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We present an improved version of a torsionally oscillating resonant pipe viscosity sensor. The new design offers the possibility to sense both, viscosity and density independently and at the same time. The first version of the sensor allowed only sensing the viscosity-density product, where the two values were not separable without additional knowledge or measurements. For the new design, density sensitive structures were additionally implemented into the pipe system. These structures force the fluid to follow the torsional oscillation of the pipe, therefore, in this region the fluid influences the behavior of the resonant structure like an additional mass. This leads to a frequency shift which is mainly density dependent. Due to this behavior it is now possible to use a higher order model to extract both viscosity and density out of one single measurement. We present the newly introduced sensor design, compare it to the first sensor design, describe the additional density sensitive structures and explain how the sensor was designed and evaluated using the Finite Element Method (FEM). We show how different values of viscosity and density influence the resonance frequency and the damping characteristics of the sensor. To prove the concept, we apply a calibrated higher order model to the simulation results and provide a first accuracy estimation.

This paper provides a tutorial introduction to recently devised technologies for transducers embedded within the organic coatings of metallic (or, more generally, of electrically conductive) mechanical components, such as organically coated flat sheet steel, and three-dimensional machine parts, such as bearing supports and mold jaws. The integration of sensors and actuators into the surface coating of these components is of particular interest: first, it allows assessment of physical parameters at locally defined positions that are not accessible with usual discrete transducers; and second, a functionalized component equipped with sensory intelligence adds value for producer and customer. However, realization of embedded transducers entails challenges posed by (i) any potential preexisting protective organic coating and (ii) the shape and surface roughness of the underlying metallic substrate. This tutorial addresses the major issues that arise when sensors or actuators are to be integrated into the organic coating of an electrically conductive machine part, and provides hints and guidelines for successful realization based on recent research.

Microfluidic co-flow viscometers require the measurement of the interface position between two fluids (one sample and one reference fluid) flowing in parallel inside a microfluidic channel. From the interface position, the flow rates of both fluids and the known viscosity of the reference fluid, the viscosity of the sample fluid can be calculated. The detection of the interface position is usually done by optical means, therefore requiring optical access, and often coloring of the liquids or suspension of tracer particles to achieve optical contrast. In this contribution we present a device that is capable of determining the interface position in an alternative manner by capacitive measurements. The fully polymeric microfluidic chip is fabricated by simple processes requiring no specialized equipment. The capacitive sensor is fabricated by screen-printing. In order to enhance sensitivity, an insulation coating made from PMMA and barium titanate is applied. To assess the interface detection by capacitive means, measurements using different water/glycerol mixtures are performed and compared to optical images of the interface position, establishing a relationship between capacitance and interface position. The capacitive measurement does not require coloring of the liquids or suspension of tracer particles, if there is a dielectric contrast at the measurement frequency.

The electrical and mechanical response of multilayered structures involving a piezoelectric layer and bull’s eye shaped electrodes is investigated. A boundary element method is employed based on spectral domain Green’s functions. With this method, the electric field distribution is determined first, and the local mechanical displacement in a second step. As will be shown, this allows us to exploit cylindrical symmetry for the electric surface charge distribution, but not for the vertical surface displacements. The effect of substrate bending due to in plane-stress, introduced by the piezoelectric constant d31, and the benefits of using bull’s eye electrode geometries with thick metallic backplates intended to reduce this effect are studied. A rigorous analysis and a largely simplified, but accurate approximation are compared. The application of this technique is demonstrated on a practical example for highly efficient and accurate determination of selected piezoelectric coefficients from surface topography measurements on such structures. Linz Center of Mechatronics COMET-K2 Osterreichische Forschungsforderungsgesellschaft (DE-588)10108858-9 H-iSlice Version of record

Probing nucleation and growth of porous crystals at a molecular level remains a cumbersome experimental endeavour due to the complexity of the synthesis media involved. In particular, the study of zeolite formation is hindered as these typically form in multiphasic synthesis media, which restricts experimental access to crystallisation processes. Zeolite formation from single phasic hydrated silicate ionic liquids (HSiL) opens new possibilities. In this work, HSiL zeolite crystallisation is investigated

For keeping control of processes in lab-on-chip applications, monitoring the flow velocity inside channels is an important task. One popular approach to this is to consider heat transfer inside the channel as a flow velocity dependent effect, which can be measured by relatively easy means. Additionally, these thermal measurement methods can be designed and applied in a way that the sensors and actuators do not disturb the flow profile. A fabrication technique suitable to fabricate such sensors is screen printing, which combines cost efficient and fast processing with layers thin enough to not alter the fluid flow. In this work, we report on a devised sensor that is fabricated by screen printing and embedded into a 3D printed channel. The sensor layout enables measuring the flow velocity in a microchannel while enabling the user to compensate for the change in thermal conductivity when switching to a different fluid. This design requires calibration only for one fluid, since a simple empirical model is presented to extrapolate the calibration data to fluids with varying thermal properties. The sensor was tested for one calibration fluid and two fluids with differing thermal properties. The flow velocities of these fluids were measured with an error below 5%.

