On-skin electronics toolkit enhances customizability for users

Two new kinds of on-skin electronics created by Cornell University researchers allow users to build and customize them directly on the body—with potential applications in biometric sensing, medical monitoring, interactive prosthetic makeup and more.

SkinLink, developed by the Hybrid Body Lab led by Cindy Hsin-Liu Kao, assistant professor of human centered design, is an on-skin electronic interface that can be fabricated right on the body, providing flexibility in design depending on the intended use. And ECSkin is an electrochromic display interface that can also be fabricated in situ and features modular design through tiles that can be arranged as desired.

"SkinLink: On-body Construction and Prototyping of Reconfigurable Epidermal Interfaces" was presented in early October at UbiComp/ISWC '24, the Association for Computing Machinery's international joint conference on pervasive and ubiquitous computing.

The work earned a Distinguished Paper Award from the journal, Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, where it was originally published in June 2023.

"Both of these projects are modular prototyping toolkits, to enable much more intricate on-skin circuitry prototyping," Kao said. "Users are also able to build the circuitry directly on the skin surface."

SkinLink represents a step forward from SkinKit, which the lab developed and presented in 2021. The earlier iteration featured slim and flexible printed circuit boards in temporary tattoo form, but the boards had predefined behaviors and larger surface areas, making customizability a challenge.

"There were several issues we didn't address in SkinKit, such as how to allow users to program the modules the way they want to," said Pin-Sung Ku, doctoral student and lab member. "For SkinKit, everything was pre-programmed; users had to attach things in a certain order. With SkinLink, there is more customizability of the functions they like."

With SkinKit, for example, the circuitry had to be built before applying it to the body; with SkinLink, users can put one module on the body, then another, for more customizability.

The SkinLink toolkit consists of functional circuit modules, made of flexible printed circuit boards, and flexible, custom-designed wiring (called trace modules, or traces) that connect the sensor and actuator modules to the microcontroller board.

The on-body fabrication process starts with selecting and programming the circuit board and trace modules. The microcontroller board can be repeatedly programmed during this step, to fine-tune the circuit functions. The boards can be temporarily placed on the body and customized, before final placement.

"Another goal is what we call 'high ceilings and wide walls,'" she said. "High ceilings means increasing the complexity of the prototypes; wide walls refers to the vast array of things that could be designed. That's what I think SkinLink really does."

Kao said she sees both SkinLink and ECSkin as "enabling technologies," with a variety of potential uses. Some of the studies with SkinLink involved artists, wearable tech researchers, and psychology researchers for physiology sensing; she also envisions applications beyond humans.

"Being able to use this as a functional technology for physiological sensing or artistic practice is one application," she said.

"Our work has focused on skin interfaces for humans, but I think there could also be potential for designing 'skin' interfaces for other living beings, such as animals, and sensing for agricultural purposes, even on plants. We are interested in bringing SkinLink to broader disciplines to support on-skin prototyping."

Provided by Cornell University