Tag Archives: hydrogel

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.

Scientists find a new way to regrow nerves in spinal injuries

Researchers have demonstrated a novel method that might regrow nerve cells at the site of spinal injuries.

Writing in the Journal of Neuroscience, scientists at the University of Aberdeen in Scotland delivered a treatment of hydrogel to rat nerve cells in a cell-culture dish.

The hydrogel contains a substance — a soluble agonist called S-220 — that activates a molecule called Epac2. Previous studies had shown that Epac2 is heavily involved in nerve growth during embryonic development.

Due to the nature of the hydrogel, the drug is released slowly, which can provide a scaffold that physically supports injured nerve cells during the regeneration process.

After the team found that the hydrogel successfully activated Epac2, they proceeded with stage two, administering it to rats with spinal injuries. The hydrogel significantly enhanced axonal outgrowth across the lesions and the rats themselves showed significant improvements in their ability to walk.

“This is something that other researchers have tried around the world in many different ways, but we found that our method actually works and is also very efficient,” said Dr. Derryck Shewan of the Institute of Medical Sciences at the University of Aberdeen.

That’s not all. The Epac2-activating drug not only ‘turbo-charged’ the injured nerve cells, promoting regeneration, but it also significantly reduced the inhibitory nature of the injury site, further enhancing recovery.

“The injured spinal nerves not only regenerated more robustly, they sensed the surrounding environment was not as inhibitory anymore, so the damaged nerves could more successfully regrow and cross the injury site,” said Dr. Guijarro-Belmar, co-author of the new study.

Spinal cord injuries can be devastating, potentially paralyzing patients below the site of injury. Currently, there is no cure for such damage to the spinal cord. But, in the future treatments based on self-assembling hydrogels injected in the spinal cord could provide speed up recovery and replace invasive surgery.

Elsewhere, scientists at the University of Michigan devised a nanoparticle solution that prevents spinal scars from forming, as well as boosts the immune response to promote healing rather than cause damage to nerve cells. In combination with this hydrogel therapy or other similar ones, it may prevent paralysis.

“Repairing the damaged spinal cord remains one of the greatest challenges in medicine,” said Mark Bacon, Executive and Scientific Director from International Spinal Research Trust who partly funded the research.

Snail.

Researchers develop very powerful but reversible glue — kind of like snail slime

An international team of snail-envious engineers has found a way to make powerful but reversive adhesives.

Snail.

Image via Pixabay.

Nobody wants weak glue. It ruins your day. But another side of this sticky situation is reversibility. A strong glue can quickly become a liability when we stick something in the wrong position, for example. With a weak glue, you can un-stick something and try again — but risk it falling apart later when you need it to hold most. With a strong glue, you just have to deal with the mistake or start over from scratch — no adjustments allowed.

Except if you’re a snail. Snails, you see, have epiphragms — that slimy wet layer of mucus lathered all over their body. The epiphragm can harden to protect a snail’s body or to allow it to anchor in place for long periods of time. However, it can quickly be deactivated when the animal needs or wants too. The present study demonstrates a man-made alternative that functions much in the same way as a snail’s epiphragm.

Slime time

“Geckos can put one hand down and then release it, so the gecko’s adhesion is reversible, but it’s very low adhesion,” says Shu Yang, a Professor in the Department of Materials Science and Engineering and in the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania, who led the study.

“A gecko is 50 grams, and a human is at least 50 kilograms. If you want to hold a human on a wall, it’s not possible using the same adhesive. You could use a vacuum, but you have to carry a cumbersome vacuum pump. We’ve been working on this for a long time, and so have other people. And no one could have a better solution to achieve superglue-like adhesion but also be reversible.”

Yang and her team have a background in adapting nature’s creations to human technology and know-how. Among others, they have worked on nanoscale structures inspired by the structure of giant clams, butterflies, and pollen. Yang herself is also the director of AESOP, the Center for Analyzing Evolved Structures as Optimized Products, which looks at biology to solve design and architecture problems.

The geckos‘ adhesive toes aren’t strong enough to adapt to human use, she explains, although her team focused a lot of effort on making it work. However, the team had a breakthrough when Gaoxiang Wu, a Penn Engineering graduate student and co-author of the current paper, worked with a hydrogel made of a polymer called polyhydroxyethylmethacrylate (PHEMA) and noticed its unusual adhesive properties. PHEMA is rubbery when wet but becomes rigid as it dries — just like an epiphragm.

