Abstract
Catalytic colloidal swimmers that propel due to self-generated fluid flows exhibit strong affinity for surfaces. Here, we report experimental measurements of a significant dependence of such microswimmers' speed on the nearby substrate material. We find that speeds scale with the solution contact angle θ on the substrate, which relates to the associated hydrodynamic substrate slip length, as V∝(cosθ+1)^{-3/2}. We show that such dependence can be attributed to osmotic coupling between swimmers and substrate. Our work points out that hydrodynamic slip at nearby walls, though often unconsidered, can significantly impact microswimmer self-propulsion.
Highlights
Colloidal swimmers constitute a new class of nonequilibrium model systems that hold great promise for applications owing to their fast directed motion in liquid environments
We find that speeds scale with the solution contact angle θ on the substrate, which relates to the associated hydrodynamic substrate slip length, as V ∝ ðcos θ þ 1Þ−3=2
Experimental observations hint at non-negligible substrate effects on the speed of synthetic swimmers [16,17,18]
Summary
Colloidal swimmers constitute a new class of nonequilibrium model systems that hold great promise for applications owing to their fast directed motion in liquid environments. Slip Length Dependent Propulsion Speed of Catalytic Colloidal Swimmers near Walls Upon approaching a surface, numerical and theoretical models predict both an increase or decrease in swimming speed depending on the considered propulsion mechanism and the physicochemical properties of the swimmer and wall [9,10,11,12,13,14,15].
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