Electrode-silicone patch to simulate pressure and vibration

A group of scientists at the University of California, San Diego, has created a flexible, pliable electronic gadget that, when applied to the skin, can sense pressure or vibration. Details of this gadget described in the journal Science RoboticsA step toward developing tactile technologies that can replicate a wide variety of realistic tactile sensations,

Electrode-silicone patch to simulate pressure and vibration
Soft, stretchable electrodes reproduce the sensation of vibration or pressure on the skin through electrical stimulation. Image credit: Lizelle Labios/UC San Diego Jacobs School of Engineering

A silicone patch is bonded to a flexible, soft electrode to create the device. It can be applied to the fingertip or arm like a sticker. The electrode is connected to an external power source and is in direct contact with the skin. Depending on the frequency of the signal, the device can induce vibration or pressure sensations by passing a small electric current through the skin.

Our goal is to create a wearable system that can provide a wide range of tactile sensations using electrical signals – without causing pain to the wearer,

Rachel Blau, study co-first author postdoctoral researcher, Jacobs School of Engineering, University of California, San Diego

Current techniques that use electrical stimulation to mimic touch often cause pain because they use rigid metal electrodes that do not fit snugly to the skin. Air spaces between these electrodes and the skin can produce painful electrical currents.

Blau and a group of scientists, under the direction of Professor Darren Lipomi of the UC San Diego Aso Yufeng Li Family Department of Chemical and Nanotechnology Engineering, created a soft, flexible electrode that easily conforms to the skin to solve these problems.

Made from the building blocks of two existing polymers — a soft, flexible polymer called PPEGMEA and a conductive, stiff polymer called PEDOT:PSS — the electrode is made of a new polymer material.

Blau said,by optimising the ratio of [polymer building blocks]We have molecularly engineered a material that is both conductive and stretchable,

The polymer electrodes are glued onto the silicon substrate after being laser cut into a spring-like, concentric design.

This design increases the stretchability of the electrodes and ensures that the electrical current targets a specific spot on the skin, thus providing localized stimulation to prevent any pain,

Abdulhamid Abdal, Ph.D. student and study co-first author, Department of Mechanical and Aerospace Engineering, University of California, San Diego

Graduate students Yi Qi, Anthony Navarro and Jason Chin in UC San Diego's Nanoengineering Department collaborated with Abdal and Blau on the synthesis and fabrication of the electrodes.

About 10 participants wore electrode devices on their arms during the test. Behavioral scientists and psychologists from the University of Amsterdam worked with researchers to determine the lowest detectable electrical current level. The frequency of the electrical stimulation was then changed, allowing participants to feel sensations related to pressure or vibration.

We found that increasing the frequency made participants feel more vibration than pressure. This is interesting because biophysically, it was never known how current is perceived by the skin,

Abdulhamid Abdal, Ph.D. student and study co-first author, Department of Mechanical and Aerospace Engineering, University of California, San Diego

The new discoveries could make it possible to create sophisticated tactile devices for use in wearable technology, medical prostheses and virtual reality.

This work was supported by the National Science Foundation Disability and Rehabilitation Engineering Program (CBET-2223566). It was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) at UC San Diego, a member of the National Nanotechnology Coordinated Infrastructure supported by the National Science Foundation (grant ECCS-1542148).

Journal Reference:

Blau, R., and others(2024) Conductive block copolymer elastomers and psychophysical thresholding for precise haptic effects. Science Robotics. doi.org/10.1126/scirobotics.adk3925

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