Light-Fueled Submarine-Like Droplet.

Flexibly and precisely manipulating 3D droplet transportation is a fundamental challenge for broad implications in diagnostics, drug delivery, bioengineering, etc. Herein, a light method is developed for manipulating a droplet to make it behave like a submarine. This light method enables flexible 3D transportation, stable suspension, and floating of a droplet, which can be freely altered. It is demonstrated that the localized photothermal effect induced thermocapillary flow in the water droplet/oil phase is responsible for energizing and manipulating the droplet. With such remarkable motility, the light-fueled submarine-like droplet successfully realizes various functions such as the acid-base detection, particle capture and transportation, and target crystal collection, dissolution and transportation. It is demonstrated that the light-fueled submarine-like droplet shows promising perspective for long-sought precise droplet manipulation in various applications.