Strain sensitivity enhancement of thin metal film strain gauges on polymer microscale structures

Abstract

Arrays of identical polyimide cantilever beams have been fabricated with nickel-chrome strain gauges covering an increasing portion of the beam. In contrast to accepted beam models, testing showed that gauge factor increased 136% for polyimide beams as the strain gauge extended over a larger length of the beam. This effect is due to the high modulus of the thin film strain gauges relative to the polymer beams, a hypothesis supported by duplicate experiments with silicon nitride beams that showed a 65% reduction in gauge factor. Comparison with an analytical model and finite element analysis is also made, giving good agreement.