Microscale Compression and Shear Testing of Soft Materials Using an MEMS Microgripper With Two-Axis Actuators and Force Sensors

This paper reports a microelectromechanical systems (MEMS)-based microgripper, integrating two-axis actuators and force sensors, for microscale compression and shear testing of soft materials. The device employs V-beam electrothermal actuators to drive an active gripping arm and compress or shear a microscale sample grasped at the gripping tips, and two triplate differential capacitive sensors to measure the compression and shear forces applied to the sample with nanonewton resolution (compressive force resolution: 7.7 nN, and shear force resolution: 57.5 nN). Using the microgripper, we demonstrate, for the first time, on-chip compression and shear testing of polydimethylsiloxane (PDMS) microstructures prepared at different crosslinking levels. We believe that this device will be useful for accurately characterizing mechanical properties of a variety of microscale soft materials.