Precisely writing/printing hydrogel patterns on polymer surfaces

[Display omitted] •Writing/printing strategies are efficient routes to produce patterned hydrogels.•The patterning strategy eliminates cumbersome equipment and complex technology.•Eliminating oxygen ensures accurate patterning and strong adhesion of hydrogels.•Coatings can store matter and energy due to its adjustable thickness and load. Patterning hydrogels on polymer surfaces is of great significance in widespread fields from bionic technology to materials science. Herein, a simple and universal writing/printing strategy for precisely patterning hydrogels on polymer surfaces with robust adhesion is reported. This strategy allows to construct surface patterns with discretionary shape and adjustable thickness of hydrogel coatings with micrometer resolution in a format that is convenient for large-scale manufacturing. The hydrogel pattern is formed by defining the region of the precursor solution, rather than the region that defines the initiator or UV, to avoid imprecise results due to initiator or thermal diffusion. Moreover, sufficient amounts of precursor solutions are widely distributed on the pretreated surfaces to minimize the effects of ambient oxygen and moisture. This strategy opens up new possibilities for the design and fabrication of new-generation surface-patterned soft materials. Based on our applicable demonstrations, the patterned hydrogel coatings show great potentials for multi-drug loaded skin patches, microreactors, and transparent ion sensors.