In this paper, stability and mechanistic simulations for a four-beam-mass-based MEMS gravimeter were conducted, and guidelines for the gravimeter design were proposed. Based on a prototyped MEMS device, the nonlinear finite element model was validated first against the experimental results. Then, we demonstrated three different scenarios in design that have three distinct modes of deformation: the mode with buckling (case 1), the mode without buckling but with a single zero-stiffness point (case 2), and the mode without both buckling and zero-stiffness point (case 3). Both case 1 and case 2 presented an unstable and sensitive region, in which a tiny perturbation could result in a rapid increase of the resonance frequency. Case 3, on the other hand, could provide a stable and low resonance frequency with a linear relationship between the displacement and gravitational acceleration. An optimized design of a beam/spring-mass-based relative gravimeter could be achieved using the above guidelines.

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This work demonstrates the first on-chip UV optoelectronic integration in 4H-SiC CMOS, which includes an image sensor with 64 active pixels and a total of 1263 transistors on a 100 mm2 chip. The reported image sensor offers serial digital, analog, and 2-bit ADC outputs and operates at 0.39 Hz with a maximum power consumption of 60 μW, which are significant improvements over previous reports. UV optoelectronics have applications in flame detection, satellites, astronomy, UV photography, and healthcare. The complexity of this optoelectronic system paves the way for new applications such harsh environment microcontrollers.@en

Accurately sensing the temperature in silicon carbide (power) devices is of great importance to their reliable operation. Here, temperature sensors by resistive and CMOS structures are fabricated and characterized in an open silicon carbide CMOS technology. Over a range of 25-200°C, doped design layers have negative temperature coefficients of resistance, with a maximum change of 79%. Secondly, CMOS devices are used to implement a CTAT, which achieves a maximum sensitivity of 7.5mV/K in a temperature range of 25-165°C. The integration of readout electronics and sensors that are capable of operation in higher temperature than silicon, opens application in harsher environments.@en

This paper presents a continuous-time integrated readout interface for inertial sensors with high energy efficiency and high resolution. A dual digital-to-analog conversion (dual DAC) scheme is proposed which reduces the large DC baseline capacitance while preserving a high gain in the capacitance-to-voltage converter (CVC). A continuous-time delta-sigma modulator (CTΔΣM) is used to digitize the output signal of the CVC without kT/C noise. This results in a precision capacitive readout IC with a 5.5aF resolution in 0.5ms conversion time. It consumes 1.8mW. An inertial sensing system, consisting of the readout IC and a MEMS inertial sensor, achieves a resolution of 17.02ng/√Hz.@en

Downscaling of transistors, also known as Moore’s law, has been the main propelling force behind the microelectronics industry. This trend will eventually come to an end due to physical limitations, hence an alternative is required to further drive technological progress. This gave an incentive to evolve in other directions as well, also known as More than Moore (MtM). This concerns all technologies adding functionality to integrated circuits (IC), all packaged as a single system. This can be done by combining digital and non-digital elements, e.g. analog/RF, passives, microelectromechanical devices (MEMS), and so on. The non-digital elements are not necessarily scalable according to Moore’s law. Therefore, in this thesis we investigated the possibilities of using silicon and silicon carbide (SiC) to fabricate a number of sensors, capable of measuring weak signals. This is done by having a multidisciplinary investigation spanning from electrical, to mechanical and optical domains. @en

Nowadays many applications require optical detection of some sorts, ranging from civil to military fields. Depending on the optical source, each sensing element needs to have distinct properties with the spectral range at the top. Choices such as sensitivity and environment play an equally important role, if not more important. The properties of the sensors can be tailored by selecting a proper material for a proper photodetector device type. The device design choice therefore will have set the performance parameters such as selectivity, sensitivity and speed. This chapter discusses such photodetection and gives requirements which need to be met. The discussion will also include the photodetection principle, device types important to this work, design considerations and relevant parameters.@en

