Systematic Study of PDMS Optical Waveguides for Pressure Sensing Using Design of Experiments

Poly(dimethylsiloxane) (PDMS) optical waveguides are highly regarded for pressure and tactile sensing due to their high sensitivity in the low-pressure range (0–100 kPa), desirable optomechanical properties, and biocompatibility. While it is known that PDMS properties are tunable via mix ratio and cure conditions, the magnitude of their effects and interactions remains unclear. To address this, response surface methodology was used to quantify the influence of mix ratio and cure conditions on key optical and mechanical properties of PDMS optical waveguides. Significant curvature was observed in the response surfaces for transverse compression sensitivity, secant modulus, and refractive index (RI). The mix ratio was the most significant factor for sensitivity and modulus, followed by a significant interaction with cure temperature. Cure temperature significantly influenced the RI, primarily due to density changes, while propagation loss showed a weak, yet statistically significant, linear dependence on mix ratio. These statistical findings are interpreted within the context of polymer science linking the empirical models to material behavior. By applying design of experiments, this work provides a systematic framework for understanding the relationship between fabrication parameters and the response of PDMS optical waveguides towards predictable and repeatable properties.