The unique structural sensitivity of photonic crystals
(PCs) endows
them with stretchable or elastic tunability for light propagation
and spontaneous emission modulation. Hydrogel PCs have been demonstrated
to have biocompatibility and flexibility for potential human health
detection and environmental security monitoring. However, current
elastic PCs still possess a fixed elastic modulus and uncontrollable
structural colors based on a tunable elastic modulus, posing considerable
challenges for in situ detection, particularly in wearable or portable
sensing devices. In this work, we introduced a novel chemo-mechanical
transduction mechanism embedded within a photonic crystal nanomatrix,
leading to the creation of structural colors and giving rise to a
visual gustation sensing experience. By utilizing the captivating
structural colors generated by the hydrogel PC, we employ abundant
optical information to identify various analytes. The finite element
analysis proved the electric field distribution in the PC matrix during
stretch operations. The elastic-optical behaviors with various chemical
cosolvents, including cations, anions, saccharides, or organic acids,
were investigated. The mechanism of the Hofmeister effect regulating
the elasticity of hydrogels was demonstrated with the network nanostructure
of the hydrogels. The hydrogel PC matrix demonstrates remarkable
capability in efficiently distinguishing a wide range of cations,
anions, saccharides, and organic acids across various concentrations,
mixtures, and even real food samples, such as tastes and soups. Through
comprehensive research, a precise relationship between the structural
colors and the elastic modulus of hydrogel PCs has been established,
contributing to the biomatching elastic-optics platform for wearable
devices, a dynamic environment, and clinical or health monitoring
auxiliary.