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Micromachines 2017, 8(2), 56; doi:10.3390/mi8020056

Faraday Waves-Based Integrated Ultrasonic Micro-Droplet Generator and Applications

1
Department of Electrical Engineering and Computer Science, University of California, Irvine, CA 92697, USA
2
Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697, USA
3
Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan
4
School of Medicine, University of Calfironia, San Diego, La Jolla, CA 92093, USA
5
Division of Pulmonary and Critical Care Medicine, Beckman Laser Institute & Medical Clinics, School of Medicine, University of California, Irvine, CA 92697, USA
6
Pulmonary, Critical Care and Sleep Medicine Division, State University of New York at Stony Brook, New York, NY 11790, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Andrew J. deMello and Xavier Casadevall i Solvas
Received: 6 November 2016 / Revised: 30 January 2017 / Accepted: 3 February 2017 / Published: 14 February 2017
(This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies, Volume II)
View Full-Text   |   Download PDF [5982 KB, uploaded 14 February 2017]   |  

Abstract

An in-depth review on a new ultrasonic micro-droplet generator which utilizes megahertz (MHz) Faraday waves excited by silicon-based multiple Fourier horn ultrasonic nozzles (MFHUNs) and its potential applications is presented. The new droplet generator has demonstrated capability for producing micro droplets of controllable size and size distribution and desirable throughput at very low electrical drive power. For comparison, the serious deficiencies of current commercial droplet generators (nebulizers) and the other ultrasonic droplet generators explored in recent years are first discussed. The architecture, working principle, simulation, and design of the multiple Fourier horns (MFH) in resonance aimed at the amplified longitudinal vibration amplitude on the end face of nozzle tip, and the fabrication and characterization of the nozzles are then described in detail. Subsequently, a linear theory on the temporal instability of Faraday waves on a liquid layer resting on the planar end face of the MFHUN and the detailed experimental verifications are presented. The linear theory serves to elucidate the dynamics of droplet ejection from the free liquid surface and predict the vibration amplitude onset threshold for droplet ejection and the droplet diameters. A battery-run pocket-size clogging-free integrated micro droplet generator realized using the MFHUN is then described. The subsequent report on the successful nebulization of a variety of commercial pulmonary medicines against common diseases and on the experimental antidote solutions to cyanide poisoning using the new droplet generator serves to support its imminent application to inhalation drug delivery. View Full-Text
Keywords: Faraday waves; Faraday instability; multiple Fourier horns (MFH); MFH ultrasonic nozzle; ultrasonic micro droplet generator; integrated ultrasonic nebulizer; ultrasonic nebulizer; onset threshold for droplet ejection; clogging free; monodisperse; polydisperse; pulmonary (inhalation) drug delivery Faraday waves; Faraday instability; multiple Fourier horns (MFH); MFH ultrasonic nozzle; ultrasonic micro droplet generator; integrated ultrasonic nebulizer; ultrasonic nebulizer; onset threshold for droplet ejection; clogging free; monodisperse; polydisperse; pulmonary (inhalation) drug delivery
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Tsai, C.S.; Mao, R.W.; Tsai, S.C.; Shahverdi, K.; Zhu, Y.; Lin, S.K.; Hsu, Y.-H.; Boss, G.; Brenner, M.; Mahon, S.; Smaldone, G.C. Faraday Waves-Based Integrated Ultrasonic Micro-Droplet Generator and Applications. Micromachines 2017, 8, 56.

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