A Microfluidic Tool for Fine-Tuning Motion of Soft Micromotors

Microfluidics is an ideal tool for the design of self-assembled micromotors. It allows for easy change of solutions, catalysts, and flow rates, which affect shape, structure, and motion of the resulting micromotors. A microfluidic tool generating aqueous-two-phase-separating droplets of UV-polymerizable poly(ethylene glycol)diacrylate (PEGDA) and an inert phase, salt, or polysaccharide, is utilized to fabricate asymmetric microbeads. Different molecular weights and branching of polysaccharides are used to study the effect on shape, surface roughness, and motion of the particles. The molecular weight of the polysaccharide determines the roughness of the motors inner surface. Smooth openings are obtained by low molecular weight dextran, while high surface roughness is obtained with a high molecular weight branched polysaccharide. Since roughness plays an important role in bubble pinning, it influences both speed and trajectory. Increasing speeds are obtained with increasing roughness and trajectories ranging from linear, circular to tumble-and-run depending on the nature of bubble pinning. This microfluidic tool allows for fine-tuning shape, structure, and motion by easy change of solutions, catalysts, and flow rates.