Micropatterning of Hydrogels by Soft Embossing

Conventional in situ hydrogel micropatterning techniques work successfully for relatively stiff hydrogels, but they often result in locally damaged surfaces upon demolding in the case of soft and fragile polymer networks formed at low precursor concentration. To overcome this limitation, we have developed a facile, versatile method, termed soft embossing, for the topographical micropatterning of fragile chemically cross-linked polymer hydrogels. Soft embossing is based on the imprinting of a PDMStemplate into a gel surface that is only partially cross-linked and thus contains free functional groups that continue to be consumed to confine the microstructure irreversibly upon complete cross-linking. Here we identify and optimize the parameters that control the soft embossing process and show that this method allows the fabrication of desired topographies with good fidelity. Finally, one of the produced gel micropatterns, an array of microwells, was successfully utilized for culturing and analyzing live single hematopoietic stem cells. Confining the stem cells to their microwells allowed for efficient quantification of their growth potential during in vitro culturing.