Reconfigurable soft materials that can bend, fold, or transform the structural symmetry in response to external stimuli have attracted significant interests in design of actuators, sensors, and smart materials and devices. It also presents scientific and engineering challenges to the designs of soft structures with reversible, fast, and controllable deformation.Here, we patterned hydrogel membranes with micro-pores (Fig. 1a, 10 �m diameter, 15 �m pitch) by replica molding and UV crosslinking hydrogel monomers (Fig. 1b): poly(2-hydroxy ethyl methacrylate) (PHEMA), pH responsive acrylic acid (AA), and thermal responsive N-isopropylacrylamide (NIPAAm) to study its structural reconfiguration upon swelling. Depending on the pH and temperature, the hydrogel matrix swells or contracts, leading to fast and reversible reconfiguration of the pore size, shape and symmetry. We observed four distinctive surface configurations at different swelling ratios of the hydrogel (Fig. 1c): initial state of circular pore arrays, buckled pore arrays of alternating mutually orthogonal ellipses, twisted pores snap-shut to form �S� shaped slits, and crease formation with locally formed surface folds. The pore deformation process can be qualitatively assessed based on the buckling instability and pattern transformation of elastomeric cellular solids having square arrays of pores (Fig. 1d).Our hydrogel microstructure has demonstrated fast and well-controlled deformation of micro-pore arrays on the membrane at the cusp of instability through buckling, bending and creasing, which may find applications in micro-actuators, micro-robotics, and microfluidics.?

Buckling, twisting, and creasing in hydrogel membranes: A new mechanism for reconfigurable soft materials

246th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.