am508621s_si_002.mpg (1.83 MB)
Self-Folding Thermo-Magnetically Responsive Soft Microgrippers
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posted on 2016-01-18, 12:08 authored by Joyce C. Breger, ChangKyu Yoon, Rui Xiao, Hye Rin Kwag, Martha
O. Wang, John P. Fisher, Thao D. Nguyen, David H. GraciasHydrogels such as poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAM-AAc)
can be photopatterned to create a wide range of actuatable and self-folding
microstructures. Mechanical motion is derived from the large and reversible
swelling response of this cross-linked hydrogel in varying thermal
or pH environments. This action is facilitated by their network structure
and capacity for large strain. However, due to the low modulus of
such hydrogels, they have limited gripping ability of relevance to
surgical excision or robotic tasks such as pick-and-place. Using experiments
and modeling, we design, fabricate, and characterize photopatterned,
self-folding functional microgrippers that combine a swellable, photo-cross-linked
pNIPAM-AAc soft-hydrogel with a nonswellable and stiff segmented polymer
(polypropylene fumarate, PPF). We also show that we can embed iron
oxide (Fe2O3) nanoparticles into the porous
hydrogel layer, allowing the microgrippers to be responsive and remotely
guided using magnetic fields. Using finite element models, we investigate
the influence of the thickness and the modulus of both the hydrogel
and stiff polymer layers on the self-folding characteristics of the
microgrippers. Finally, we illustrate operation and functionality
of these polymeric microgrippers for soft robotic and surgical applications.