Soft multimodal opto-electric biointerfaces for co-localized optical and electrical recording of cell function

Optical fluorescence and electrical monitoring of cell activity are two powerful approaches to study organ functions. Simultaneous recording of optical and electrical data types will provide complementary information from and take advantage of each approach. However, devices that can concurrently record optical signals from the same cell population underneath the microelectrodes have not been widely explored and remain a grand technical challenge. This work presents an innovative flexible opto-electric device that monolithically integrates transparent gold nanogrid microelectrodes directly above microscale light-emitting diodes, photodetectors, and optical filters to achieve co-localized crosstalk-free optical fluorescence and electrical recording. The optimized gold nanogrid microelectrodes show excellent optical transparency (>81%) and low normalized 1 kHz electrochemical impedance (6.3 Ω cm2). The optical recording subsystem offers high wavelength selectivity (>1,300) and linearity (R2 >0.99) for exciting and capturing green fluorescence from various fluorescent reporters in measurement ranges relevant to in vivo applications with minimal thermal effects. The opto-electric device exhibits remarkable durability under soaking for 40 days and repetitive mechanical bending for 5,000 cycles. The work may provide a versatile approach for constructing mechanically compliant biointerfaces containing crosstalk-free optical and electrical modalities with widespread application potentials in basic and clinical research. ### Competing Interest Statement The authors have declared no competing interest.