Dependence of Phoretic Propulsion of Sub-Micron Urease Motors on the Fraction of the Particle Covered by Catalyst

TL;DR

This study investigates how the surface coverage of urease enzyme on micro/nano motors influences their propulsion speed, revealing a peak velocity near 50% enzyme coverage and highlighting design considerations for efficient nanoscale propulsion.

Contribution

It demonstrates the effect of enzyme coverage percentage on propulsion velocity of urease motors, providing insights into optimal design for enhanced motility.

Findings

Propulsion velocity increases with enzyme coverage up to 50%.

Velocity trend may reverse at lower enzyme coverage levels.

Limitations in constructing motors with very low enzyme coverage.

Abstract

Micro/Nano motors are micro to nano-sized particles and systems that are capable of motion in fluidic systems. Their motion can be a result of many mechanisms, one of the most well-known of which is electrolyte diffusiophoresis, in which asymmetric production of charged ions across the surface of the particle leads to phoresis. The focus of this work is to construct Urease motors with careful control of their Janus balance, i.e., to control the percentage of surface covered with the enzyme and study the effect of this asymmetry on the propulsion velocity of the particles. In that regard, we were successful in constructing particles with varied coating percentages. The observation made was that as the percentage coating approaches 50%, the propulsion velocity of the particle increases steadily. The trend may reverse at lower catalytic cap heights after reaching a certain threshold of enzyme activity and per cent coverage. However, the method used had limitations in constructing motors with lower catalytic cap heights. We aim to shed light on the design principles of efficient urease-driven phoretic motors, which could have significant implications for the development of next-generation nanoscale devices.