Remote Manipulation of Droplets on a Flexible Magnetically Responsive Film.

Jeong Hun Kim,Moon Kyu Kwak,Byung Jun Lee,Seong Min Kang,Won-Gyu Bae,Kahp Yang Suh,Hangil Ko,Hoon Eui Jeong

doi:10.1038/srep17843

Abstract

The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces. Although a variety of droplet manipulation techniques have been proposed, active, fast and reversible manipulation of pure discrete droplets remains elusive due to the technical limitations of previous techniques. Here, we describe a novel technique that enables active, fast, precise and reversible control over the position and motion of a pure discrete droplet with only a permanent magnet by utilizing a magnetically responsive flexible film possessing actuating hierarchical pillars on the surface. This magnetically responsive surface shows reliable actuating capabilities with immediate field responses and maximum tilting angles of ~90°. Furthermore, the magnetic responsive film exhibits superhydrophobicity regardless of tilting angles of the actuating pillars. Using this magnetically responsive film, we demonstrate active and reversible manipulation of droplets with a remote magnetic force.

Highlights

The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces
The coating of carbon nanoparticles (CNPs) over the arrays resulted in magnetically actuating hierarchical pillar arrays with superhydrophobicity
This is because the CNP coating creates nanoscale roughness over the surface of the micropillars, resulting in micro- and nanoscale combined hierarchical structures. These hierarchical architectures enable the array to maintain reduced contact with the droplet and a superhydrophobic wetting state regardless of the bending angle of the pillar arrays. These results indicate that a discrete droplet would not wet these self-assembled hierarchical pillar arrays even when the arrays are actuating under a magnetic force, which may enable active and reversible manipulation of a droplet on the pillar arrays

Summary

Introduction

The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces. We describe a novel technique that enables active, fast, precise and reversible control over the position and motion of a pure discrete droplet with only a permanent magnet by utilizing a magnetically responsive flexible film possessing actuating hierarchical pillars on the surface. This magnetically responsive surface shows reliable actuating capabilities with immediate field responses and maximum tilting angles of ~90°. We report a novel technique that enables active and dynamic control over the position and motion of a pure discrete droplet by utilizing a magnetically responsive flexible film comprising reversibly actuating hierarchical pillars on the surface. Using this novel magnetically responsive film with a superhydrophobic nature, we demonstrate highly precise and dynamic manipulation of a discrete droplet in an active and instant manner using only a permanent magnet

Methods

Results

Conclusion