The field of machine health and system monitoring has gained interest in different application fields, e.g., monitoring of lubricants, vibrations, surroundings, environmental conditions or the temperature of critical machine parts. This work presents two different condition monitoring devices, which are fabricated in a low cost printing process directly on the non-planar surface of the object to be monitored. The first system is used for thermal condition monitoring, where temperature monitoring is performed by 24 thermocouples resulting in a 24 pixel temperature image of the sample. The thermocouples are printed in an array arrangement, which enables the reduction of the required electrical connections from 48 to 25. The second device is intended for the use in aerodynamic systems, e.g., airplane wings, rotor blades of wind turbines, and helicopters where icing is a critical issue. The aerodynamic lift of aircraft is critically influenced by deposits on the wing or rotor blade surface. Also in other rotor blade systems, e.g., wind turbines the efficiency is drastically dropped and in worst case the icing can cause the failure of the system. The aim is the fabrication of an active monitoring system which is able to detect and also remove the ice from the monitored surface. To this end the system is directly fabricated on the 3D shaped substrate like a wing or rotor blade and the icing is detected using a capacitive sensor and a thermocouple sensor array. In case of icing a heater removes the critical ice deposit.

The design and fabrication of a dual electrochemical quartz crystal microbalance sensor unit with dissipation monitoring (EQCMD) for in situ monitoring of crystallization processes, such as the formation of zeolites from liquid media, is reported. The integrated temperature unit is based on Peltier elements and precision temperature sensors with accurate and fast temperature control. In this design, two thickness-shear mode quartz disk resonators are oppositely arranged, enabling the application of an electric field through the sample while concurrently being able to monitor the resonance frequencies and quality factors of both resonators. As demonstrated experimentally, this allows for the characterization of the sample by means of the viscosity, via the acoustic impedance, and the electrical conductivity. Monitoring zeolite formation based on these parameters, however, turned out to be challenging, mainly because the electrodes suffered from severe corrosion. Despite the use of chemically resistant materials and insulating coatings, the electrodes were attacked by the reaction medium, presumably due to surface defects. Furthermore, air bubbles, which developed over time and adhered persistently to the quartz surfaces, also had a negative influence on the measurement. Despite the encountered issues, we want to communicate our sensor design, as its basic functionality, including the dedicated electronics and software perform well, and reporting the observed issues will enable further progress in this field.

We present a design for a photonic crystal waveguide made on a plasmonic integrated photonic platform, optimized for gas sensing. The waveguide benefits from both aspects to exhibit high sensitivity and low footprint.

In this study, we investigate the potential of one-dimensional plasmonic grating structures to serve as a platform for, e.g., sensitive refractive index sensing. This is achieved by comparing numerical simulations to experimental results with respect to the excitation of surface plasmon polaritons (SPPs) in the mid-infrared region. The samples, silver-coated poly-silicon gratings, cover different grating depths in the range of 50 nm–375 nm. This variation of the depth, at a fixed grating geometry, allows the active tuning of the bandwidth of the SPP resonance according to the requirements of particular applications. The experimental setup employs a tunable quantum cascade laser (QCL) and allows the retrieval of angle-resolved experimental wavelength spectra to characterize the wavelength and angle dependence of the SPP resonance of the specular reflectance. The experimental results are in good agreement with the simulations. As a tendency, shallower gratings reveal narrower SPP resonances in reflection. In particular, we report on 2.9 nm full width at half maximum (FWHM) at a wavelength of 4.12 µm and a signal attenuation of 21%. According to a numerical investigation with respect to a change of the refractive index of the dielectric above the grating structure, a spectral shift of 4122nmRIU can be expected, which translates to a figure of merit (FOM) of about 1421 RIU−1. The fabrication of the suggested structures is performed on eight-inch silicon substrates, entirely accomplished within an industrial fabrication environment using standard microfabrication processes. This in turn represents a decisive step towards plasmonic sensor technologies suitable for semiconductor mass-production.

