Cytocompatible asymmetrical coating for Janus carrier synthesis through capillary wetting and ascending

Despite the successful implementation of elegant strategies for the fabrication of Janus microstructures, two critical factors have limited the applicability of most techniques for the partial modification of living cell surfaces: harsh conditions that could disintegrate cells, and the lack of an effective route to accomplish a mild modification for living cells. In this study, an expeditious synthesis, named lower-half occupation by capillary ascended liquids (LOCAL), is proposed for the fabrication of asymmetrical structures surrounding not only microbeads but also both living adherent and buoyant mammalian cells. The microbeads or living cells are safely supported and trapped on the apical sides of a micropillar array, which prevents them from contacting the bottom substrate. As the coating agents further transfer and contact the trapped particles through interpillar capillary flow, the autonomous capillary ascending coats the free bottom surfaces of the target particles within 2 min, with significantly small quantities of coating agents. The self-assembled architectures of the cells demonstrate thoroughly maintained cell viability, highlighting the potential of the LOCAL method as a desirable alternative to the widely applied state-of-art methods for developing Janus beads and Janus cells.