These acoustic tweezers ride evanescent wavesS. Himmelstein | September 19, 2019
A new acoustomicrofluidic technology for manipulating micro- and nanoscale samples uses evanescent sound waves to attract fluids and living cells. The approach could replace existing methods based on high-frequency propagative surface acoustic waves to move microscopic samples on complex substrates.
The approach developed by CEA-Leti produces an evanescent Bessel beam in the low-frequency ultrasound range, which arranges bacteria along concentric circles on a simple substrate. Evanescent waves are localized waves in the vicinity of the emitting substrate with a small wavelength gradient. Unlike propagative waves generated by conventional optical tweezers, evanescent waves do not radiate or decay as they propagate along the substrate.
The low-cost system for contactless manipulation of biological samples does not require cleanrooms. A commercially available glass plate substrate of 30 μm thich is attached to a ring-shaped piezo ceramic, facing a cover that confines the liquid. The design supports the attainment of high resonant frequencies, allowing researchers to pattern bacteria and other microorganisms along concentric circles. The Bessel beam was also demonstrated to extract plasma from blood samples.
The research is published in Communications Physics.