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Micro Nano Bio-Fluidics group

Research

Our research spans the areas of Interfacial Microfluidics, Lab on Chip Technology, and Nanofluidics. Our interests lie in the fundamental understanding of the dynamics of fluid streams, interfaces, droplets, particles, and cells and energy transport at the micro/nanoscale. We are equally committed to utilizing the fundamental principles and techniques for the development of Lab on Chip technology for applications related to healthcare, energy, and water.

The topics are synergic and serve towards the common objective of the CoE, to excel in the MNBF research domain and evolve as one among the top-most groups in the area, globally. The fundamental understanding of the dynamics of fluid streams, interfaces, particles, droplets, and cells at microscale inside microchannels and on open surfaces, and energy transport at the solid-fluid interface are studied under the Interfacial microfluidics sub-theme. In Nanofluidics research, flow through nanomembranes and dynamics of flows at nanoscales is being investigated. The fundamental principles and techniques developed under Interfacial Microfluidics and Nanofluidics are being applied to the development of Lab on Chip technology for applications related to healthcare, energy, and water.

Interfacial microfluidics

Interfacial microfluidics refers to the transport phenomena at a micro-scale involving fluid-fluid and fluid-solid interfaces. The study of interfacial microfluidics could enrich the fundamental understanding of such phenomena occurring at the interfaces and lead to the development of improved techniques for handling and manipulation of fluid streams, drops, particles, and cells as well as energy transport. A better understanding of the behavior of fluid streams, interfaces, drops, particles, cells, and energy transport at micro-scale have tremendous applications in Lab on Chip, micro total analysis systems, liquid handling, and micro-thermal systems.

Acoustofluidics

Acoustofluidics, handling of particles and fluid interfaces using ultrasonic waves has emerged as a powerful tool in the recent past due to its inherent nature of gentle, precise, and contactless manipulation. Two types of waves, namely bulk and surface acoustic waves can be employed to perform manipulations. Bulk acoustic waves (BAW) can be generated using piezoelectric transducers. Bulk acoustic standing waves can be produced in a channel by adjusting the frequency of the wave with respect to the channel dimensions. Surface Acoustic waves (SAW) can be generated using an array of inter digitated electrodes patterned on a piezoelectric substrate. Both traveling surface acoustic waves (TSAW) and standing surface acoustic waves (SSAW) can be employed for the manipulation of particles and fluid interfaces.

Magnetofluidics

Magnetofluidics, manipulation of particles and fluid interfaces using a magnetic field, has emerged as a powerful tool in the recent past due to its inherent nature of contactless actuation, low energy requirement, and biocompatibility. The technique is versatile and enables the manipulation of both magnetic (ferromagnetic) as well as non -magnetic (diamagnetic) objects. Depending upon the nature of the objects to be manipulated, the technique can be classified into positive and negative magnetofluidics. When the magnetic susceptibility of the medium is less than that of the object, the motion of the object is toward the maximum magnetic field and the technique is known as positive magnetofluidics. Similarly, when the magnetic susceptibility of the medium is more than that of the object, the motion of the object is toward the minimum magnetic field and the technique is termed negative magnetofluidics .

Capillarity and wettability

Liquid manipulation on open surfaces has a broad range of applications starting from electronic chip cooling to Lab-on-a-chip and point-of-care diagnostics. A better understanding of the behavior of the liquid on an open surface is essential for optimizing the method of liquid manipulation. Generally, a droplet/liquid can be manipulated on an open surface with the help of external energy, whereas it is also possible to manipulate a droplet passively. Few passive droplet manipulation techniques are 1) By creating a gradient of wettability on the surface either by creating texture gradient (physical) or by creating energy gradient (chemical) on the surface, and, 2) By creating shape gradient surface. The droplet moves on such surfaces due to the Laplace pressure difference across the droplet. We are currently working on optimizing such open surface passive droplet manipulation techniques using both numerical simulation and experiments.

Surface engineering

Surface engineering is a fascinating aspect of the wettability manipulation of surfaces. Engineering of surfaces can be done in micro-scale, nano-scale, or the mix of two which is known as a hierarchy. The energy of a surface can be controlled by manipulating the surface morphology. We are working on the fabrication of a superhydrophobic coating that is biocompatible and, can also be used for energy harvesting. Along with that, we are also working on wettability patterning using chemical treatment, laser ablation, and lithography techniques to manipulate droplet/liquid on open surfaces.

