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Selected Works

Aloke Kumar

2012

Articles 1 - 6 of 6

Full-Text Articles in Nanoscience and Nanotechnology

Optically Induced Electrokinetic Patterning And Manipulation Of Particles, Stuart Williams, Aloke Kumar, Steven Wereley Feb 2012

Optically Induced Electrokinetic Patterning And Manipulation Of Particles, Stuart Williams, Aloke Kumar, Steven Wereley

Aloke Kumar

The ability to easily and dynamically control fluid mo- tion as well as manipulate particles in suspension is impor- tant for the development and characterization of a variety of lab-on-a-chip processes. Recently, we have introduced an op- tically induced electrokinetic technique termed rapid electro- kinetic patterning (REP) that can rapidly concentrate, trans- late, and pattern colloids of many different sizes and compositions. We have tested polystyrene, latex, and silica beads in sizes ranging from 49 nm to 3.0 um.1,2

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Optically Modulated Electrokinetic Manipulation And Concentration Of Colloidal Particles Near An Electrode Surface, Aloke Kumar, Jae-Sung Kwon, Stuart J. Williams, Nicolas G. Green, Nung Kwan Yip, Steven Wereley Feb 2012

Optically Modulated Electrokinetic Manipulation And Concentration Of Colloidal Particles Near An Electrode Surface, Aloke Kumar, Jae-Sung Kwon, Stuart J. Williams, Nicolas G. Green, Nung Kwan Yip, Steven Wereley

Aloke Kumar

We study a recently demonstrated AC electrokinetic technique for manipulation and concentration of colloidal particles on an electrode surface. The technique uses indium tin oxide (ITO)-based parallel-plate electrodes on which highly localized infrared (1064 nun) laser illumination is shone. We show that the highly localized laser illumination leads to a highly nonuniform heating of the electrode substrate, which in turn drives an electrothermal microvortex resulting in a rapid transport of particles toward the illuminated site. Hundreds of polystyrene particles, with diameters ranging from 2.0 to 0.1 mu m, suspended in a low conductivity solution (2.0 mS/m) could be aggregated at …

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Dynamic Manipulation By Light And Electric Fields: Micrometer Particles To Microliter Droplets, Aloke Kumar, Han-Sheng Chuang, Steven Wereley Feb 2012

Dynamic Manipulation By Light And Electric Fields: Micrometer Particles To Microliter Droplets, Aloke Kumar, Han-Sheng Chuang, Steven Wereley

Aloke Kumar

We demonstrate a new hybrid optoelectric technique that can manipulate objects across several length scales. The technique leverages a variety of different physical mechanisms to achieve the dynamic manipuladon old roplets and also the in situ concentration of colloidal particles suspended in the droplets. Various physical mechanisms such as optoelectrowetting, electrothermal flows, and ac electroosmosis are leveraged through different modes of operation of the device. Each operational mode, which is activated through die proper combination of an applied ac bias and the illumination used, is characterized by the ability to manipulate objects on a certain length scale. We also demonstrate …

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Hybrid Opto-Electric Manipulation In Microfluidics-Opportunities And Challenges, Aloke Kumar, Stuart Williams, Han-Sheng Chuang, Nicolas Green, Steven Wereley Feb 2012

Hybrid Opto-Electric Manipulation In Microfluidics-Opportunities And Challenges, Aloke Kumar, Stuart Williams, Han-Sheng Chuang, Nicolas Green, Steven Wereley

Aloke Kumar

Hybrid opto-electric manipulation in microfluidics/nanofluidics refers to a set of methodologies employing optical modulation of electrokinetic schemes to achieve particle or fluid manipulation at the micro-and nano-scale. Over the last decade, a set of methodologies, which differ in their modulation strategy and/or the length scale of operation, have emerged. These techniques offer new opportunities with their dynamic nature, and their ability for parallel operation has created novel applications and devices. Hybrid opto-electric techniques have been utilized to manipulate objects ranging in diversity from millimetre-sized droplets to nano-particles. This review article discusses the underlying principles, applications and future perspectives of various …

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Electrokinetic Patterning Of Colloidal Particles With Optical Landscapes, Stuart J. Williams, Aloke Kumar, Steven T. Wereley Feb 2012

Electrokinetic Patterning Of Colloidal Particles With Optical Landscapes, Stuart J. Williams, Aloke Kumar, Steven T. Wereley

Aloke Kumar

We demonstrate an opto-electrokinetic technique for noninvasive particle manipulation on the surface of a parallelplate indium tin oxide (ITO) electrode that is biased with an alternating current (AC) signal and illuminated with nearinfrared (1064 nm) optical landscapes. This technique can generate strong microfluidic vortices at higher AC frequencies (>100 kHz) and dynamically and rapidly aggregate and pattern particle groups at low frequencies (<100 kHz).

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Experiments On Opto-Electrically Generated Microfluidic Vortices, Aloke Kumar, Stuart Williams, Steven Wereley Feb 2012

Experiments On Opto-Electrically Generated Microfluidic Vortices, Aloke Kumar, Stuart Williams, Steven Wereley

Aloke Kumar

Strong microfluidic vortices are generated when a near-infrared (1,064 nm) laser beam is focused within a microchannel and an alternating current (AC) electric field is simultaneously applied. The electric field is generated from a parallel-plate, indium tin oxide (ITO) electrodes separated by 50 lm. We present the first l-PIV analysis of the flow structure of such vortices. The vortices exhibit a sink-type behavior in the plane normal to the electric field and the flow speeds are characterized as a function of the electric field strength and biasing AC signal frequency. At a constant AC frequency of 100 kHz, the fluid …

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