Sub-millinewton capacitive MEMS force sensor for mechanical testing on a microscope

摘要

Most mechanical tests (compression testing, tensile testing, flexure testing, shear testing) of samples in the sub-mm size scale are performed under the observation with an optical microscope or a scanning electron microscope. However, the following problems exist with prior art force sensors as e.g they cannot be used for in-plane mechanical testing (a- and b-direction) of a sample; they cannot be used for vertical testing (c-direction) of a sample. In order to overcome the before mentioned drawbacks the invention comprises the following basic working principle: A force is applied to the probe (2) at the probe tip (1) of the sensor. The force is transmitted by the sensor probe (2) to the movable body (3) of the sensor. The movable body is elastically suspended by four folded flexures (4), which transduce the force into a deflection dx. This deflection is measured by an array of capacitor electrodes, called capacitive comb drive (6).

主权项

1. A single-axis capacitive MEMS force sensor for sub-Millinewton force sensing, comprising:
a sensor probe with a probe tip on which the force is applied, the sensor probe configured to transmit the force to a movable body; at least one comb drive for capacitive measurement of an amount of deflection of the moveable body in response to the force transmitted by the sensor probe, the at least one comb drive comprising two non-movable capacitor electrodes located next to each other and a movable common electrode; a substrate for supporting the sensor probe and the at least one comb drive, wherein the probe tip of the sensor probe overhangs the substrate on two adjacent sides of the substrate, wherein the two non-movable capacitor electrodes and the movable common electrode form a differential comb drive.