Supplementary Figure 3: Optical characterization of the multifunctional fibers.

(a) Optical transmission spectra of multifunctional fibers. The relative transmission is shown for wavelengths within the visible range illustrating the utility of the integrated waveguides for activation of various opsins (ChR2: 473 nm, eNpHR3.0: 589 nm, VChR1: 542 nm, and Chrimson: 627 nm)^1,2. (b) Characterization of optical losses for waveguides integrated within multifunctional fiber probes. Optical powers for straight and bent multifunctional fiber-probes were measured at different lengths. Bending angle was 90° and radius curvature was 2.5 mm. The optical losses were calculated to be 1.32 dB/cm and 1.50 dB/cm for straight and bent fiber-probes, respectively. Error bars represent standard deviation (Number of samples n=6). (c, d) Optical losses of integrated polymer waveguides. (c) Infrared thermometry of a fiber probe transmitting 473 nm laser light. The temperature increase of 3.1 °C was observed at steady state (thermodynamic equilibrium) during continuous delivery of 10 mW of 473 nm light, which places upper boundary for simulation energy and duty cycle. For pulsed stimulation at 10 Hz (5 ms pulse width), which was used for experiments in vivo, the temperature increase was 0.8 °C. Scale bar = 500 μm. (d) Transmission losses measured for straight and dent fibers at room temperature, 20 °C and body temperature, 37 °C. Bending angle was 90° and radius curvature was 2.5 mm. No significance was identified between measurements taken at different temperatures. Unpaired student’s t-test: p = 0.6412 for flat fiber, p = 0.5419 for bent fiber. Error bars represent standard deviation, Number of samples n=6. (e, f) Relative optical transmission of waveguides integrated within multifunctional fibers during extreme bending and repeated deformation. (e) Optical transmission for multifunctional fibers measured for repeated bending at 180° with a 2.5 mm radius of curvature (even cycles = straight fiber, odd cycles = bent fiber). Shaded area represents standard deviation (Number of samples n=6). (f) Optical transmission at radii of curvature 0.5, 1, 2.5, 5, 7.5, 10, 12.5, and 15 mm was measured for fibers bent by 90°, 180°, and 270°. Error bars represent standard deviation (Number of samples n=3). (g) Optical transmission losses of the integrated waveguides following multifunctional fiber implantation into the mouse brain. No statistically significant change in transmission loss was observed for devices implanted for up 3 months. Number of samples n=6, One-way ANOVA and Tukey’s comparison test were performed. p = 0.878, F_{7, 40} = 0.429. Error bars represent standard deviation.

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