Flow actuation

The piezoelectric chip generating the SAW is coupled to microfluidic devices. The flow actuated by the SAWs is nonintrusive. There are no mechanical moving parts inside. It can comprise sealed containers without external plumbing. SAWs have been used to manipulate droplets [2-4] and to mix and pump liquids [5-10]. 

In the literature, the fluid flow actuated by moving boundary of the wall and driven by hydrodynamic shear stresses is referred to as the... 

Flaps are types of flow actuators, which are hinged surfaces on the wings of air vehicles... 

Manipulating fluids in a two-phase flow system is much more complicated than in single-phase systems. Fluid flows can be actuated spontaneously, nonmechanically, or mechanically. The most frequently used flow actuation method, till now, is still pressure-driven pumps due to their availability and versatility. Especially, for a two-phase flow system, the naturally existing inhomogeneity makes other methods much more difficult to be applied. Electroosmosis, for instance, resulting from the force exerted on a space-charge region in the liquid by an electric field, will not work if the conductivity continuum in the fluid is interrupted by an entrapped dielectric liquid droplet or gas bubble. 

Valve-Less Rectification Pumps, Fig. 8 The term rectifying bridge is based on the underlying idea of the two-phase alternating-flow actuator (alternator) bridging the gap between the two paths that lead from suction to delivery terminals. Note that the simplest case in Kg. 1 is one half of such bridge... 

Figure 5.3a shows the result of applying this recipe to the system with effort actuation (when dualised, the effort source Se so becomes the flow source Sf so) one component (C ki) is in integral causality and so it is confirmed that this system is not structurally controllable with effort actuation. Conversely, Fig. 5.3b shows the result of applying this recipe to the system with flow actuation no component remains in integral causality and so it is confirmed that this system is structurally controllable with effort actuation. 

Fig. 5.3 Maximising derivative causality (a) dual effort actuation and (b) dual flow actuation...

In the literature, the fluid flow actuated by moving boundary of the wall and driven by hydrod)uiamic shear stresses is referred to as the Stokes second problem, and is specifically referred to as the slip velocity approach in electroosmotic flows. More general discussions of the applicability of such slip velocity approach in electrokinetic flows were provided elsewhere [6]. Using the slip velocity approach, the steady velocity field of a fully-developed flow driven by an applied electric field, E and a pressure gradient, dp/dz is governed by the Stokes equation, expressed as... 

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