When PHEMA is wet, it can squish thoroughly into a surface texture, be that visible or microscopic. This part of the process makes it ‘sticky’. But what makes it a good adhesive is that when PHEMA begins to dry, it becomes very rigid — about as rigid as a plastic bottle cap, the team reports — but doesn’t shrink at all. This last step is the real meat and potatoes of the whole ‘adhesive’ thing. As the material hardens inside the cavities, it becomes securely tied to it.

“[PHEMA] is like those childhood toys that you throw on the wall and they stick. That’s because they’re very soft. Imagine a plastic sheet on a wall; it comes off easily. But squishy things will conform to the cavities,” says Yang.

“When materials dry, they usually shrink. If it shrinks from the surface, it no longer wants to conform to the microcavities and it’ll pop out. Our PHEMA adhesive doesn’t pop out. It stays conformal. It remembers the shape even when it’s dry and rigid.”

PHEMA works much like a snail’s epiphragm. This biological material, initially wet as it covers the snail’s body, sticks to any surface the animal moves over and eventually hardens. Snails often use their epiphragm to anchor them in place when they retreat into their shell. The material hardens into a solid ‘barricade’ around the shell’s opening, keeping it in place and insulating the snail from the dry, warm air during the day.

Shells.

Which is why you see these hanging around.
Image credits Ulrike Leone.

At night, when temperatures drop and humidity rises, the epiphragm softens and the snail goes along its merry way.

The team tested both wet flexibility and dry adhesion for the PHEMA hydrogel in the lab, also evaluating its ability to hold weight and how long it needs to rehydrate and reverse its adhesive properties. The material was 89 times stronger than gecko adhesion but was easily broken after being rehydrated, the team reports. To showcase just what the material can pull off, the study’s co-first author Jason Christopher Jolly volunteered to suspend himself from a harness held only by a postage-stamp-sized patch of the PHEMA adhesive.

The glue held. The team says that although PHEMA may not be the strongest adhesive in existence, it is currently the strongest known candidate available for reversible adhesion.

“When it’s conformal and rigid, it’s like super glue. You can’t pull it off. But, magically, you can re-wet it, and it slips off effortlessly,” says Yang. “Additionally, PHEMA doesn’t lose its strong adhesion when scaled up. Usually, there’s a negative correlation between adhesion strength and size. Since PHEMA is not dependent on a fragile structure, it doesn’t have that problem.”

On the one hand, PHEMA could a huge development for scientific, industrial, and household applications. On the other hand, it’s also quite limited, since its activation is mediated by water. For example, a car glued together with PHEMA would, in other words, fall apart in the rain. So Yang acknowledges that it’s just a starting point.

“Car assembly uses adhesives, and, you can imagine, if there are any mistakes putting parts together, the adhesive is set and the parts are ruined,” she says.  “A car is pretty big. Usually they don’t glue things together until the last step, and you need a room-sized oven to host the car and cure the adhesives. An adhesive that’s strong and reversible like PHEMA could completely change the process of car assembly and save money because mistakes wouldn’t be so costly.”

“[However], with a lot of things you don’t want to use water. Water takes time to diffuse. In the future, we want to find the right material that can switch the property like that.”

The researchers hope to eventually find or engineer adhesives that could respond to cues like pH, specific chemicals, light, heat, or electricity, to broaden the potential applications of reversible adhesion.

The paper “Intrinsically reversible superglues via shape adaptation inspired by snail epiphragm” has been published in the journals Proceedings of the National Academy of Sciences.

MIT technique can shrink objects down to the nanoscale

Researchers at MIT have figured a way to create nanoscale structures by shrinking down existing objects by up to 1,000 times their original volume.

MIT engineers have crafted a new technique to create 3-D nanoscale structures by first making a larger structure and then shrinking it. The image shows a complex structure prior to shrinkage. Credit: Daniel Oran.

Producing nanoscale objects smaller than the width of the human hair can be very tricky. Existing technique involve etching patterns with lasers, for instance, but most only work for 2-D surfaces or are very slow and prone to errors when it comes to stacking 3-D objects. There are so challenging limitations as to what materials you can use.

The research team led by MIT professor Edward Boyden found a creative solution. Instead of painstakingly raising a new structure from scratch, the researchers took existing structures and shrunk them down to the desired size.

