Flexible and highly sensitive optical polymeric strain gauge

In this work, the theoretical analysis of an innovative polymeric strain sensor is proposed. In this device, composed of chalcogenide glass (As
2
S
3
) stripes, periodically repeated on a substrate of polydimethylsiloxane (PDMS), an applied strain stretches the soft substrate, altering the periodic arrangement of stripes and introducing a variation of the resonant peak of the optical response of the structure. The amount of strain is measured by analyzing the entity of the resonance displacement or intensity in the reflection spectra. In order to realize strain-sensing application, two regimes have been investigated, in dependence of the aperture between two adjacent stripes: large and small aperture. Numerical computations reveal that, for large aperture, this device is characterized by an excellent sensitivity equal to 1.4 nm/nm and by a linear intensity reflection-deformation calibration curve at a fixed wavelength equal to 1.5 µm. Similarly, the device with smaller aperture exhibits a resonance displacement-deformation calibration curve with a sensitivity of approximately 1.33 nm/nm and 1 nm/nm for first and second resonance, respectively.