Foolproof Method for Fast and Reversible Switching of Water-Droplet Adhesion by Magnetic Gradients

Self Cite

113

103

Smart manipulation of liquid/bubble transport has garnered widespread attention due to its potential applications in many fields. Designing a responsive surface has emerged as an effective strategy for achieving controllable transport of liquids/bubbles. However, it is still challenging to fabricate stable amphibious responsive surfaces that can be used for the smart manipulation of liquid in air and bubbles underwater. Here, amphibious slippery surfaces are fabricated using magnetically responsive soft poly(dimethylsiloxane) doped with iron powder and silicone oil. The slippery gel surface retains its magnetic responsiveness and demonstrates strong affinity for bubbles underwater but shows small and switching resistance forces with the water droplets in air and bubbles underwater, which is the key factor for achieving the controllable transport of liquids/bubbles. On the slippery gel surface, the sliding behaviors of water droplets and bubbles can be reversibly controlled by alternately applying/removing an external magnetic field. Notably, compared with slippery liquid-infused porous surfaces, the slippery gel surface demonstrates outstanding stability, whether in air or underwater, even after 100 cycles of alternately applying/removing the magnetic field. This surface shows potential applications in gas/liquid microreactors, gas-liquid mixed fluid transportation, bubble/droplet manipulation, etc.

Section: Resultssupporting

confidence: 81%

Magnetocontrollable Droplet and Bubble Manipulation on a Stable Amphibious Slippery Gel Surface

Guo

Wang

Heng

et al. 2019

Self Cite

113

103

“…[85,86] As reported by Lee et al, when an MR elastomer film was subjected to a magnetic field, its surface roughness changed accordingly. [84] MR Gels: Different from the MR elastomers, the polymer network in an MR gel is swollen by a low-viscosity solvent, which significantly decreases the surface friction against droplet motion. [81] Figure 8e shows that on an MR elastomer surface containing 60 wt% carbonyl iron particles, a magnetic field of 250 mT could induce a significant increase of water contact angle from 100° to 160° accompanying a drastic decrease of sliding angle from 180° to 10°, attributed to the magnetic-field-induced roughening of the surface.…”

Section: Magnetic Surfaces With Switchable Roughnessmentioning

confidence: 99%

“…However, a relatively Adv. [84] For normal electromagnets without cooling systems, the accessible magnetic field is even weaker. Mater.…”

Section: Ferrofluid-infused Surfacesmentioning

confidence: 99%

“…Magnetic-field-induced change of water contact angle and sliding angle, switching between slippery state and pinned state [51,81,84] MR elastomer with switchable local topology (dent or ridge)…”

Section: Droplet-based Microfluidics and Microreactorsmentioning

confidence: 99%

“…[84,106,107] For example, Yang et al fabricated a superhydrophobic surface with a dense array of magnetic micropillars for controlling droplet adhesion. Such property can be used to capture and release droplets, enabling transferring droplets from one surface to another.…”

Section: D Droplet Operationmentioning

confidence: 99%

See 2 more Smart Citations

Magnetoresponsive Surfaces for Manipulation of Nonmagnetic Liquids: Design and Applications

Zhou

Huang

Tian

2019

Magnetic actuation provides a remote, nondestructive, and real-time way for controllable liquid manipulation, which has promising technological applications for areas ranging from digital microfluidics, biochemical assays, and microreactors, to liquid collection. However, conventional magnetic liquid manipulation usually relies on incorporating magnetic particles into a liquid to empower its motion in response to an external magnetic field, resulting in considerable limitations of magnetic actuation in various applications. Recently, a range of magnetoresponsive surfaces (MRSs) with elaborately designed surface structures and/or compositions have enabled on-demand liquid manipulation using magnetic fields, even when the liquids do not contain any magnetic particles. Here, the state-of-the-art of MRSs capable of manipulation of nonmagnetic liquids is reviewed. Their preparation, different manipulation modes, including directed propulsion, spreading, and rebound, and the underlying working mechanisms are discussed. Based on the working principles, MRSs are classified into three categories, including surfaces with magnetic bendable microstructures, surfaces with switchable topographies, and surfaces infused with ferrofluids. Their applications in microfluidics, microreactors, liquid distributors and pumps, fog collection, and anti-icing are presented. Finally, key challenges and the future prospects of MRSs are provided.

Recent Progress on the Development of Magnetically‐Responsive Micropillars: Actuation, Fabrication, and Applications

Wang

2023

Stimuli-responsive micro-pillared structures can perform complex and precise tasks at the microscale through dynamic and reversible deformation of the pillars in response to external triggers. Magnetic field is one of the most common actuation strategies due to its incomparable advantages such as instantaneous response, remote and nondestructive control, and superior biocompatibility. Over the past decade, many researches are attempted to design and optimize magnetically-responsive micropillars for a wide range of applications and great progresses are accomplished. In this review, the most important aspects of recent progress of magnetically-responsive micropillars are covered to give a comprehensive and systematical introduction to this new field, from the actuation mechanisms, fabrication methods, and deformation patterns to the practical applications. The increasingly maturing fabrication techniques can provide low-cost and large-scale magnetic micropillars with homogeneous responses. Some advanced techniques are developed to fabricate micropillars with programmable and reprogrammable responses for site-specific and reconfigurable actuations. On the other hand, practical applications for particle/droplet/light manipulation, flow generation, miniature swimming/climbing/carrying microrobots, tunable adhesion, cellular probe, fog collector, and anti-ice surfaces are also summarized. Finally, current challenges that limit the industrial implementation are discussed and the authors' perspectives on the future directions of magnetically-responsive micropillars are stated.