Equivalent circuit models of two-layer flexure beams with excitation by temperature, humidity, pressure, piezoelectric or piezomagnetic interactions

Marschner, Uwe; Gerlach, Gerald; Starke, Eric; Lenk, Arno

doi:10.5194/jsss-3-187-2014

Cited by 18 publications

(15 citation statements)

References 7 publications

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“…However, in process control 70 % of all sensors are used as threshold switches and in building monitoring more than 90 %. In Bellmann et al (2015), a novel approach for a non-powered humidity threshold switch based on the BIZEPS (binary zeropower sensor) principle was proposed (see also Frank et al, 2012;Rangelow et al, 2009;Rittersma, 2002). With this principle, the energy is taken directly from the measured variable.…”

Section: Motivationmentioning

confidence: 99%

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Modelling and model verification of an autonomous threshold sensor for humidity measurements

Gulnizkij

Gerlach

2020

J. Sens. Sens. Syst.

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Abstract. Autonomous sensors that receive their energy from an energy harvester or directly from the environment have the potential to save energy for applications in numerous sectors. For humidity sensing, the swelling behaviour of a water vapour-sensitive hydrogel is used. To trigger an electrical contact the mechanical energy is taken from the hydrogel swelling by the bimorph effect. As long as a defined threshold is not reached, the electrical microcontact remains open. By passing the threshold value, a switching will be triggered causing the closure of the contact. This sensor principle does not need any electrical power supply because the switching power is provided directly by the surrounding humidity as quantity to be measured. For the description of the deflection versus the hydrogel pattern of such a sensor, a model was developed by means of the beam theory. Goal of the model was to derive design guidelines for the dimensioning of the sensors bending plate and the patterned hydrogel layer. Experiments then should show the applicability of the model approaches. The deflection of the bending plate depends on the ratio between the lengths of the uncoated and the coated part of the bending plate where the maximum occurs at a ratio of ca. 0.5. The swelling behaviour of the hydrogel shows a high sensitivity with regard to slight changes in relative humidity. This can be used for humidity threshold sensors that open and close microcontacts with respect to very small changes in relative humidity. To avoid voltage peaks and arcs during the switching process that could arise and destroy the microcontact, a bistable characteristic with hysteresis is needed. Experiments demonstrate the feasibility of this concept and are in good agreement with the modelling results.

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Section: Motivationmentioning

confidence: 99%

“…To calculate the deflection as a function of the hydrogel pattern, a simple mechanical model is used based on the beam theory for monomorph and bimorph beams (Marschner et al, 2014). Figure 2 shows the setup of the sensor and the corresponding mechanical model.…”

Section: Model Without Axial Forcesmentioning

confidence: 99%

Modelling and model verification of an autonomous threshold sensor for humidity measurements

Gulnizkij

Gerlach

2020

J. Sens. Sens. Syst.

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“…As shown in Reference [31], the effect of a bimorph bending element can be considered as a conventional monomorph bending element with an additionally acting internal moment source (affecting the bending behavior), as well as an internally generated in-plane force, due to the effective thermal length expansion.…”

Section: Deflection Of a Bending Plate Due To The Bimorph Effectmentioning

confidence: 99%

“…In the case of silicon plates, both the pre-deflection and the axial pre-stress can be achieved by depositing an SiO 2 layer in the center of the plate. SiO 2 has a coefficient of thermal expansion (5.6 × 10 −7 K −1 ) that is much smaller than that one of Si (2.3 × 10 −6 K −1 ) [31]. After cooling down the structure from higher temperatures to room temperature, both the targeted pre-deflection and the compressive stress in the plane are established (Figure 13).…”

Section: Set-upmentioning

confidence: 99%

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Bistable Threshold Humidity Sensor Switch with Rectangular Bimorph Bending Plate

