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Fluid drops covered by particles: Physics and applications

Instituto de Física de Líquidos y Sistemas Biológicos

Fluid drops covered by particles: Physics and applications

Expositor: Mg. Alexander Mikkilsen – Department of Physics, NTNU (Norges Teknisk-Naturvitenskapelige Universitet = Norwegian University of Science and Technology), Norway.

Contacto: alexander.mikkelsen@ntnu.no

Fecha: Miércoles 27/05/2015 – 14:30 hs.

Abstract: You’ve seen Hollandaise sauce or mayonnaise that has separated, or that shiny layer of oil that forms on top of skin cream. This mixture of water and oil is called an emulsion, but it can be difficult to keep emulsions from separating. A special substance called an emulsifier is used to keep the mixture stable and prevent separation. This is an ongoing problem for the food and medical wholesale jerseys from china industries, as well as for oil recovery. In fact, the petroleum industry also has to deal with the opposite problem, which is to separate oil that is pumped up from a well in a mix of water and gas.

Emulsions are generally stabilized by the use of surfactants, but solid particles dissolved in one phase can also stabilize emulsions [1]. This is known as Pickering emulsion. Clay and colloidal particles adsorb strongly at liquid interfaces where they display a wide range of applications [2], for instance to encapsulate materials such as medicine, food or oil, and to produce complex architectures [3]. The talk will show and explain how weakly conductive (leaky-dielectric) drops behave when suspended in another weakly conducive fluid and subjected to an external electric field. Especially how electrohydrodynamic and eletrorheological effects in such drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-field-assisted convective assembly of jammed colloidal “ribbons” (see figure 1, left), electrorheological colloidal chains confined to a two-dimensional surface and spinning colloidal domains.

In addition, the talk will demonstrate the size control of “pupil” like openings in colloidal shells (figure 1, middle) [4], present a simple and robust method to assemble colloidal shells of controlled heterogeneity (figure 1, right) [5] and discuss some of the many applications for particle covered drops.

10 µm sized clay particles forming a ribbon on a silicone oil drop surface (left). Contraction and expansion of a pupil-like colloidal shell (middle). A Janus colloidal capsule consisting of  500 and 1000 nm sized glass and plastic particles (right). Figures from [4] and [5].
10 µm sized clay particles forming a ribbon on a silicone oil drop surface (left). Contraction and expansion of a pupil-like colloidal shell (middle). A Janus colloidal capsule consisting of 500 and 1000 nm sized glass and plastic particles (right). Figures from [4] and [5].

References:

[1] B. P. Binks, Curr. Opin. Colloid In. 7, 21 (2002).

[2] C. Zeng, H. Bissig, and A. D. Dinsmore, Solid State Commun. 139, 547 (2006).

[3] Y. Wang, D. R. Breed, V. N. Manoharan, L. Feng, A. D. Hollingsworth, M. Weck, and D. J. Pine, Nature 491, 51 (2012).

[4] P. Dommersnes, Z. Rozynek, A. Mikkelsen, R. Castberg, K. Kjerstad, K. Hersvik, and J. O. Fossum, Nat. Commun. 4, 2066 (2013).

[5] Z. Rozynek, A. Mikkelsen, P. Dommersnes, and J. O. Fossum, Nature communications 5 (2014).

L@s esperamos a partir de las 11.15 hs con café y facturas!

 

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