleton

When we have small wounds on our skin or muscles, they usually heal by themselves. But in deeper wounds repair is more difficult. These sorts of issues often require more serious treatments, and in very extreme cases, may even need an amputation or a transplant if healing is not complete. This is when technology such as bioprinting enters the stage.

Bioprinting means using materials or inks made from biological sources such as seaweed gels or printed with biological ingredients such as human skin cells. These bio-inks can be combined and printed to create structures that can grow new tissue in the desired place or shape. They can be controlled chemically at the molecular level.

Researchers from the ARC Centre of Excellence for Electromaterial Science (ACES) and the University of Wollongong have been working on one particular type of bio-ink from an Australian green seaweed — a seaweed with a molecular structure similar to that in human connective tissue. The ink belongs to a group of molecules know as ulvan.

Marine algae are nature’s most abundant plant source of sulfated polysaccharides (complex glycan sugars) – such as fucans in brown algae (Phaeophyta), carrageenans in red algae (Rhodophyta), and ulvans in green algae (Chlorophyta). These gel-like glycans are large molecules with biological properties that carry many health benefits. Ulvan has a long list of biological properties including antibacterial, anti-inflammatory, and anti-coagulant, which has made it especially interesting to researchers. Its molecular signature can trigger functions in human cells such as attachment, growth and production of other molecules such as collagen. This means that bio-inks with ulvan could be used for wound healing and tissue regeneration.

In a new paper, ACES Director Professor Gordon Wallace and his team described the potential of such a bio-ink with ulvan. The presence of it leads to the proliferation of cells involved in wound healing, they argued. Ulvan also helps to regulate the function of cells in producing key biomolecules used during wound healing.

“Wound healing occurs in a 3D environment involving a number of cell types and biomolecules, so the use of 3D bioprinting to create scaffolds for wound healing has attracted much attention,” Wallace said in a statement. “Ulvan acts as molecular reinforcement in 3D printed scaffolds, a key feature in preventing structure contraction.”

Together with bioinks that create molecular architecture, the researchers at ACES are targeting the fabrication of 3D scaffolds for skin tissue culture. This aims to combine bioinks and biomaterials through 3D bioprinting into structures that deliver the desired outcomes of reconstructed skin. Advances in printing engineering have made structural architecture of artificial skin tissue possible.

“It has been so exciting to begin the journey of unlocking molecules from seaweed and delivering them to new heights in partnership with researchers in biomaterials,” Pia Winberg, co-author said in a statement. “Particularly when the molecules that we have found from a unique species of Australian green seaweed are uncannily similar in structure and function to the molecules that exists in human skin.”

The study was published in the journal Biomaterials Science.

Dump the plastic: Scientists create edible food packaging films from seaweed

Ever been so hungry that you could hardly wait until the packaging was removed from your food? Don’t worry, this will soon be something of the past.

Researchers and companies have been working for a while now on edible, cost-effective food films as a way to tackle food waste and plastic pollution. Now, an international team has taken it a step forward, creating a film based on sodium alginate – a well-known naturally occurring seaweed biopolymer.

Rammohan Aluru and Grigoriy Zyryanov, part of the team that developed edible food films based on seaweed (stripped off solution of ferulic acid and sodium alginate in a Petri dish). Image credit: UrFu

Sodium alginate is a carbohydrate that can be used to form packaging fils, says Rammohan Aluru, a co-author of the paper describing the material, in a statement. It’s also stable enough to serve as packaging.

Alginates are refined from different species of brown seaweeds such as the giant kelp Macrocystis pyrifera and Ascophyllum nodosum. They are currently used in many industries such as food, fertilizers, textile printing, and pharmaceuticals. Even dental impression material uses alginate as its means of gelling.

The film, created with natural ingredients, is safe for health and the environment, is water-soluble, and can dissolve by almost 90% in 24 hours. The researchers crossed-linked the alginate molecules with linked with a natural antioxidant ferulic acid, making the film strong, homogeneous, rigid, and capable of prolonging the life of the products.

