Creep adjustment of strain gauges based on granular NiCr-carbon thin films

Mathis, M.V.; Vollberg, Dennis; Langosch, Matthäus; Göttel, Dirk; Lellig, Angela; Schultes, Günter

doi:10.5194/jsss-10-53-2021

Cited by 3 publications

(1 citation statement)

References 10 publications

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“…Xudong Cheng and Xiaochun Li [11] designed and fabricated a PdCr thin-film strain sensor, and embedded it in a metal structure to measure milling forces. Maximilian Mathis et al [12] used a NiCr-C thin-film strain gauge to reduce the influence of strain deviation on sensor accuracy. Much research has been done on the preparation of thin-film strain sensors.…”

Section: Introductionmentioning

confidence: 99%

Structural Design and Optimization of the Milling Force Measurement Tool System Embedded with Thin-Film Strain Sensors

Song,

Wu,

Zhao

et al. 2023

Micromachines

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A milling force measurement tool system is designed with an elastic beam structure, which is divided into a two-end ring hoop compression sensor mode and a two-end square hoop compression sensor mode to improve the strain sensitivity. A simplified mechanical model of the elastic beam is established, and the relationship between the strain and force of the elastic beam under the action of three cutting force components is investigated, which can act a guide for subsequent milling force measurement tool system calibration tests. Thin-film strain sensors occupy a central position in the milling force measurement tool system, which consists of a substrate, transition layer, insulating layer and resistance grid layer. The resistance grid layer has a particularly significant effect on the thin-film strain sensor’s performance. In order to further improve the sensitivity of thin-film strain sensors, the shapes of the substrate, the transition layer, the insulating layer and the resistance grid layer are optimized and studied. A new thin-film strain sensor is designed with a resistance grid beam constructed from an insulating layer and a resistive grid layer double-end-supported on the transition layer. The flow of the wet-etching process of thin-film strain sensors is studied and samples are obtained. The surface microforms of the sensor samples are observed by extended depth-of-field microscopy, confocal microscopy and atomic force microscopy. It can be seen that the boundary of the resistance grid layer pattern is tidy and has high dimensional accuracy, thus enabling the basic achievement of the expected effect of the design. The electrical performance of the samples is tested on an experimental platform that we built, and the results show that the resistive sensitivity coefficient of the samples is increased by about 20%, to 51.2%, compared with that of the flat thin-film strain sensor, which fulfils the design’s requirements.

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Section: Introductionmentioning

confidence: 99%

Structural Design and Optimization of the Milling Force Measurement Tool System Embedded with Thin-Film Strain Sensors

Song,

Wu,

Zhao

et al. 2023

Micromachines

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Preliminary Characterization of a Novel Aerosol Jet-Printed Strain Sensor for Feasibility Assessment in a Variable Stiffness Arterial Simulator Application

Filippi,

Fiori,

Genovesi

et al. 2024

Sensors

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Wearable strain sensors are widespread in many fields, including the biomedical field where they are used for their stretchability and ability to be applied to non-regular surfaces. The study of the propagation speed of the pressure wave generated by the heartbeat within vessels, i.e., the Pulse Wave Velocity (PWV), is of significant relevance in this field to assess arterial stiffness, a parameter commonly used for the early diagnosis of cardiovascular diseases. In this context, arterial simulators are useful tools to study the relationship between the PWV and other hemodynamic quantities in vitro. This study aims to characterize novel strain sensors to assess their suitability within an arterial simulator capable of varying the stiffness of an arterial surrogate by varying the transmural pressure. Six sensors deposited on arterial surrogates by Aerosol Jet Printing technology were subjected to deformation through a load frame. The results show that the sensors were able to distinguish strains of 0.1%, the maximum strain was around 6–8%, and the fatigue strength depended strongly on the strain rate.

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Improving the electrical and structural stability of highly piezoresistive nickel–carbon sensor thin films

Schultes

Cerino

Lellig

et al. 2022

J. Sens. Sens. Syst.

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Abstract. The family of sputter deposited granular metal-based carbon-containing sensor films is known for their high sensitivity transforming force-dependent strain into electrical resistance change. Among them nickel–carbon thin films possess a gauge factor of up to 30, compared to only 2 for traditional sensor films of metal alloys. This high sensitivity is based on disordered interparticle tunneling through barriers of graphite-like carbon walls between metal–carbon particles of columnar shape. Force and pressure sensors would benefit a lot from the elevated piezoresistivity. A disadvantage, however, is a disturbing temporal creep and drift of the resistance under load and temperature. This contribution shows how to stabilize such sensor films. A significant stabilization is achieved by partially replacing nickel with chromium, albeit at the expense of sensitivity. The more chromium used in these NixCr1−x-C layers, the higher the optimum annealing temperature can be selected and the better the electrical stabilization. A good compromise while maintaining sensitivities well above the standard of 2 is identified for films with x=0.5 to 0.9, stabilized by optimized temperature treatments. The stabilizing effect of chromium is revealed by transmission electron microscopy with elemental analysis. The post-annealing drives segregation processes in the layer material. While the interior of the layer is depleted of chromium and carbon, boundary layers are formed. Chromium is enriched near the surface boundary, oxidized in air and forms chromium-rich oxide sub-layers, which are chemically very stable and protect against further reactions and corrosion. As a result, creep and drift errors are greatly reduced, so that the optimized sensor coatings are now suitable for widespread use.

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Creep adjustment of strain gauges based on granular NiCr-carbon thin films

Cited by 3 publications

References 10 publications

Structural Design and Optimization of the Milling Force Measurement Tool System Embedded with Thin-Film Strain Sensors

Structural Design and Optimization of the Milling Force Measurement Tool System Embedded with Thin-Film Strain Sensors

Preliminary Characterization of a Novel Aerosol Jet-Printed Strain Sensor for Feasibility Assessment in a Variable Stiffness Arterial Simulator Application

Improving the electrical and structural stability of highly piezoresistive nickel–carbon sensor thin films

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