The magic of droplet templates: Advances in the fabrication and applications of structurally anisotropic photonic microparticles

Non-spherical photonic microparticles have emerged as a burgeoning research frontier due to their unique optical properties, enhanced interfacial interactions, and versatile multifunctional integration potential. Compared to their spherical counterparts, these microparticles offer superior performance in applications requiring directional optical responses, rapid stimulus responsiveness, and targeted adhesion, making them highly attractive in different areas. However, a synergistic review regarding their advances in the fabrication approaches and corresponding properties is yet to be presented. This review systematically summarizes the advances in the fabrication of non-spherical photonic microparticles that all originated from spherical droplet templates laden with different building blocks, including different colloidal particles, homopolymers, or amphiphilic block copolymers. The droplets were subjected to different processes and eventually evolved into photonic microparticles with different morphologies and properties. Their underlying formation mechanisms are thoroughly summarized. Current challenges such as achieving morphological uniformity, scalable production, and environmental stability are critically analyzed. Finally, future perspectives are proposed; the need for programmable, multifunctional, and sustainable material systems that integrate multi-stimuli-responsive functionalities to meet the demands of high-security anti-counterfeiting, wearable devices, biosensing, and precision medicine is also highlighted. This review aims to provide a comprehensive reference and forward-looking insights to guide the continued advancement and practical applications of non-spherical photonic microparticles. • Droplet templates unlock anisotropic photonic microparticles with structural colors. • Strategy map: evaporation, extraction, confinement/molding, and field/bio guidance. • Mechanisms link flow/jamming, coffee-ring control, and interfacial-tension topology. • A structure–function guide compares morphologies with pros/cons for applications. • Roadmap: data-driven process windows and composites/encapsulation for scalability.