Controllable Three-Dimensional Well-Like Asymmetric Meniscus for Multiphase and Multimode Particle Manipulation

The magnetic manipulation of multiphase particles has garnered worldwide attention in diverse fields due to its high penetration, rapid response, and nondamaging advantages. However, the type of manipulatable particles and the accuracy of manipulation are limited by the current lack of knowledge of the micronano interface mechanism. Here, we observed a well-like asymmetric meniscus (WAM) automatically created around a tilted microneedle, enabling the trapping of various particles, including droplets and bubbles. The trap force arises from the horizontal differences in the interface tension induced by the meniscus height gradient, which is greatly impacted by the structural and kinematic parameters conjointly. By controlling the tilt direction, the tilt angle, and the distance between both microneedles in the array, versatile manipulation strategies for multiphase particles were proposed, such as capture-release, rotation, and directional transport. The experimental results demonstrated that bubble movement acceleration increased by over 900% when the meniscus height was raised by 70%. The WAM has a high application potential in microchemical reactions, multiphase particle classification, and beyond.