Magnetically hybridized inkjet-printed und photo-polymerized multi-hydrogel thermo-responsive soft gripper

Abstract:
Manipulation of objects by gripping is essential for microrobots and polymer-based actuators. Additionally, remote steering of grippers by magnetic fields expands the application possibilities. Small hydrogel-based grippers were fabricated by serial photolithography based on masks by the groups [1] and [2]. Here we present the realization of a millimeter-sized inkjet-fabricated soft hydrogel gripper that is actuated by thermal stimuli-induced bending of its two bilayer fingers and magnetically functionalized to manipulate the position of the gripper. Inkjet printing of water-based photocurable monomer solutions by drop-on-demand approach requires determined deposition of the droplets to achieve well shaped structures. Here we print a soft rectangular shaped hydrogel gripper composed of an active thermo-responsive hydrogel (PNIPAAM) and a passive hydrogel (PDMAA) structure. The printed and photo-polymerized composite was magnetically functionalized by coprecipitation of magnetic particles inside the hydrogel. This actuator closed when heated above the phase transition temperature of PNIPAAM and recovered its shape after cooling. It was pulled in liquid or at liquid-gas interface to the desired location by gradients of magnetic fields.