Recent Advances in Scalable and Defect‐Controlled Colloidal Photonic Crystals: From Assembly Mechanisms to Wearable Sensors

Colloidal photonic crystals (CPCs) serve as versatile optical platforms for healthcare sensing and real‐time physiological monitoring. Recent developments have focused on scalable assembly techniques and the integration of CPCs with stimuli‐responsive hydrogels. To systematically review these recent developments, this article first provides an analysis of the kinetic mechanisms governing defect formation in CPC systems. This analysis is followed by a summary of emerging strategies based on fluidic regulation and mechanical assistance for large‐area fabrication with improved structural quality. We then elaborate on the incorporation of assembled CPC templates into stimuli‐responsive hydrogel networks, illustrating the developmental trajectory of stretchable photonic sensors. Furthermore, the sensing capabilities of these composites are highlighted. These platforms can transduce diverse physical and biochemical stimuli into visual signals, facilitating biomechanical motion tracking, thermal environmental perception, and targeted biochemical analyte recognition. We emphasize that signal‐decoupling architectures can reduce crosstalk between sensing channels within defined operating ranges, thereby improving the reliability of multimodal sensing. Continued advances in scalable fabrication and multifunctional sensing can support the further development of these platforms for wearable electronics.