Controlled construction of ellipsoidal microcapsules via tannic acid/cellulose nanocrystal interfacial engineering

Non-spherical microcapsules have recently attracted significant research attention due to their remarkable advantages, including a high specific surface area, improved adhesion efficiency, enhanced targeted delivery capability, and distinctive hydrodynamic behavior. However, effective strategies for precisely controlling microcapsule morphology remain limited. Herein, we developed an interfacial assembly strategy to fabricate ellipsoidal microcapsules by orchestrating the co-assembly of cellulose nanocrystal (CNC) and NH₂-PDMS-NH₂ at the oil-water interface using tannic acid (TA). The spherical morphology of emulsion droplets, quantified by roundness values ranging from 0 to 1.5, could be precisely controlled by modulating both the shear rate and processing time during emulsion formation. TA was found to participate and accelerate interfacial assembly, enhance the storage modulus and viscosity of emulsions, and enhance the thickness of interfacial films by interfacial tension, rheology, and atomic force microscopy. Molecular dynamics simulations further confirmed that NH₂-PDMS-NH₂ assembles at the interface with CNC and TA via electrostatic interactions. Additionally, quartz crystal microbalance with dissipation (QCM-D) measurements revealed superior adhesion properties of ellipsoidal microcapsules compared to their spherical counterparts. This work establishes a novel strategy for fabricating morphology-controlled microcapsules, offering a promising pathway for industrial-scale production and broad applications of non-spherical microcapsules.