通俗演講 Colloquium

2019/09/10(Tue)     14:00 -15:00    一樓演講廳 1F, Auditorium

Title

Multi-scale Investigations of “Soft” Materials: From Molecules to Mechanics

Speaker

陳彥龍博士 (中央研究院物理研究所)

Dr. Yeng-Long Chen (Institute of Physics, Academia Sinica)

Abstract

Soft materials can exhibit complex physical properties resulting from hierarchical structure from nano- to the micro-scale. I will discuss our group's recent studies on abnormal dynamics and phase behavior of strongly confined polymers, non-linear response of soft particles to flow, and how gas presence affect nanobubble and lipid bilayer properties. Our recent highlight found that polymers such as DNA can diffuse faster in more crowded environments. We discovered that when obstacles attract DNA, conformational fluctuations allow DNA to “reach” across small gaps, resulting in faster diffusion in more crowded environments with smaller gaps between obstacles. This result upended the assumption that molecular transport slows down in more crowded environments. This finding also suggested a novel molecular separation mechanism based on the conformational fluctuation length.
To study the physics of soft microparticles in flow, we developed hybrid particle-fluid modeling methods. In dense soft particle suspensions, we found shear-induced order-disorder microstructural transition and that packing constraints can result in long wavelength zig-zag particle trajectories, resulting in disrupted collective structure. Additionally, we developed the model to study how a cancer cell cluster could extravasate through very small constrictions in blood vessel walls in a collaborative study. Our model predicted an optimal range of inter-particle attraction for the cluster to pass through cell-by-cell, instead of break-up or becoming stuck. This provided a physics-based insight on how inter-cell adhesion could control the dynamics of cancer cell clusters in a cancer metastatic process.
On the molecular scale, we used molecular dynamics to investigate the stability of “nanobubbles” on hydrophobic surfaces. We found that surface gas enrichment layers and the gas accumulation near the water-air interface, in agreement with AFM observations. Most recently, we found that gas accumulation in lipid bilayers enhances the rigidity of lipid vesicles in a joint effort. Our study demonstrated that the ubiquitous gas presence affect the lipid bilayer area compressibility and bending rigidity, which in turn affect the mechanical property of cells.

Language

演講語言 (Language): in English