Grigory Zyryanov, professor at Ural Federal University and co-author of the paper, said the film keeps food fresh for a longer time thanks to its antioxidant components that slow down the oxidation processes. Plus, natural antiviral agents obtained from garlic, turmeric, and ginger can be added to the film to prevent the spread of viruses and extend the shelf life of food, thus granting it anti-pathogen properties while maintaining its all-natural appeal.

The researchers said the film could be produced without any special requirements, making it accessible by food producers and film manufacturers. They could even be produced at a polymer production plant, Zyryanov argued. And if there’s an ocean nearby, it would be even simpler for any industrial manufacturer to create the films at low cost.

The new film is part of a much larger trend of innovating research being done on edible bio-films or coating materials – with a key role in food preservation, manufacturing, and extending the shelf-life of food materials. They are eco-friendly, easily degradable, and don’t cause health issues even if you forgott to remove them. But most importantly, they would help rid us of our dependence on plastic: a whopping 40% of the plastic we produced is used for packaging.

Expanding the use of bio-films and coating materials would help address food waste, a growing problem. The UN estimates that around one-third of the world’s food is lost or wasted every year. While harvest and retail are usually the main problems, a significant amount of food is also wasted at purchase and consumption. Plus, the food films would help tackle plastic pollution, which grows every year.

Several startups have been working with them for a while now. Evoware is looking at using seaweed to create a plastic-like packaging that can be safely eaten, while Loliware has created edible cups out of seaweed and has now branched to straws. Skipping Rocks Lab is also working to replace the plastic water bottle with a seaweed alternative.

The study was published in the Journal of Food Engineering.

Cheap plastics could soon be turned into sustainable fabrics

Every year, the textile industry produces 62 million tons of fabrics. It’s one of the most polluting industries on Earth, second only to the oil and gas industry, using massive amounts of water and generating a lot of waste in the process. But it could become a bit more sustainable by incorporating plastic and using it as fabrics.

Plastic made fabrics. Image credits: Svetlana Boriskina.

In April 2016, world leaders gathered in Paris to sign an agreement to curb global greenhouse gas emissions. At the major event, mixed between countless press conferences and presentations, one small stand showed how plastic could be used to make fabric. The resulting fabric is surprisingly soft and durable, and a great way to repurpose plastic. The idea got lost in the great turmoil caused by the Paris Agreement — but it warrants more attention, researchers say.

The fashion industry is responsible for 5-10% of global greenhouse gas emissions. It’s not just manufacturing — maintenance and chemical treatments often consume even more energy (and water) than the production phase. But polyethylene yarns are resistant by default.

Svetlana Boriskina and colleagues at MIT focused on polyethylene because it is one of the most commonly used plastics. It’s lightweight and durable, which makes it excellent as a packaging material, but horrendous as a pollutant. Its uses rang for films, tubes, plastic parts, etc — and it’s still widely used throughout the world.

Sweater knitted by Emily Holtzman, who is also modelling it. Image courtesy of Svetlana Boriskina.

Polyethylene (PE) can be colored cheaply through environmentally friendly methods and is durable, offering exactly the type of properties you want in clothing. It offers the potential to create sustainable fabrics, Boriskina says, and the whole process is quite cheap.

“The process of converting PE materials to textiles is indeed cost-effective, scalable and eco-friendly,” Boriskina explains for ZME Science. “Even starting from fossil PE provides a more environmentally-friendly textile solution, but there is also a possibility to recycle vast amounts of already accumulated PE waste into high-added-value-products such as fabrics and garments. Finally, it has been shown that PE can be derived from biomass, making the fabrics bio derived yet completely recyclable.”

A close-up of the plastic-made fabrics. Image credits: Svetlana Boriskina.

