Fabrication of Microstructured Hydrogels via Dehydration for On-Demand Applications.

Microstructured hydrogels show promising applications in various engineering fields from micromolds to anisotropic wetting surfaces and microfluidics. Although methods like molding by, e.g., casting as well as 3D printing are developed to fabricate microstructured hydrogels, developing fabrication methods with high controllability and low-cost is an on-going challenge. Here, a method is presented for creating microstructures through the dehydration of double network hydrogels. This method utilizes common acrylate monomers and a mask-assisted photopolymerization process, requiring no complex equipment or laborious chemical synthesis process. The shape and profile of microstructures can be easily controlled by varying the exposure time and the mask used during photopolymerization. By altering the monomer and the mask used for fabricating the second network hydrogel, both convex and concave microstructures can be produced. To showcase the utility of this method, the patterned hydrogel is utilized as a mold to fabricate a polydimethylsiloxane microlens array via soft lithography for imaging application. In addition, a patterned hydrogel surface exhibiting obvious anisotropic wetting properties and open microfluidic devices which can achieve fast directional superspreading within milliseconds are also fabricated to demonstrate the versatility of the method for different engineering fields.