Foster's seminal treatise on lossless networks has been published almost 100 years ago and a particularly notable conclusion drawn therein, i.e. that the reactance (and susceptance) functions are always monotonically increasing with frequency, is frequently referred to as Foster?s theorem. In this paper we present two variants for an alternative simple derivation of a stronger form of this theorem, which holds for the driving point reactance (susceptance) of general lossless devices, i.e. also configurations without lumped elements. One version introduces a realizable lumped element equivalent circuit approximating the considered circuit in a narrow band around a particularly considered frequency. It turns out that this avenue of proof also facilitates an alternative validation of the realizability of the so called Foster 1 and 2 realizations.

An online condition monitoring system based on the measurement of viscosity and density of liquids is presented and applied to three different measuring tasks relevant for industrial and automotive applications. One topic is oil characterization in hydraulic systems. It is shown that by measuring over varying temperature and pressure, additional physical properties can be made available for online condition monitoring, which are difficult to measure otherwise. These include, for example, the coefficient of thermal expansion and the bulk modulus, which is also related to the proportion of dissolved air. In the second application we investigate the efficiency of a passive oil defoamer and estimate the percentage of free air. Finally, the suitability of the measurement system for the determination of the diesel fraction in the engine oil as caused by the regeneration cycles of the diesel particulate filter is demonstrated.

In this paper, we propose and numerically investigate a novel concept for a mid-infrared bandpass filter based on a single stepwise linearly chirped Bragg grating, which can be used to create narrowband emitters in the mid-infrared region. We devised the filter on a silicon platform for a transmission wavelength of 4.26 μm, which can be used for carbon dioxide sensing. In order to comply with industrial design rules, we limited the resolution of the design grid to $\text{1 nm}$ , which made it necessary to repeat each individual grating pitch in order to optimize the performance. The devised filter features a transmission band of $\text{100 nm}$ , tailored to the absorption band of carbon dioxide, in combination with a spectrally broad rejection band.

We present a fabrication method for polymer based microfluidic devices using gallium as a sacrificial material during the sealing process based on solvent bonding, allowing for lab-scale prototyping of microfluidic chips. The microfluidic channels are structured by laser engraving of poly(methyl methacrylate) (PMMA) sheets. The devices are temporarily closed by clamping the engraved parts on a flat surface with a thin polymer film in between. Liquid gallium is then injected into the temporarily sealed channels and is subsequently cooled to form a solid sacrificial layer preventing clogging and distortion of the microchannels during the subsequent bonding process. After finally sealing the device, it is warmed up to liquefy the gallium, which is then flushed from the channels. The feasibility of this approach is demonstrated by fabricating a microfluidic flow focusing device and a chemical gradient generator. The proposed method using gallium features distinct advantages compared to previously reported similar approaches that successfully make use of, e.g., wax, hydrogels or water as sacrificial materials.

Devising a cost effective way to fabricate sensors onto non-planar surfaces is of particular interest in many industrial applications such as condition monitoring or process controlling. This paper presents a low cost and low tech alternative approach for the fabrication of sensors on non-planar substrates in a two-step process. Screen printing is used to create a 2D pattern of the sensor on a water transfer foil which, in a second step, is transferred on a non-planar substrate using water transfer printing. We demonstrate the feasibility of this water transfer technique by fabricating a strain as well as a temperature sensor, which are both characterized and compared with state of the art screen printed sensors on planar substrates.

The dynamic behavior of an electrowetting-on-dielectrics (EWOD) actuation process can be linked to certain fluid properties of the actuated polar liquid droplet. After actuation, inertia will lead to droplet oscillations, where the contact angle asymptotically approaches the newly created surface tension equilibrium value. The decay behavior, frequency, and amplitude of these oscillations can be related to material parameters, such as density, viscosity, and mass. In this paper, we study the characteristics of these oscillations, present simulation results, and develop a measurement setup for first observations of oscillations on deionized water droplets. We show that there is a big difference between two grounding schemes, in particular, regarding the dynamic movement of the liquid-gas interface. It turns out that only an electrical grounding from below leads to utilizable oscillations. Finally, we point towards applications for future Lab-on-a-Chip applications.

