Bassindale, P.G., Phillips, D.B., Barnes, A.C. and Drinkwater, B.W. (2014) Measurements of the force fields within an acoustic standing wave using holographic optical tweezers. Applied Physics Letters, 104(16), 163504. (doi: 10.1063/1.4872462)
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Abstract
Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN pp ) and streaming forces (<0.2 pN) were measured. A 5 μm silica micro-sphere was used to characterise a 6.8 MHz standing wave, λ = 220 μm, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2 nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.
Item Type: | Articles |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Phillips, Dr David |
Authors: | Bassindale, P.G., Phillips, D.B., Barnes, A.C., and Drinkwater, B.W. |
College/School: | College of Science and Engineering > School of Physics and Astronomy |
Journal Name: | Applied Physics Letters |
Publisher: | American Institute of Physics |
ISSN: | 0003-6951 |
ISSN (Online): | 1077-3118 |
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