Magnetowetting and Sliding Motion of a Sessile Ferrofluid Droplet in the Presence of a Permanent Magnet

Nguyen, Nam‐Trung; Zhu, Guiping; Chua, Yong Chin.; Phan, Vinh-Nguyen; Tan, Say Hwa

doi:10.1021/la101474e

Cited by 128 publications

(114 citation statements)

References 26 publications

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“…These effects have been applied for various microfluidics applications including smart actuation of droplets and micro-droplets [1][2][3][4][5][6][7][8]. A smart actuation of droplets deposited on nano-structured surfaces is of particular interest.…”

Section: Mathematics Subject Classification: 76t10mentioning

confidence: 99%

Contact Angles of Sessile Droplets Deposited on Rough and Flat Surfaces in the Presence of External Fields

Bormashenko

2012

Math. Model. Nat. Phenom.

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Abstract. The paper proposes a general framework allowing the analysis of wetting problems in the situation when interfacial tensions depend on external fields. An equation predicting apparent contact angles of sessile droplets deposited on rough surfaces in the presence of external fields is derived. The problem of wetting is discussed in the framework of the variational approach. Derivation of a general equation generalizing the Cassie and Wenzel approaches is presented. The effects related to the line tension which are important for nano-structured surfaces are considered. Keywords and phrases: electrowetting, dependence of interfacial tensions on external fieldsCassie and Wenzel models, line tension, excess free energy variation, transversality conditions Mathematics Subject Classification: 76T10The phenomena of electro-magneto-and optowetting have attracted the attention of researchers recently. These effects have been applied for various microfluidics applications including smart actuation of droplets and micro-droplets [1][2][3][4][5][6][7][8]. A smart actuation of droplets deposited on nano-structured surfaces is of particular interest. Krupenkin et al demonstrated the dynamic electrical control of the wetting behavior of liquids on nanostructured surfaces, which spans the entire possible range from superhydrophobic behavior to nearly complete wetting [4]. Electro-, magneto-and optowetting techniques exploit the dependence of interfacial tensions on external fields [7]. A general approach to the calculation of contact angles of droplets deposited on flat surfaces in the presence of external fields is given in Ref. [9]. Below, a general theoretical framework is presented, which allows calculation of apparent contact angles of droplets deposited on a rough surface and exposed to an external field. The Cassie and Wenzel models [10][11][12][13] are believed to give the theoretical background of wetting of rough surfaces. The Wenzel model implies the complete wetting of a rough surface, i.e. liquid penetrates into grooves constituting the surface; whereas the Cassie wetting describes the situation where a droplet partially wets the rough surface and sits on air pockets [10][11][12][13]. The Wenzel and Cassie models helped to explain a considerable diversity of wetting phenomena occurring on rough surfaces. However, these models have been criticized recently and gener-

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Section: Mathematics Subject Classification: 76t10mentioning

confidence: 99%

Contact Angles of Sessile Droplets Deposited on Rough and Flat Surfaces in the Presence of External Fields

Bormashenko

2012

Math. Model. Nat. Phenom.

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“…A promising alternative to electrowetting [97] to achieve active control of the drop motion relies on the use ferrofluids in the presence of external magnetic fields [98][99][100][101][102][103][104][105]. Ferrofluids along with a magnetic field that locks them in place form magnetic slippery surfaces with no required micro/nano fabrication more icephobic than standard LIS [106].…”

Section: Discussionmentioning

confidence: 99%

Drop mobility on chemically heterogeneous and lubricant-impregnated surfaces

Mistura

2017

Advances in Physics: X

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Controlling the motion of liquid drops in contact with a solid surface has broad technological implications in many different areas ranging from textiles to microfluidics and heat exchangers. The wettability of a surface is determined by specifying the apparent contact angle and contact angle hysteresis (CAH) that depend on the surface chemistry and morphology. The presence of chemical inhomogeneity and morphological disorder usually increases CAH. A liquid substrate, whose surface is atomically flat and homogenous, is then expected to exhibit a very low CAH. Low CAH determines high drop mobility, while high CAH favours drop pinning. Very slippery surfaces with exceptional omniphobicity are obtained by impregnating a textured solid with a lubricant. To guide and control the motion of drops, the solid surface can be decorated with suitable chemical patterns. In this review, we briefly outline the main results obtained in the past few years to passively control drop motion and produce robust omniphobic surfaces, highlighting some of the most promising applications of these novel functional surfaces.

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“…A key design constraint in electrowetting, however, is that there must be direct electrical contact between the substrate and droplet. In contrast, magnetic fields offer the possibility of non-intrusively modifying droplet contact angles, and indeed ferrofluids have been widely demonstrated to dramatically alter their contact angle and undergo a variety of instabilities in response to sufficiently strong magnetic fields [498,499].…”

Section: Wetting Of Surfacesmentioning

confidence: 99%

Template-based syntheses for shape controlled nanostructures

Pérez-Page

et al. 2016

Advances in Colloid and Interface Science

136

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A variety of nanostructured materials are produced through template-based synthesis methods, including zerodimensional, one-dimensional, and two-dimensional structures. These span different forms such as nanoparticles, nanowires, nanotubes, nanoflakes, and nanosheets. Many physical characteristics of these materials such as the shape and size can be finely controlled through template selection and as a result, their properties as well. Reviewed here are several examples of these nanomaterials, with emphasis specifically on the templates and synthesis routes used to produce the final nanostructures. In the first section, the templates have been discussed while in the second section, their corresponding synthesis methods have been briefly reviewed, and lastly in the third section, applications of the materials themselves are highlighted. Some examples of the templates frequently encountered are organic structure directing agents, surfactants, polymers, carbon frameworks, colloidal sol-gels, inorganic frameworks, and nanoporous membranes. Synthesis methods that adopt these templates include emulsion-based routes and template-filling approaches, such as self-assembly, electrodeposition, electroless deposition, vapor deposition, and other methods including layer-by-layer and lithography. Templatebased synthesized nanomaterials are frequently encountered in select fields such as solar energy, thermoelectric materials, catalysis, biomedical applications, and magnetowetting of surfaces.

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Magnetowetting and Sliding Motion of a Sessile Ferrofluid Droplet in the Presence of a Permanent Magnet

Cited by 128 publications

References 26 publications

Contact Angles of Sessile Droplets Deposited on Rough and Flat Surfaces in the Presence of External Fields

Contact Angles of Sessile Droplets Deposited on Rough and Flat Surfaces in the Presence of External Fields

Drop mobility on chemically heterogeneous and lubricant-impregnated surfaces

Template-based syntheses for shape controlled nanostructures

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