Substrate‐Independent Microdroplet Transport via Simple Superhydrophobic Tweezers

Abstract Liquid droplet transfer is important for a wide range of applications, such as medical diagnostics, drug delivery, and microchemical reactors. Superhydrophobic surfaces have been used for droplet transfer. However, existing droplet‐transfer techniques remain substrate‐dependent or rely on special materials and complex external controls, greatly limiting their usability in various applications. In this study, a substrate‐independent droplet transfer technique based on simple materials and facile actuation mechanisms is developed by transforming common tweezer tips superhydrophobic using femtosecond laser processing. The tweezer tip superhydrophobicity and adhesion strength are controlled by varying the laser processing parameters and optimized through a machine learning‐assisted approach. In addition to the altered tweezer tip adhesion strength, the adhesion force can be controlled in real‐time by varying the tip separation. The superhydrophobic tweezers can transfer various types of liquids, including water and various biomedical solutions, over a wide range of volume (1–35 µL), independent of the substrate. The tweezers can make volume‐selective transfer or multiple‐droplet simultaneous transfer with no content loss or cross‐contamination (<0.01 parts per billion). The superhydrophobic tweezers provide a simple, cost‐effective, and highly versatile solution for droplet transfer, with significant potential applications in pharmaceutical manufacturing, biomedical diagnostics, and biological research systems.