Fig. 1

Scheme for controlled expansion of DNA-crosslinked hydrogels gated by biomolecular signals. Colors within DNA strands show sequence domains, drawn to scale; complementary regions are shown in the same colors. a Device architecture. A controller interprets stimuli and decides whether to switch the device from an inactive to an active state. The controller takes low-concentration inputs and processes them with low-concentration molecular circuit elements; the output is then amplified to activate the high-concentration crosslinks within the device that interact with high-concentration fuel to drive material shape change. b In a DNA-crosslinked hydrogel, hybridized DNA oligonucleotides crosslink polyacrylamide chains. c Schematic of the hairpin monomer incorporation process that drives size change. Two types of hairpin monomers are inserted into crosslinks in alternating series at a single active site. d Control over whether size changes is achieved by control over device activation through crosslink unlocking. Unlocked crosslinks can extend by incorporating hairpin fuel