Tag Archives: compression

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.

dna genetics

Zipping genetic data in DNA could enable scientists to implant complex ‘programmes’ into cells

Whenever you need to e-mail a friend digital file that’s way too large, such as a video recording or a high-resolution image, the usual course of action is to zip the file to a more manageable size. Softwares that ‘zip’ or compress files work their magic by removing redundant information and then restoring it during uncompression. Nothing is lost in the process. Now, scientists at ETH Zurich are experimenting with zipping nature’s most efficient data storage medium: DNA.

dna genetics

Credit: Pixabay.

The basic principles behind DNA compression are basically the same as those for the digital counterpart. If an element comes up often in the DNA sequence, it will simply only show up once instead of getting unnecessarily repeated every time. One important area where this can work applies to promoters, which are sections of DNA that regulate how and whether or not a particular gene is read. For instance, if a DNA sequence contains four different genes that all have the same promoter, it will be included only once by the ETH method.

Removing redundancies is one piece of the puzzle. Swiss researchers were also careful to craft assembly rules, familiarly known as ‘compressed encoding’. For instance, after receiving a joint promoter, the four genes in the aforementioned example are equipped with stop sequences and different binding sites for the enzyme that opens, rotates, and reassembles DNA strands. The enzyme, called recombinase, effectively takes on the role of the decompression software. Once reassembled, each of the four genes will receive its own promoter.

Compressing DNA could prove highly useful to transport genetic information into cells where the ‘compressed DNA’ can assemble into functioning genetic code. Such an approach could prove invaluable in certain synthetic biology or biotech applications where scientists face challenges in implanting large amounts of information into cells. You can only load limited amount of DNA into the transport vehicles currently employed for this purpose.

The ETH method allows scientists to implant large ‘genetic programmes’, for lack of a better term, into mammalian cells. Just like a software, these man-made instructions carry out specific tasks within cells in order to achieve a specific goal. For instance, the zipped code can decompress inside a cell to instruct the production of complex substances such as active ingredients for medicines.

In the future, such genetic programmes could carry out some incredibly complex tasks, like as cancer targeting. After detecting cancer (i.e. the marker), the programme could potentially send the necessary instruction to eliminate the tumor cells. Scientists have proven that such an approach works in cell cultures and are experimenting with the method in an animal model.

“Our research is often inspired by computer science and information technology,” explains Kobi Benenson, Head of the Synthetic Biology Group at ETH’s Department of Biosystems Science and Engineering in Basel.

Scientific reference: Genetic programs can be compressed and autonomously decompressed in live cells, Nature Nanotechnologynature.com/articles/doi:10.1038/s41565-2017-0004-z.