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Journal of Sensors
Volume 2011 (2011), Article ID 360173, 5 pages
Research Article

Design and Characterization of Nano-Displacement Sensor with High-Frequency Oscillators

Division of Electrical Engineering and Computer Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan

Received 21 April 2011; Accepted 29 June 2011

Academic Editor: Tuan Guo

Copyright © 2011 Akio Kitagawa. 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.


The circuitry of a capacitive nanometer displacement sensor using the ring oscillator has been analyzed and characterized. We focus on the sensitivity of the sensor to detect the nanometer displacement or strain. The displaced target object must be conductive and the medium around the target object must be an insulator or a vacuum. The sensitivity in the range of L < 1 μm is enhanced with decreases in the size of the sensor electrode, and using a higher free-running oscillation frequency can increase sensitivity. The proposed sensor, which converts the displacement of the target object to the oscillation frequency, was fabricated with CMOS 350 nm technology, and the sensitivity was estimated at 8.16 kHz/nm. The results of our study indicated that the presented sensor has enough sensitivity to detect the nanometer displacement of the target object at a distance within 1 μm from the surface of the sensor electrode.