Jiarul Midya

My research interests lie within the broad area of statistical mechanics and soft matter. I have working experience on the following topics

Cellular uptake of hard and deformable nanoparticles
Membrane-mediated interaction of nanoparticles
Evaporation induced self-assembly
Phase behavior and wetting phenomena of flexible and semiflexible polymers
Structural, mechanical, and transport properties of polymer-grafted nanoparticle systems
Phase transition and critical phenomena
Domain coarsening phenomena in the kinetics of phase transitions
Domain coarsening in active matter systems
Aging dynamics in out-of-equilibrium systems

Cellular uptake of hard and deformable nanoparticles:

The movement of particles across lipid-bilayer membranes is key to how cells communicate and exchange materials with their environment. While the wrapping of rigid particles by membranes has been widely studied, many real-world particles—such as vesicles, viruses, and microgels—are soft and deformable. We use vesicles as model deformable particles to explore how their shape, size, and stiffness affect their interaction with flat membranes. Using physical models like the Helfrich Hamiltonian, triangulated membrane surfaces, and energy minimization, we investigate how the membrane wrapping process depends on the particle’s deformability. Our results reveal how deformation energy drives transitions between non-wrapped, partially wrapped, and fully wrapped states—offering insights relevant to drug delivery, viral infection, and nanomaterial safety.

Membrane-mediated interaction of elastic nanoparticles:

The wrapping of particles leads to local membrane deformation. Such deformation induces membrane-mediated interaction between partial-wrapped particles. We calculate the membrane-mediated pair interaction between partial-wrapped vesicles. We predict purely repulsive interaction between the vesicles in deep-wrapped states. For shallow-wrapped states, the interaction potential depends on the orientation of the vesicles, with attraction for tip-to-tip orientation, and repulsion for side-by-side orientation. Our predictions may guide the design and fabrication of deformable particles for efficient use in diagnostics and therapeutics.

Evaporation-induced self-assembly:

Self-assembly of the colloidal particles via evaporation of colloidal drop suspensions is crucial for various applications, e.g., painting, coating, washing, or agriculture. The complete evaporation of the solvent from a suspension leaves a deposited solid, called supraparticle. Depending on material properties and evaporation rate, the structure of the supraparticles can be porous, amorphous, or crystalline. For a binary (particles with different sizes) colloidal suspension we have shown that the morphology of the supraparticles is controlled by the evaporation rate and the colloid size ratios. At fast evaporation rate a supraparticle with core-shell morphology can be achieved where the outer region is predominantly occupied by small colloids with crystalline structures, and the interior region is amorphously packed with a mixture of small and large colloids.

Phase behavior and wetting phenomena of flexible and semiflexible polymers:

Phase behavior of flexible and semiflexible polymers is investigated by systematically varying the polymer length, stiffness, and solvent quality. The stiff polymers exhibit a single transition from an isotropic fluid to a nematic fluid. For less stiff polymers, however, also unmixing between isotropic fluids of different concentrations (ends at a critical point) occurs for temperatures above a triple point. We have shown that the critical behavior of these systems is compatible with the Ising universality class. Further, we study the wetting phenomena of flexible and semiflexible polymer solutions by systematically varying the polymer length, stiffness, and solvent quality. The wetting transitions of flexible and semiflexible polymers were quantified using Young’s equation for contact angle. Furthermore, we have studied the phase behavior of binary semiflexible polymer mixtures. The phase diagrams are predicted either with a triple point (isotropic phase coexists with two nematic phases) or with a nematic-nematic critical point.

Structural and mechanical properties of polymer-grafted nanoparticle melts:

Polymer-grafted nanoparticles (GNPs) have gained significant attention due to their wide range of applications in drug delivery, desalination, and photonic and phononic materials. Typically, GNPs exhibit core-shell morphology (a hard core and a soft corona). The softness of the corona can be tuned by changing the degree of polymerization of the grafted chains (on the surface of the nanoparticles) and grafting density. We have studied the structural and mechanical properties of GNP melts systematically varying the grafting density and degree of polymerization at fixed core size. At high grafting density, chain-sections close to the NP are extended and form a dry-layer. Further away from the NP, there is an interpenetration-layer with overlapping polymers from neighboring GNPs and the chain-sections have almost unperturbed conformations. Such partitioning is understood by developing a two-layer model, where the grafted polymers around an NP is represented by a spherical dry-layer and an interpenetration-layer. Our model quantitatively predicts the thicknesses of the two layers that depend on one universal parameter called the “overcrowding parameter” which represents the degree of overcrowding of grafted chains relative to chains in the melt. We have shown that the relative chain extension free energy non-monotonically increases with chain lengths at a fixed grafting density, and exhibits a well-defined maximum in the intermediate chain length which indicates the crossover from the dry layer-dominated to interpenetration layer-dominated regime. Such non-monotonic behavior of the relative chain extension energy is connected to the anomalous transport property of GNP melts.

The mechanical property of these systems is also understood by looking at the elastic moduli which can be tuned by varying the NP loading through the grafting density and/or the length of the grafted polymers [8]. We have shown that even at a fixed NP loading, the mechanical properties of GNPs depend on their microscopic details. Further, we have investigated the transport of free molecules/macromolecules through GNP melts.

Kinetics of phase transition and critical phenomena:

Our research focuses on understanding equilibrium and nonequilibrium statistical mechanics, particularly in systems undergoing phase transitions—such as paramagnetic to ferromagnetic, solid-solid, vapor-liquid, and vapor-solid transitions. We use simplified models and simulation techniques like Monte Carlo, molecular dynamics, and continuum models to explore these phenomena. When a system undergoes a phase transition, it moves from a disordered to an ordered state through the formation and growth of domains. The structure and evolution of these domains depend on factors like dimensionality, composition, and density. We analyze how domain patterns emerge and grow, often following power-law scaling, and quantify the growth exponents for various systems.

We also investigate aging dynamics, studying how systems relax over time after being quenched out of equilibrium. By analyzing two-time correlation functions and applying finite-size scaling, we estimate aging exponents with high precision. In the realm of dynamic critical phenomena, we examine how transport properties behave near critical points, identifying critical singularities using finite-size scaling methods. Our work provides a deeper understanding of pattern formation, scaling laws, and relaxation dynamics in phase-transition systems.

Page updated

Google Sites

Report abuse