Gulnizkij

Gerlach

2020

Micromachines

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Energy-autonomous bistable threshold sensor switches have the potential to reduce costs because they do not need any electrical energy supply for monitoring physical quantities, such as relative humidity. In previous work, a bistable beam-like sensor switch with switching hysteresis was manufactured from sheet metal and a partially coated water vapor-sensitive hydrogel (poly(vinyl alcohol)/poly(acryl acid)). Based on the beam theory, a corresponding mechanical model was developed. However, bending plates should be used instead of bending beams to separate the humidity to be measured from the electrical contacts. For this reason, this work deals with the development and realization of a mechanical model based on the plate theory to describe the deflection of a silicon bimorph bending plate partially coated with hydrogel that swells with increasing humidity. For implementing a switching hysteresis a plasma-enhanced chemical vapor deposition silicon dioxide (SiO2) layer is used, which was deposited and structured on top of the silicon plate. The hydrogel layer itself is patterned on the surface of the bending plate using a stamp technique. To validate the mechanical model, the switching hysteresis of the miniaturized sensor switch was measured optically by a camera measurement device.

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Experimental Investigation and Modeling of the Dynamic Resistance Response of Carbon Particle‐Filled Polymers

Mersch

Winger

Nocke

et al. 2020

Macro Materials & Eng

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An important aspect of soft robotics, next to the different actuation mechanisms, is the monitoring of the robot's position and condition and, thus, the local and global strains via integrated sensors. Currently investigated actuation classes and materials like dielectric elastomer actuators or twisted-coiled polymeric actuators offer large strain potentials, rendering conventional metal or semiconductor strain gauges unsuitable. [3] Apart from their inherent strain limit of less than 5%, the difficult integration into and adhesion to smart materials is preventing their use in novel complex and compact soft robots. [4,5] Additionally, as some of the currently researched actuator mechanisms and principles offer high strain rate actuation, the necessity of not only a quasistatic but also dynamic monitoring and suitable control strategies is conspicuous. One approach to integrate actuators and sensors and to achieve resilient but flexible structures is using fiber-shaped active materials similar to muscles and nerves in biological systems. [6] A popular choice as a sensor material are carbon-based particle-filled highly stretchable elastomers (CPFEs). Such particles can be carbon black (CB), carbon nanotubes (CNT), graphene, or combinations thereof. Until today, there has been a vast amount of studies investigating different polymer materials, fillers, and mixing ratios as well as their applications to monitor soft robots or body posture. [7,8] Additionally, the conducting particles can also be used in order to tailor the electro-thermal response of shape memory polymers. [9] The standard analysis performed to evaluate the different soft sensor systems is a quasistatic tensile test while tracking the resistance. Investigations of dynamic sensor properties with systematically varied strain rates and loading scenarios are scarce. This lack of data also contributes to the poorly understood phenomena occurring during cyclic, dynamic loading of CPFEs. [10] To employ CPFEs as sensors, their linearity, sensitivity, and monotonicity are important features. [11] Unfortunately, the few investigations so far on dynamic mechano-electrical properties show non-monotonic responses, meaning that, apart from the resistance peak at maximum strain, additional peaks occur. [12,13,14] These peaks either appear while releasing or when the imposed strain is fully released and have been called shoulder phenomenon or secondary peaks. The phenomenon appears independently whether the filler material is CB, CNT, or graphene. [11,15,16] To distinguish between the different phenomena described in literature, the nomenclature in Figure 1 Carbon particle-filled polymers are frequently used as stretchable conductors and strain sensors. Many of the proposed resistance-based stretchable strain sensors show non-monotonic strain response, especially under dynamic conditions. This is commonly attributed to the competing destruction and reformation of the conductive network, but the underlying mechanism is still unknown. Therefore, systematic cyclic tens...

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Equivalent circuit models of two-layer flexure beams with excitation by temperature, humidity, pressure, piezoelectric or piezomagnetic interactions

Cited by 18 publications

References 7 publications

Modelling and model verification of an autonomous threshold sensor for humidity measurements

Modelling and model verification of an autonomous threshold sensor for humidity measurements

Bistable Threshold Humidity Sensor Switch with Rectangular Bimorph Bending Plate

Experimental Investigation and Modeling of the Dynamic Resistance Response of Carbon Particle‐Filled Polymers

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