Tensile elongation measurement device with in-plane bimorph actuation mechanism

This paper describes the development of a bimorph-actuated twin-probe device utilized for uniaxial tensile test to measure tensile elongation of a film specimen. The device consists of two sets of microscale cantilever probes with piezoresistive sensor to detect the position of two gauge marks on a specimen, and multiple pairs of bimorph actuators to produce in-plane motion for scanning those marks. By Joule's heating, the bimorph actuators connecting two cantilever probes are able to move along the tensile direction. When those probes climb the gauge marks having convex line structure, the sensor signals originating from the piezoresistive effect are output by the cantilever's deflection. The elongation of a tensile specimen can be calculated from the moving velocity of cantilever probes and the time difference between two sensor signals. The performance of the device produced through conventional micromachining technologies was investigated. Elongation of single-crystal silicon (SCS) film specimen was measured during uniaxial tensile loading. The mean Young's modulus of 165.1 GPa which was measured by using the device was in good agreement with the analytical value. The proposed bimorph-actuated twin-probe device would be useful for measuring elongation of a film specimen during the tensile test.