The technique is based on a process for imaging brain tissue called expansion microscopy. Used by thousands of researchers in biology labs around the world, expansion microscopy involves embedding tissue into a hydrogel and then expanding it. This then enables a high-resolution imaging with a regular microscope. When the process is run in reverse, something which scientists call “implosion fabrication”, relatively large objects can be scaled down to one-thousandth their original size.

First, the process starts with creating a scaffold out of polyacrylate. Then, the scaffold is soaked into a solution that contains certain molecules that attach to the frame when activated by a laser’s light. The fluorescein molecules can be coaxed to attach to certain points of the structure with a high degree of precision.

“It’s a bit like film photography,” co-author Daniel Oran, an MIT graduate student, said in a statement. “A latent image is formed by exposing a sensitive material in a gel to light. Then, you can develop that latent image into a real image by attaching another material, silver, afterwards. In this way implosion fabrication can create all sorts of structures, including gradients, unconnected structures, and multi-material patterns.”

Finally, the object is bathed in an acid, which blocks the negative charges in the polyacrylate, causing the whole structure to shrink.

The biggest limitation of this kind of approach is the inherent trade-off between size and resolution. For instance, an object that’s 1 cubic millimeter can have a resolution of 50 nanometers, whereas a 1 cubic centimeter object has a 500-nanometer resolution.

But even so, the technique’s potential applications are numerous, from optics to medicine to robotics.

“There are all kinds of things you can do with this,” said Edward Boyden, an associate professor of biological engineering and of brain and cognitive sciences at MIT. “Democratizing nanofabrication could open up frontiers we can’t yet imagine.”

“With a laser you can already find in many biology labs, you can scan a pattern, then deposit metals, semiconductors, or DNA, and then shrink it down,” Boyden added.

The findings were described in the journal Science

Soft, eel-inspired device can produce up to 110 volts

Taking inspiration from one of nature’s more bizarre creatures, researchers have developed a device that can reach up to 110 volts, powered by nothing else but water-filled gels and biology. This device could pave the way for a new generation of biological implants.

This photo depicts the printed, high voltage implementation of the artificial electric organ. A 3-D bioprinter was used to deposit arrays of gel precursor droplets onto plastic substrates, which were then cured with a UV light to convert them into solid gels. Alternating high-salinity and low-salinity gels (red and blue gels, respectively) were printed onto one substrate, and alternating cation-selective and anion-selective gels (green and yellow gels, respectively) were printed onto a second substrate. When overlaid, these gels connect to form a conductive pathway of 612 tetrameric gel cells that can be used to generate up to 110 volts. Credits: Anirvan Guha and Thomas Schroeder.

The electric eel (Electrophorus electricus) is an electric fish, and despite its name, it’s not really an eel — although it does kind of look like one. The “eel” can produce electrical current through three pairs of abdominal organs, which make up about 80% of its body. It can administer a shock of up to 860 volts and 1 ampere of current (860 watts) for two milliseconds, which it uses to defend itself or to stun prey.

Researchers have long looked towards this ability in an attempt to generate current in biological settings. Let’s say you want a biocompatible power source, to fuel a pacemaker or a sensor, you’re bound to have difficulties when merging the systems.

Now, a team led by Michael Mayer from the University of Fribourg, along with researchers from the University of Michigan and UC San Diego, have created a device that uses hydrogels (water-filled gels) and can create a voltage of up to 110 volts.

“Our artificial electric organ has a lot of characteristics that traditional batteries don’t have,” Thomas Schroeder, a chemical engineer at the University of Michigan in Ann Arbor, who co-led the research, told Nature. As well as its desirable physical features, “it isn’t as potentially toxic, and it runs on potentially renewable streams of electrolyte solution”.

The electric eel produces current through cells called electrocytes. Researchers tried to mimic these cells, using four different hydrogels made of polyacrylamide and water. They then stacked over 2,000 of these hydrogels, generating a potential difference — a difference of electrical potential between the top and the bottom.

[alert style=”alert-default” close=”false”]Ions are atoms or molecules with an electric charge due to the loss or gain of one or more electrons. When ions accumulate on either side of a membrane (in this case, the hydrogel) they form an ion gradient, favoring current flow. This can be used to produce a current, which is what the researchers did here. Essentially, the system draws on a biological system’s chemical energy to produce a current.

