#Light blue gradient series
Utilizing these dynamics, a series of artificial soft-matter robots on the micro- or nanoscale powered by chemical fuels have been reported. Central to the realization of stimuli-directed motility is the evocation of an out-of-equilibrium state within the colloidal body, such as via chemical concentration gradients or physical triggering events. Many of these applications rely on the ability to control, program, configure, and direct the motion of microswimmers as opposed to exhibiting random Brownian motion 10. Artificial microswimmers have further garnered considerable interest for potential applications in drug and cargo delivery, biosensing, environmental remediation, precise manipulation of objects, including in medical surgery or manufacturing, as well as to study complex emergent properties arising from the interaction of stimuli-responsive multibody systems such as swarm behavior 4, 5, 6, 7, 8, 9. Such bodies can act as artificial model systems to better understand the fundamental mechanisms of inter-colloidal communication within biological systems. The design of artificial microswimmers that can undergo an externally triggered or spontaneously induced chemotactic motion targets the design of bodies that can emulate the autonomous behavior observed within natural systems 2, 3. Directional chemotactic locomotion represents a key feature of inter-colloidal communication and cooperation, and as such provides a fundamental mechanism for Nature’s ability to design adaptive chemo-mechanical feedback networks 1. Striking examples of this autonomous behavior include white blood cells that use their unique chemotactic ability to search, sense, and react to external insults and thereby fundamentally contribute to our body’s inflammatory response. Cells, for instance, are capable of interacting with and responding to small changes in their chemical environment by translating specific chemical recognition events at their surface into an oriented chemotactic motion. This has implications for the design of smart and adaptive soft microrobots that can autonomously regulate their response to changes in their chemical environment by chemotactically moving towards or away from a certain target, such as a bacterium.Īutonomous regulation of chemotactic motility represents a fundamental ability of living organisms. Our findings provide insight into how compositional anisotropy can affect the chemotactic behavior of purely liquid-based microswimmers. Regulation of the competitive fluid convections then enables a controllable alteration of the speed and the direction of the droplets’ chemotactic motion. By permanently breaking the symmetry of the droplets’ geometry and composition, externally evoked gradients in surfactant concentration or effectiveness induce anisotropic Marangoni-type fluid flows adjacent to each of the two different exposed interfaces. Our approach is based on using biphasic Janus emulsion droplets, where each phase responds differently to chemically induced interfacial tension gradients. We report, for the first time, a chemotactic motion of emulsion droplets that can be controllably and reversibly altered.