Benchtop Fabrication and Integration of Laser-Induced Graphene Strain Gauges and Stimulation Electrodes in Muscle on a Chip Devices

Muscle on a Chip devices are valuable research tools for interrogating the structure and physiology of engineered heart, skeletal, or smooth muscle tissue constructs from the molecular to the multi-cellular level. However, many existing devices rely on functional assays with limited throughput, such as optical microscopy, to measure contractility. Although electrical components have been integrated to automate recordings in advanced devices, their fabrication typically requires specialized equipment found in cleanroom facilities. In this work, miniature strain gauges are engineered to record the contractions of engineered skeletal muscle bundles using only benchtop fabrication equipment. A commercial CO2 laser is employed to generate patterns of laser-induced graphene (LIG) on polyimide (PI) films. LIG is then transferred from PI to thin polydimethylsiloxane (PDMS) films to make conductive and intrinsically flexible and stretchable layers that demonstrate long-term stability under repeated cycles of stretch. Engineered skeletal muscle bundles are anchored to LIG-PDMS strain gauges and their contraction is sensed in response to electrical stimulation, which is delivered by LIG-PI stimulation electrodes also integrated into the device. Collectively, these results demonstrate that LIG is an attractive material for rapidly and inexpensively integrating electrical components for in situ strain sensing and electrical stimulation in Muscle on a Chip devices.