Human skin is populated by millions of nerve endings, called corpuscles, which can sense a wide range of stimuli. For instance, each square centimeter of skin hosts three and a half million pain-detecting corpuscles, five hundred thousand used for touch, two hundred and fifty thousand that perceive cold and thirty thousand specialized in heat. This is our interface for interacting with the outside world. In the animal kingdom, however, there are other extremely efficient sensors, like seals’ whiskers. These hairs allow them to detect very subtle movements under water in order to track fish. These natural sensors were a source of inspiration for the researchers at the University of Texas (US) to improve the sense of touch in robots.
We have already covered several technological innovations aimed at providing robots and prosthetics with synthetic skin. This technology will help machines ascertain the pressure exerted on a given material. However, it was the use of artificial hairs to improve sensitivity that piqued the interest of Jonathan Reeder, from the Erik Jonsson School of Engineering and Computer Science. His research, carried out together with Dr. Walter Voit (University of Texas), blossomed into an article published by Advanced Materials that shows the possibilities of e-whiskers technology surpassing the sensitivity of human skin.
Their prototype is based on an array of laser-cut wires, made with shape-memory polymers and coated with a highly conductive gold layer. The endings of each wire, measuring the width of a human hair, also incorporate microsensors able to measure tension. The memory of the polymer makes them flexible when exposed to heat, so they rise by blowing hot air over them. This innovative technology can measure variables such as pressure, rigidity, proximity or temperature with the utmost precision. In fact, the hairs react to the slightest pressure within less than 250 microseconds.
The e-whiskers devised by Reeder and Voit also react to friction and can map textures when rubbed against a surface, distinguishing its level of coarseness. Together with this property, they can also establish the rigidity of a surface when pushed against it by detecting the resistance offered by the material. Finally, they can distinguish oscillations in temperature across very small areas.
The path towards sensitive prosthetics
In the long run, the aim is for robots to interact with their environment in a much more precise manner, without damaging the objects they manage or hurting humans. Up until now, the technologies employed could only detect variations in pressure in a comparatively rudimentary way.
Additionally, the researchers behind this robotic technology state that, besides endowing robots with enhanced sensitivity, their technology will one day also improve the sensitivity of human prosthetics, even beyond the properties of natural skin.
Nevertheless, the main obstacle for this leap still lies in the need to “translate” the electrical signals of these sensors into the language of the human nervous system.
Source: University of Texas