Nanofluidics

Research directed towards understanding the structural and dynamical properties of organic and polar fluids confined to nanoscale channels has provided a major impetus to the field of fluid mechanics. Pioneering research in nanofluidics reported with great excitement that the various features of a nanochannel, such as its pore size, length, roughness, and morphology greatly influence the transport characteristics of the fluid. The nanoconfinement effects and the interfacial dynamics can be exploited in the development of novel devices beneficial in blue energy harvesting, water desalination, electronic cooling, hydrogen storage, drug delivery, etc [78-86]. Limited theoretical understanding of the physics of nanoscale fluid flows in promising carbonaceous materials like graphene, carbon nanotubes, and boron nitride nanotubes have been achieved using molecular dynamics (MD) computations and few experiments.

Lab on chip technology

Advances in the field of micro nanotechnology have led to the development of miniaturized devices called Lab on Chip (LOC). LOC technology facilitates the integration of several laboratory functions on a single integrated device (chip) of only millimeters to a few square centimeters to achieve biochemical assays. LOC technology has tremendous potential in healthcare and environmental sensing. The use of LOC in healthcare fosters affordability due to the low cost of reagents and chemicals involved owing to the small sample volume requirement. Ease of use and reliability due to the automation via integration with control systems/electronics makes this technology widely accessible. As part of the CoE, one of our goals is to develop novel techniques for the rapid measurement of blood-based biomarkers and cell-based assays. Specifically, our immediate focus is to develop a microfluidic platform for the measurement of gasotransmitters in blood for early prediction of sepsis, which is a global healthcare challenge and the phenotyping, isolation, and analysis of circulating tumor cells (CTCs) in single cell format for improved cancer prognosis, towards personalized therapy.

Blood based markers

Early detection of systemic inflammatory response syndrome (SIRS) helps in managing sepsis and minimizing its adverse effects in patients. Gaseous signaling molecules also referred to as gasotransmitters, play a vital role in the process of inflammation. The concentration of these compounds gives crucial information about the state of inflammation. Thus, the change in the level of such gasotransmitters in patients’ blood is a prognostic marker of sepsis. We have developed a microfluidic device that utilizes fluorimetry for the continuous monitoring of the concentration of different gasotransmitters such as H2S, H2O2 , NO and CO in patients’ blood. We have also integrated the optofluidic detection device with a microfluidic plasma separation unit for on-chip blood cell separation and sepsis detection for use in clinical settings.

Cell based assays

Single-cell analysis has emerged as a powerful method for genomics, transcriptomics, proteomics, and metabolomics characterisation at the individual cell level. Here, we demonstrate a technique for the detection and selective isolation of target cells encapsulated in microdroplets in single-cell format. A sample containing a mixed population of cells with fluorescently labelled target cells can be focused using a sheath fluid to direct cells in single file toward a droplet junction, wherein the cells are encapsulated inside droplets. The droplets containing the cells migrate toward the centre of the channel owing to non-inertial lift force. The cells present in the droplets are studied and characterised based on forward scatter (FSC), side scatter (SSC), and fluorescence (FL) signals. The FL signals from the target cells can be used to activate a selective isolation module based on electro-coalescence, using suitable electronics and a program to sort droplets containing the target cells in single-cell format from droplets containing background cells.

Sensing of chemicals

We also plan to develop paper-based LOC sensors for detecting contaminants in milk. Milk adulteration is a grave and significant problem now in developing countries. According to a report of FSSAI (Food Safety and Standard Authority of India) in 2019, 41% (in 2018, it was 70%) of milk produced in India is adulterated. Nowadays, urea, melamine, detergents, boric acid, formalin, ammonium sulfate, caustic soda, starch, sugars, hydrogen peroxide, soaps, caramel, and many other harmful substances are added to milk to contaminate it. Lack of strict enforcement laws and the unavailability of quick and easy detection techniques are the major bottleneck for fixing this issue. Good quality milk can be determined based on fat percentage, SNF (Solid Not Fat) value, protein content, etc. For improving these parameters, adulterants are added to milk to serve various purposes . Here, we plan to identify the common adulterants using a LOC technique comprising of a paper-based device. In the future, we will generalize the device to identify contaminants in other liquid food/beverages, for example, syrup, wines, etc.