A shape-reconfigurable, light and magnetic dual-responsive shape-memory micropillar array chip for droplet manipulation

Abstract

Droplet manipulation on an open surface has great potential in chemical analysis and biomedicine engineering. However, most of the reported platforms designed for the manipulation of water droplets cannot thoroughly solve the problem of droplet evaporation. Herein, we report a shape-reconfigurable micropillar array chip for the manipulation of water droplets, oil droplets and water-in-oil droplets. Water-in-oil droplets provide an enclosed space for water droplets, preventing the evaporation in an open environment. Perfluoropolyether coated on the surface of the chip effectively reduces the droplet movement resistance. The micropillar array chip has light and magnetic dual-response due to the Fe3O4 nanoparticles and the reduced iron powder mixed in the shape-memory polymer. The micropillars irradiated by a near-infrared laser bend under the magnetic force, while the unirradiated micropillars still keep their original shape. In the absence of a magnetic field, when the micropillars in a temporary shape are irradiated by the near-infrared laser to the transition temperature, the micropillars return to their initial shape. In this process, the surface morphology gradient caused by the deformation of the micropillars and the surface tension gradient caused by the temperature change jointly produce the driving force of droplet movement.