Combined acoustic and optical trap:
Combining several methods for contact free micro-manipulation of small particles such as cells or micro-organisms provides the advantages of each method in a single setup: Optical tweezers, which employ focused laser beams, offer very precise and selective handling of single particles. On the other hand, acoustic trapping with wavelengths of about 1mm allows the simultaneous trapping of many, comparatively large particles.
3D acoustic trapping
By using three independent transducers (one transparent transducer for the vertical direction, and two transducers mounted on wedge to excite acoustic waves in the horizontal direction) we realize 3D acoustic trapping with independent control of the the trapping strength in each direction.
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(music: Firewater music, composed by Werner Pirchner, performed by Brass Connection Tirol) |
Trapping of large motile micro-organisms
We have realized combined optical and acoustic trapping of motile micro-organisms in a microfluidic environment, be adding a piezo-transducer to the optical macro-tweezers, which offer a large field of view and working distance of several millimeters - and therefore match the typical range of acoustic trapping. The acoustic trap confines the swimming protists to one or several nodes of the MHz sound field; this "specimen enrichment" facilitates optical trapping considerably.
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 Movie (36.2MB) |
Particle sorting
Particle sorting is easily implemented with radiation pressure being applied to sort particles between acoustic trapping nodes.
 Movie (4MB) |
Publication(s):
G. Thalhammer, R. Steiger, M. Meinschad, M. Hill, S. Bernet, and M. Ritsch-Marte: Combined acoustic and optical trapping, Biomedical Optics Express 2, 2859-2870 (2011).