Artificial, Touch-Sensitive 'E-Skin' Developed by Scientists

Scientists develop an "e-skin" that could be applied to robots and people with prosthetic limbs.

The nature magazine Nature Materials reported on the efforts of two independent US research groups had developed an artificial, electronic skin that has the ability to sense, and respond to, a very light touch. This "e-skin" is made of semiconductor nanowires that operate using very low voltage. It is the first such material made out of inorganic single crystalline semiconductors. The skin can be applied by rubbing it or rolling it onto a surface and can detect pressure around 0 to 15 kilopascals, which would allow a robot helper, for instance, to do the dishes or handle a pet without causing damage.

"If we ever wanted a robot that could unload the dishes, for instance, we'd want to make sure it doesn't break the wine glasses in the process. But we'd also want the robot to grip the stock pot without dropping it," Ali Javey, an associate professor of computer sciences at the University of California at Berkeley, who led the research teams, said. "The idea is to have a material that functions like the human skin, which means incorporating the ability to feel and touch objects."

She said a longer term goal would be to use the e-skin to restore the sense of touch to patients with prosthetic limbs, which would require significant advances in the integration of electronic sensors with the human nervous system: Previous attempts to develop an artificial skin relied upon organic materials because they are flexible and easier to process. "The problem is that organic materials are poor semiconductors, which means electronic devices made out of them would often require high voltages to operate the circuitry," said Javey. "Inorganic materials, such as crystalline silicon, on the other hand, have excellent electrical properties and can operate on low power."

Research member and co-author Kuniharu Takei wrote in Nature Materials that large-scale integration of high-performance electronic components on mechanically flexible substrates might also enable new applications in electronics, sensing and energy. He also noted that contact printing of parallel arrays of semiconductor nanowires (NWs) has been explored as a versatile route to enable fabrication of high-performance, bendable transistors and sensors.

"The development of an electronic skin is critical to the realization of artificial intelligence that comes into direct contact with humans, and to biomedical applications such as prosthetic skin. To mimic the tactile sensing properties of natural skin, large arrays of pixel pressure sensors on a flexible and stretchable substrate are required," an excerpt from the article explained. "We demonstrate flexible, capacitive pressure sensors with unprecedented sensitivity and very short response times that can be inexpensively fabricated over large areas by microstructuring of thin films of the biocompatible elastomer polydimethylsiloxane."

An article summary explained the pressure sensitivity of the microstructured films far surpassed that exhibited by unstructured elastomeric films of similar thickness, and is tunable by using different microstructures. "The microstructured films were integrated into organic field-effect transistors as the dielectric layer, forming a new type of active sensor device with similarly excellent sensitivity and response times," the article reported.

John J. Boland, who is at the School of Chemistry and the CRANN Nanoscience Institute in Trinity College in Dublin, said thanks to flexible electronics, the world is within touch of skin. Flexible arrays of transducers can now be fabricated with pressure sensitivity and response times approaching those of natural human skin, he said. "As humans, we interact with our immediate environment through our senses - sight, sound, smell, taste and touch," he said. "Emulation of the senses by electronic means has long been a grand challenge of artificial intelligence and is pivotal in the development of accessible and natural interfaces between man and machine."