Design of a piezoresistive triaxial force sensor probe using the sidewall doping method

Abstract

In this study, we propose a triaxial force measurement sensor probe with piezoresistors fabricated via sidewall doping using rapid thermal diffusion. The device was developed as a tool for measuring micronewton-level forces as vector quantities. The device consists of a 15 µm thick cantilever, two sensing beams and four wiring beams. The length and width of the cantilever are 1240 µm and 140 µm, respectively, with a beam span of 1200 µm and a width of 10–15 µm. The piezoresistors are formed at the root of the cantilever and the sidewalls of the two sensing beams. The sensor spring constants for each axis were measured at kx = 1.5 N m−1, ky = 3.5 N m−1 and kz = 0.64 N m−1. We confirmed that our device was capable of measuring triaxial forces with a minimum detectable force at the submicronewton level.

Ultra miniature force plate for measuring triaxial forces in the micro newton range

“…Furthermore, individual experiments with loads of up to 4 mN proved the same characteristics and confirmed the particular robustness of our force plate. This property in particular is a distinct advantage compared with other highly sensitive MEMS devices described in the literature (Bartsch et al, 2007;Muntwyler et al, 2010;Kan et al, 2013). These sensors are extremely fragile and are not able to resist the maximum forces that, for instance, ants can produce with their mandibles.…”

“…Various prototypes and their principal usability in the field of insect biomechanics have already been demonstrated (Bartsch et al, 2007;Muntwyler et al, 2010;Kan et al, 2013). However, a major problem with these sensors is their high fragility and the associated small measuring range.…”

“…As standard deviations are smaller than the marker size, no error bars are plotted (see Table 2). Blickhan and Barth, 1985 Plastic/bronze beams/strain gauge 3 1 mN Full and Tu, 1990 Brass beams/semiconductor strain gauge 2 1 mN Full et al, 1991 Brass beams/semiconductor strain gauge 3 1 mN Katz and Gosline, 1993 Brass beams/semiconductor strain gauge 3 1 mN Drechsler and Federle, 2006 Metal beams/strain gauge 2 0.1 mN Autumn et al, 2006 Brass beams/semiconductor strain gauge 3 0.5 mN Bartsch et al, 2007 MEMS-based 3 1 µN Wood et al, 2009 Invar ® FeNi36/capacitive sensor 2 5 µN Reinhardt et al, 2009 PVC-based/semiconductor strain gauge 3 10 µN Muntwyler et al, 2010 MEMS-based 3 1 µN Dai et al, 2011 Aluminium beams/strain gauge 3 1 mN Lin and Trimmer, 2012 Acrylic/strain gauge 2 0.3 mN Kan et al, 2013 MEMS-based 3 1 µN MEMS, microelectromechanical systems.…”

On accuracy of sensitivity relations for piezoresistive microcantilevers used in surface stress studies

“…Only the deflection in the piezoresistor section induces the stress in the piezoresistor. Thus, (8) can be modified to give the deflection in piezoresistor section of the cantilever as: (9) And, the longitudinal stress induced in the piezoresistor can be given as: (10) Thus, the surface stress sensitivity in case of CMOS piezoresistive microcantilever sensor subject to surface stress can be approximated as: (11) It should be mentioned here that the relation for determining the neutral axis given above is valid for bending in beams or plates subjected to force and moments. However, as discussed later, in case of surface stress the original neutral axis shifts downwards to a new apparent neutral axis at η' = 2t/3 from the top cantilever surface.…”

Quad-axial piezoresistive force sensor probe by four sensing elements with sidewall doping method

“…Not single but multi-axis force detection is required in various applications because force is generally a vector quantity in nature [4][5][6]. Our group also has developed a three-axis force probe with piezoresistive element [7][8]. Recently, several researches reported sensor probes which can measure both forces and torques simultaneously [9][10].…”