Droplet Micro-Robotic System with Generality of Liquid Types and Biocompatibility

The flexible and deformable nature of micro soft robots offers an alternative for transporting soft, fragile or microscale materials. Among them, droplet robots, based on their fluidity, are capable of adaptively navigating through tortuous environments with physical obstacles, as well as carrying and transporting biological/chemical samples of interest for medical diagnostics, drug development, and chemical/material synthesis. However, different target samples will require different droplets environments that serve as their carrier. For example, living cells require specific buffers as carriers to maintain biological activity, while some water-soluble nanoparticles need to be transported in organic fluids. Therefore, a robotic system that is compatible with a variety of organic/inorganic liquids and the carried bio/chemical samples needs to be developed. Here, we propose a multi-physics droplet robotic system that can actuate various liquids through a movable electrostatic field. In particular, the droplet-driven unit is composed of a hybrid of electret and magnetic materials. The electret section which carries electrostatic charge can generate a non-uniform electrostatic field that polarizes and attracts the droplet, while the magnetic section can be controlled under a programmed localized electromagnetic field. In our work, the droplet robotic system demonstrates a high compatibility with droplet volume (nL-mL), liquid types (inorganic/organic), and samples carried by the droplet (living cells/proteins/nanoparticles), thus providing a general hardware platform for delivering a wider range of different biological/chemical samples in an automated manner.