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The more hydrogel layers you stack, the more current you can produce. But it’s not just “more is better” — researchers also want to make the layers thinner, to reduce their resistance, and this is pushing the edges of existing technology. To print the fine layers, the team used a printer that “deposits little droplets of gel … with the precision and spatial resolution to print an array of almost 2,500 gels on a sheet the size of a normal piece of printer paper,” said Anirvan Guha, a graduate student who worked in the project. They also want to increase the current, tens to hundreds of microamperes. So far, their total power output has been between 10 and 100 times lower than that of the eel, not enough to power most devices. However, researchers are optimistic and after all, these are only the early days of this technology. We can certainly expect much more to come in the future.

Having a flexible, transparent, and biocompatible power source could make a big difference for medical implants, and potentially even power up the future’s prosthetics.

The study has been published in Nature, and additional findings will be presented at the Biophysical Society Annual Meeting.

New hydrogel can glue retina back into eye

The retina is extremely important for vision. It processes light and sends all visual information to the brain through the optic nerve. Therefore, it’s very serious when the retina detaches from its normal position; the eye can’t function, and it can result in permanent blindness. To fix the problem, the retina needs to be repositioned to the back of the eye as soon as possible. Vitreous, the gel-like substance that fills the space between the retina and the lens needs to be replaced during this surgery.

The structure of the eye: vitreous fills up the whole inner chamber. Image credits: Holly Fischer

The problem

Current procedures involve injecting silicone oil or gas bubbles in the eye to push the detached retina back into place. However, these substances don’t mix well with water and don’t function well in the long term. In addition, it is necessary for the patient to have his or her head secured facing downwards during this surgery. For an extended period after surgery, doctors recommend keeping the head only in certain positions and not flying in an airplane or venturing to high altitudes.

Hydrogels, which are elastic gels that are composed mostly of water, are a promising alternative to replace vitreous because they are similar to human soft tissue.  Also, keeping the head in a certain position is not necessary. However, one problem with hydrogels is that they can absorb water after a few months and swell, putting pressure on other parts of the eye and causing damage.

The solution

Associate Professor Tadamasa Sakai of the University of Tokyo and his lab group developed a new hydrogel. It has a low concentration of polymers so it can be placed in an eye as a liquid and still form a gel in only 10 minutes. They used special techniques to get it to gel quickly. The scientists mixed two types of polymers to create branched polymer clusters in liquid and incited them to form a solid when injected into an eye. The hydrogel stays transparent, while other gels turn cloudy over time, which makes additional surgery unnecessary.

This hydrogel stays clear and doesn’t become cloudy. Image credits: 2017 TAKAMASA SAKAI

“Hydrogels are promising biomaterials, but their physical properties have been difficult to control. We wanted to show that these difficulties can be overcome by designing molecular reactions and I think we’ve been successful”— Tadamasa Sakai

In a jar the hydrogel forms after 30 seconds, but in the eye, it takes up to 10 minutes. Video credits: 2017 TAKAMASA SAKAI

This technique was tested successfully on rabbits. The test subjects didn’t experience any side effects: the gels were not rejected after 410 days. No significant swelling was noted. In another experiment, the new hydrogel gel was shown to cure rabbits with detached retinas.

The hydrogel still needs to be tested for safety and efficiency in humans but could replace other soft tissues when dealing with tumours, trauma, and degenerative diseases. In this way, this hydrogel could pave the way for new surgery techniques.

 

By adding fibers, scientists have turned a soft gel into a material tougher than many metals. Credit: Hokkaido Uni.

Adding fibers to hydrogel, a soft material mostly made of water, makes it 5 times tougher than steel

By adding fibers, scientists have turned a soft gel into a material tougher than many metals. Credit: Hokkaido Uni.

By adding fibers, scientists have turned a soft gel into a material tougher than many metals. Credit: Hokkaido Uni.

Hydrogels are made of a network of polymer chains that are hydrophilic. For this reason, this material can absorb up to 90% of its weight in water making the hydrogel highly flexible, mimicking natural tissue. On the flipside, hydrogels aren’t very strong. However, Japanese researchers from Hokkaido University have found a way to make very strong hydrogels by introducing fibers into their composition without compromising too much flexibility. The fiber-reinforced hydrogels are five times tougher than steels according to tests ran in the lab.

Due to its properties, hydrogel is used for medical purposes in tissue engineering as well as sustained-release of drug delivery system or rectal diagnoses. It also has the potential to become a very useful structural material if only it could be coaxed to be stronger for long-term use.

The Japanese team led by Dr. Jian Ping Gong looked at the problem and decided to go with a time-honored approach: just mix and match with some other material to create a composite material that has all of the desired properties. For instance, mud is mushy but add some straw to it and leave it to bask in the sun for a while and you have some pretty functional solid bricks. It’s how people used to make their homes for thousands of years.

