Multitemperature Responsive Self-Folding Soft Biomimetic Structures.

Untethered, millimeter-scale, stimuli-responsive shape change structures are critical to the function of autonomous devices, smart materials, and soft robotics. Temperature in a range compatible with physiological or ambient environmental conditions is an excellent cue to trigger actuation of soft structures for practical biomimetic applications. Previously, a range of thermally responsive self-folding soft structures has been described and utilized in a variety of applications from tissue engineering to minimally invasive surgery. In order to extend these concepts to more complex devices, thermally responsive bilayer structures composed of poly[oligo (ethylene glycol) methyl ether methacrylate] (POEGMA) gels that swell at three different temperatures are described. The lower critical solution temperature and volume transition temperature of POEGMA are tuned by varying the side chain length and the extent of copolymerization. The swelling properties of the POEGMA gels are characterized and a multilayer photopatterning process is described that is used to create soft biomimetic structures that change shape in a sequential manner while displaying multistate behaviors.