Development of Microscopic Hardness and Stiffness Investigation System with MicroRobot

Abstract

In order to investigate micro hardness and stiffness in a special chamber, the development of a small-force generator mechanism and a piezodriven microrobot is described in this paper. This small-force generator is simply composed of a Voice Coil Actuator (VCA) and the tandem leaf spring mechanism. The small force can be controlled by an electrical current, which is supplied to the coil and positioned precisely at the balance point with the parallel leaf spring with no mechanical friction. The full bridge strain gauges on both sides of the double leaf spring can detect a small force that is applied to the sample with a microindenter. This handmade small device can produce and verify small forces up to 17 mN with good linearity and a 50 µN resolution. The displacement of the indenter head can be also measured by the Linear Valuable Differential Transformer (LVDT) on the machine for monitoring the depth behavior of the indenter during the whole dwell time. The small force generator with the indenter can be implemented on the piezodriven microrobot to check the microscopic hardness and stiffness. This microrobot can move around the measurement area precisely step by step with 1 µm steps on a metal plate, so that the sample can be scanned with microscopic resolution in situ, such as in an SEM chamber. In the experiment results, the basic performance of microelasticity investigations with a certified hardness block was successfully checked and the indentation load-depth characteristics were precisely acquired on the path of the microrobot.