Opto-Myomatrix: μLED Integrated Microelectrode Arrays for Optogenetic Activation and Electrical Recording in Muscle Tissue

OBJECTIVE: Optogenetics is a valuable and widely-used technique that allows precise perturbations of selected groups of cells with high temporal and spatial resolution by using optical systems and genetic engineering technologies. This study aims to develop Opto-Myomatrix, a novel optogenetic tool for localized muscle fiber control and high-resolution electrophysiological recording. METHOD: Based on a flexible and biocompatible polymer substrate, the device incorporates an integrated μLED that delivers light at 465 nm for optogenetic stimulation and 32 PEDOT:PSS-coated electrodes for electromyography (EMG) recording. We also added a reflector to improve optical power output. RESULTS: The fabricated Opto-Myomatrix device achieves an optical output intensity as high as 129.46 mW/mm$^{2}$ at a driving current of 20 mA in the direction of interest, which is enhanced by nearly 100%. The PEDOT:PSS-coated electrodes exhibit 85% lower impedance than uncoated contacts, enabling high signal-to-noise EMG acquisition. We investigated heat dissipation characteristics of the μLED through measurements of the device on a PDMS tray in air and finite element simulations, confirming that temperature changes remain within safe limits. The Opto-Myomatrix device was implanted in transgenic mice and successfully stimulated targeted jaw muscles, inducing movement while simultaneously capturing EMG signals. CONCLUSION: The Opto-Myomatrix effectively combines localized optical stimulation and high-quality EMG recording in a flexible and biocompatible device, focusing on optogenetic applications in muscle. SIGNIFICANCE: While optogenetic tools are well-established for brain and central nervous system (CNS) research, the development of Opto-Myomatrix addresses a critical gap by enabling localized muscle fiber control and high-resolution recording for advancing neuromuscular studies.