Using plastic for clothes isn’t as crazy as it seems. Throughout history, the textile industry generally made use of natural fibers such as wool, cotton, silk, and linen. In the past century, however, synthetic materials such as polyester and nylon have become a common occurrence. Polyethylene has been generally overlooked until now.

The authors found that PE fabrics are resistant to staining and allow for fast drying, as well as efficient moisture-wicking. These properties, along with the cheap price and durability, make PE an excellent alternatives for existing fabrics.

“This work shows that not only the full lifecycle analysis confirms that PE is more environmentally friendly than other materials, but also the alternative way of dry-coloring further reduces the environmental footprint and allows adding other properties to the fabrics beyond color,” Boriskina tells me.

Finally, the conversion process from plastic to textiles is also cheap and scalable, and it’s possible to use plastic already accumulating in waste sites.

“The process of converting PE materials to textiles is indeed cost-effective, scalable and eco-friendly. Even starting from fossil PE provides a more environmentally-friendly textile solution, but there is also a possibility to recycle vast amounts of already accumulated PE waste into high-added-value-products such as fabrics and garments. Finally, it has been shown that PE can be derived from biomass, making the fabrics bio-derived yet completely recyclable,” Boriskina adds.

Image credits: Svetlana Boriskina.

Polyethylene seems like a truly well-suited material for clothes. But will it catch on? The fashion industry is often unpredictable and it doesn’t often choose the most sustainable or efficient materials. But PE has an advantage that could make it more attractive, especially in the summer.

“It is literally cool to wear our PE textiles, and the pun is intended. The fabric offers a ‘cold touch’ tactile sensation and keeps the wearer cool, dry, and comfortable,” Boriskina concludes.

As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market.

The study “Sustainable polyethylene fabrics with engineered moisture transport for passive cooling” has been published in Nature Sustainability.

Researchers find a way to grow wood in a lab, and it could curb global deforestation

You’ve probably heard about lab-grown meat, sparing animals from slaughter, and lowering greenhouse gas emissions. Well, it turns out this isn’t the only thing researchers are trying to recreate at a laboratory. A team at MIT in the United States is already working on “growing” wood without relying on sunlight or even soil.

Image credit: Flickr / Chuck Coker

The process is strikingly similar to lab-grown meat. The researchers create structures made of plant cells that mimic wood, but without having to clear down forests. The cells don’t come from trees but instead from a flowering plant called Zinnia originally from Mexico. They are then turned into a rigid structure using plant hormones. They essentially “grow” the wood.

They chose the Zinnia plant because it grows fast and is well studied. The cells reproduced before being transferred to a gel for further development. Once they grew in volume, the cells were tested against different variables such as pH and hormone concentration. It will be a long road to make this cost-effective but the work represents a starting point for novel approaches to biomaterial production, reducing the environmental pressure from forestry and agriculture.

Between 1990 and 2016, over 500,000 squared miles of forests were lost due to wood consumption and the clearing of wooded areas to access arable lands.

The researchers highlighted a number of inefficiencies inherent to agriculture and forestry, some that can be managed such as fertilizer draining off fields, and some that are out of the control of the farmer, such as weather and seasonality. Also, only a fraction of the harvested plant ends up being used for food or materials production.

“The way we get these materials hasn’t changed in centuries and is very inefficient. This is a real chance to bypass all that inefficiency,” Luis Fernando Velásquez-García, who is overseeing the MIT research, said in a statement. “Plant cells are similar to stem cells in the sense that they can become anything if they are induced to.”

To achieve wood-like properties, the researchers used a mix of two plant hormones called auxin and cytokinin. They varied the levels of these hormones so to control the cell’s production of lignin – an organic polymer that gives wood its firmness. The cellular composition and structure of the final product were assessed using fluorescence microscopy.

The researchers acknowledged that they are in a very early stage with these lab-grown plant tissues. They have to keep working on the specifics, such as the hormone levels and the Ph of the gel. “How do we translate this success to other plant species? It would be naïve to think we can do the same thing for each species,” Velázquez-García said in a statement.

