Computational studies of bio-related surface and interfacial interactions

Researcher: Yongsheng Leng

Research and figures/videos

1. Hydration force and hydrophobic interactions in aqueous system

Figure 1. Snapshot of the hydration structures of 1 M KCl electrolyte confined between mica surfaces. The dark-pink and green spheres represent K+ ions and Cl− co-ions, respectively.

 

Figure 2. Repulsive hydration force profile between two mica surfaces in 1M KCl electrolyte solution. The numerical numbers 6, 5, 4, and 3 represent different layers of hydration film. Experimental hydration pressures (green triangle, in the unit of MPa on the right axis) and continuum double-layer forces (black triangle) are also shown for comparison. Error bars indicate the force variance.

 

2. Membrane-foulant interactions in water purification

Figure 3. Snapshot of the hydration water layer near a polyethylene glycol (PEG) coating: (a) side view and (b) top view. The PEG coating is represented by a van der Waals surface for clarity.

 

Figure 4. Drift of an alginate gel towards the PEG-polyamide (PA) complex membrane by molecular dynamics simulations. PEG grafting density is 0.23 chains/nm2 (50% PEG coverage). The left (a) and the right (b) figures show the two stages of the gel motion. The upper and lower panels show the side and top views. The red and blue van der Waals contours represent the PEG coating and the PA membrane surface, respectively.

Facilities/software:

34 Quad-core AMD 2.6 GHz Aspen Systems cluster (272 compute cores); molecular dynamics (MD) codes for nanoconfined systems, atomic force microscope (AFM) simulation, gold nanowires in organic solvent, grand-canonical Monte Carlo (GCMC) simulation code for metal-organic systems; LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) and MCCCS Towhee code for GCMC. VASP (Vienna Ab-initio Simulation Package) and GoVASP graphical tool.
Funding:
NSF: CAREER: Squeezing and Shear Behaviors of Liquid Films in Confined Geometry, $420 K
NSF: Probing and Controlling Binding Structure and Electron Transport in Molecular Electronic Devices - A Coordinated Computational and Experimental Study, $181 K

 

 

Relevant publications:

1. Xu, R. G. and Leng, Y. S., “Contact Stiffness and Damping of Liquid Films in Dynamic Atomic Force Microscope,” J. Chem. Phys., 144, 154702 (2016).
2. Xiang, Y., Xu, R. G. and Leng, Y. S., “Molecular Dynamics Simulations on a Poly(ethylene glycol) Grafted Polyamide Membrane and Its Interactions with a Calcium Alginates Gel," Langmuir, 32, 4424-4433 (2016).
3. Xiang, Y., Liu, Y. L., Mi, B. X. & Leng, Y. S., “Molecular Dynamics Simulations of Polyamide Membrane, Calcium Alginate Gel, and Their Interactions in Aqueous Solution," Langmuir, 30, 9098-9106 (2014).
4. Xu, R. G. and Leng, Y. S., “Solvation force simulations in atomic force microscopy,” J. Chem. Phys., 140, 214702 (2014).
5. Leng, Y. S., “Hydration force between mica surfaces in aqueous KCl electrolyte solution”, Langmuir 28, 5339 (2012).
6. Lei, Y. J. and Leng, Y. S., “Hydrophobic drying and hysteresis at different length scales by molecular dynamics simulations”, Langmuir 28, 3152 (2012).