Statistical Materials' Modeling

Research Interests

Colloidal self-assembly: The formation of ordered structures utilizing colloidal nanoparticles holds significant technological promise in photonic circuits and biosensing fields. Achieving precise assembly of targeted structures necessitates meticulous control over interactions among colloidal building blocks. Colloids coated with deoxyribonucleic acid (DNA) have emerged as a favored option for regulating interactions due to the specificity and adjustability afforded by Watson–Crick base pairing. Leveraging DNA-mediated interactions, a diverse array of extended structures has been observed. This project aims to craft colloidal structures with prospective photonic properties using DNA-mediated interactions.

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1. Nanoscale (RSC) 2019, 11, 5450-5459

2. Physical Review E Rapid Communications (APS) 2019, 100, 060601(R) 

3. Soft Matter (RSC) 2020

4. Langmuir (ACS) 2019, 35, 2002-2012

5.  Physical Review E (APS) 2018, 98, 032406-032416

1. Macromolecules (ACS) 2022, 55, 5550

2. Macromolecules (ACS) 2021, 54, 8693

3. Macromolecules (ACS) 2021, 54, 2740

Method for multi-scale modeling of polymer-nano-composite: The rheological properties of polymer composites depend on the interfacial interactions between solid fillers and a polymer fluid. In highly coarse-grained (hCG) models, where one coarse-grained segment represents multiple monomeric repeat units, the solid surface of a filler appears smooth on the hCG scale. Thus, special simulation techniques are required to control the single-chain dynamics and friction at the solid-fluid contact. We devise a simulation strategy─the wall-spring (WASP) thermostat where, transient bonds are formed between the solid surface and the polymer segments based on a grand canonical Monte Carlo (MC) algorithm. These transient bonds mimic strong, specific interactions of the polymer segments with the solid. The attraction, induced by the transient bonds, can be compensated with a permanent, analytically known potential such that static properties do not differ from the system without WASPs. 

Friction at the nanoscale: Controlling friction by understanding the atomic-scale processes at the interfaces of interacting bodies in relative motion has been a long-standing challenge, with applications in micro- and nanoelectromechanical systems for energy savings. There are two main strategies to control friction: a. modulating the surface properties that come into contact and b. using lubricants between the surfaces. Experiments reveal that nematic liquid crystals (LCs) have the potential to be the next-generation lubricants because of their tendency to exhibit long-range ordering. However, the friction reduction mechanism and connection with the properties of confining surfaces were explored less. 

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Molecular self-assembly: Understanding the structure formation of organic molecules on surfaces is of significant interest because of technological importance. For example, the performance of thin-film transistor is mostly controlled by the molecular structure and thin film morphology of the semiconducting layer, because larger and smooth cluster sizes of molecules can give better mobilities. The structure formation in a non-equilibrium set-up like Physical Vapor Deposition is intriguing and may exhibit unusual self-assembly pathway to the thermodynamically stable structure. 

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Reversible to irreversible transition in polycrystals: Cyclic deformation tests allow one to unambiguously identify irreversible rearrangements. Colloidal polycrystals lie between perfectly ordered crystals and disordered amorphous solids, where crystalline regions are separated by extended grain boundaries formed by dislocation arrays (particles with 5 and 7 neighbors). The simulation results revealed that, for large enough strain amplitudes, grain boundaries disappeared, and the system became ordered, while at small strain amplitudes, the system settled to a state very close to the original metastable configuration, and further deformation cycles did not lead to any grain boundary motion. Thus, an effective phase transition is controlled by the strain amplitude between two asymptotic steady-states.

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