Likewise, the researchers added glass fiber fabric to polyampholyte (PA) hydrogels that contained high levels of water. Though the fibers were no bigger than 10μm in diameter, slightly thinner than the human hair, the resulting composite material proved to be bendable and very strong at the same time.

Scanning Electron Microscopy (SEM) images of the fiber-reinforced hydrogels. The polymer matrix (arrows) filled the interstitial space in the fiber bundles and connected the neighboring fibers. (Huang Y. et al., Advanced Functional Materials, January 16, 2017)

Scanning Electron Microscopy (SEM) images of the fiber-reinforced hydrogels. The polymer matrix (arrows) filled the interstitial space in the fiber bundles and connected the neighboring fibers. (Huang Y. et al., Advanced Functional Materials, January 16, 2017)

Lab tests show the fiver-reinforced hydrogels are 25 times tougher than glass fiber fabric and 100 times tougher than unaltered hydrogels. That makes it 5 times tougher than carbon steel. The researchers measured the energy required to destroy them when assessing the materials’ strength.

It’s not certain yet but the Japanese researchers think this high toughness is due to an increase in dynamic ionic bonds between the fiber and hydrogels, as well as within the gels themselves.

The manufacturing process is quite simple — you only have to immerse the fabric in PA precursor solutions for polymerization — and should prove scalable.

“The fiber-reinforced hydrogels, with a 40 percent water level, are environmentally friendly,” Gong said in a statement. “The material has multiple potential applications because of its reliability, durability and flexibility. For example, in addition to fashion and manufacturing uses, it could be used as artificial ligaments and tendons, which are subject to strong load-bearing tensions.”

The same process, reported in the journal Advanced Functional Materials should be able to make other polymers tougher, like rubber.

Scientists hack a $40 cotton candy maker to spin artificial blood vessels

Creating artificial blood vessels is a pivotal aspect of reconstructive medicine. However, time and time again this has proven very tricky to accomplish. Now, a researcher believes he has found the key: weaving blood vessels with cotton candy machines.

Three-dimensional slab of gelatin that contains a microvascular network. (Bellan Lab / Vanderbilt)

Traditionally, researchers would allow cultured cells to spontaneously develop capillary systems of their own. This process can be very lengthy, taking weeks or months, and is very delicate. Leon Bellan, assistant professor of mechanical engineering at Vanderbilt University, wanted to try something different so he went for a top-bottom approach, finding help in an unexpected area: cotton candy.

“So far the other top-down approaches have only managed to create networks with microchannels larger than 100 microns, about ten times the size of capillaries,” he said. In addition, many of these other techniques are not able to form networks as complex as the cotton candy approach.

In an article published online on Feb. 4 by the Advanced Healthcare Materials journal, Bellan and colleagues report that they have finally succeeded in their unorthodox technique, creating a three-dimensional artificial capillary system that can keep living cells viable and functional for more than a week – a great breakthrough, especially when considering today’s alternatives.

“Some people in the field think this approach is a little crazy,” said Bellan, “But now we’ve shown we can use this simple technique to make microfluidic networks that mimic the three-dimensional capillary system in the human body in a cell-friendly fashion. Generally, it’s not that difficult to make two-dimensional networks, but adding the third dimension is much harder; with this approach, we can make our system as three-dimensional as we like.”

Microvascular network perfused with liquid. Figure B is magnification of the area in Figure A outlined in white. (Bellan Lab / Vanderbilt)

Like many other artificial tissues, this relies on a class of materials called hydrogels. A hydrogel is a network of polymer chains that are hydrophilic, they don’t absorb water because they are saturated with it. Hydrogels are very interesting because their properties can be tuned to closely mimic those of the natural extracellular matrix that surrounds cells in the body.

However, even when you have the right technique, creating bio-materials from hydrogels isn’t easy. Especially when designing materials for blood vessels, you encounter a specific paradox, something that Bellan calls the “Catch 22“:

“First, the material has to be insoluble in water when you make the mold so it doesn’t dissolve when you pour the gel. Then it must dissolve in water to create the microchannels because cells will only grow in aqueous environments,” he explained.

So he and his team worked with many materials before they got the right fit. They finally developed one that somehow satisfied this condition: it’s insoluble at temperatures above 32 degrees Celsius and soluble below that temperature, so it can be developed outside the human body at lower temperatures, and inside the human body it becomes insoluble. It gets even better, because this material has already been proven to be compatible with the human body.

