Flexible polymer-based liquid crystal sensor for label-free electro-optical recording of electrophysiological activity

Recent advances in optical technologies have opened new possibilities for electrophysiological interfacing, offering alternatives to traditional electrically-based methods. Here, we present a flexible optical-electrode ‘optrode’ that employs a passive transduction mechanism to convert biopotentials into quantifiable optical signals. Our design integrates liquid crystals into a multilayered polymeric structure that enables light transmission and reflection while carrying the signal to a photodetection system with a relative responsivity of 13 ± 1%/V and an operating bandwidth of 2.2 ± 0.1 kHz for electrophysiology applications ( N = 25 total measurements). Additionally, we demonstrated its cytocompatibility and effectiveness in detecting electrograms from cardiac tissues. This approach addresses major limitations of biomedical optoelectronics, providing label-free and conductive lead-free signal detection while maintaining a soft, tissue-like interface and demonstrating strong potential for integration into advanced electrophysiological platforms.