Light- and Heat-Responsive Superhydrophobic Surfaces with Shape Memory Capacity Prepared by 4D Printing

The precise manipulation of microdroplets on solid surfaces is crucial for the practical application and future development of microfluidic control technology. Traditionally, methods to achieve precise control over microdroplets often involve complex fabrication processes. Herein, the control of surface wettability is achieved based on the light- and heat-responsive shape memory effect of the microstructure. An innovative superhydrophobic shape-memory material with a simplified and efficient manufacturing process is proposed to precisely control microdroplets through surface wettability switching. Firstly, microplates with shape-memory effects are manufactured using 4D printing technology and polylactic acid as the base material. Then, a mixture of carbon black and epoxy resin is sprayed onto the surface for superhydrophobic modification, resulting in a contact angle of up to 165°. The addition of carbon black endows the surface with excellent photothermal conversion effects. Anisotropy and photothermal response studies are incorporated. Through periodic heating, pressing, and deformation, the microplate array exhibits controllable wettability switching. Based on the shape-memory effect of polylactic acid, the superhydrophobic surface has adjustable adhesion and is successfully applied to microfluidic platforms and microdroplet size screening. This innovative material and process offer significant potential for advancing the field of microfluidic control technology.