Laser-Induced Fast Assembly of Wettability-Finely-Tunable Superhydrophobic Surfaces for Lossless Droplet Transfer

Rose-petal-like superhydrophobic surfaces with strong water adhesion are promising for microdroplet manipulation and lossless droplet transfer. Assembly of self-grown micropillars on shape-memory polymer sheets with their surface adhesion finely tunable was enabled using a picosecond laser microprocessing system in a simple, fast, and large-scale manner. The processing speed of the wettability-finely-tunable superhydrophobic surfaces is up to 0.5 cm(2)/min, around 50-100 times faster than the conventional lithography methods. By adjusting the micropillar height, diameter, and bending angle, as well as superhydrophobic chemical treatment, the contact angle and adhesive force of water droplets on the micropillar-textured surfaces can be tuned from 117.1 degrees up to 165 degrees and 15.4 up to 200.6 mu N, respectively. Theoretical analysis suggests a well-defined wetting-state transition with respect to the micropillar size and provides a clear guideline for microstructure design for achieving a stabilized superhydrophobic region. Droplet handling devices, including liquid handling tweezers and gloves, were fabricated from the micropillar-textured surfaces, and lossless liquid transfer of various liquids among various surfaces was demonstrated using these devices. The superhydrophobic surfaces serve as a microreactor platform to perform and reveal the chemical reaction process under a space-constrained condition. The superhydrophobic surfaces with self-assembled micropillars promise great potential in the fields of lossless droplet transfer, biomedical detection, chemical engineering, and microfluidics.

Automated summary

This article investigates rose-petal-like superhydrophobic surfaces with strong water adhesion. By assembling self-grown micropillars on shape-memory polymer sheets, the surface adhesion can be finely tuned. The contact angle and adhesive force of water droplets can be adjusted by controlling the height, diameter, bending angle, and chemical treatment of the micropillar-textured surfaces. Various droplet handling devices were fabricated from these surfaces, enabling lossless liquid transfer among different surfaces. These superhydrophobic surfaces have great potential in microfluidics, biomedical detection, chemical engineering, and lossless droplet transfer.