Acoustic droplet ejection

<h2 id="history">History</h2>
<p>Acoustic droplet ejection was first reported in 1927 by <a href="/facts/Robert_W._Wood/yj1Py5T8">Robert W. Wood</a> and <a href="/facts/Alfred_Lee_Loomis/DvDt3UI5">Alfred Loomis</a>,<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> who noted that when a high-power acoustic generator was immersed in an oil bath, a mound formed on the surface of the oil and, like a "miniature volcano", ejected a continuous stream of droplets. Ripples that appear in a glass of water placed on a loud speaker show that acoustic energy can be converted to kinetic energy in a fluid. If the sound is turned up enough, droplets will jump from the liquid. This technique was refined in the 1970s and 1980s by <a href="/facts/Xerox/qyxVVqaa">Xerox</a> and <a href="/facts/IBM/QszA7nwd">IBM</a><a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> and other organizations to provide a single droplet on-demand for printing ink onto a page. Two California-based companies, EDC Biosystems Inc. and Labcyte Inc. (both now acquired by <a href="/facts/Beckman_Coulter/As0jIHkP">Beckman Coulter</a>), exploit acoustic energy for two separate functions: 1) as a liquid transfer device and 2) as a device for liquid auditing.
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<h2 id="ejection-mechanism">Ejection mechanism</h2>
<p>To eject a droplet, a transducer generates and transfers acoustic energy to a source well. When the acoustic energy is focused near the surface of the liquid, a mound of liquid is formed and a droplet is ejected. The diameter of the droplet scales inversely with the frequency of the acoustic energy—higher frequencies produce smaller droplets.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>  Unlike other liquid transfer devices, no <a href="/facts/Pipette/uA39c1UB">pipette</a> tips, pin tools, or <a href="/facts/Nozzle/9z8wqmEC">nozzles</a> touch the source liquid or destination surfaces. Liquid transfer methods that rely on droplet formation through an orifice, e.g., disposable tips or capillary nozzles, invariably lose precision as the transfer volume decreases. Touchless acoustic transfer provides a <a href="/facts/Coefficient_of_variation/V8ddKkz4">coefficient of variation</a> (CV) that is significantly lower than other techniques and is independent of volume at the levels tested.
</p><p>ADE shoots a droplet from a source well upward to an inverted receiving plate positioned above the source plate. Liquids ejected from the source are captured by dry plates due to surface tension. For larger volumes, multiple droplets can be rapidly ejected from the source (typically 100 to 500 droplets/sec) to the destination with the coefficient of variation typically <4% over a volume range of two orders of magnitude.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>
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<h2 id="applications-of-acoustic-transfer">Applications of acoustic transfer</h2>
<p>The following applications are among those that can benefit from the features of acoustic droplet ejection:
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<ul><li><a href="/facts/High_throughput_screening/503vkz1b">High throughput screening</a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a></li>
<li><a href="/facts/Microelectromechanical_systems/TkhEzDpm">Microelectromechanical systems</a></li>
<li>Assay miniaturization</li>
<li>Eliminating cross-contamination</li>
<li>Reducing plastic waste in biological research</li>
<li>Direct loading of mass spectrometers</li></ul>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Acoustic_droplet_vaporization/GkNH2ISl">Acoustic droplet vaporization</a></li>
<li><a href="https://journals.sagepub.com/toc/jlac/21/1/">Journal of Laboratory Automation Special Issue: Advancing Scientific Innovation with Acoustic Droplet Ejection</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>R. W. Wood; A. L. Loomis (1927). "The Physical and Biological Effects of High Frequency Sound Waves of Great Intensity". Philosophical Magazine. 4 (22): 417–436. <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>K. A. Krause (1973). "Focusing Ink Jet Head". IBM Technical Disclosure Bulletin. 16 (4): 1168. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>R. Ellson; M. Mutz; B. Browning; L. Lee; M.F. Miller; R. Papen (2003). "Transfer of Low Nanoliter Volumes between Microwell Plates Using Focused Acoustics – Automation Considerations". Journal of the Association for Laboratory Automation. 8 (5): 29–34. doi:10.1016/S1535-5535(03)00011-X. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>R. Ellson (2002). "Picoliter: enabling precise transfer of nanoliter and picoliter volumes". Drug Discovery Today. 7 (5): 32–34. doi:10.1016/S1359-6446(02)02176-1. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>J. Comley (2004). "Continued Miniaturisation of Assay Technologies Drives Market for Nanolitre Dispensing". Drug Discovery World. Summer: 43–54. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Yin, Xingyu; Scalia, Alexander; Leroy, Ludmila; Cuttitta, Christina M.; Polizzo, Gina M.; Ericson, Daniel L.; Roessler, Christian G.; Campos, Olven; Ma, Millie Y.; Agarwal, Rakhi; Jackimowicz, Rick; Allaire, Marc; Orville, Allen M.; Sweet, Robert M.; Soares, Alexei S. (2014). "Hitting the target: fragment screening with acoustic in situ co-crystallization of proteins plus fragment libraries on pin-mounted data-collection micromeshes". Acta Crystallographica Section D. 70 (5): 1177–1189. doi:10.1107/S1399004713034603. PMC 4014116. PMID 24816088. <a href="http://academicworks.cuny.edu/cgi/viewcontent.cgi?article=1055&context=si_pubs" target="_blank">http://academicworks.cuny.edu/cgi/viewcontent.cgi?article=1055&context=si_pubs</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
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Acoustic droplet ejection open-in-new

Acoustic droplet ejection