Towards Differentiation in Untethered Microactuators: A Soft Fabrication Strategy.

Abstract

This work describes a microfluidic high-throughput fabrication method for untethered soft microactuators which, while initially unspecific, develop distinct shapes, surface textures, and actuation modes based on various environmental cues. Analogous to the core concept of cell differentiation, the central idea of this technique is to apply controlled mechanical and chemical stimuli to a deformable hydrogel fiber and transmit the induced geometrical and textural changes to embedded droplets. Using liquid crystal (LC) monomer droplets as a core allows us to orthogonally program the geometric, textural, and molecular architecture of the resulting microactuators upon droplet polymerization. Fine-tuning of the microfluidic parameters yields microdroplets that dry and transform into microparticles with a variety of shapes, including spindle, rod, pancake, dumbbell, pyramid, and worm-like assemblies with a range of aspect ratios. Leveraging mechanical instability via rapid dehydration of hydrogel fibers allows us to generate and impart stable 3D patterns to the core, resulting in microparticles that vary both in global shape and surface texture. After polymerizing these precursor droplets in a magnetic field to encode the mesogenic orientation, LCE microactuators are realized with a rich library of shapes, surface patterns, and molecular structures, each displaying distinct deformations upon heating, validated via finite element analysis.