The finer touch: when ‘artificial skin’ is more sensitive than the original

Researchers at TU Graz have developed a "smart skin" material that is more sensitive than human skin, capable of sensing pressure, moisture, and temperature. The material has potential applications in prosthetics and healthcare.

In the city of Graz, flanking both sides of the river Our in Austria, it sometimes gets so cold you cannot feel your finger tips, or even your fingers anymore. Here in a lab at TU Graz, the city’s public university, on a petri dish lies a patch of ‘artificial skin’, or smart skin, its creators say is even more sensitive than the human fingertip.

As the world pursues ever more intently materials that will ease the alien feel of wearables, and render them more human-like, here’s a move in the right direction, as far as the future of material science goes. Last year, Anna Maria Coclite and her team of researchers from the Institute of Solid State Physics at Graz University of Technology (TU Graz) presented the results of their research to the European Research Council, to land Proof of Concept funding for their project ‘SmartCore’. 

What is SmartCore? Dr. Coclite and her team had succeeded in developing a three-in-one “smart skin” hybrid material, which closely resembles human skin by simultaneously sensing pressure, moisture and temperature and converting them into electronic signals. With 2,000 individual sensors per square millimetre, the hybrid material is more sensitive than a human fingertip, giving it its reputation, and, at 0.006 millimetres thick, many times thinner than human skin. The team argued that by reacting to these three human sensory impressions, the smart skin prototype surpasses all electronic skin materials on the market to date which only react to pressure and temperature. 

Dr. Coclite, a solid physics domain expert, not only works on cutting edge emerging tech, but also has the facility of explaining her science in a way that is easily comprehensible. In video interview with The Hindu, she set out to decode her brainchild: “Artificial skins are a series of materials that try to emulate the functionality of our skin. Of course, you know, our human skin is very complex, it has a lot of functions, not only sensing, but also thermal regulation and protection. Artificial skin projects try to emulate at least some of the functions. In our particular case, we focused on the sensing properties. So we tried to include in our device, some sensors for humidity, temperature and pressure. To show that like in human skin, you would feel as if you’re touching something colder or warmer. Similarly, also this artificial skin differentiates between colder warmer objects, objects with spikes, without spikes, and so on.”

Further, “Human skin has a resolution of one millimetre square. So this means that if you have an object that is one millimetre square or bigger, you can feel it with your finger . With the device that we have produced, we were able to even measure the electrical current from a pixel that was 0. 25 millimetre square, smaller than one millimetre square. So, this means that you can get information also on smaller areas than human skin. How is this beneficial? First of all, it could give maybe a more integrated response with a more precise response than human scale. And also it could be used for for example, sensing smaller objects.” It has been years in the making. While work on the artificial skin project began in 2016 as funding came in, “ before that, we were working on the materials that have been used in this type of device, for example, one of the material is a smart polymer, which changes thickness, depending on humidity and temperature.”

All about materials

Which puts everything in the hands, literally, of the materials used for the prototype, they are the fundamental constituents of the whole process. Dr. Coclite explains: “So, one is a piezoelectric material which when compressed or stretched, generates an electric current. This type of material for example, is the one that allows the artificial skin to sense force or pressure. The other material that is also very fundamental in this is the smart polymer that changes thickness depending on humidity and temperature, and in particular, these two materials have been combined in various nano rods. So very, very, very small rods in which the polymer is in the middle and the piezoelectric material is on the outside. And what happens is that when the polymer expands, because the temperature or humidity changes, it applies a pressure on the piezoelectric material, and then consequently, an electrical current.”