Laser-Induced Graphene\nfrom SU‑8 Photoresist:\nToward Functional Micromolding

Micromolding silicone elastomers has many uses in microfluidics,\nsoft lithography and microfabrication but usually requires further\nprocessing to integrate functional materials like electrodes. Herein,\nwe report a simple method to pattern and integrate electrodes into\nmicromolded elastomers by using laser-induced graphene (LIG) on SU-8,\nwhich is a popular photoresist. LIG derived from SU-8 generates a\nconductive carbon layer that transfers to the cured elastomer when\npeeled away from the mold, producing microchannels with embedded electrodes.\nWe characterized the role of laser power on the resulting graphitized\nSU-8, resulting in an unprecedented sheet resistance of 4 Ω\nsq<sup>–1</sup>, substantially lower than anything reported\nto date. Raman spectroscopy confirms the porous carbon film is composed\nof large graphene domains, thereby demonstrating that SU-8 is an excellent\nLIG precursor. SU-8 is frequently used for molding silicones, and\nlaser graphitized SU-8 embeds conductive traces during the molding\nstep. This process is used to produce a soft heater that can generate\ntemperatures in excess of 40 °C with 15 V applied.