Self-folding materials offer an approach for generating cell-friendly structures with 3D complexity along a range of length scales that is difficult to achieve with printing and lithography. Folding is induced when there are differential stresses generated within a flexible or elastic material and the bending moment is larger than the gravitational force that maintains an otherwise flat, relaxed structure. Polymeric materials, and hydrogels in particular, are well-suited for living self-folding applications because they undergo more pronounced volume changes in response to cell-friendly stimuli than metals and ceramics before failing. Currently, self-folding films are either not cell compatible or they are pre-patterned with the heterogeneities that generate folding due to differential swelling. While novel, these methods restrict flexibility for designing cell culture experiments that require originally flat surfaces or timed response to induced shape changes. We have designed photodegradable films, containing <i>ortho</i>-nitrobenzyl moieties, that permit encapsulation or cell seeding on swollen planar films. Upon long wave UV light exposure, heterogeneities in crosslink density are introduced in the film causing it to fold. We generated heterogeneities in crosslink density in either the lateral or depth planes of the film by using photomasks or taking advantage of light attenuation through the film’s thickness respectively. By carefully tuning the photodegradable material composition (both the crosslink density and amount of <i>ortho</i>-nitrobenzyl groups), light dose and patterning, we induced folding of planar sheets in to biologically relevant shapes—such as tubes and containers. We characterized the material’s photo-degradation profile, and swelling and mechanical properties. Our approach for generating shape-changing materials offers a flexible platform for producing cell friendly structures with 3D complexity along a range of length scales. These materials can be tuned with an understanding of crosslink density, visco-elastic properties of polymers and light attenuation.

Self-folding photodegradable hydrogels: From planar sheets to 3D structures

251st National Meeting (2016)

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