Unraveling the physiochemical nature of colloidal motion waves among silver colloids.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35613263.
- Also identified by DOI 10.1126/sciadv.abn9130 and PMC identifier 9132452.
- Licence recorded as CC BY-NC.
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Abstract
Traveling waves are common in biological and synthetic systems, including the recent discovery that silver (Ag) colloids form traveling motion waves in H<sub>2</sub>O<sub>2</sub> and under light. Here, we show that this colloidal motion wave is a heterogeneous excitable system. The Ag colloids generate traveling chemical waves via reaction-diffusion, and either self-propel through self-diffusiophoresis ("ballistic waves") or are advected by diffusio-osmotic flows from gradients of neutral molecules ("swarming waves"). Key results include the experimental observation of traveling waves of OH<sup>-</sup> with pH-sensitive fluorescent dyes and a Rogers-McCulloch model that qualitatively and quantitatively reproduces the key features of colloidal waves. These results are a step forward in elucidating the Ag-H<sub>2</sub>O<sub>2</sub>-light oscillatory system at individual and collective levels. In addition, they pave the way for using colloidal waves either as a platform for studying nonlinear phenomena, or as a tool for colloidal transport and for information transmission in microrobot ensembles.