What if we did not have skin? We would not have a sense of touch, no detection of cold or pain, leaving us unable to respond to every situation. The skin is not just a protective covering for the organs, it is a survival signal system that provides information on external stimuli or temperature, or a meteorological observatory that reports the weather. Tactile receptors, tightly packed throughout the skin, sense temperature or mechanical stimuli – such as touching or squeezing – and convert them into electrical signals to the brain.
The challenge for electronic skins, developed for use in artificial skins or human-like robots such as humanoids, is to make them as sensitive to temperatures and movements as human skin can feel. So far there are electronic skins that can detect movement or temperature separately, but no one can recognize both at the same time as human skin.
A joint research team consisting of Professor POSTEH Union Jeong and Dr. Insang Yee of the Department of Materials Science and Engineering and Professor Henenan Bao of Stanford University have jointly developed a multimodal ion-electronic skin that can measure temperature and temperature at the same time. . The findings of the survey, published on November 20, issue of Science, are characterized by the construction of very simple structures by applying special properties of ionic conductors.
There are various tactile receptors in human skin that can detect hot or cold temperatures, as well as other sensations of touch, such as squeezing, twisting, or pushing. Through these receptors, humans can distinguish between mechanical stimuli and temperature. Conventional electronic leather invented so far had the problem of having large errors in temperature measurement if mechanical stimuli were applied to the skin.
Human skin is freely stretchable but unbreakable because it is full of electrolytes, so a joint research team made the sensor using them. They also took advantage of the fact that the ionic conductive material containing the electrolyte may have different measurable properties according to its measurement frequency. Based on the new discovery, a multifunctional artificial receptor has been created that can simultaneously measure tactile sensation and temperature.
In addition, the research team performed variables – charge relaxation time and normalized capacitance – that respond only to ionic conductor temperatures and variables that respond only to mechanical stimuli. The outputs of the variables can be obtained by measuring only two measuring frequencies. The charge relaxation time, which is the time required for ion polarization to disappear, can measure temperature and not respond to motion, and normalized capacitance can measure motion without responding to temperature.
This artificial receptor with a simple electrode-electrolyte-electrode structure has great potential for commercialization and accurately measures the temperature of the applied object as well as the direction or stress profile of external stimuli, such as squeezing, squeezing, spreading and twisting.
Multimodal ion-electron skin, which can be freely stretched or modified but can also detect temperature, is intended to be applicable to load-bearing temperature sensors or to skin robots for human-like robots, such as humanoids.
When the index finger touches electronic skin, the electronic skin detects contact as a change in temperature, and when the finger pushes the skin, it extends to the back of the contact area and recognizes it as motion. “I doubt that this mechanism is one of the ways in which real human skin recognizes different stimuli such as temperature and movement.”
Dr. Insang Wei from POSTEH, first author of the paper
“This study is the first step in opening the door to multimodal electronic examination of the skin using electrolytes,” noted Professor Unjong Jeong of POSTECH and the author. “The ultimate goal of this research is to create artificial ion-electron skin that simulates human tactile receptors and neurotransmitters, which will help restore the sense of touch in patients who have lost their sense of sensitivity due to illness or accident.”
Pohang University of Science and Technology (POSTECH)