The electromechanical properties of thin films and the thin film strain gauge

Abstract

Abstract The thin film strain gauge was first patented, in outline form, in 1951 1 . In its simplest form it consists of a vacuum-deposited thin film formed directly on the surface of a strainable member. Existing strain gauge technology uses “bonded” strain gauges 2 . These are foil gauges glued onto the surface of the strainable member. The use of glue can, in some instances, limit both the degree of strain transmission from member to gauge and the temperature at which the device may be used. The use of thin film technology is seen as a way of obviating both these limitations. The purpose of this paper is to review the development of the thin film strain gauge. The paper begins with a discussion of the physical principles underlying the response of thin films to both strain and temperature. After a review of existing experimental results there is a description of the device and its fabrication. Although in general the paper is based on a detailed discussion of metal films, the range of materials also includes cermets 3 , semiconductors 4 and alloys 5 . The paper ends with a discussion of the possible role of the thin film strain gauge in future transducer technology.