My background is in the area of biotechnology and molecular biology. As my research project, I want to build/design platforms for detection/quantification of biochemicals by employing microfluidics technology. The goal in long run is miniaturizing various detection and quantification techniques for bringing down the cost and making their handling simpler. 

Spray dryer is used in many industrial processes in the food, cosmetics, detergent, and pharmaceutical industries. The spray dryer dries colloidal droplets and delivers dry granules made of colloidal particles. During the drying of the colloidal droplets in the spray dryer, shrinkage of the droplets takes place due to evaporation. When compressive capillary stress is less than the shell strength, the shell shrinkage will stop. Evaporation will be induced by the small thickness of the shell, and the packed shell will be converted into a hollow shell. When shell capillary pressure is higher than the critical pressure, the hollow shell will buckle into other morphologies like doughnut-like or deflated balloons, and it is undesirable for certain industrial applications. The final dried granules morphology is dependent on drying conditions and the mechanical and physical properties of the particles. To control the morphology of drying particles, it is important to understand the influence of the mechanical properties of the drying droplet, the effect of ingredients (polymer or salt), and the process condition in a spray dryer. The purpose of this research is to understand the buckling phenomenon and the factors needed for controlling the morphology of shell in terms of mechanical stability and colloidal interaction of nanoparticles.

4th year PhD student (ChE)

B.Tech (2016)- Pandit Deendayal Petroleum University

Email: anwesha1398 at gmail.com

Controlled drug release through oral osmotic systems

The controlled release (CR) drug delivery systems release drugs in a controlled manner that maintains the plasma concentration within the therapeutic range, which is impossible in conventional drug delivery systems. There are three types of CR drug delivery systems- reservoir, matrix, and osmotic-based.  Out of these systems, only osmotic-based drug delivery systems provide an added advantage of delivering drugs independent of pH and other external factors. These systems are pretty helpful for the treatment of chronic diseases. The drug release profile is governed by zero-order kinetics, ensuring constant and controlled drug delivery. This drug release profile is affected by several factors, including core formulation factors (like drug dosing, amount and location of osmogent, etc.), solubility, osmotic pressure, coating thickness, etc. Understanding these factors becomes crucial when we try to increase the drug dosing in the tablet to reduce further the number of times the patient takes the drug. 

3rd year Ph.D. student

BS-MS Chemical Engineering (2022) – IISER Bhopal

Email: viplav1024 at gmail.com

Adhesion of polymers in pharmaceuticals

The phenomenon of adhesion holds substantial importance within the pharmaceutical industry. Typically, in all solid oral dosage forms of medications, a coating is applied to provide the tablet's core mechanical strength. This process also serves to mask the odour and taste of the drug to enhance patient compliance, as well as to enhance the tablet's appearance. Furthermore, this coating plays a critical role in packaging and storage, thereby extending the tablet's shelf life. Therefore, ensuring adequate adhesion between the tablet core and the polymer coating is crucial for achieving optimal coating in solid dosage forms. Conventionally, adhesive strength is assessed using techniques such as peel tests, scratch tests, and probe tests. However, by considering the physical and chemical properties of both the substrate and the polymer coating, it is possible to predict adhesion, potentially eliminating the need for adhesion tests.

PhD Student (2023-)

Research Assistant: City University of Hong Kong, Dept. of Neuroscience (2018-2020) 

M.Tech (Biomedical Engineering) - Indian Institute of Technology(BHU), Varanasi  (2016-2018) 

B.Tech (Biomedical Engineering) - National Institute of Technology, Rourkela (2012-2016)

Development of Biomedical Devices and Liposome based drug delivery systems

My research focuses on a portable 5-part flow cytometer at affordable cost and its downstream application in detection and biosensing. It includes the system's compactness and comparable performance to commercial instruments. Moreover, I'm interested in spectral flow cytometry which enables better detection of fluorophores in the samples which can spatially differentiate light based on wavelength. 

I am also interested in developing small unilamellar liposome-based drug delivery systems that focus on delivering small molecules such as iron and calcium using a colloidal packed bed system. These are needed to cater to the Indian anemic patient diaspora with oral supplementation having side effects from the current oral medication regime.

My Google Scholar link for publications: https://scholar.google.com/citations?user=oHXS-fcAAAAJ&hl=en

My work broadly envelopes areas in microfluidics, physics and applications in biomedical engineering. The commercial flow cytometers, which are highly efficient in performing a myriad of tests and medical diagnosis, are, however, very expensive, bulky and not manufactured in India. This may pose a limit to research and diagnosis in a country like ours. The project aims at building an in-house flow cytometer with necessary electronics and data acquisition system capable of performing clinical diagnosis and research. During my doctoral research at IIT Bombay, I tackled biomedical challenges by creating cost-effective solutions, such as an in-house flow cytometer and a unique smearing method to measure viscosity with minimal sample volumes, the same technique used in screening anemia and sickle cell anemia.

Atomization is a process which involves transformation of bulk liquid into tiny droplets and has diverse applications including spray combustion, spray drying, nebulizers etc. In this work, we have studied the atomization of a radially expanding thin liquid sheet formed by impingement of a liquid jet on a circular impactor in ambient conditions. Sheet thickness decreases as we move away from the centre, and with decreasing sheet thickness, growth rates of the disturbances increases, till the waves reach a critical amplitude. This is when the sheet becomes unstable, and breaks down in ligaments (primary atomization), which further breaks into droplets (secondary atomization). It may be noted that the formation of droplets are not only after formation for ligaments, but can also occur directly from the liquid sheet and we get an array of different drop sizes. As important it is to understand the physical aspect of drop formation, it is also important to study and control the drop size distribution, which is the main focus of the present work.

