Magnetically Actuated Superhydrophilic Robot Sphere Fabricated by a Femtosecond Laser for Droplet Steering.

Droplet steering has important applications in biomedical detection, local chemical reactions, liquid collection, and microfluidic control. Presently, droplet steering methods typically require specific paths and can be challenging to operate, involving complex fabrications for the operating systems. Here, we show a magnetically actuated superhydrophilic robot sphere (MSR) based on femtosecond laser direct writing technology for droplet steering. Through femtosecond laser treatment, uniform micro-/nanostructures are constructed on the surface of a MSR. Additionally, the contactless magnetic actuator makes it possible to remotely steer the MSR to transport droplets. After preliminary exploration of the mechanism by which MSR drives the droplet movement, the ability of MSR to control the droplet movement was systematically tested and analyzed. Moreover, the applications of the MSR in complex path liquid collection and transport, three-dimensional space transport, self-cleaning, etc., are further verified. This strategy provides a novel and reliable path for droplet manipulation and broadens its application.