nn0c03849_si_005.mp4 (23.4 MB)
Droplet Self-Propulsion on Superhydrophobic Microtracks
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posted on 2020-08-06, 22:19 authored by Christos Stamatopoulos, Athanasios Milionis, Norbert Ackerl, Matteo Donati, Paul Leudet de la Vallée, Philipp Rudolf von Rohr, Dimos PoulikakosLiquid
transport (continuous or segmented) in microfluidic platforms
typically requires pumping devices or external fields working collaboratively
with special fluid properties to enable fluid motion. Natural liquid
adhesion on surfaces deters motion and promotes the possibility of
liquid or surface contamination. Despite progress, significant advancements
are needed before devices for passive liquid propulsion, without the
input of external energy and unwanted contamination, become a reality
in applications. Here we present an unexplored and facile approach
based on the Laplace pressure imbalance, manifesting itself through
targeted track texturing, driving passively droplet motion, while
maintaining the limited contact of the Cassie–Baxter state
on superhydrophobic surfaces. The track topography resembles out-of-plane,
backgammon-board, slowly converging microridges decorated with nanotexturing.
This design naturally deforms asymmetrically the menisci formed at
the bottom of a droplet contacting such tracks and causes a Laplace
pressure imbalance that drives droplet motion. We investigate this
effect over a range of opening track angles and develop a model to
explain and quantify the underlying mechanism of droplet self-propulsion.
We further implement the developed topography for applications relevant
to microfluidic platform functionalities. We demonstrate control of
the rebound angle of vertically impacting droplets, achieve horizontal
self-transport to distances up to 65 times the droplet diameter, show
significant uphill motion against gravity, and illustrate a self-driven
droplet-merging process.
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fluid motiondroplet self-propulsionimpacting dropletsDroplet Self-Propulsiondroplet diameterLaplace pressure imbalancerebound anglefluid propertiesself-driven droplet-merging processdroplet motion65 timessuperhydrophobic surfacessurface contaminationopening track anglesmicrofluidic platformsapplicationtrack texturingdevicetrack topographydrives droplet motionSuperhydrophobic Microtracks Liquid...microfluidic platform functionalities
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