A fabrication method of out-of-plane stretchable and flexible electrodes based on PDMS

We developed stretchable and flexible out-of-plane electrodes based on PDMS substrate using general MEMS fabrication processes. The electrodes were designed to be used for devices that require large elongation without electrical disconnection. Thus, the stretchable electrode was designed to have serpentine metal line suspended above the substrate along its entire length. To fabricate the out-of-plane structure, the metal pattern of the electrode was created on a parylene layer that was suspended above the PDMS substrate by using sacrificial photoresist layer. The metal line was covered by a second parylene layer, thereby encapsulated and electrically insulated. In serpentine electrodes, the parylene layer was attached with PDMS substrate through parylene posts located nearby the metal line, which restrained lateral movements of the metal line. The stretch test, bending test, and twist test were performed using our customdesigned test modules to characterize the stretchability and flexibility of the fabricated electrodes. With up to 32 % strain, with various bending radii, and up to 360° twist angle, stable electrical connection was demonstrated. From these results, the proposed out-of-plane electrodes would be useful in stretchable and flexible applications such as wearable electronics and biomedical devices.