David Stern, a plant biologist and President of Boyce Thompson Institute, who was not involved with the research, told Wired that scaling up the study would take “significant financial and intellectual investment” from government and private sources. “The question is whether the technology can scale and be competitive on an economic or lifecycle basis,” he added.

The study was published in the Journal of Cleaner Production.

Scientists zoom in on snake skin to see how they navigate sandy surfaces

Despite having a similar body shape and structure, not all snakes move in the same way. Most, when they move from A to B, slither head-first. But a minority of them (especially desert snakes) do it differently: they slither with their mid-sections first, slithering sideways across the loose sand. Now, researchers know why.

At first glance, you’d think that snakes have a hard time moving around — after all, they have no legs. But here’s the thing: not only do snakes do just fine by slithering, they’re found in almost all environments on Earth, managing to thrive on a variety of surfaces, including sandy environments.

If you’ve ever tried jogging on a beach, you know how hard moving across loose sand is. Now imagine you’re a snake, and your whole body is essentially a sole, how would you even manage moving around?

Researchers have known for a while that snakes in sandy environments tend to move in a different way than others, and they suspected it has something to do with the sand itself. So they set out to investigate it.

“The specialized locomotion of sidewinders evolved independently in different species in different parts of the world, suggesting that sidewinding is a good solution to a problem,” says Jennifer Rieser, assistant professor of physics at Emory University and a first author of the study. “Understanding how and why this example of convergent evolution works may allow us to adapt it for our own needs, such as building robots that can move in challenging environments.”

Rieser’s work joins together biology and soft matter physics (flowable materials, like sand). She studies how animals move around on these surfaces, and how this could help us develop new technologies by adapting what we see in nature (something called biomimicry).

Snakes are particularly interesting because they move in such a peculiar way. Even though snakes “have a relatively simple body plan, they are able to navigate a variety of habitats successfully,” she says. What we’ve learned from snakes has already been applied in several fields. Their long flexible bodies have inspired robots used in surgical procedures or search missions in collapsed buildings, for instance.

The key to the movements of these sidewinder snakes lies in their bellies — in the tiny details of their bellies, to be precise. Rieser and colleagues analyzed three sidewinder snakes (all vipers). They gathered skin the snakes had shed and looked at it with an atomic microscope, zooming in to the atomic level. They also scanned skins shed by non-sidewinders for comparison.

A zoomed-in comparison between holes on a sidewinder snake skin (left) and a non-sidewinder snake skin (right). A mathematical model developed by the researchers shows that the lack of spikes allows sidewinder snakes to move on loose surfaces. Image credits: Tai-De Li.

The regular, non-sidewinder snakes had tiny spikes on their skin, invisible to the human eye. These spikes create friction between the snake and the surface, which acts as a grip allowing them to propel themselves forward headfirst. The sidewinders, however, didn’t have the spikes. Instead, they had tiny holes, because you can’t really create friction or a grip with a surface like sand (that’s also why it’s harder to run on sand than concrete or soil).

“You can think about it like the ridges on corduroy material,” Rieser says. “When you run your fingers along corduroy in the same direction as the ridges there is less friction than when you slide your fingers across the ridges.”

However, some snakes also seemed to have a few spikes, which researchers interpret as a sort of evolutionary “work in progress”. These snakes are younger in their evolutionary history, and haven’t yet had time to fully shed their spikes, the team explains.

“That may explain why the sidewinder rattlesnake still has a few micro spikes left on its belly,” Rieser says. “It has not had as much time to evolve specialized locomotion for a sandy environment as the two African species, that have already lost all of their spikes.”

As for biomimicry, it’s a good lesson: if you want to build a robot that can move on a sand or sand-like surface, you need to pay attention to the texture of its skin.

Journal Reference: Jennifer M. Rieser el al., “Functional consequences of convergently evolved microscopic skin features on snake locomotion,” PNAS (2021).