Investigations of water droplet formation on conical micromanipulation probe at microscale

The liquid droplet is usually adopted as the vehicle to pick micro-objects during micromanipulation tasks, and the conical manipulation probe is constantly employed as the capillary micromanipulation tool. We focus on investigations on water droplet on conical micromanipulation probe during air-cooled condensation. Mathematical models of microdroplet formation, including initial droplet formation, droplets coalescence and droplets motion, were established to analyze critical parameters. Parameter of the degree of subcooling that dominates the minimum radius and the growth rate of individual droplet was theoretically characterized. Accordingly, the process of droplet formation on a conical probe was simulated based on mathematical modeling. Subsequently, extensive experiments, with the assistance of a customized cooling module, were conducted to investigate the droplet formation on conical probes. The experimental results indicate that microdroplets formed on the conical probe during air-cooled condensation. A stable droplet was obtained via initial droplet formation, droplets coalescence and droplets motion. Droplet formation is various because of implementations of conical probe with varied apex angles and shapes, which directly influence the microdroplet formation.