High Precision Dynamic Manipulations of Large‐Volume‐Range Water‐Based Droplets by a Soft Gripper with Robust Water‐Repellent Superhydrophobic Surface

Abstract

AbstractDroplet manipulation has emerged as a key enabling technology in various scientific and engineering fields with great potentials in advanced applications such as bioanalysis and reagent microreactors. The current strategies generally involve external stimuli or chemical/structural surface gradients to provide the driving force for in plane droplet manipulations, which suffer from low efficiency, poor controllability, and small volume ranges (generally Vmax/Vmin < 10) due to their inherent limitations. Herein, a dynamic gripping based droplet manipulation method is proposed by employing a flexible gripper with a notch covered by superhydrophobic silicon rubber membrane (SRM) between the gripper fingers to dynamically pick up, constrain and release droplets, capable of consecutively manipulating large‐volume‐range (Vmax/Vmin >130) droplets with minimal liquid loss. The robust Cassie‐to‐Wenzel transition (CWT) resistance and mechanical stability of the produced superhydrophobic surface well support the dynamic operations of various droplets, where the superhydrophobic surface presents great water‐repellent performance during stretching and impinging experiments as well as remains superhydrophobicity even after mechanical abrasion against 600 grit SiC sandpaper for 15 m at an applied pressure of 3.2 kPa. Lossless manipulations of 3–180 µL droplets have been experimentally validated, where an application of the proposed method in droplet‐based microreactors for chemical analysis and bioassay is demonstrated.