Optically Active Birefringent Polymer–Lipid Hybrid Microparticles With Dual‐Stimuli Responsiveness

ABSTRACT

Organic‐material‐based hybrid microstructures that integrate structural anisotropy with dual‐stimuli responsiveness offer emerging opportunities for externally driven functional systems. We present multi‐functional dual‐stimuli‐responsive microparticles that exhibit optical birefringence due to their lamellar crystalline architecture, enabling label‐free detection under a polarized light. The anisotropic internal structure generates polarization‐dependent optical contrast, enabling label‐free tracking through birefringence‐based microscopy, with birefringence values (Δn) ranging from 0.04 to 0.07. Simultaneously, these microparticles are composed of polymer‐lipid material (polycaprolactone and stearic acid), magnetic nanoparticles (MNPs), and polypyrrole nanoparticles (PPy NPs), enabling responsiveness to both magnetic and near‐infrared (NIR) stimuli. The magnetic and photothermal responses of microparticles are investigated in aqueous solutions and under biologically relevant conditions. As a proof‐of‐concept demonstration, we show directional actuation in response to magnetic fields and NIR light in these multifunctional anisotropic microstructures, highlighting their potential for microrobotic applications. Furthermore, we show their low hemolytic activity and cytotoxicity, thereby confirming their biocompatibility. The present study introduces a pioneering integration of birefringent optical tracking into a dual‐stimulus soft‐material platform that possesses shapes depending on the formation condition, ranging from flower‐like to ship‐like. This innovation establishes a structure‐enabled, multifunctional soft‐material platform in which optical, magnetic, and thermal responses are intrinsically coupled within a single microstructure.