We numerically simulate and experimentally demonstrate the excitation of mid-infrared surface plasmon polaritons (SPPs) in one-dimensional silver grating structures. In particular, the feasibility to fabricate plasmonic grating structures for the mid-infrared region within an industrial fabrication environment by using standard microfabrication processes represents a decisive step towards plasmonic sensor technologies suitable for semiconductor mass-production. The experimental part covers angle-resolved, free-beam reflection measurements on silver-coated poly-silicon gratings, fabricated on eight-inch silicon wafers. Different grating depths in the range of 50 nm-375 nm are investigated, which lead to the optimal control of the SPP excitation depending on practical applications. In particular, the shallow gratings feature ultra-narrow SPP resonances in reflection of only 2.9 nm full width at half maximum (FWHM) at a wavelength of $4.12\ \mu\mathrm{m}$ . The data obtained indicate that the suggested structures constitute a promising platform for sensitive refractive index sensing. Simulations evidence a spectral shift of SPP resonances of about 4122 nm/RIU that translates to a Figure-Of-Merit of about 1421 RIU−1.

We present a method to design specific heater electrode distributions on substrates with high thermal conductivity such as sheet metal. The substrate is covered with a thin polymer insulation layer on both sides, which are, in turn, carrying screen printed, electrically conductive heater electrodes and another protective polymer layer. The temperature inside a predetermined optimization area is demanded to be as uniform as possible, which is required for various high-precision heating applications. A uniform temperature distribution is required when realizing a newly proposed "lab on metal" approach. For this purpose, an optimization algorithm yields the required distances between the electrodes. The resulting electrode distribution was numerically obtained for certain optimization areas. We show the electrode positions relative to the distance from the centermost electrode and the optimization error for each distribution. Finally we describe the fabrication of a test device and show infrared measurements of the FEM modeled uniform temperature distribution on the experimental realized device.

Optical measurement approaches have proven to provide intrinsic selectivity and the sensitivity, required for the development of integrated gas sensors. In an ongoing project, we work towards a Si-photonics non-dispersive infrared gas sensor and are investigating the possibility of the incorporation of IR-plasmonic materials, which could allow an increase in sensitivities and reduce the size of such sensors. Here we present the basic concept and discuss in some detail first results concerning fabrication and characterization of the plasmonic properties.

The sensing of ambient gases is of growing interest for many applications as for example indoor air quality monitoring, gas leakage or fire detection. We present the fabrication of high aspect-ratio silicon (Si) pillar-based hybrid plasmonic-photonic crystal waveguides. This type of waveguide is suitable for ultra-sensitive gas sensing applications by providing enhanced light-matter interaction due to low group velocities (slow light) in photonic crystal waveguides and high evanescent field ratio. Eight-inch silicon substrate wafers are processed by means of lithography and deep reactive ion etch (DRIE, aka. Bosch etch), which took place in the industrial clean-room facilities of Infineon Technologies Austria AG in Villach. The fabrication processes were optimized to a level such that aspect ratios of around seven for pillars of 510 nm diameter could be reached. The discrepancy of measured diameters and diameters given by the design was found to be lower than 50 nm, with a standard deviation for the measured diameters lower than 20 nm.

We have devised a method that employs moving electrode electrochemical impedance spectroscopy to monitor the sedimentation of particles in conductive suspensions. In contrast to standard electrochemical cells with a fixed geometry, our cell has a flexible design with a movable counter electrode that allows precise adjustment of the electrode distance. Measuring the electrical impedance at various electrode spacings and utilizing the linear dependence of this function on the electrode displacement enables probing of a small section of the sample. This has considerable advantages when heterogenous liquids (e.g., suspensions) are to be analyzed. We applied our moving electrode approach to various test cases and obtained the following results: (i) We demonstrated by experiment that the bulk conductivity can be measured correctly even if particle sediments cover the electrode surface. (ii) We studied monodisperse suspensions of various compositions and investigated the effect of particle concentrations and size on conductivity. (iii) We monitored the particle sedimentation process and, by combining experimental and theoretical results, identified a correlation between the growing mass of the sedimentation layer and the impedance measured. The intended application of our approach is to monitor crystallization processes in ionic liquids for use in zeolite synthesis.

