A research team led by the University of California, San Diego, has developed a soft, stretchy electronic device that can simulate the sensation of pressure or vibration when worn on the skin. This device was reported in a paper published in . Scientific RoboticsIt represents a step toward creating haptic technology that can reproduce a more diverse and realistic range of touch sensations.
The device consists of soft, stretchy electrodes attached to a silicone patch. You can attach it like a sticker to your fingertip or forearm. Electrodes that come into direct contact with the skin are connected to an external power source through wires. By sending a mild electrical current through the skin, the device can create a pressure or vibration sensation depending on the frequency of the signal.
“Our goal is to create a wearable system that can deliver a wide range of tactile sensations using electrical signals without causing pain to the wearer.” said Rachel Blau, a postdoctoral fellow in nanoengineering at UC San Diego's Jacobs School of Engineering and co-first author of the study.
Existing technologies that reproduce the sense of touch through electrical stimulation use hard metal electrodes, which often do not fit the skin well and cause pain. The air gap between these electrodes and the skin can cause painful electrical currents.
To solve this problem, Blau and a research team led by Darren Lipomi, professor of chemistry and nanoengineering at the University of California, San Diego, developed a soft, stretchy electrode that adheres perfectly to the skin.
The electrodes are made of a new polymer material composed of components from two existing polymers. PEDOT:PSS, a conductive, hard polymer, and PPEGMEA, a soft, stretchy polymer. “By optimizing these ratios, [polymer building blocks]“We molecularly engineered a material that is both conductive and stretchable,” Blau said.
The polymer electrodes are cut by a laser into a spring-like concentric design and attached to a silicon substrate. “This design increases the elasticity of the electrodes and allows the current to target specific locations on the skin, providing localized stimulation to prevent pain.” said Abdulhameed Abdal, a doctoral student in the UC San Diego Department of Mechanical and Aerospace Engineering and the study's other co-first author. Abdal and Blau worked with UC San Diego nanoengineering undergraduate students Yi Qie, Anthony Navarro, and Jason Chin on the synthesis and fabrication of the electrodes.
In the test, the electrode device was worn on the forearm of 10 participants. Working with behavioral scientists and psychologists from the University of Amsterdam, the researchers first identified the lowest detectable current level. They then adjusted the frequency of the electrical stimulation so that the participants experienced a sensation classified as pressure or vibration.
“We found that when we increased the frequency, participants felt more vibration than pressure,” Abdal said. “This was interesting because we didn’t know exactly how biophysically the electrical current would be perceived by the skin.”
These new insights could pave the way for developing advanced haptic devices for applications such as virtual reality, medical prosthetics, and wearable technology.
This research was supported by the National Science Foundation Disability and Rehabilitation Engineering program (CBET-2223566). This research was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) at UC San Diego, part of the National Nanotechnology Coordinated Infrastructure, and was supported by the National Science Foundation (grant ECCS-1542148).