Degassed micromolding lithography for rapid fabrication of anisotropic hydrogel microparticles with high-resolution and high uniformity
Replica molding techniques, which are used to synthesize microparticles inside anisotropic micromolds, have been developed to enable the mass production of hydrogel particles. However, the technique is limited in its ability to synthesize only a narrow range of particle composition and shape because of the difficulty in loading precursors into the micromolds as well as the low particle homogeneity due to the uneven evaporation of the precursors. Herein, we describe a simple yet powerful technique, called degassed micromolding lithography, which can load hydrophilic precursors within 1 min regardless of the wettability. This technique is based on the gas-solubility of a degassed micromold that acts as a suction pump to completely fill the mold by drawing precursor liquids in. The semi-closed system within the micromold prevents the uneven evaporation of the precursor, which is essential for the production of homogenous particles. Furthermore, controlled uniformity of the hydrogel microparticles (C.V. < 2 %) can be achieved by engineering the design of the micromold array.