Traditional lighting is focused on the prevention of hardware failures. With the trend towards controlled and connected systems, other components will start playing an equal role in the reliability of it. Here reliability needs to be replaced by availability and other modeling approaches are to be considered. System prognostics and health management is the next step to service the connected complex systems in the most effective way possible. In this chapter, we will highlight the next frontiers that will need to be taken in order to move the traditional lighting catastrophic failure thinking into a thinking more towards new ways how system (degraded) functions can fail or be compromised. Results in the failure mode of lumen maintenance and its uncertainty are presented. An industrial use case is presented demonstrating how smart lighting will eventually be able to forecast maintenance schedules more efficiently.@en

Capacitors made of interdigitated electrodes (IDEs) as a transducer platform for the sensing of volatile organic compounds (VOCs) have advantages due to their lower power operation and fabrication using standard micro-fabrication techniques. Integrating a micro-electromechanical system (MEMS), such as a microhotplate with IDE capacitor, further allows study of the temperature- dependent sensing response of VOCs. In this paper, the design, fabrication, and characterization of a low-power MEMS microhotplate with IDE capacitor to study the temperature-dependent sensing response to methanol using Zeolitic imidazolate framework (ZIF-8), a class of metal-organic framework (MOF), is presented. A Titanium nitride (TiN) microhotplate with aluminum IDEs suspended on a silicon nitride membrane is fabricated and characterized. The power consumption of the ZIF-8 MOF-coated device at an operating temperature of 50 ∘ C is 4.5 mW and at 200 ∘ C it is 26 mW. A calibration methodology for the effects of temperature of the isolation layer between the microhotplate electrodes and the capacitor IDEs is developed. The device coated with ZIF-8 MOF shows a response to methanol in the concentration range of 500 ppm to 7000 ppm. The detection limit of the sensor for methanol vapor at 20 ∘ C is 100 ppm. In situ study of sensing properties of ZIF-8 MOF to methanol in the temperature range from 20 ∘ C to 50 ∘ C using the integrated microhotplate and IDE capacitor is presented. The kinetics of temperature-dependent adsorption and desorption of methanol by ZIF-8 MOF are fitted with double-exponential models. With the increase in temperature from 20 ∘ C to 50 ∘ C, the response time for sensing of methanol vapor concentration of 5000 ppm decreases by 28%, whereas the recovery time decreases by 70%.

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Commercially available gravimeters and seismometers can be used for measuring Earth’s acceleration at resolution levels in the order of ng∕Hz (where g represents earth’s gravity) but they are typically high-cost and bulky. In this work the design of a bulk micromachined MEMS device exploiting non-linear buckling behaviour is described, aiming for ng∕Hz resolution by maximising mechanical and capacitive sensitivity. High mechanical sensitivity is obtained through low structural stiffness. Near-zero stiffness is achieved through geometric design and large deformation into a region where the mechanism is statically balanced or neutrally stable. Moreover, the device has an integrated capacitive comb transducer and makes use of a high-resolution impedance readout ASIC. The sensitivity from displacement to a change in capacitance was maximised within the design and process boundaries given, by making use of a trench isolation technique and exploiting the large-displacement behaviour of the device. The measurement results demonstrate that the resonance frequency can be tuned from 8.7 Hz–18.7 Hz, depending on the process parameters and the tilt of the device. In this system, which combines an integrated capacitive transducer with a sensitivity of 2.55 aF/nm and an impedance readout chip, the theoretically achievable system resolution equals 17.02 ng∕Hz. The small size of the device and the use of integrated readout electronics allow for a wide range of practical applications for data collection aimed at the internet of things.@en

This work describes the design, modelling and realisation of the mechanical part of a non-linear MEMS accelerometer intended for large displacement behaviour. For this, a mass/spring system was designed with an extremely low resonance frequency. In this work the mechanical behaviour was verified by measurements done using an optical setup, including a laser and photodiode. The results are a resonance frequency of 12.6 Hz, which can be further tuned depending on the application by varying the mass, beam thickness and tilt of the structure. This results in a mechanical sensitivity of 0.16 [mm/ms-2]. The future goal of this work is to integrate a read-out scheme on wafer level, for example electrostatically.

