Microscale hydrogels have been shown to be beneficial for various applications such as tissue engineering and drug delivery. A key aspect in these applications is the spatial organization of biological entities or chemical compounds within hydrogel microstructures. For this purpose, sequentially patterned microgels can be utilized to spatially organize either living materials to mimic biological complexity or to encapsulate multiple chemicals to design functional microparticles for drug delivery. Photolithographic methods are the most common way to pattern microscale hydrogels, but are limited to photocrosslinkable polymers. So far, conventional micromolding approaches use static molds to fabricate structures, which limits the resulting shapes that can be generated. In this study, we describe a dynamic micromolding technique to fabricate sequentially patterned hydrogel microstructures by exploiting the thermo-responsiveness of poly(N-isopropylacrylamide) based micromolds. These responsive micromolds exhibited shape changes under temperature variations, facilitating the sequential molding of microgels at two different temperatures. We fabricated multi-compartmental striped, cylindrical, and cubic microgels that encapsulated fluorescent polymer microspheres or different cell types. These responsive micromolds can be used to immobilize living materials or chemicals into sequentially patterned hydrogel microstructures which may potentially be useful for a range of applications at the interface of chemistry, biology, materials science and engineering.
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