Artificial flesh is growing ever closer to the real thing. Scientists in Australia have now created a new jelly-like material which they claim has the strength and durability of actual skin, ligaments, or even bone.
"With the special chemistry we've engineered in the hydrogel, it can repair itself after it has been broken like human skin can," explains chemist Luke Connal from the Australian National University.
"Hydrogels are usually weak, but our material is so strong it could easily lift very heavy objects and can change its shape like human muscles do."
Having a squishy material with such remarkable properties could be huge for the development of next-generation soft robotics and biomedical devices. Creating a shape-changing hydrogel that has multiple functions has proved an ongoing challenge for scientists, even with natural inspiration from jellyfish, sea cucumbers, and Venus fly traps.
While some hydrogels can withstand mechanical stress, others have self-healing properties, and a few more have the abilities to memorise shapes or change colours.
As far as the ANU researchers know, no one else has been able to incorporate all these functions into one all-encompassing gel. At least, not at the speed and efficiency they've achieved.
Putting their material through multiple tests, the authors claim to have created the first dynamic hydrogel that is strong, tough, fatigue resistant, self-healing and able to change shapes and 'remember' them afterwards.
"The advantages of using such a multifunctional hydrogel is further demonstrated through an ability to lift heavy objects in a reversible and repeatable way upon thermal stimulus," the team writes.
Using this material, the researchers made extremely thin films of 'flesh' without any breakage. When these films were heated or cooled, they then changed into different shapes, bending one way or the other before returning back to their original state along with the temperature.
Unlike many other hydrogels, which can sometimes take 10 minutes or more to change shape, the authors say their gel takes only 10 seconds to bend. Here, the key is said to be the gel's dynamic hydrogen bonds and dynamic imine (carbon-nitrogen) bonds, which work together to form "unprecedented properties".
Dynamic bonds have a high response to stimuli, which makes them perfect for environmental adaptation and self-repair, and imine bonds in particular have fast reaction kinetics that can enable rapid self-healing.
What's more, the authors say these materials can be easily prepared using simple chemistry, and if other polymers are added to the molecular mix, perhaps even more functions can be achieved.
If temperature is somehow used as a control, the authors think this gel could one day be moved like an artificial muscle.
"In a lot of science fiction movies, we see the most challenging jobs being done by artificial humanoid robots. Our research has made a significant step towards making this possible," says material engineer Zhen Jiang.
"We anticipate that researchers working on the next-generation of soft robots will be interested and excited about our new way of making hydrogels."
In the meantime, the team is hoping to turn their hydrogel into a 3D-printable ink.
The study was published in Advanced Materials.