March 11, 2013


 Complex fluids

A substantial part of recent activity in our group deals with complex fluids, such as polymeric fluids. These polymeric fluids often have a strong non-Newtonian character. Here our lasting contribution is to the discovery of phenomena of ‘bacterial streamers’; later generalized to ‘colloidal streamers’ by our group. The manuscripts related to this phenomena are:

I. Biswas, A. Kumar and M. Sadrzadeh, “Microfluidic membrane filtration systems to study biofouling”, Microfluidics and Nanofluidics, Editor: M. S. Kandelousi, Intechopen (2018)

I. Biswas,M. Sadrzadeh, A. Kumar, “”Impact of bacterial streamers on biofouling of microfluidic filtration systems”, Biomicrofluidics, 12, 044116 (2018)

I. Biswas, R. Ghosh, M. Sadrzadeh, A. Kumar, “Near wall void growth leads to disintegration of colloidal bacterial streamer”, Journal of Colloid and Interface Science, 522,249-255 (2018) (Pre-print available at

N. Debnath, M. Hassanpourfard, R. Ghosh, J. Trivedi, T. Thundat, Mohtada Sadrzadeh,A. Kumar, “Abiotic streamers in a microfluidic system”, Soft Matter,13, 8698-8705 DOI: 10.1039/c7sm01771e, (2017) (Pre-print available at (Back-Cover Art)

M. Hassanpourfard, R. Ghosh, T. Thundat, A. Kumar, “Dynamics of bacterial streamers induced clogging in microfluidic devices”, Lab on a Chip, 16, 4091-4096 (2016) (Back-Cover Art)

I. Biswas, R. Ghosh, M. Sadrzadeh, A. Kumar, “Nonlinear deformation and localized failure of bacterial streamers in creeping flows”, Scientific Reports, 6, 32204 (2016)(Article highlighted by

M. Hassanpourfard, Z. Nikakhtari, R. Ghosh, S. Das, T. Thundat, Y. Liu and A. Kumar*, “Bacterial floc mediated rapid streamer formation in creeping flows”, Scientific Reports, 5, 13070 (2015) (Also available at arXiv:1504.00098) (Article highlighted by

M. Hassanpourfard, X. Sun, A. Valiei, P. P. Mukherjee, T. Thundat, Y. Liu, A. Kumar, “Protocol for biofilm streamer formation in a microfluidic device with micro-pillars”, Journal of Visualized Experiments, 90, e51732 (2014)

S. Das, A. Kumar, “Formation and post-formation dynamics of bacterial biofilm streamers as highly viscous liquid jets”, Scientific Reports, 4, 7126 (2014) (Also available at arXiv:1312.6056)

A. Valie, A. Kumar, P. P. Mukherjee, Y. Liu, T. Thundat, “A web of streamers: biofilm formation in a porous microfluidic device”, Lab-on-a-chip, 12 , 5115 (2012) (featured as HOT article )


Development of electrokinetic platforms is another area of research in our group. We have played a foundational role in the development of a new field of research in electrokinetics that has is being referred to as ‘opto-electrofluidics’ or ‘opto-electric’ techniques. Opto-electric techniques combine optics and electrokinetics synergistically to achieve control over matter at the micro and nano length scales.Our lab discovered an electrothermal tweezer that is named ‘Rapid Electrokinetic Patterning’ or REP. Manuscripts relating to REP are:

H-S. Chuang, H-Y. Ku, F-T. Li, A. Kumar, J-C. Wang and K-C. Wang, “Optoelectrokinetic manipulation for cell analysis”, Essentials of Single Cell Analysis, Editors: F-G. Tseng and T. S. Santra, Springer (2016)

K-C Wang, A. Kumar, S.J. Williams, N.G. Green, K.C. Kim and H-S. Chuang, “An optoelectrokinetic technique for programmable particle manipulation and bead-based biosignal enhancement”, Lab on a Chip, 14, 3958 (2014) (Back Cover Article)

J-S Kwon, S. P. Ravindranath, A. Kumar , J. Irudayaraj, S. T. Wereley, “Opto-electrokinetic manipulation technique for high-performance on-chip biological assay”, Lab-on-a-chip, 12 , 4955 (2012) (Cover Art Article ;also listed in ‘Top 10%’ Articles in Nov 2012; Highlighted by Nature Photonics, 7, 12 (2012))

H-S. Chuang, A. Kumar , S J. Williams, S. T. Wereley, “Optoelectrically-Enabled Multiscale Manipulation”, Encyclopedia of Nanotechnology, Editor: B. Bhushan, Springer, New York (2012)

A. Haque and A. Kumar, “Hybrid opto-electric techniques for molecular diagnostics”, Expert Review of Molecular Diagnostics, 12 , 9 (2012) (Invited Editorial )

A. Kumar , H-S. Chuang, S. T. Wereley, “Dynamic manipulation by light and electric fields: micrometer particles to microliter droplets”, Langmuir, 26 , 7656 (2010)

A. Kumar , J-S. Kwon, S. J. Williams, N. G. Green, N. K. Yip and S. T. Wereley, “Optically modulatedelectrokinetic manipulation and concentration of colloidal particles near an electrode surface”, Langmuir, 26 , 5262 (2010)

S. J. Williams, A. Kumar , N. G. Green and S. T. Wereley, “Optically induced electrokinetic concentration and separation of colloids”, J. Micromechanics and Microengineering, 20 , 015022 (2010) (IOP Select; also Highlights of 2010 Paper )

S.J. Williams, A. Kumar , S.T. Wereley, “Optically induced electrokinetic patterning and manipulation of particles”, Phys. Fluids, 21 , 091104 (2009) (Top 20 monthly most downloaded – October 2009 )

S. J. Williams, A. Kumar , N. G. Green and S. T. Wereley, “A simple, optically induced electrokinetic method to concentrate and pattern nanoparticles”, Nanoscale, 1 , 133 (2009)

A. Kumar , S. J. Williams and S. T. Wereley, “Experiments on opto-electrically generated microfluidic vortices”, Microfluidics and Nanofluidics, 6 , 637(2009)

S. J. Williams, A. Kumar and S. T. Wereley, “Electrokinetic patterning of colloidal particles with optical landscapes”, Lab-on-a-chip, 8 , 1879 (2008)

 Bacterial dynamics

Our research focuses understanding bacterial dynamics and its inter-relationship with hydrodynamics. Specifically, we are currently using biomicrofluidics to investigate bacterial biofilms. Biofilms are an aggregative surface associated state of bacteria that are relevant to diverse disciplines including human health and the environment.


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