Development of 3D Force Sensors for Nanopositioning and Nanomeasuring Machine

Abstract

In this contribution, we report on different miniaturized bulk micro machined three-axes piezoresistive force sensors for nanopositioning and nanomeasuring machine (NPMM). Various boss membrane structures, such as one boss full/cross, five boss full/cross and swastika membranes, were used as a basic structure for the force sensors. All designs have 16 p-type diffused piezoresistors on the surface of the membrane. Sensitivities in x, y and z directions are measured. Simulated and measured stiffness ratio in horizontal to vertical direction is measured for each design. Effect of the length of the stylus on H:V stiffness ratio is studied. Minimum and maximum deflection and resonance frequency are measured for all designs. The sensors were placed in a nanopositioning and nanomeasuring machine and one point measurements were performed for all the designs. Lastly the application of the sensor is shown, where dimension of a cube is measured using the sensor.

Micromechanical force sensors based on SU-8 resist

“…As described by various groups (Brand et al 2009;Brand 2005, 2006;Nesterov and Brand 2006;Tibrewala et al 2008Tibrewala et al , 2009a the development of three dimensional force sensors forms the problem of a different bending stiffness K i in the x-, y-and z-direction. Typical values of the vertical to lateral ratio of bending stiffness K z /K x in the range of 30-60 have been achieved with conventional silicon force sensors of comparable designs Brand 2005, 2006;Tibrewala et al 2008Tibrewala et al , 2009a. The objective of the development of a micro force sensor is to build a sensor design which provides equal stiffness in all probing directions.…”

“…The design is chosen in order to compare the sensor characteristics with a conventional force sensor made of silicon (Tibrewala et al 2008(Tibrewala et al , 2009a and to advance the design of the SU-8 force sensor on the basis of the scientific findings on these first test patterns. The membrane design fundamentally influences properties of the sensor, such as sensitivity and stiffness.…”

“…However, the silicon sensor designs are geometrically constricted due to the anisotropic wet chemical etching process used to form the basic sensor structures. Moreover, to thin down the thickness of the sensor membranes for improving sensitivity results in fragile and brittle structures in the long term (Liu 2007;Tibrewala et al 2008;Tibrewala et al 2009a). Latter can be obviated by using polymer materials which are providing greater mechanical yield strain than silicon (Liu 2007).…”

“…Tactile force sensors based on silicon boss-membranes with diffused piezoresistive elements have been developed for applications in (micro) coordinate measurement machines to meet these demands (Brand et al 2009;Brand 2005, 2006;Tibrewala et al 2008Tibrewala et al , 2009a. However, the silicon sensor designs are geometrically constricted due to the anisotropic wet chemical etching process used to form the basic sensor structures.…”

Fabrication and characterisation of a novel smart suspension for micro-CMM probes

“…Due to symmetry, vertical displacement of the stylus tip results in a pure vertical load applied to the suspension structure, whereas pure lateral load results in a moment being applied to the suspension structure. For optimal performance the probe sensor design should ensure both the vertical and lateral stiffness are equal; a case which leads to a number of benefits in terms of minimising error sources, and simplifying the control of coordinate measurements machines when used in scanning mode [15,16].…”