A measurement cell for the use of accurate conductivity measurements of corrosive ionic media is presented. Based on the concept of moving electrode electrochemical impedance spectroscopy, exceptional measurement accuracy is achieved in a large conductivity range. Extensive testing with corrosive ionic media demonstrated the robust operation of the cell under harsh chemical conditions, up to temperatures of 130 °C. The novel design allows monitoring small conductivity changes during chemical reactions in ionic media, for instance, zeolite formation from hydrated ionic liquids. ispartof: ACS SENSORS vol:5 issue:11 pages:3392-3397 ispartof: location:United States status: published

In this work, a resonant quartz tuning fork sensor based measurement system is employed to study the settlement of small particles in suspension as they pass the sensing element. The resonator features varying sensitivity to fluid parameter changes along its length, with the tip being most sensitive. The spatial averaging effect is analyzed theoretically and measured by passing the sensor through a fluid–fluid interface. Subsequently, the averaging function is used for particle distribution determination from recorded resonance frequency and quality factor measurements. The associated inverse problem is of Fredholm type and is solved numerically. Based on the system specifications, detection limits, required temperature stability and expected precision are assessed and particle distribution functions of defined test dispersions are measured.

The miniaturization of optical gas sensors is of interest for automotive and consumer electronics. We recently presented the use of silicon waveguides for evanescent-field gas detection in the mid-infrared by using an external laser source. However, the feasibility of the method is not guaranteed when the laser source is replaced by an integrated light source, typically a thermal emitter, due to the lower emitted power of the latter. Here, after experimentally characterizing the evanescent-field ratio of the fabricated structures, we demonstrate the feasibility of gas detection using a silicon waveguide and a low-cost integrated thermal emitter. Specifically, using the first demonstrators we achieve CO2 detection down to a concentration of 10% with a confidence level of three standard deviations. The current detection limit is close to that previously measured with an external laser source and it is mainly limited by the yet not-optimized waveguide structure. This research represents a promising advancement for the development of fully-integrated photonic gas sensors in the mid-infrared.

We present a measurement system for the viscosity and density of a fluid featuring a permanent magnet as measurement body, which is levitated in an actively controlled magnetic field. The behavior of the system is illustrated using different measurement body shapes. The basic concepts and the modeling of the electromechanical system are discussed. Utilizing special measurement modes, the sensor system allows for measuring viscosity and density independently. When put into operation, the magnet is controlled to stay at a constant levitation position. Due to a special actuation scheme, the magnet also rotates around its vertical axis. Using this setup and immersing the magnet in a fluid, it is possible to analyze viscosity and density of all kinds of fluids, except ferrofluids (which would distort the magnetic fields). The magnetic levitation system avoids any electrical or mechanical connections penetrating the walls of the measurement chamber; only the levitated permanent magnetic measurement body is in contact with the sample fluid.

This work reports on the characterization of the strain response of printed strain gauges particularly with respect to achievable gauge factors and associated spurious effects. In particular, three different effects are observed, first a set-in effect, which only occurs after production, second a nonlinear response that is more or less only visible without mechanical stabilizing top coating. Third and finally, a hysteresis behavior was found. We subsequently investigated the performance over an extended period of time, which revealed interesting and partially unexpected material properties of printed strain gauges made from silver and carbon. Both silver- and carbon-based strain gauges show a hysteresis behavior of the gauge factor and non-negligible nonlinear characteristics. Furthermore, the carbon-based sensors show a strong initial base line drift within the first 50–100 cycles. All three effects, namely hysteresis, nonlinear gauge factor and initial base line drift, are confirmed within their respective standard deviations.

We present a fully spray processed polymer based temperature sensor which can be embedded in the organic coating of metallic machine components. The main aim of the sensor is to measure the temperature in such coatings. This could be used, e.g., in friction bearings for condition monitoring. For the present demonstrator, the sensor element is embedded on a steel substrate. Here, the sensing element is a thermocouple, which is made out of two conductive paints with carbon black and silver as organic or metallic filler particles, respectively. The used carbon black paint is custom-made and uses polyamide-imide as polymer binder which serves also as the polymer backbone of the insulation and the encapsulation layer. The commercially available silver paint is based on polyimide which yields the desired bond strength with respect to the insulation and encapsulation layer. The investigated thermocouples are characterized on a temperature test rig with and without top coating up to a junction temperature of 200 °C. Subsequently, the influence of prolonged heat treatment (in total 16.5 days at 200 °C) on the thermocouple sensitivity is investigated. Finally, the thermocouple cross-sensitivity study of the pressure influence on the temperature sensitivity is performed. First a test was made with pure pressure load of 40 MPa without a temperature gradient between junction and terminal. The final cross-sensitivity measurement was performed in a climatic chamber including a pressure test rig which is able to apply a load of 200 MPa at a maximum temperature of 141.5 °C.

