Abstract
Surface acoustic waves (SAWs) with large normal (vertical) surface displacement at the surface are commonly utilized in microfluidic actuators in order to provide the desired momentum transfer to the fluid. We present an alternative concept using a SAW with comparatively small vertical displacement. Such a SAW passes underneath the microfluidic vessel walls with minimum losses but it needs to be converted inside the vessel into surface vibrations with large vertical displacements. The principal operability of the above idea is illustrated by experimental and numerical studies of the polarization conversion of a leaky SAW on 64° rotated Y-cut of lithium niobate owing to the partial metallization of the substrate surface. In particular, it is found that vertical displacements on the metallized surface can be up to 3.5 times higher as compared to their values on the free surface. Results of computations agree reasonably well with measurements carried out with a laser Doppler vibrometer and allow the clarification of some specific features of this polarization conversion by means of spatial frequency analysis.
Highlights
Actuators mainly deploy SAW with large surface normal, i.e., vertical, displacement in order to ensure the transfer of momentum between the substrate surface and the fluid
Such a SAW passes underneath the microfluidic vessel walls with minimum losses but it needs to be converted inside the vessel into surface vibrations with large vertical displacements
The principal operability of the above idea is illustrated by experimental and numerical studies of the polarization conversion of a leaky SAW on 64 rotated Y-cut of lithium niobate owing to the partial metallization of the substrate surface
Summary
Actuators mainly deploy SAW with large surface normal, i.e., vertical, displacement in order to ensure the transfer of momentum between the substrate surface and the fluid (e.g., see Refs. 22 and 23). For free surface (no scitation.org/journal/apl metallization), a rather small amplitude juzj can be observed from experiment [Fig. 2(a)] and simulation [Fig. 2(b)] due to the dominant horizontal polarization of the LSAW excited by the IDT.
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