Extended Data Fig. 3: Patterning of EGaIn electrodes.
From: High-speed and large-scale intrinsically stretchable integrated circuits
a, Schematic diagram showing the process of patterning EGaIn. Printed EGaIn via blade coating using PDMS will form an alloy with the Cr/Au adhesion layer to make a stretchable conductor. b-c, Optical microscope images of photoresist on soft substrates using normal development process (b) and quasi-static development process (c). d-e, Optical microscope images of EGaIn lines w/o sonication (d) and w/ sonication (e). Ultrasonication is necessary to achieve small feature sizes. This method was adopted from a previous report (ref. S2) and modified for working on soft substrates. Because of the large modulus mismatch between the photoresist (GPa) and the soft substrate (MPa), the edges of photoresist can easily form fractures during the development and rinsing process. To solve this issue, we immersed the sample into the developer and DI water without any shaking, and then dried it by keeping the sample sitting vertical in air.