3-in-1 hybrid material for the next generation of smart artificial skin

The “intelligent skin” developed by Anna Maria Coclite closely resembles human skin. It simultaneously detects pressure, humidity and temperature and produces electronic signals. More sensitive robots or more intelligent prostheses are thus possible.

The skin is the largest sensory organ and at the same time the protective coat of the human being. It “feels” multiple sensory inputs at the same time and reports information about humidity, temperature and pressure to the brain. For Anna Maria Coclite, a material with such multisensory properties is “a kind of ‘holy grail’ in the technology of intelligent artificial materials. In particular, robotics and intelligent prostheses would benefit from a better integrated and more precise detection system. similar to human skin”. .” The ERC grant winner and researcher at the Institute for Solid State Physics of the University of Graz succeeded in developing the three-in-one hybrid material “smart skin” for the next generation of artificial and electronic skin in using a new process. The result of this pioneering research has just been published in the journal Advanced materials technologies.

As delicate as a finger

For nearly six years, the team has been working on smart skin development as part of Coclite’s ERC Smart Core project. With 2,000 individual sensors per square millimeter, the hybrid material is even more sensitive than a human fingertip. Each of these sensors is made of a unique combination of materials: a smart polymer in the form of a hydrogel inside and a piezoelectric zinc oxide shell. Coclite explains: “The hydrogel can absorb water and thus expand with changes in humidity and temperature. In doing so, it puts pressure on the piezoelectric zinc oxide, which responds to this and all other mechanical stresses with an electrical signal. The result is an ultra-thin material that simultaneously reacts to force, humidity and temperature with extremely high spatial resolution and emits corresponding electronic signals. “The first samples of artificial skin are six micrometers thick, or 0.006 millimeters. But they could be even thinner,” explains Anna Maria Coclite. In comparison, the human epidermis is 0.03 to 2 millimeters thick. Human skin perceives things from a size of about one square millimeter. The smart skin has a thousand times smaller resolution and can record objects too small for human skin (such as microorganisms).

Nanoscale Materials Processing

The individual sensor layers are very thin and at the same time equipped with full-surface sensor elements. This was possible thanks to a unique process in the world for which the researchers combined for the first time three known methods of physical chemistry: chemical vapor deposition for the hydrogel material, atomic layer deposition for the zinc and nanoimprint lithography for the polymer template. The lithographic preparation of the polymer template was the responsibility of the “Hybrid electronics and structuring” research group directed by Barbara Stadlober. The group is part of the Materials Institute of Joanneum Research based in Weiz.

Several fields of application are now open for the skin-like hybrid material. In healthcare, for example, the sensor material could independently detect microorganisms and flag them accordingly. We can also imagine prostheses that give the wearer information on temperature or humidity, or robots that can perceive their environment with more sensitivity. On the way to application, the smart skin scores a decisive advantage: the sensory nanorods – the “intelligent heart” of the material – are produced using a steam-based manufacturing process. This process is already well established in factories producing integrated circuits, for example. Smart skin production can thus be easily scaled up and implemented in existing production lines.

The properties of smart skin are now further optimized. Anna Maria Coclite and her team – here in particular the doctoral student Taher Abu Ali – want to extend the temperature range at which the material reacts and improve the flexibility of the artificial skin.

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Material provided by Graz University of Technology. Original written by Susanne Filzwieser. Note: Content may be edited for style and length.

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