I have been involved in the development and application of computational methods for studying interfacial systems at molecular scales. Here, I describe my current, past and planned future research projects, respectively. Please feel free to contact me regarding any questions or opinions about my research. I have classified my current projects into the following themes: 1) Interfacial phenomena associated with the motion at nanoscale, 3) Computational methods to investigate the molecular-scale fluctuations, 3) Connecting molecular scale phenomena to the macroscopic properties, and 4) Energy costs associated with the Chemical Engineering computations.
1. Interfacial phenomena associated with the motion at nanoscale
Understanding the motion of nanoscopic objects is useful for developing new technologies and understanding biological processes. Though an interface may not be strictly defined at the molecular scale, suitable analogies between the molecular-scale systems and “interfaces that exist between phases” can provide useful insights. We are using such analogies to help develop nanofluidic technologies and to understand biological systems that involve motion. Following are our projects in this area:
1.1 Thermodynamic constraints to the motion of a liquid droplet
In this project, we investigate the possibility of translating a liquid droplet on a solid surface by using the periodic changes in a suitable field-variable associated with the system. The field variable can be either temperature, chemical potential of a surface-active compound or an external field. The objective is to identify the thermodynamic constraints on the solid-liquid interface so that the above translation is possible. We start by considering a model of liquid droplet that translates on a solid surface via a quasistatic process. The complete system is exposed to the same field variable λ, which alternates between two values (see the adjacent figure). Different thermodynamic states correspond to the different locations of the liquid droplet along the solid surface. The motion is possible if the free-energy of the system changes as shown in the figure. Since the system is exposed to same conditions, the free-energy will vary only if the nature of the solid surface changes along the direction of the motion. In this project, we are identifying the molecular-scale features of the surface that can lead to such variation.
Students working on the project: Shubham Chouksey, Ashu Gupta and Utkarsh Saxena
1.2 Employing interfacial science to study the motion of biological motors
In this project we are using the tools of statistical mechanics, molecular simulations, and the insights gained from the interfacial systems to understand the operation of biological motors. We are currently focusing on the family of motor proteins called Kinesins that transport substances within the cell by translating along the microtubules (adjacent figure). The alteration of the function of certain Kinesins is associated with neurodegenerative diseases because of their role in the axonal transport. The motor domain (MD) is the part of the Kinesin that is in contact with the microtubule, and also acts as the site for ATP hydrolysis. We are particularly interested in the “interface” between the MD and the microtubule. For example, we are presently studying the role of MD-microtubule adhesion on the speed of the motors. Due to significance of multiple scales, we are using different tools ranging from the stochastic modeling of the complete motor-microtubule system to the molecular simulations of the MD-microtubule interface. Along with our experimental collaborators, we are also looking at the possibility of understanding the molecular-scale processes in the motor proteins by performing select mutations and tracking the motion.
Student working on this project: Atul Sharma, Nashit Jalal
1.3 Temperature dependence of wetting behavior
As discussed in section 1.1 above, we think that there is great scope for exploiting the thermal response of solid-liquid interfacial properties in nanofluidics. Will a drop of liquid spread on a solid surface after increasing temperature? A brief review of literature tells us that the answer is not trivial. It is an interesting scenario where many things – at multiple scales – remain to be understood. Then, there is the challenging design problem: Can we design solid-liquid systems that show the desired thermal response? The technological implications extend beyond the translation of nanodroplets described above. In this project we are employing theoretical and computational methods to study the thermal response of the liquid-on-solid wetting. We are initially using statistical mechanics and molecular simulations to study the temperature dependence of solid-liquid interfacial properties.
Students working on this project: Ishan Arora, Shubham Chouksey and Ashu Gupta
2. Computational methods to investigate the molecular-scale fluctuations
Molecular-scale fluctuations refer to the fluctuations in the positions of atoms and molecules. Such fluctuations are inevitable at finite temperature, and contribute to several macroscopic properties. The above fluctuations can be also characterized by the fluctuations in the density of molecules or atoms in a small region at a particular location in space. We are particularly interested in studying the correlations between density-fluctuations at different positions in space, or those between the fluctuations of atoms or molecules. In this project we are developing computationally efficient techniques to calculate properties that characterize the above fluctuations from molecular simulations. Our goal is to use these techniques to study different interfacial systems described on this page. One application is the study of transverse correlations (TCs) near the solid surface, and their role in the thermal response of wetting (adjacent figure).
Student working on this project: Ishan Arora
3. Connecting molecular-scale phenomena to macroscopic properties
Molecular simulation is an important tool to get the molecular-level insights of a particular system. The inferences from simulation studies are routinely drawn by calculating a macroscopic property (like surface tension) on one hand, performing some sort of visual analysis on the other, and relating the two observations. For example, the visual analysis may mean determining the distribution of certain molecular species using the simulation-data. There is a good chance that such an analysis may not provide the actual extent of the role of a particular molecular phenomena to the macroscopic observable. In some cases, a deeper theoretical analysis indicates that a particular molecular-scale phenomena should not affect the concerned macroscopic observable.
In this project we are developing a generic statistical-thermodynamics-based approach to analyze the molecular simulation data. The main objective is to quantify the contribution of a particular class of molecular-scale phenomena to a particular macroscopic observable. The project is inspired by our previous work on molecular solutes at water-vapor interfaces. One can think of the proposed approach as a “functional” microscope that not only allows us to observe a molecular-scale phenomenon, but also illuminates its relationship with a given macroscopic property.
I have classified my previous research projects into different subject areas. I find such classification useful in tracking the knowledge gained while working on them. Such an exercise can help me teach the related topics in future. Also, note that the classification may change with time, and some of the past questions may be addressed in detail in my current projects. Please click on the images below to know the details.
I am always fascinated by the ability of theoretical models to provide insights into a natural phenomenon by allowing us to tweak the reality. In the long run I am interested in sharing this fascination with other students of interfacial science by developing suitable computational methods. The webpage linked below explains the research strategy that will be used, in cooperation with my present and future colleagues, to achieve this goal. Details about my specific research interests will be provided on request. More information