Patterned Substrates Unlock Self-Electrophoretic Phenomenon in Active Janus Microswimmers
Abstract
Inert colloids half-coated with platinum (Pt) are a standard model of chemically powered active particles, yet the microscopic origins of their propulsion in hydrogen peroxide (H2O2) remain difficult to dissect experimentally. Whereas self-diffusiophoresis was the prevailing theory, self-electrophoresis has been more recently suggested as the main mechanism of propulsion. According to the latter mechanism, the pole-to-equator Pt-thickness gradient produced by directional metal deposition is sufficient to create anodic and cathodic regions on the metal cap and thereby generate an electric field sustained by H2O2 decomposition. Enhancing self-propulsion performance of such particles thus requires precise control over the Pt thickness distribution, which is currently not achievable with standard methods (e.g. evaporation or sputtering). Here, we propose a method to fabricate Janus active particles by assembling silica microspheres on patterned substrates containing spherical grooves whose depth and spacing set the degree of particle coating while simultaneously suppressing proximity-led defects (Pt bridges). The resulting particles exhibit a tunable platinum-thickness contrast, as verified by Focused-Ion-Beam cross-sections. In 2.5% H2O2, our results suggest that this control can significantly increase propulsion efficiency, while providing evidence indirectly supporting the hypothesis that self-electrophoresis is the dominant mechanism. These results demonstrate that our patterned-substrate route can enhance control over the catalyst deposition and enable novel Janus morphologies, allowing for more precise engineering of active colloids.
Related
- Microswimmers lose by swimming selfishly
- Tunable asymmetric swimming in biflagellate microswimmers
- Transverse transport of microswimmers in oscillatory channel flows
- Valence-Selective Electrophoretic Transport in Neutral Carbon Nanotubes
- The effects of hydrodynamic interactions on the swimming velocity and stability of a swarm of microswimmers
BibTeX
@misc{sharma2026patterned,
title = {{Patterned Substrates Unlock Self-Electrophoretic Phenomenon in Active Janus Microswimmers}},
author = {Jyoti Sharma and Yashpal Singh Brar and Omar Tricinci and Paola Parlanti and Mauro Gemmi and Stefano Palagi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03605},
eprint = {2609.03605},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03605},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Patterned Substrates Unlock Self-Electrophoretic Phenomenon in Active Janus Microswimmers
AU - Jyoti Sharma
AU - Yashpal Singh Brar
AU - Omar Tricinci
AU - Paola Parlanti
AU - Mauro Gemmi
AU - Stefano Palagi
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03605
UR - https://arxiv.org/abs/2609.03605
AB - Inert colloids half-coated with platinum (Pt) are a standard model of chemically powered active particles, yet the microscopic origins of their propulsion in hydrogen peroxide (H2O2) remain difficult to dissect experimentally. Whereas self-diffusiophoresis was the prevailing theory, self-electrophoresis has been more recently suggested as the main mechanism of propulsion. According to the latter mechanism, the pole-to-equator Pt-thickness gradient produced by directional metal deposition is sufficient to create anodic and cathodic regions on the metal cap and thereby generate an electric field sustained by H2O2 decomposition. Enhancing self-propulsion performance of such particles thus requires precise control over the Pt thickness distribution, which is currently not achievable with standard methods (e.g. evaporation or sputtering). Here, we propose a method to fabricate Janus active particles by assembling silica microspheres on patterned substrates containing spherical grooves whose depth and spacing set the degree of particle coating while simultaneously suppressing proximity-led defects (Pt bridges). The resulting particles exhibit a tunable platinum-thickness contrast, as verified by Focused-Ion-Beam cross-sections. In 2.5% H2O2, our results suggest that this control can significantly increase propulsion efficiency, while providing evidence indirectly supporting the hypothesis that self-electrophoresis is the dominant mechanism. These results demonstrate that our patterned-substrate route can enhance control over the catalyst deposition and enable novel Janus morphologies, allowing for more precise engineering of active colloids.
ER -