Small is the New "BIG"

We, at the Microscale Transport Processes (MTP) lab, theorize, formulate, design, experiment and model the dynamics of several interfacial phenomena with a focus on the final applications. Since, most of these dynamics are apposite to the micro-scale, our expertise lies in specifically fabricating systems, the dimensions of which are in the order ranging from few nanometers to several micrometers. Our research is highly diverse, encompassing droplets, thin liquid films, liquid crystals at one end, and proteins (HSA and BSA), and more recently blood and plasma proteins at the other end. A brief description of our work is as follows:

Microfluidics:

1. Droplet Microfluidics:

Dynamics of droplets have been investigated by subjecting them to AC and DC electrical field of differing magnitudes, providing applications in hot-spot cooling and protein fibrillation. Droplet movement has also been studied and analyzed over chemically-induced gradient surfaces, providing an impetus-free droplet movement. These studies have also been corroborated with molecular dynamic simulations, providing an in-depth visualization of the pertinent phenomena. Moreover, the dual functionalities of superhydrophobicity and adhesion of a rose petal are investigated by soft-lithographically replicating the structures of the petal. Also, an innovative method has been designed for transforming an elastomeric film in to a highly adhesive surface without sacrificing its wetting characteristics, via creation of wrinkles on the elastomeric film surface. In addition, micro/nano wrinkled surfaces are also being fabricated by various mask-less and stamp-less fabrication methods. Also, their wetting characteristics are studied by varying parameters like mechanical strain and softness etc. These wrinkled surfaces with tailored topography have advantages in droplet manipulation, cell adhesion and proliferation, with an added functionality in sorting of the colloidal particles, etc.

i. M. Chakraborty, R. Anand, P. Srinivasa Rao, S. Sen and S. DasGupta, Oscillating Nanofluid Droplets for Micro-cooling", Sensors & Actuators: B. Chemical, DOI information: 10.1016/j.snb.2016.06.145, 239, 562-570, 2017.

ii. M. Chakraborty, A. Chowdhury, R. Bhusan, S. DasGupta, Molecular Dynamics Study of Thermally Augmented Nano-Droplet Motion on Chemical Energy Induced Wettability Gradient Surfaces, Langmuir, 31 (41), pp 11260–11268, 2015.

iii. M. Chakraborty, U. Ghosh, S. Chakraborty, S. DasGupta Thermally Enhanced Self-Propelled Droplet Motion on Gradient Surfaces, RSC Advances, 5, 45266–45275, 2015.

2. Liquid Crystals and Crack Suppression:

Crack formation in thin colloidal films is detrimental to products like surface coatings. To circumvent the same, we propose a unique additive – nematic liquid crystal (NLC) droplet that suppresses crack formation and produces crack-free films. This additive can be recovered easily after the process of crack suppression has taken place.

3. Thin Liquid Films:

The work includes studying the dynamics of thin liquid films (TLF’s), subject to various modes of perturbation including thermal, electric and magnetic. A recent work regarding the effect of magnetic body-force on the dynamics of thin liquid films provided a novel and highly promising alternative, towards a non-intrusive mode of TLF manipulation. The dynamics could be used for applications in Point of Care (PoC) diagnostic systems and towards development of lab on chip devices in general.

i. S. Tenneti, S. G. Subramanian, M. Chakraborty, G. Soni, S. DasGupta, Magnetowetting of Ferrofluidic Thin Liquid Films, Scientific Reports, Article number: 44738, DOI: 10.1038/srep44738, 2017.

ii. U. Ghosh, M. Chakraborty, S. De, S. Chakraborty and S. DasGupta, Contact line Dynamics during Evaporation of Extended Colloidal Thin Films: Influence of Liquid Polarity and Particle Size, Langmuir, 32 (48), 12790–12798, 2016.

iii. M. Chakraborty, R. Chatterjee, U. Ghosh, S. DasGupta, Electrowetting of Partially Wetting Thin Nanofluid Films, Langmuir, 31 (14), 4160–4168, 2015.

4. Micro-channel based flow control and modeling:

Cell micro-patterning and cell sorting has important applications in the development of biosensors and lab-on-a-chip devices, tissue engineering and fundamental cell biology studies. The colloidal self assembly and lattice formation is observed inside a micro-channel of varying its width. The flow inside the channel is achieved via capillary flow by altering the hydrophilicity of the channel. These fundamental studies can further help in sorting of diseased RBCs from healthy RBCs based on their shapes and sizes.

i. A. Sett, U. Bano, D. Sarkar, A. Mitra, S. Das, S. Dasgupta, S. DasGupta, Capillary Driven Flow in Wettability altered Microchannel, AIChE, DOI:10.1002/aic.15787, 2017.

ii. K. Raj, S. DasGupta, S. Chakraborty, Hydrodynamics in Deformable Microchannels, Microfluidics and Nanofluidics, 21(4), 70, DOI: 10.1007/s10404-017-1908-5, 2017.

Bio-Microfluidics:

1. Protein Fibrillation:

Coffee-ring effect could be used as a tool in diagnostic assays to enhance the sensitivity of biomarker detection at the ring position. Protein drying pattern in presence of polystyrene beads have been undertaken. It has been observed that, for a particular type of nanoparticle the drying pattern changes, depending on the nature of protein. The variation in the drying pattern can be used to quantify protein fibrillation.

i. S. Sen, M. Chakraborty, S. Goley, S. Dasgupta, S. DasGupta, Fibrillar Disruption by AC Electric Field Induced Oscillation: A Case Study with Human Serum Albumin, Biophysical Chemistry, 226, 23–33, 2017.

ii. S. Sen, S. Dasgupta, S. DasGupta, Does Surface Chirality of Gold Nanoparticles Affect Fibrillation of HSA?, The Journal of Physical Chemistry, Part C, Accepted for publication, 2017

iii. S. Bag, A. Sett, S. DasGupta and S. Dasgupta, Hydropathy: the controlling factor behind the inhibition of Ab fibrillation by graphene oxide, RSC Adv., 6, 103242–103252, 2016.

2. Blood and Plasma Proteins:

Red blood cells (RBCs) are the major cellular components of blood (~ 45% by volume). In the present study, RBC-laden blood droplets are subjected to natural evaporation over substrates possessing different functional groups. The process of evaporation/ drying of these droplets are monitored using real time optical microscopy to outline the kinetics of RBC deformation as a function of substrate property. Based on these experimental results, a deformation index specific to variation in substrate property can be formulated, leading to effective disease identification, without the need for any complex analytical procedures.