Reversibility and repeatability of the tensile deformation response in holographic sensors

Reversibility and repeatability of the tensile deformation response in holographic sensors formed by highly stretchable acrylamide polymers have been investigated. The diffraction spectrum of the volume grating was used to characterize the deformation. Two-way shifts of peak wavelengths, i.e., redshift in transmission and blueshift in reflection, were observed in stretching. The reduction of the average refractive index provided experimental evidence for the physical mechanism. To achieve a linear response and high repeatability, the limitation of tensile displacement was determined as 5.0 mm, and the relevant deformation is 6.6%. This value can be considered as a boundary between the elastic and plastic deformations in samples with thicknesses less than 120 μm. There was a totally linear relation between peak wavelength and deformation within the elastic range. The reversible and repeatable deformation response validated the practical applicability of a holographic sensor.