RT Journal Article
SR Electronic
T1 Designing Responsive Buckled Surfaces by Halftone Gel Lithography
JF Science
JO Science
FD American Association for the Advancement of Science
SP 1201
OP 1205
DO 10.1126/science.1215309
VO 335
IS 6073
A1 Kim, Jungwook
A1 Hanna, James A.
A1 Byun, Myunghwan
A1 Santangelo, Christian D.
A1 Hayward, Ryan C.
YR 2012
UL http://science.sciencemag.org/content/335/6073/1201.abstract
AB When thin sheets are compressed they can buckle and wrinkle, such as when the edges of a sheet of paper, or two areas of skin, are pushed together. Variations in local thickness and stiffness will alter the buckling patterns, but controlling this in a simple and predictable way is difficult. Kim et al. (p. 1201; see the Perspective by Sharon) used halftone lithography with two photomasks to create highly cross-linked dots embedded in a lightly cross-linked matrix of a swellable polymer. This material could generate “smooth” swelling profiles on thin sheets with arbitrary two-dimensional geometries so that complex three-dimensional structures could be produced.Self-actuating materials capable of transforming between three-dimensional shapes have applications in areas as diverse as biomedicine, robotics, and tunable micro-optics. We introduce a method of photopatterning polymer films that yields temperature-responsive gel sheets that can transform between a flat state and a prescribed three-dimensional shape. Our approach is based on poly(N-isopropylacrylamide) copolymers containing pendent benzophenone units that allow cross-linking to be tuned by irradiation dose. We describe a simple method of halftone gel lithography using only two photomasks, wherein highly cross-linked dots embedded in a lightly cross-linked matrix provide access to nearly continuous, and fully two-dimensional, patterns of swelling. This method is used to fabricate surfaces with constant Gaussian curvature (spherical caps, saddles, and cones) or zero mean curvature (Enneper’s surfaces), as well as more complex and nearly closed shapes.