So far so good – now they’re working on improving the method and making it available to as many people as possible.

“Our goal is to create a basic ‘toolbox’ that will allow other researchers to use this simple, low-cost approach to create the artificial vasculature needed to sustain artificial livers, kidneys, bone and other organs,” Bellan said.

 
See a video of how it works here:

MIT’s smart wound dressing is incredibly cool and I want one

Smart phones, smart tvs, smart cars, it’s a trend that’s picking up more and more and for good reason — from making work easier, entertainment more accessible and increasing safety, automation is the name of the game. And the latest member to join club Smart is a bandage designed by MIT associate professor Xuanhe Zhao:

This sticky bandage is made out of a hyrdogel matrix, a stretchy rubbery material that’s actually mostly water. It can bond strongly to materials such as gold, titanium, aluminium, glass, silicone or ceramic.

As seen in the picture above, the bandage can incorporate varied sensors, LED lights and other electronic equipment. Zhao also designed tiny and just-as-stretchy drug-delivering reservoirs and channels to be incorporated into the material.

“If you want to put electronics in close contact with the human body for applications such as health care monitoring and drug delivery, it is highly desirable to make the electronic devices soft and stretchable to fit the environment of the human body,” Zhao said.

This allows the “smart wound dressing” to be fitted to any area of the body where it’s needed, and to deliver medicine to the patient without the need for a human nurse or doctor. The prototype Zhao tested was fitted with heat sensors and LEDs, and programmed to administer the stored drug when the patient developed a fever.

However, the bandage’s uses are only limited by the electronics we can fit into it.

The LEDs can be programmed to light up if a drug is running low, or in response to changes in the patient — increased or lowered blood pressure, increases in temperatures, and so on.

Zhao says that the electronics in the bandage aren’t limited to the surface of the patient’s skin either. The hydrogel can be used to fix sensors inside the body, such as implanted bio-compatible glucose sensors or even soft, compliant neural probes.

And you can even use it to bandage traditionally tricky, flexible areas such as elbows or knees — the gel stretches with the body and keeps the devices inside functional, intact and where they’re needed.

Finally, a bandage worthy of the tech-savvy!

The study was published in the journal Advanced Materials.

All image credits go to techweeklynews

New biocompatible, self-healing gel is perfect replacement for cartilages

A team of experts in mechanics, materials, medicine and tissue engineering have managed to create a self replicating gel which can stretch about 21 times its length. The water-based tough gel is also self-healing and biocompatible, which means it could be perfect for people with cartilage injuries.

When 1+1 isn’t 2

The new hydrogel (names this way because water is its main ingredient) is a hybrid between two other gels, two rather common polymers, soft on their own, but which become much tougher when put together.

“Conventional hydrogels are very weak and brittle — imagine a spoon breaking through jelly,” explains lead author Jeong-Yun Sun, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS). “But because they are water-based and biocompatible, people would like to use them for some very challenging applications like artificial cartilage or spinal disks. For a gel to work in those settings, it has to be able to stretch and expand under compression and tension without breaking.”

For example, one of the polymers, alginate, can only stretch 1.2 times its length before it breaks, but combined in the 8:1 ratio with polyacrylamide (known for its use in soft lenses), boom! They form a complex network of chains that crosslink between them and reinforce one another.

Heal me, stretch me

The alginate part of the gel consists of polymer chains that form weak ionic bonds with one another, practically trapping calcium ions into the matrix, while the other, polyacrylamide part forms a grid like structure of covalent bonds. As the gel stretches beyond its limit, calcium ions are eliminated, and the gel is ‘unzipped’, as researchers put it; as a result, the gel expands slightly, but the polymers themselves remain intact. Researchers note that even with a huge crack, the hybrid gel can still stretch some 17 times beyond its initial length.

But what’s even more important, the hydrogel can maintain its toughness and elasticity after multiple stretches and fractures, and the ionic bonds between the alginate and the calcium can “re-zip”, especially after rising the temperature.

“The unusually high stretchability and toughness of this gel, along with recovery, are exciting,” says Suo. “Now that we’ve demonstrated that this is possible, we can use it as a model system for studying the mechanics of hydrogels further, and explore various applications. It’s very promising,” Suo adds.

Beyond being used as a replacement for cartilages, scientists explain it could also play a role in robotics, optics, and even artificial muscle.