Remote-Controlled Peristaltic Locomotion in Free-Floating PNIPAM Hydrogels

摘要

Peristalsis-driven locomotion, by nature of its flexibility and deformability, is a highly advantageous mechanism for mobility in soft materials and robots; however, utilization of this mechanism has been limited to restricted, frictional environments. (Seok et al., presented at 2010 IEEE International Conference on Robotics and Automation, Anchorage, AK May 3–8, 2010; Boxerbaum et al., Int J Robotics Res 2012, 31, 302; Boxerbaum et al., presented at 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, San Francisco, CA, 2011; Arora et al., J Polym Sci Part A: Polym Chem 2009, 47, 5027). We have removed this limitation and expanded the use of peristaltic locomotion to open aqueous environments by remotely inducing peristalsis via spatially controlled volume phase transitions in thermosensitive poly(N-isopropylacrylamide) (PNIPAM) hydrogels. The resulting asymmetry causes steady, incremental linear displacement in the hydrogel's center of mass, thus producing directed, remote-controlled locomotion. In our proof-of-principle system, we controlled the peristaltic locomotion of the hydrogels using a handheld laser to selectively induce volume phase transitions in the hydrogel. The PNIPAM hydrogels' energy absorbance capability was enhanced by incorporating the New Indocyanine Green laser dye (IR-820) into the gel. The use of IR-820 is likely to expand the application space for these hydrogels due to new opportunities for conjugation chemistry. (Prajapati et al., Molecular Imaging 2009, 8, 45; Fernandez-Fernandez et al., Molecular Imaging 2011, 11, 1). Overall, such an approach increases the capability of both peristaltic locomotion as a mechanism for mobility in soft robots, and PNIPAM hydrogels as a biotechnological platform.