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Published March 13, 2006 | public
Journal Article

Unpowered spiral-tube parylene pressure sensor for intraocular pressure sensing


This paper presents the first biocompatible, unpowered, micromachined pressure sensor for intraocular pressure (IOP) sensing. This device is designed for implantation in the eye so that IOP can be faithfully measured externally. It features a parylene-based high-aspect-ratio spiral-tube structure fabricated using a buried-channel process. This passive sensor requires no power from other physical (i.e. electrical and/or magnetic) domains and registers pressure variations by changes of a mechanical in-plane spiral rotation that can be gauged by direct and convenient optical observation. The fabricated device has been tested in various media, and a 1 mm-radius device with a 10-turn spiral has successfully demonstrated continuous spiral rotation when immersed in liquids, with 0.22°/mmHg sensitivity in isopropyl alcohol (IPA) and 0.13°/mmHg sensitivity in water. This pressure sensing technology is proposed as a convenient method to monitor in situ IOP in glaucoma patients and to facilitate treatment and scientific study of the disease.

Additional Information

© 2005 Elsevier. Received 1 March 2005; revised 22 August 2005; accepted 25 August 2005. Available online 27 September 2005. This work was supported in part by the Engineering Research Centers Program of the National Science Foundation under NSF Award Number EEC-0310723 and by a fellowship from the Whitaker Foundation (D.R.). The authors would like to especially thank Dr. Ellis Meng and Mr. Chi-Yuan Shih for their valuable comments, as well as Mr. Trevor Roper and other members of the Caltech Micromachining Laboratory for their fabrication assistance.

Additional details

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October 23, 2023