Imaging the proton concentration and mapping the spatial distribution of the electric field of catalytic micropumps

TL;DR

This study employs fluorescence confocal microscopy and particle tracking to visualize proton concentration and electric field distribution in catalytic micropumps, enhancing understanding of their chemo-mechanical actuation mechanisms.

Contribution

It introduces a combined experimental and numerical approach to map proton gradients and electric fields in catalytic micropumps, revealing their interrelated processes.

Findings

Proton concentration gradients correlate with electric field variations.

Particle motion analysis maps electrostatic potential distribution.

Numerical simulations successfully reproduce experimental observations.

Abstract

Catalytic engines can use hydrogen peroxide as a chemical fuel in order to drive motion at the microscale. The chemo-mechanical actuation is a complex mechanism based on the interrelation between catalytic reactions and electro-hydrodynamics phenomena. We studied catalytic micropumps using fluorescence confocal microscopy to image the concentration of protons in the liquid. In addition, we measured the motion of particles with different charges in order to map the spatial distributions of the electric field, the electrostatic potential and the fluid flow. The combination of these two techniques allows us to contrast the gradient of the concentration of protons against the spatial variation in the electric field. We present numerical simulations that reproduce the experimental results. Our work sheds light on the interrelation between the different processes at work in the chemo-mechanical actuation of catalytic pumps. Our experimental approach could be used to study other electrochemical systems with heterogeneous electrodes.