(679b) Brownian Motion of a Soft Particle Near a Fluctuating Lipid Bilayer
AIChE Annual Meeting
2024
2024 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Interfacial Transport Phenomena
Thursday, October 31, 2024 - 12:48pm to 1:06pm
The dynamics of a soft particle suspended in a viscous fluid can be changed by the presence of an elastic boundary. Understanding the mechanisms and dynamics of soft-soft surface interactions can provide valuable insights into many important research fields including biomedical engineering, soft robotics development and materials science. This work investigates transport properties of a soft nanoparticle near a visco-elastic interface, where the particle consists of a polymer assembly in the form of a micelle and the interface is represented by a lipid bilayer membrane. Mesoscopic simulations using a dissipative particle dynamics model are performed to examine the impact of micelle’s proximity to the membrane on its Brownian motion.
Several independent simulations allowed to compute the nanoparticle trajectories during an observation time smaller than the diffusive time scale (which order of magnitude is similar to the membrane relaxation time of the largest wavelengths), this time scale being hardly accessible by experiments. From the probability density function of the micelle normal position with respect to the membrane, it is observed that the position remains close to the starting position during ∼ 0.05τd (where τd corresponds to the diffusion time), which allowed to compare the negative excess of mean-square displacement (MSD) to existing theories. In that time range, the MSD exhibits different behavior along parallel and perpendicular directions. When the micelle is sufficiently close to the bilayer (its initial distance from the bilayer equals approximately twice its gyration radius), the micelle motion becomes quickly subdiffusive in the normal direction. Moreover, the temporal evolution of the micelle MSD excess in the perpendicular direction follows that of a nanoparticle near an elastic membrane. However, in the parallel direction, the MSD excess is rather similar to that of a nanoparticle near a liquid interface. The measurement of the nanoparticle mobility allowed to support those observations.
Several independent simulations allowed to compute the nanoparticle trajectories during an observation time smaller than the diffusive time scale (which order of magnitude is similar to the membrane relaxation time of the largest wavelengths), this time scale being hardly accessible by experiments. From the probability density function of the micelle normal position with respect to the membrane, it is observed that the position remains close to the starting position during ∼ 0.05τd (where τd corresponds to the diffusion time), which allowed to compare the negative excess of mean-square displacement (MSD) to existing theories. In that time range, the MSD exhibits different behavior along parallel and perpendicular directions. When the micelle is sufficiently close to the bilayer (its initial distance from the bilayer equals approximately twice its gyration radius), the micelle motion becomes quickly subdiffusive in the normal direction. Moreover, the temporal evolution of the micelle MSD excess in the perpendicular direction follows that of a nanoparticle near an elastic membrane. However, in the parallel direction, the MSD excess is rather similar to that of a nanoparticle near a liquid interface. The measurement of the nanoparticle mobility allowed to support those observations.