Electronic touch
Scientists have created artificial skin from nanowiresNanonews Network according to UC Berkeley:
Engineers make artificial skin out of nanowiresEngineers from the University of California at Berkeley (UC Berkeley) have developed a pressure-sensitive electronic material from semiconductor nanowires.
The idea was to create a material that would perform the functions of human skin, i.e. would give the opportunity to feel and touch objects," says Ali Javey, associate professor of electrical Engineering and Computer Science and head of a research group at the University of California at Berkeley, engaged in the development of artificial leather.
Optical image of an electronic skin device with a matrix scheme of nanowires.
Each dark square represents one pixel.
(Photo: Ali Jawi and Kuniharu Takei, UC Berkeley)
Artificial leather, called E-skin, is described in an article in the online version of the journal Nature Materials on September 12. E-skin is the first material made from inorganic monocrystalline semiconductors.
Sensitive artificial leather can help solve a key problem in robotics: reducing the force needed to hold and skillfully handle a wide range of objects.
As a rule, people know how to hold a fragile egg so as not to break it," said Javi, who is also a member of the Center for Sensors and Actuators (The Berkeley Sensor & Actuator Center) and a researcher in the Materials Science Department of the National Laboratory. Lawrence Berkeley National Laboratory Materials Sciences Division.
Previous attempts to create artificial leather were based on the use of organic materials, since they are flexible and easy to process.
The problem is that organic materials are weak semiconductors, which means that electrical devices made of them require high voltage to function," says Javi. "Inorganic materials, such as crystalline silicon, have excellent electrical properties and can operate at low power. They are also more resistant to chemical attack. But in the past they were quite inflexible and fragile. The work of various groups, including ours, has recently shown that miniature tapes or wires of inorganic substances can be very malleable – ideal for high performance flexible electronics and sensors."
UC Berkeley engineers used an innovative manufacturing technology that works on the principle of a sticky roller for clothes, only vice versa – instead of collecting fibers, the "hairs" of nanowires form a coating.
The researchers began by "growing" germanium-silicone nanowires on a cylindrical drum, which was subsequently rolled over a sticky substrate. Polyamide film was used as a substrate, but, according to scientists, various plastics, paper or glass are suitable for this purpose. As the drum rotated, nanowires were applied or "printed" in an orderly manner on a substrate, forming the basis of thin, flexible sheets of electronic materials.
Another approach used by scientists was to "grow" nanowires on a flat substrate and then transfer them to a polyamide film.
To make electronic skin, scientists "printed out" nanowires on an 18-19-pixel square matrix with a side of 7 cm. Each pixel contained a transistor made of hundreds of semiconductor nanowires. These transistors were then integrated with flexible rubber sensitive to pressure changes to achieve tactile function. Less than 5 volts were required for the matrix to work and maintain strength after more than 2000 bending cycles.
Scientists have demonstrated the ability of electronic skin to detect pressure in the range from 0 to 15 kPa, which is comparable to the force applied for such daily actions as typing on a keyboard or holding an object. As a sign of gratitude to their native university, the researchers laid out the letter C (from Cal, the informal name of the University of California) on the surface of the electronic skin.
This is truly the first macro–level integration of nanowire materials with a functional system such as electronic skin," said the study's lead author Kuniharu Takei, PhD in Electrical Engineering and Computer Science. "This technique could potentially be more ambitious. After all, the size of the electronic skin we have created is now limited by the size of the tools we use."
The co-authors of this study are also Ron Fearing, Professor of Electrical Engineering and Computer Science, Toshitake Takahashi, PhD student in electrical engineering and computer science, Johnny C. Ho), PhD student in Materials Science and Engineering, Hyunhyub Ko and Paul Leu, PhD in Electrical Engineering and Computer Science, Andrew G. Gillies, PhD student in Mechanical Engineering.
This study was supported by the National Science Foundation and the Defense Advanced Research Projects Agency.
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