Photodegradable Hydrogels to Generate Positive and Negative Features over Multiple Length Scales

Here we present a photodegradable hydrogel as a biocompatible, nonfouling photoresist capable of presenting positive and negative features through single-photon and two-photon degradation. All ortho-nitrobenzylether (o-NBE) moiety is used as a polymerizable cap for poly(ethylene glycol) chains to create a photodegradable macromer. Positive and negative features can be patterned into/onto a hydrogel over a broad range of length scales (similar to 10(-7) to 10(-2) in (nm-cm)) in single- and two-photon photolysis. Phase contrast micrographs and profilometry data show that a partially degradable hydrogel network undergoes swelling to produce positive features with varying size (10-100 mu m). Conjugation of a coumarin fluorophore to the o-NBE macromer enhances the sensitivity of the hydrogel to two-photon degradation, simultaneously incorporating fluorescence visualization with no added dye.