Patrick Heinickel

Functionality of a novel overload resistant silicon high pressure sensing element

This paper presents a novel miniaturized overload resistant piezoresistive silicon high-pressure sensor for a pressure range up to 500 MPa. The novel composite element is made of a solid body silicon chip with implanted piezoresistive resistors. A solid body glass substrate is jointed to the silicon by anodic bonding. The operating mode is based on mechanical strain of all-round pressurized silicon and mechanical mismatched substrate. This paper also presents the verification of the functionality on the basis of repeatable metrological investigations with 200 MPa of experimental designs and analytical investigations as well as finite element analysis.

Experimental comparison of piezoresistive MEMS and fiber bragg grating strain sensors

We report on the experimental comparison of piezoresistive MEMS sensors and optical fiber BRAGG grating sensors (FBGS) for strain measurements in force sensors. To our knowledge, this is the first direct comparison of piezoresistive and FBG transducers as force sensors. Cantilevers are used as deformation elements. The sensors are bonded on top and bottom side of the cantilever using a heat-curing epoxy adhesive. The piezoresistive ones are micro machined silicon chips with decoupled adhesive areas, and four ion implanted piezoresistive areas (R<inf>sq</inf> = 125 Ωcm, (1 × 2)mm²×350 µm). The FBGS are draw-tower-gratings (0.78mm² × 9 mm). The measured values are compared by analyzing nominal strain, sensitivity, resolution, measurement uncertainty and thermal behavior. The MEMS sensor is more sensitive than the FBGS (0.28%, /N ≫ 0.004%/ N), its measurement uncertainty is lower (2% ≪ 5%) and the resolution Δ∈ = 10⁻³ µm /m is 100 times higher than in case of FBGS Δ∈ = 1.38 µm / m.

Hydrostatisches Hochdruck-Messelement bis 5.000 bar mit einem Silizium-Glas-Verbundkörper

Zusammenfassung Das Verbundelement als piezoresistives Hochdruck-Messelement für 5000 bar basiert auf einem neuartigen Prinzip der mechanischen Verspannung infolge allseitiger Druckbelastung. Der Einfluss des Dickenverhältnisses von Silizium und mechanisch fehlangepasstem Glas anhand eines analytischen Ansatzes wird durch messtechnische Charakterisierung von sieben Verbundelementen mit drei unterschiedlichen Dickenverhältnissen bestätigt. Es zeigt sich ein nichtlineares Verhalten bei den Elementen mit den dicksten Glasgegenkörpern, die mehr als doppelt so dick wie das Silizium sind. Abstract The composite-element of our pressure sensor is a piezoresistive high-pressure sensing element for 500 MPa. The functionality is based on mechanical stress due to the hydrostatic pressure load. The effect of the ratio of the thicknesses of silicon and the mechanical mismatched glass resulting from analytical approach is shown by metrological characterization of seven sensing elements with different thickness ratios. The composite elements with the highest glass thicknesses — more than twice that of silicon — exhibits a strong nonlinearity.