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Delocalizing Strain in Interconnected Joints of On-Skin Interfaces

Durable and reliable fabrication of on-skin systems remains an open research question to enable developing on-skin interfaces at scale. One of the main challenges is the complexity in achieving robust devices to connect hard goods (printed circuit boards and electronics) with extremely soft materials (slim on-skin interface traces). This paper presents a systematic study evaluating the durability of 5 interconnection designs (including PCB shape, solder pad positions, and rigid versus flexible PCB) for on-skin systems under stretching and bending tests. The study results show the significant robustness of interconnects on flexible PCBs over rigid PCBs under bending and the better performance of elongated shaped flexible PCBs over shorter flexible PCBs. Further, we demonstrate that an interposer design consisting of 2 layers of flexible PCBs combines the benefits of both the rigid and flexible boards. Based on our experimental results, we present a set of design guidelines for PCB interconnect design for resilient on-skin systems.