Piezoresistive cantilever as portable micro force calibration standard

Abstract

Design, fabrication and test of cantilever-type sensors for active micro force calibration are described. The cantilever comprises a probing tip at its free end where a force can be applied which is measured using a piezoresistive strain gauge at the cantilever suspension. The stiffness of the cantilever is approximately given by the spring constant of a beam with a rectangular cross section as confirmed by finite element modelling. Prototypes with a stiffness of 0.66 N m−1 and 7.7 N m−1 are realized using standard silicon bulk micromachining technology. Testing is performed using a high-resolution micro force measuring set-up. In either case a highly linear relationship between the gauge output voltage and the probing force is revealed in the µN range. Low scatter and drift corresponding to a standard deviation of ±0.22% was found for the resulting force sensitivity.

Investigation of a small force standard with the mass based method

“…Generally, there are two kinds of small force sensors: passive and active types [5]. The cantilever is a commonly used passive sensor.…”

“…The small standards in PTB and KRISS, which are based on the electromagnetic compensation balance and a nano-positioning stage, were applied for this comparison [5], [6]. Three types of commercial cantilevers for AFM, which is mentioned in Section 3.1, were used in this comparison.…”

“…Generally, there are two kinds of small force standards in the micro-newton to nano-newton range: the first one is based on the mass method, such as the micro-force measuring devices at PTB [5], and NFC (the nano force calibrator) at KRISS [6]; the second one is based on the electrostatic force realization principle, such as the EFB (electrostatic force balance) at NIST [7], the primary low force balance at NPL [8], and the force measurement system at CMS [9]. The establishment of these SI traceable standards significantly improves the reliability of small force measurement results.…”

Traceable profile and roughness measurements inside micro sonic nozzles with the Profilscanner

“…The key element of the Profilscanner is a long silicon cantilever type microprobe [15][16][17][18][19] (called as cantilever in the following) with an integrated probing tip at the free end, which is designed by PTB together with the Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH (CiS) Erfurt and the Institute for Semiconductor Technology of Technical University of Braunschweig. A full-bridge piezoresistive strain gauge on the cantilever close to its clamping measures the bending of the cantilever.…”

An Integrated Compact Unit for Wide Range Micro-Newton Force Measurement

“…For measuring tactile forces, force sensors can broadly be classified as active and passive cantilever types. In active sensors, e.g., millimeter to micrometer scale silicon cantilevers comprising piezoresistive strain gauges provide a voltage output for a direct measurement of forces (4)(5)(6)(7)(8)(9)(10) . Active sensors are reasonably good in size; however, a particular active sensor can produce only a particular set of force range and sensitivity for which its uses become limited.…”