How to

6 February 2017

New Heat-Sensitive Artificial Skin Could Revolutionise Bioengineering & Robotics

Img: Caltech/Science Robotics 
Prosthetic limbs have come a long way since the ol’ wooden peg of pirates past. In the modern age, technology has advanced far enough so as to allow increasingly realistic prosthetics that look and behave more and more like the real thing. However, while the aesthetics and motions of artificial limbs have seen remarkable improvement over the years, many of the sensory capabilities of real skin and tissue have proven more difficult to effectively replicate through artificial means.

As you’re likely aware by now, here at Keep Me Warm we have a particular interest in one specific sensory capability – temperature sensitivity – and that is exactly the focus of a new pectin-based electronic skin designed by a research team made up of scientists from the Swiss Federal Institute of Technology, the California Institute of Technology (Caltech) and the University of Salerno, Italy.

Detailing their findings in the journal Science Robotics, the team claim to have developed a form of artificial skin that is capable of detecting changes in temperature as subtle as one-hundredth of a degree (°C) within a range of 45°C. To put that into perspective, that’s twice the temperature sensitivity of human skin, comparable to that of pit vipers such as rattlesnakes.

‘Skins’ or flexible sensors developed in the past have been able to successfully detect changes in temperature, but only changes of around one-tenth of a degree within  a range of 5°C, so the new development is certainly a sign of positive progress.

The discovery at the heart of the development came when the team were attempting to fabricate synthetic wood in a petri dish. They found that pectin, a form of sugar found within the cell walls of plants, could display an electrical response to changes in temperature. The researchers then incorporated microscopically thin flexible films comprised of pectin and water into other skins made of elasticated materials such as silicone rubber.

When enriched with positively charged calcium ions, the film reacts to rises in temperature by ‘unzipping’ the strands of pectin and releasing calcium ions. This in turn reduces the electrical resistance of the film, a reduction which is detected by electrodes embedded in the film, thereby allowing the ‘skin’ to accurately detect subtle differences in temperature.

The artificial skin is able to recognise gentle finger pokes and precisely map temperature variations across its surface, even after substantial physical deformation via bending or twisting. On top of that, the skin doesn’t actually need to make contact with an object to detect its temperature, as the research team showed that it is perfectly capable of sensing warm bodies, in this case a teddy bear microwaved up to a temperature of 37°C, from a distance of up to one metre.

Best yet, according to senior author of the study and mechanical engineer/materials scientist at the California Institute of Technology, Chiara Daraio, the required pectin films are “extremely easy to fabricate and extremely low cost - you can buy pectin at your local supermarket to make gelatin, jams, or jellies.”

As such, Daraio states that “it’s pretty straightforward to scale up to large-scale production if needed.”

In terms of real world applications in fields such as robotics, Daraio is confident that the film could be incorporated into other technologies within the next two years. When it comes to bioengineering and prosthetics however, it is felt that a little more time is needed. Daraio expects “much longer timeframes of five to 10 years at minimum, because of the issues that come whenever you have to interact with the human body.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.