Effects of colloidal particles on interfacial rheology

这项拟议中的研究重点是亚微米颗粒(或称纳米颗粒)如何在油水界面积聚并改变其物理性质。这项研究是由一种名为“微生物增强采油”(MEOR)的工业过程推动的，即将对石油有“胃口”的细菌注入油井，以帮助回收剩余的碳氢化合物。过去，人们在这项技术的生化方面做了很多工作。但相比之下，对充满微生物的油水界面的物理研究很少或根本没有。尤其是，重要的是要了解这些表面在外力作用下会如何变形和流动。我们不是与实际的细菌合作，而是创造出模仿微生物的小型无生命物体。例如，这些物体可以是亚微米的玻璃球，其表面覆盖着长链糖分子(多糖)。这样就可以让“模型细菌”聚集在油水界面上(例如，在水下油滴的表面)。由此产生的表面力学性能将被量化。众所周知，界面上粒子的存在不会对其界面张力产生影响。然而，我们关注的是表面粘度和表面弹性(统称为流变性)等更高阶的力学性能。这些性能将使用振荡悬滴和微吸管等技术进行量化。

The proposed study focuses on how submicron particles (or "nanoparticles") may accumulate at the oil-water interface and modify its physical properties.  This research is motivated by an industrial process known as "microbial enhanced oil recovery" (MEOR), where bacteria with "appetites" for petroleum are injected into oil wells to help recover residual hydrocarbon.  Much work has been done in the past on the biochemical aspects of this technology.  In contrast, there has been little or no research on the physics of oil-water interfaces that are laden with microorganisms.  In particular, it is important to understand how these surfaces will deform and flow under applied forces.  Instead of working with actual bacteria, we propose to create small inanimate objects that will mimic the microorganisms.  These, for example, can be submicron glass spheres whose surfaces are covered with long chain sugar molecules (polysaccharides).  The "model bacteria" will then be allowed to accumulate at oil-water interfaces (e.g. on the surfaces of submerged oil droplets), and the resulting surface mechanical properties will be quantified.  It is commonly-known that the presence of particles at interfaces can have no effect on their interfacial tensions.  We are, however, concerned with higher-order mechanical properties such as surface viscosities and surface elasticities (collectively known as "rheological properties").  These properties will be quantified using techniques such as the oscillating pendant drop and the micropipette.