LAUSR

DNA molecules direct the swelling of cross-linked hydrogels with shape changes in response to different biomolecular signals. Getting a hold with DNA Stimuli-responsive materials can respond to physical or chemical cues to trigger changes in color, shape, or other properties. Cangialosi et al. used photolithography to define multilayer planar soft machines from polyacrylamide coupled to single strands of DNA. When presented with the complementary strands, the machines can change shape in complicated and programmable ways, including stepwise or sequential shape changes. Science, this issue p. 1126 Shape-changing hydrogels that can bend, twist, or actuate in response to external stimuli are critical to soft robots, programmable matter, and smart medicine. Shape change in hydrogels has been induced by global cues, including temperature, light, or pH. Here we demonstrate that specific DNA molecules can induce 100-fold volumetric hydrogel expansion by successive extension of cross-links. We photopattern up to centimeter-sized gels containing multiple domains that undergo different shape changes in response to different DNA sequences. Experiments and simulations suggest a simple design rule for controlled shape change. Because DNA molecules can be coupled to molecular sensors, amplifiers, and logic circuits, this strategy introduces the possibility of building soft devices that respond to diverse biochemical inputs and autonomously implement chemical control programs.