Microfabricated calibration tool for direct shear stiffness measurements with applications in cell mechanics

We have developed a novel microelectromechanical system (MEMS) calibration tool that for the first time allows direct calibration of widely used traction force microscopy (TFM) substrates used for cell mechanics measurements. MEMS calibration tool (MCT) designs incorporate both capacitive force sensing and electrostatic actuation. The offset sensor detects vertical interaction with the sample to monitor preload with a resolution of approximately IfF/μm while the actuator generates up to 100μN of shear forces on the substrate. We have characterized 40:1 Polydimethylsiloxane (PDMS) polymer with several MCT devices and successfully treated devices with a hydrophobic coating to enable characterization of soft hydrogels used in cellular experiments. When used to characterize these soft hydrogels, the MCT improves the calibration accuracy, spatial force resolution, and ease of analysis for examining force generation in cells.