Self-Organization of Microcompartments Powered by Enzyme-Driven Solutal Flows at the Water-Oil Interface

Design of microcompartments capable of self-organization via consumption of energy or fuel to power opposable short-range forces is a step toward realization of adaptive cellular materials capable of intelligent behaviors. Here, we report active microgel compartments (a-MC) containing urease capable of self-organization at the water-oil interface via the regulation of short-range interparticle interactions consisting of urease-powered repulsive solutal flows and attractive capillary forces. The conversion of urea into denser products of ammonia and bicarbonate by urease within the a-MC causes density-driven outward flows leading to repulsive interactions with neighboring a-MCs at the water-oil interface. The modulation of repulsive solutal flows allowed the a-MCs to self-organize into nonclose-packed 2D lattices at high urease activity and 1D chains at low urease activity and high population density. These repulsive solutal flows are fueled by urea, so by limiting the supply of urea, we could achieve disassembly of 2D clusters at high urea concentration and reassembly upon a drop in urea levels. In binary mixtures of active and passive (no urease) microgel compartments, the passive microgel compartments showed increasing orthogonal assembly with a rise in their population density. Immobilization of 2D clusters of a-MCs allowed us to set up long-range collective solutal flows to execute microcompartment cargo logistics and to form fluidic traps for controlling assembly and position of binary/ternary microcompartment clusters for enhanced chemical signaling. Our work presents opportunities for the development of autonomous soft microbots, precision microscale cargo logistics, and intelligent matter.