Fabrication and Characterization of PDMS Waveguides for Flexible Optrodes

With the growth of optogenetic research, the demand for optical probes tailored to specific applications is ever rising. Specifically, for applications like the coiled cochlea of the inner ear, where planar, stiff, and nonconformable probes can hardly be used, transitioning from commonly used stiff glass fibers to flexible probes is required, especially for long‐term use. Following this demand, polydimethylsiloxane (PDMS) with its lower Young's modulus compared to glass fibers can serve as material of choice. Hence, the long‐term usability of PDMS as a waveguide material with respect to variations in transmission and refractive index over time is investigated. Different manufacturing methods for PDMS‐based flexible waveguides are established and compared with the aim to minimize optical losses and thus maximize optical output power. Finally, the waveguides with lowest optical losses (−4.8 dB cm−1 ± 1.3 dB cm−1 at 472 nm) are successfully inserted into the optogenetically modified cochlea of a Mongolian gerbil (Meriones unguiculatus), where optical stimuli delivered by the waveguides evoked robust neuronal responses in the auditory pathway. The demand for optical probes tailored to applications is ever rising for optogenetic research. Specifically, for applications such as the cochlea, transitioning from stiff glass fibers to flexible probes is required, especially for long‐term use. Polydimethylsiloxane with its low Young's modulus can serve as material of choice. Its long‐term usability as a waveguide material is investigated, and different manufacturing methods are established. The waveguides with lowest optical losses are successfully inserted into the optogenetically modified cochlea of a Mongolian gerbil (Meriones unguiculatus).