Microelectromechanical Systems for Nanomechanical Testing: Displacement- and Force-Controlled Tensile Testing with Feedback Control

Abstract

Background: MEMS-based nanomechanical testing has received much interests. However, it remains challenging to perform displacement- and force-controlled nanomechanical tests (e.g., stress relaxation and creep). Objective: We report a MEMS-based device for displacement- and force-controlled tensile testing of 1D nanomaterials using feedback control. Methods: The device consists of an electrostatic actuator, a load cell, and two differential capacitive sensors. A specimen is mounted between a fixed anchor on one side and a displacement sensor on the other side. Using a multi-channel capacitive readout, both specimen displacement and force (thus strain and stress) can be measured from the readout simultaneously, without the need of imaging that is often used for displacement measurement. Results: With the feedback control, both displacement- and force-controlled tensile testing can be achieved. The capability of the device is demonstrated in three representative tests of metallic nanowires – stress relaxation test, tensile test capturing rapid stress drop, and creep test. Conclusions: The reported MEMS device can be used for a range of tests where imaging for displacement measurement is not feasible, such as ex-situ tests, high-rate tests, and fatigue tests in different environments.