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Fabrication of microfluidic cavities using Si-to-glass anodic bonding

Cornell Affiliated Author(s)

Author

N. Zhelev
T.S. Abhilash
R.G. Bennett
E.N. Smith
B. Ilic
J.M. Parpia
L.V. Levitin
X. Rojas
A.J. Casey
J. Saunders

Abstract

We demonstrate the fabrication of ∼1.08 μm deep microfluidic cavities with characteristic size as large as 7 mm × 11 mm or 11 mm diameter, using a silicon-glass anodic bonding technique that does not require posts to act as separators to define cavity height. Since the phase diagram of 3He is significantly altered under confinement, posts might act as pinning centers for phase boundaries. The previous generation of cavities relied on full wafer-bonding which is more prone to failure and requires dicing post-bonding, whereas these cavities are made by bonding a pre-cut piece of Hoya SD-2 glass to a patterned piece of silicon in which the cavity is defined by etching. Anodic bonding was carried out at 425 °C with 200 V, and we observe that pressurizing the cavity to failure (>30 bars pressure) results in glass breaking, rather than the glass-silicon bond separation. In this article, we discuss the detailed fabrication of the cavity, its edges, and details of the junction between the coin silver fill line and the silicon base of the cavity that enables a low internal-friction joint. This feature is important for mass coupling torsional oscillator experimental assays of the superfluid inertial contribution where a high quality factor (Q) improves frequency resolution. The surface preparation that yields well-characterized smooth surfaces to eliminate pinning sites, the use of transparent glass as a cover permitting optical access, low temperature capability, and attachment of pressure-capable ports for fluid access may be features that are important in other applications. © 2018 Author(s).

Date Published

Journal

Review of Scientific Instruments

Volume

89

Issue

7

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050003954&doi=10.1063%2f1.5031837&partnerID=40&md5=92ef3aaddb535e8d9bb34e09c4b3fa21

DOI

10.1063/1.5031837

Group (Lab)

Jeevak Parpia Group

Funding Source

DMR1202991
1202991
1708341
EP/J022004/1
DMR1664043
DMR1708341

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