Light, Matter, Action: Shining Light on Active Matter

Abstract

Light carries energy and momentum. It can therefore alter the motion of objects on the atomic to astronomical scales. Being widely available, readily controllable, and broadly biocompatible, light is also an ideal tool to propel microscopic particles, drive them out of thermodynamic equilibrium, and make them active. Thus, light-driven particles have become a recent focus of research in the field of soft active matter. In this Perspective, we discuss recent advances in the control of soft active matter with light, which has mainly been achieved using light intensity. We also highlight some first attempts to utilize light's additional properties, such as its wavelength, polarization, and momentum. We then argue that fully exploiting light with all of its properties will play a critical role in increasing the level of control over the actuation of active matter as well as the flow of light itself through it. This enabling step will advance the design of soft active matter systems, their functionalities, and their transfer toward technological applications.

Microscopic origin of tunable assembly forces in chiral active environments

“…2 The interactions between passive materials immersed in such active matter systems remain poorly understood. Many recent works have sought to explore 3–6 and characterize 7–9 the consequences of an active environment for self-assembly. Experimental active matter systems, including Janus particles 10 and active dumbbells, 11,12 may provide driving forces that stabilize assemblies of passive particles that, in equilibrium conditions, have no propensity to self-assemble.…”

Engineering Light‐Driven Rod‐Shaped Micromotors for Exhibiting Controlled and Tunable Multimode Swimming

“…[ 1–3 ] To date, several kinds of MNMs have been proposed, and their swimming behavior has been studied. To facilitate the autonomous movements of these tiny synthetic cordless machines, various energy sources like light, [ 4–8 ] chemical, [ 9 ] magnetic field, [ 10,11 ] electric field, [ 12–14 ] heat, [ 15,16 ] and acoustic waves [ 17–19 ] have been explored and employed. In addition, synthetic micromotor actuation is also triggered by biological entities like bacteria, muscle cells, sperm, and algae, a phenomenon known as the biohybrid mode of propulsion.…”

Photocharging of Carbon Nitride Thin Films for Controllable Manipulation of Droplet Force Gradient Sensors

“…Various nature-inspired active colloidal systems convert chemical concentration gradients into mechanical energy as a basis to control motile, interactive, and collective behaviors. − Despite broad applications, − available techniques are limited to methods that require elaborate and sophisticated substrate design for surface-encoded transportation schemes, − involve intrusive anisotropic surface modification of colloids, − or require an intensive energy input. − Simple generalizable methods to generate chemical gradients are a compelling scientific need, where a non-destructive, reversible, and selective evocation of spatio­temporally controlled chemical gradients inside a solution has not yet been reported.…”