Magnetically tunable self-assembly of colloidal rings

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2010-08-23

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Abstract

We present a technique using ferrofluid to induce bidisperse suspensions of superparamagnetic and diamagnetic beads to assemble into colloidal ring configurations. The separation distance between particles within the ring can be tuned by adjusting the ferrofluid concentration, which has the effect of enhancing the effective dipole moment of one of the components while screening the dipole moment of the other, leading to a wealth of different ring configurations. © 2010 American Institute of Physics.

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10.1063/1.3483137

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Li, KH, and BB Yellen (2010). Magnetically tunable self-assembly of colloidal rings. Applied Physics Letters, 97(8). p. 83105. 10.1063/1.3483137 Retrieved from https://hdl.handle.net/10161/3358.

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Yellen

Benjamin Yellen

Associate Professor in the Department of Mechanical Engineering and Materials Science

Yellen's group is interested in developing highly parallel mechanisms for controlling the transport and assembly of ensembles of objects ranging from micron-sized colloidal particles to single cells.  As of 2013, Professor Yellen is active in two main areas of research:
1) Development of single cell analysis tools using magnetic circuits. The goal of this project is to develop an automated single cell analysis platform that allows for highly flexible and highly parallel manipulation of single cells. Our approach draws inspiration from electronic circuit theory through the development highly flexible methods for transporting particles above magnetic thin film patterns either reversibly (conductor) or irreversibly (rectifier), storing cells in well-defined regions of space either temporarily (capacitor) or permanently (data storage), switching current pathways at selected junctions (transistor) and coordinating a large set of electronic functions with few input wires (multiplexer). When combined with microfluidic systems that allow for repeated doses of pharmaceuticals, we will have a developed a platform that is ripe to have a major impact on the field of HIV eradication and cancer suppression.
2) Multiparticle assembly of colloidal crystals. The goal of this project is to understand the formation and phase transitions occuring inside single crystals composed of alloys of colloidal particles.  Here, we are interested in observing crystals forming from magnetic and non-magnetic colloidal particles dispersed inside ferrofluid.  We are just beginning to solve the questions of how to grow large single crystals, and how to transform these crystals by tilting of an external magnetic field.  The results of this project will serve as useful models for understanding how crystals form and transform in the corollary atomic scale materials in nature.


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