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The mechanical part of inertial sensors can be designed to have a large mechanical sensitivity, but also requires the transduction mechanism which translates this displacement. The overall system resolution in mechanical inertial sensors is dictated by the noise contribution of each stage and the magnitude of each sensitivity, see also Figure 1. Maximizing the capacitive sensitivity, results in suppression of noise in the electronics domain. This work focuses on the design and realization of a mechanical to electrical transduction using a capacitive readout scheme. Design considerations and measures are taken to maximize the latter are considered and illustrated using FEM simulations. A capacitive transducer showing a sensitivity of 100 [aF/nm] was designed and realized, by exploiting the large displacement behavior of the inertial sensor which was considered.

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In this work a method is described to investigate process variations across a wafer. Through wafer MEMS spiral resonators were designed, simulated, fabricated and characterized by measuring the eigenfrequency and corresponding mode shapes. Measuring the eigenfrequency and resulting spectral behavior of resonators on different locations on the wafer was performed by using an optical measurement setup. Two laser beams were used where one is modulated by the periodic movement of the center mass of the resonator. One of the beams is reflected back from the modulated resonator and this beam hits a photo diode. Variations in light intensity due to movement of the resonator is providing a measurement signal correlated to movement. Preliminary measurements showed that measured eigenfrequencies are in correspondence with the simulations within a range of 0-10% deviation.

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Traditional lighting is focused on the prevention of hardware failures. With the trend towards controlled and connected systems, other components will start playing an equal role in the reliability of it. Here reliability need to be replaced by availability and other modelling approaches are to be taken into account. System prognostics and health management is the next step to service the connected complex systems in the most effective way possible. In this keynote we will highlight the next frontiers that will need to be taken in order to move the traditional lighting catastrophic failure thinking into a thinking more to-wards new ways how system (degraded) functions can fail or be compromised.@en

The in situ electrochemical growth of Cu benzene-1,3,5-tricarboxylate (CuBTC) metal-organic frameworks, as an affinity layer, directly on custom-fabricated Cu interdigitated electrodes (IDEs) is described, acting as a transducer. Crystalline 5-7 μm thick CuBTC layers are grown on IDEs consisting of 100 electrodes with a width and a gap of both 50 μm and a height of 6-8 μm. These capacitive sensors are exposed to methanol and water vapor at 30 °C. The affinities show to be completely reversible with higher affinity toward water compared to methanol. For exposure to 1000 ppm methanol, a fast response is observed with a capacitance change of 5.57 pF at equilibrium. The capacitance increases in time followed diffusion-controlled kinetics (k = 2.9 mmol s^-0.5 g^-1 _CuBTC). The observed capacitance change with methanol concentration follows a Langmuir adsorption isotherm, with a value for the equilibrium affinity K_e = 174.8 bar^-1. A volume fraction f_MeOH = 0.038 is occupied upon exposure to 1000 ppm of methanol. The thin CuBTC affinity layer on the Cu-IDEs shows fast, reversible, and sensitive responses to methanol and water vapor, enabling quantitative detection in the range of 100-8000 ppm.

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In this paper, we present electro-thermal analysis and design of a combined MEMS micro hotplate and interdigitated-capacitance impedance sensor for gas sensing application using nano-porous materials like metal organic framework (MOF). The effects of design parameters of interdigitated electrodes such as width(W) and gap(G) of the capacitor, metallization ratio, number of electrodes and area of the capacitor. The influence of height of the electrode material, thickness of the insulation layer between the capacitance electrodes and the micro hotplate electrodes are studied. These design parameters are optimized to obtain a high bare capacitance of the electrodes using analytical and electric and thermal domain simulations in COMSOL 5. The design and thermal analysis of the micro hotplate for a temperature range of (150-300°C) and low power consumption is modelled and results are discussed.@en