Stimuli‐Responsive Hydrogels for Optical Applications: Mechanisms, Architectures, and Translational Challenges

ABSTRACT The use of stimuli‐responsive hydrogels in optoelectronics holds promise due to their capacity to turn chemical or physical stimuli into optical signals by virtue of network dynamics, swelling equilibria, and microstructure. This review provides an insight into the chemistry and microarchitecture of hydrogels that influence optical transduction via refractive index modulation, scattering, birefringence, diffraction, and transparency. The review also highlights the important classes of stimuli involved in adaptive optics, including light, temperature, magnetic fields, ionic environment, metabolites, and enzymes. The hierarchical structuring, nanocomposites, and photonic structures can be used to modulate the magnitude of these responses. An important finding is that the limitations in designing stimuli‐responsive devices are not necessarily linked to the sensitivity of the material but rather with the challenge of combining optical quality, mechanical strength, reversibility, and stability in real‐world environments. Another important challenge is the absence of standardized criteria for measuring optical modulation, kinetic response, fatigue, and biostability. Future research will rely on data‐driven strategies, such as polymer informatics and machine learning.