Thin coatings of polymer films find numerous industrial applications in the formation of protective and functional coatings. These coatings are initially wet, and then evaporation of the solvent leads to the solidification of the film. This solidification process is often accompanied by shrinkage of the film. The strong adhesion between the film and substrate prevents the contraction of the film in the transverse direction, whereas it can freely shrink in the normal direction. This constraint shrinkage in the plane of coating develops transverse stresses in the film. If these stresses exceed a critical value, the polymer film may fracture, thereby compromising the integrity of the film. On the other hand, a weak adhesion between the film and substrate leads to the debonding of the film instead of cracking. The occurrence of cracks during drying of polymer films makes the drying process very complex, and it is crucial to understand this mechanism to get the crack-free films. 

During drying, the colloidal film shows crack when the generated tensile stresses reach critical stress. Cracking causes the limitation of these colloidal films in paints, ink, ceramic industry, coating of tablets, cosmetics products, and cracks in mud/clay. To understand the dynamics of this crack and effects of micro-structural details like particle size, shape, modulus, and nature of packing on it is a subject of work. The derived model predicts the crack speed at which a crack propagates in thin drying colloidal film, close to experimental values. 

My research project is on bacterial chemotaxis. The main focus of my study is to elucidate the behaviour of the bacterial flagellar motor in presence of different attractants. The widely accepted fact is that chemotaxis is regulated by the change in the motor bias until recently. We have shown using E. coli as a model organism that besides the change in bias, motor speed is also modulated in response to certain ligands. The two main ligands used in the study are Glucose and its non-metabolisable analogue, 2Dg, both of which are sensed by the Trg receptor present on the bacterial membrane. Interestingly, speed modulation in response to sensing takes place via stator recruitment, the exact mechanism however remains a mystery. Thus, we can say that bias change along with speed modulation make the phenomenon of chemotaxis more efficient. 

My research is in the area of foams and emulsions with a focus towards the role of particles in stabilizing interfaces. Investigating the interaction of colloidal particles with the fluid-fluid interface is always fascinating from experimental point of view. Further, these experimental observations help researchers in theorizing intricate phenomena taking place at the particle-fluid interface. Also, the stability of water in oil and oil in water emulsions can be understood and addressed thermodynamically. 

E. coli swims in viscous fluid with the help of peritrichous flagella bundled together and rotating in a counter-clockwise direction. The directional rotation is dictated by the nano-meter sized motor present at the base and is the current chemotaxis paradigm. My research is about characterizing the response of the flagellar motor to a metabolizable attractant such as glucose and its non-metabolizable analogue 2-deoxy-glucose. These sugar ligands are sensed by the transmembrane Trg receptor and metabolized by the phospho-transferase pathway. With the help of dark-field microscopy techniques, the swimming velocity of the population is measured and correlated with the single-cell tethered experiments. The tethered cell experiment gives a direct measurement of the change in motor speed and rotational direction of the individual cell. Such analysis is performed on Wild-type, and mutant strains that have key proteins deleted to study the interplay between different pathways. Our experiments from fluorescent microscopy also reveal that ligand sensing impacts the flagellar bundle geometry deferentially on sensing different ligands. This work will help us understand how bacteria fine tunes its motility under nutrient limitation condition and the underlying mechanism.

Stresses in drying coatings are critical to the understanding of various failure mechanisms in them. One may obtain good predictions for these stresses by correctly modeling the drying phenomenon and the coating materials. Currently, we are developing various theoretical models for both the drying phenomenon and the coating materials. The drying coatings' rheological properties, which change over time, play a crucial role in the drying process and, hence, the stresses developed. Measuring these properties during drying is difficult. We are working on a measurement technique to obtain the realtime rheological properties of the drying coatings. 

Drying of polymer film and stress growth on soft substrate has fascinating applications in cosmetics, electronics industry. The polymer film is dried in different environmental conditions on soft, flexible substrates and stretched uni-axially under different strain conditions. The film has a tendency to crack depending upon the Young’s Modulus of substrate and film. Simultaneously, due to compressive strain in the lateral direction, the film shows buckling instability and wrinkling, delamination-buckling phenomena may occur. This understanding is necessary to determine the mechanical strength of materials and to select an appropriate film-substrate composition for various applications. 

Modeling the stress development in polymer coatings:

Drying stress, Failure stress and Adhesion

Polymer coatings on various substrates with different elastic moduli undergo transverse stresses in the plane of the film upon evaporation of the solvent. If the tensile stresses exceed the tensile strength of the coating material, the film may crack or de-bond. Hence, understanding the drying stresses in polymer coatings is essential to safeguard the coatings against specific failure mechanisms such as cracking, delamination, or debonding. The objective of my work is to accurately measure the drying stress and assess the mechanical and adhesion properties of polymer coatings. Furthermore, the goal is to develop comprehensive mathematical models that precisely describe the process of film formation in polymer coatings. These models will incorporate the properties of the polymer and the solvent, allowing for the determination of concentration variation and stress development in the drying film.

Blood cell count is essential in evaluating an individual's overall health and detect variety of conditions and diseases. In India, where major fatalities occur due to diseases such as dengue, cell count especially platelets holds a high significance. Our aim is to develop a low cost device that gives us precise blood cell count using a drop of blood. It is based on the principle of Coulter counter and impedance measurement. Commercially available bench top blood counters are expensive and not portable owing to big sizes. We target at building a compact, portable and inexpensive device that can provide precise data essentially benefitting healthcare services in rural India.