Microhydrodynamics

Other than hydrodynamic flows one must also take into account Brownian motion.Brownian motion is observed as the random displacement of colloids caused by thermal energy. Batchelor deemed this force as a microhydrodynamic force because only small objects with a low Reynolds number exhibit Brownian motion. Low Reynolds numbers are present in microhydrod)uiamic systems because inertia forces are small with respect to viscous forces. 

G. K. Batchelor, Developments in microhydrodynamics. In Theory and Applied Mechanics, edited by W. T. Koiter, (North-Holland, Amsterdam) pp. 33-35. 

First, the renewed elements of liquid are considered solidlike, without a microhydrodynamic structure, even though it is difficult to visualize how solid bodies can replace one another. It is clear that these elements of liquid should be able to deform for such a replacement to occur. 

A practically useful predictive method must provide quantitative process prediction from accessible physical property data. Such a method should be physically realistic and require a minimum number of assumptions. A method which is firmly based on the physics of the separation is likely to have the widest applicability. It is also an advantage if such a method does not involve mathematics which is tedious, complicated or difficult to follow. For the pressure driven processes of microfiltration, ultrafiltration and nanofiltration, such methods must be based on the microhydrodynamics and interfacial events occurring at the membrane surface and inside the membrane. This immediately points to the requirement for understanding the colloid science of such processes. Any such method must account properly for the electrostatic, dispersion, hydration and entropic interactions occurring between the solutes being separated and between such solutes and the membrane. 

Rajagopalan, R. (2000), Atomic force and optical force microscopy Applications to interfacial microhydrodynamics, Coll. Surf. Physicochem. Eng. Aspects, 174(1-2), 253-267. 

Kim S, Karrila SJ (1991). Microhydrodynamics Principles and Selected Applications, Butter-worth-Heinemann, Boston. 

Microhydrodynamics Principles and Selected Applications Sangtae Kim and Seppo J. Karrila... 

Batchelor (1976) has termed the study of flow systems of the small scale considered as microhydrodynamics because of the numerous distinctive features, many of which are physical-chemical in nature. Among the more important characteristics are... 

This chapter is essentially concerned with the hydrodynamics of mixtures containing non-charged particles and macromolecules, that is, molecules with molecular mass exceeding 10 and particles with sizes in the range 0.1-100 pm. For the branch of hydrodynamics concerned with the study of motion of liquids containing macromolecules and small particles, G.K. Batchelor [1] coined the term microhydrodynamics . The distinctive features of microhydrodynamics may be summarized as follows ... 

Chang HC, Yossifon G, Demekhin EA (2012) Nanoscale electrokinetics and microvortices how microhydrodynamics affects nanofluidic ion flux. Annu Rev Eluid Mech 44 401-426... 

We next show evidence for a phenomenon that can be positively affected by SIS that is not related to dilution mitigation. We call it microhydrodynamic lubricalion, or MHL, and will define it after presenting the relevant data. MHL occurs mainly when the platen speed is high and the polishing pressure is low. 

Figure 15.16 SIS with no rinse gives a higher removal rate than PA with no rinse due to microhydrodynamic lubrication.

Experiments suggest that two main mechanisms are at work in a successful SIS application, dilution mitigation in exposed pores and valleys, and elimination of microhydrodynamic lubrication at contacts. The latter occurs in processes operating with a fast platen and low down force. The same experiments also provide some suggestive new clues about what may be happening in the gap between the pad and the wafer. 

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