Jpn. J. Appl. Phys. 50 (2011) 067202 (6 pages) |Previous Article| |Next Article| |Table of Contents|
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Experimental and Computational Analysis of Water-Droplet Formation and Ejection Process Using Hollow Microneedle
Department of Mechanical Engineering, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan
1Department of Mechanical Systems Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
2Department of Intelligent Machines and System Engineering, Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
(Received December 28, 2010; accepted March 23, 2011; published online June 20, 2011)
In this paper, we present the possibility of liquid delivery using fabricated hollow silicon dioxide microneedles of approximately 2 µm in diameter. As a fundamental study, the water-droplet formation and ejection process was examined via dynamic observations during water ejection tests and computational fluid dynamics (CFD) analysis. The experimental results indicated that fluid flow in a microneedle follows the Hagen–Poiseuille law, i.e., the flow rate is approximately directly proportional to the fourth power of the inner diameter. Moreover, the ejection pressure and maximum droplet curvature obtained using the proposed microfluid ejection model were in good agreement with the experimental results. The resulting ejection pressure is equal to the theoretical pressure difference of a spherical droplet, which is determined using the Young–Laplace equation. The maximum curvature of a droplet formed at the tip of a microneedle can be estimated on the basis of the contact angle theory expressed by the Young equation.
PACS: 85.85.+j, 81.05.Je, 47.60.Kz
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