Programmable, Spatiotemporal Control of Colloidal Motion Waves via Structured Light

Abstract

Traveling waves in a reaction-diffusion system are essential for long-range communication in living organisms and inspire biomimetic materials of similar capabilities. One recent example is the traveling motion waves among photochemically oscillating, silver (Ag)-containing colloids. Being able to manipulate these colloidal waves holds the key for potential applications. Here, we have discovered that these motion waves can be confined by light patterns and that the chemical clocks of silver particles are moved forward by reducing local light intensity. Using these discoveries as design principles, we have applied structured light technology for the precise and programmable control of colloidal motion waves, including their origins, propagation directions, paths, shapes, annihilation, frequency, and speeds. We have also used the controlled propagation of colloidal waves to guide chemical messages along a predefined path to activate a population of micromotors located far from the signal. Our demonstrated capabilities in manipulating colloidal waves in space and time offer physical insights on their operation and expand their usefulness in the fundamental study of reaction-diffusion processes. Moreover, our findings inspire biomimetic strategies for the directional transport of mass, energy, and information at micro- or even nanoscales.

Steering Micromotors via Reprogrammable Optoelectronic Paths

“…Light of appropriate wavelength is needed to activate the substrate. Finally, a device capable of generating dynamic light patterns is needed, such as the digital micromirror device (DMD) used in this work or a specialized projector used in our recent work. , More details of the experimental setup can be found in the Methods, as well as in ref .…”

Light, Matter, Action: Shining Light on Active Matter

“…(b) Structured light can guide the motion waves among photochemically activated colloids. Adapted from ref . Copyright 2022 American Chemical Society.…”

Light, Matter, Action: Shining light on active matter

“…68 Furthermore, structured light has been used to guide traveling motion waves among photochemically-activated oscillating colloids. 148 Silver chloride (AgCl) particles in dilute hydrogen peroxide solutions under UV light illumination exhibit both single-particle and collective oscillations in their motion, which arise due to an oscillatory, reversible conversion of AgCl to silver metal at the particle's surface. 149 These motion waves can be guided by spatial light patterns, thus enabling a precise and programmable control over the motion waves' origin, path and direction (Fig.…”

“…6b). 148 In biological systems, structured UV light enabled the creation of defined 3D spatio-temporal chemical landscapes by releasing caged chemoattractants, which were used to investigate the chemotactic navigation mechanism of sperm (Fig. 6c).…”