Capillary forces microstructural

The PS layer thickness may show fluctuations over the electrode area on different length scales. The thickness variations may originate from a waviness of the bulk-PS interface, or the electrolyte-PS interface. The latter case, which is usually due to a dissolution of PS during anodization or a collapse of the PS microstructure due to capillary forces during drying, is discussed in Section 6.5. 

Capillary forces induce morphological evolution of an interface toward uniform diffusion potential—which is also a condition for constant mean curvature for isotropic free surfaces (Chapter 14). If a microstructure has many internal interfaces, such as one with fine precipitates or a fine grain size, capillary forces drive mass between or across interfaces and cause coarsening (Chapter 15). Capillary-driven processes can occur simultaneously in systems containing both free surfaces and internal interfaces, such as a porous polycrystal. 

On a high surface energy substrate, the water contact angle is small and the capillary forces thus generated are sufficiently strong to collapse a typical suspended microstructure to the substrate. ... 

In lateral flow tests, also known as test strips (e.g. pregnancy test strip), the liquids are driven by capillary forces. Liquid movement is controlled by the wettability and feature size of the porous or microstructured substrate. All required chemicals are pre-stored within the strip. The presence of an analyte is typically visualized by a colored line. 

The centrifugal microfluidic platform uses inertial and capillary forces on a rotating microstructured substrate for liquid actuation. Relevant inertial (pseudo-) forces include the centrifugal force, Euler force and Coriolis force. The substrate is often disk-shaped. Liquid flow is possible in two dimensions but with the limitation that active liquid transport is always directed radially outwards. Active components can be limited to one rotational axis. 

U. Srinivasan, D. Liepmann, and R. T. Howe, Microstructure to substrate self-assembly using capillary forces. JMEMS 10 p. 17-24 (2001). 

Up to now, the development of microneedles has focused on microfabrication techniques for Si and other biocompatible materials. Currently, there are several commercially available microneedle products, such as MTS (Microstructured Transdermal System) by 3 M, Macroflux by ALZA, and Micro-Trans by Bio Valve Technologies, and most of them are designed to increase skin permeability and adopt passive delivery methods (i.e., capillary force). As the feasibility of microneedles is well established, the next step is to understand the characteristics of fluid transport by microneedles,... 

If not discharged, the CO2 gas produced in the anode reaction would fill and block the fiow field [50]. Therefore, the gas flow has to be separated from the liquid flow of the methanol-water solution in the anode. One approach is to use microstructured flow flelds with a T-shaped channel design. The methanol is distributed in a wide channel on the bottom. If CO2 bubbles evolve, they will grow until they reach the ceiling of the channel. If the channel ceiling is tapered and leads to a small channel, set on top of the wide channel, the bubbles will be driven into the small channel by capillary forces [51]. The same principle is used for separating water droplets from a gas stream, as described above. 

Mastrangelo CH, Hsu CH (1993) Mechanical stability and adhesion of microstructures under capillary forces - part I basic theory. J Microelectromech Syst 2(l) 33-43 Mulhem GT, Soane DS, Howe RT (1993) Supercritical carbon dioxide drying of microstructures. In Technical digest 7th international conference on solid-state sensors and actuators (Transducers 93), Yokohama, p 296... 

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