Self-driven gel conveyer: Autonomous transportation by peristaltic motion of self-oscillating gel

A novel self-driven gel conveyer for microparticles in controlled direction was developed by utilizing the autonomous peristaltic motion of a self-oscillating gel. The self-oscillating gel was composed of temperature-responsive N-isopropylacrylamide (NIPAAm), 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and ruthenium tris(2,2′-bipyridine) as a catalyst for the Belousov–Zhabotinsky (BZ) reaction. The swelling ratio of the gel changes due to the periodical redox changes of the catalyst for the BZ reaction polymerized in the gel, and the autonomous peristaltic motions are generated with the propagation of the chemical wave. In our previous study, cylindrical gel cargos were transported like isotropic diffusion by circular or spiral waves on the flat self-oscillating gel surface but the transport system could not apply to other figures like spherical cargos. In this study, the surface figure capable of transporting microparticles in one direction was designed to fabricate more versatile self-driven gel conveyer. The self-oscillating gel having a grooved surface was fabricated and the effectiveness of the surface design was investigated. Poly(AAm-co-AMPS) gel beads with the diameter of several hundred micrometer to several millimeter were transported on the grooved surface of the self-oscillating gel by its autonomous peristaltic motions. It was found that the travelling direction of the peristaltic motion could be confined to the direction along the grooves by designing the groove-distance shorter than the wavelength of the chemical wave. Consequently, several gel beads were transported in parallel. The contact areas of loaded cargos and the self-oscillating gel surface were calculated theoretically to investigate the relationship between the transportability and the surface figure. It was found that the surface design to form grooves was efficient to increase contact areas when the wave front of the peristaltic motion reaches the loaded cargo and useful to transport not only cylindrical cargos but also spherical cargos in desired directions.