Self-Moving Polymer beads

Self-propelled motion through internalized chemical reaction, a characteristic of living systems, has led to the design of various synthetic bio-inspired systems. Here, we design a self-moving macroscopic system through careful use of self-oscillating chemical reaction inside a polymeric gel. Specifically, we use poly-N-isopropylacrylamide (NIPAAm) gel bead as a miniaturized reactor and harness chemical oscillations of the Belousov Zhabotinsky (BZ) reaction to produce sustained motion. In a typical experiment, the gel beads are charged with BZ reagents and placed on an oil-covered substrate. Due to the porous nature of the gel beads, the intermediates of BZ reaction ooze out of the gel and react with oil, thereby producing spontaneous motion of the bead via Marangoni effect. We further demonstrate that the velocity of the beads can not only be controlled by tuning the kinetics of BZ reaction but also by varying the external stimuli. In particular, we show that by using Ru decorated graphene nanosheets as catalysts the velocity of the beads can be enhanced significantly compared to the traditional solution based catalysts. Our findings can be used to design self-propelled conveyor belts that can deliver cargo from micron to mm length scale.