A simple superhydrophobic/superhydrophilic Janus-paper with enhanced biocompatibility by PDMS and candle soot coating for actuator

Janus-materials were processed though different characteristics integrate to achieve important functions which have aroused great interest among the scientific research and industrial applications. However, the facile fabrication of Janus-materials with the attributes of chemical-free, low-cost, and simple process is still a great challenge. Herein, inspired by the mimosa and lotus leaf, a Janus-paper with superhydrophobicity /superhydrophilicity is successfully fabricated by a conjunction of PDMS and candle soot coating. The water and sliding contact angles of the superhydrophobic surface are 162° and 1°, respectively, and it also shows a good antifouling properties and mechanical durability. Additionally, the cell biocompatibility of superhydrophobic surface is significantly improved, holding the potential as a cell culture carrier. Due to the inhomogeneous swelling inside the internal structure, the Janus-paper exhibits a mimosa-like behavior when immersed in water, endowing the actuation of a boat model on the water surface. Moreover, due to the different adhesions, the superhydrophobic and superhydrophilic surfaces can be used for microdroplet transportation and water storage devices. This bio-inspired approach provides a new generic route for fabrication of Janus-paper for potential multifunctional applications.