PDMSkin - On-Skin Gestures with Printable Ultra-Stretchable Soft Electronic Second Skin.

Innovative enabling technologies are key drivers of human augmentation. In this paper, we explore a new, conductive, and configurable material made from Polydimethylsiloxane (PDMS) that is capillary doped with silver particles (Ag) using an immiscible secondary fluid to build ultra-stretchable, soft electronics. Bonding silver particles directly with PDMS enables inherently stretchable Ag-PDMS circuits. Compared to previous work, the reduced silver consumption creates significant advantages, e.g., better stretchability and lower costs. The secondary fluid ensures self-assembling conductivity networks. Sensors are 3D-printed ultra-thin (<100μm) onto a pure PDMS substrate in one step and only require a PDMS cover-layer. They exhibit almost stable electrical properties even for an intense stretching of >200%. Therefore, printed circuits can attach tightly onto the body. Due to biocompatibility, devices can be implanted (e.g., open wounds treatment). We present a proof of concept on-skin interface that uses the new material to provide six distinct input gestures. Our quantitative evaluation with ten participants shows that we can successfully classify the gestures with a low spatial-resolution circuit. With few training data and a gradient boosting classifier, we yield 83% overall accuracy. Our qualitative material study with twelve participants shows that usability and comfort are well perceived; however, the smooth but easy to adapt surface does not feel tissue-equivalent. For future work, the new material will likely serve to build robust and skin-like electronics.