Biodegradable thermomagnetically responsive soft untethered grippers.

Soft-robotic devices such as polymeric microgrippers offer the possibility for pick-and-place of fragile biological cargo in hard to reach conduits with potential applications in drug delivery, minimally invasive surgery and biomedical engineering. Previously, millimeter-sized self-folding thermomagnetically responsive soft-grippers have been designed, fabricated, and utilized for pick-and-place applications but there is the concern that such devices could get lost or left behind after their utilization in practical clinical applications in the human body. Consequently, strategies need to be developed to ensure that these soft-robotic devices are biodegradable so that they would disintegrate if left behind in the body. In this paper, we describe the photopatterning of bilayer gels composed of a thermally responsive high swelling poly[oligo ethylene glycol methyl ether methacrylate (Mn=500)-bis(2-methacryloyl)oxyethyl disulfide], P(OEGMA-DSDMA) and a low swelling poly[acrylamide- N, N'- bis(acyloyl) cystamine], P(AAm-BAC) hydrogel in the shape of untethered grippers. These grippers can change shape in response to thermal cues and open and close due to the temperature induced swelling of the P(OEGMA-DSDMA) layer. We demonstrate that the grippers can be doped with magnetic nanoparticles so that they can be moved using magnetic fields or loaded with chemicals for potential applications as drug-eluting theragrippers. Importantly, they are also biodegradable at physiological body temperature (~ 37 °C) based on cleavage of disulfide bonds by reduction. This approach which combines thermoresponsive shape change, magnetic guidance, and biodegradability represents a significant advance to the safe implementation of untethered shape change biomedical devices and soft-robots for medical and surgical applications.