Optical sensing is an emerging field for photonic microsystems that operate in the mid-infrared spectral range. In this work we present a photonic gas sensor based on infrared evanescent field absorption, designed for CO2 sensing. The sensing structure comprises a strip waveguide on a silicon nitride layer. A modal analysis was performed using the finite element and the finite difference time domain method. The fabricated waveguides were characterized and the concept was validated with quantitative CO2 measurements. The measured transmittance at various CO2 concentrations was fitted using the Beer–Lambert law, and the results proved that the presented concept is feasible for CO2 gas sensing. The devised demonstrator device allowed to detect CO2 concentrations down to 5000 ppm, which is the workplace exposure limit in most jurisdictions.

In this work, we present a method for the realization of printed strain gauges on pre-coated sheet steel substrates. The state of the art is to glue strain gauges on foil onto a substrate. This, however, has inherent disadvantages in terms of force coupling between the bent substrate and the glued strain gauge sensors. The fact that the glue and the substrate have in general different moduli of elasticity affects the achievable gauge factor of the final sensor stack. The method presented in this work circumvents these problems completely by eliminating the gluing process and integrating the sensor into a cover layer on the substrate. In the considered case, the substrate is a steel sheet with an organic coating. We integrate the sensor in this coating by screen-printing it on a pre-coated layer. The results in terms of the various determined gauge factors including the influence of a top coating layer, as well as temperature dependences of the strain sensors fabricated with carbon black and silver ink are presented in this work.

A design for a high quality factor photonic crystal ring resonator (PCRR) is presented. The PCRR is based on pillar type photonic crystals, which consist of a hexagonal array of silicon rods. The cavity is created by removing elements from the regular photonic crystal (PhC) grid. Achieving strong confinement of light intensity in the low index region is the advantage of this PCRR. In that manner, the interaction of light and analyte, which can be a liquid or a gas, will be enhanced. The high quality factor of the cavity ( Q = 1.0229 × 10 5 Q=1.0229\times {10}^{5} ), along with strong overlap between the field of the resonant mode and the analyte as well as the low group velocity of PCRR modes yield enhanced light-matter interaction. An enhancement factor of γ = 2.127 × 10 4 \gamma =2.127\times {10}^{4} compared to the bulk light absorption in a homogenous material provides the potential for highly sensitive gas detection with a photonic crystal ring resonator.

The fabrication procedure and characterization of low-cost electrodes for capacitive level sensors realized on a flexible substrate are presented in this paper. The aim was to prepare conductive electrodes by printing of silver and PEDOT:PSS pastes on coated PET foil. Individual interdigital capacitors and a system with embedded microcontroller readout were designed for a comparative study. Individual capacitors in the form of interdigital electrodes (IDT) were designed with different finger width/spacing dimensions from 300/300 μm to 800/800 μm, a finger length 10 mm and 15 mm and an overall length of 100 mm. A demonstrator device featuring an integrated microcontroller, sensing and reference capacitive sensors and a resistive temperature sensor was realized to proof a practical utilization. The microcontroller is used to calculate capacitances of IDT electrodes in terms of charging time proportional to the fluid level. The design with reference capacitor can be directly applied to different fluids with a wide range of conductivities and dielectric constants without recalibration. The printed structures were thermally laminated with covering PET foil. The sensitivity of the fabricated devices was characterized in liquids with different relative permittivity and conductivity (water and oil). The highest measured sensitivity was 0.7 pF/mm and 0.08 pF/mm for water and oil respectively, with resolution down to 0.1 mm.

We numerically and experimentally investigate aluminum metal (Al), gold-tin (AuSn) and titanium-tungsten (TiW) metallic alloys as plasmonic materials in the mid-infrared (MIR) region using spectroscopic ellipsometry and reflection measurements of gratings. The angle dependence of the specular reflectance of shallow gratings is investigated using a free-beam measurement setup and compared to simulations. It is shown that the deep and narrow resonances observed for all three materials match the associated prediction from simulations.

In this work we report on a computational study regarding the enhancement of the absorption of mid infrared (MIR) light for gas sensing applications. In order to address this goal, a photonic crystal ring resonator (PCRR) with a quality factor of more than 3.85 × 10 5 was designed. The considered PCRR is based on 2D pillar type photonic crystals, which consist of a hexagonal array of silicon rods. The high quality factor of the cavity, along with strong overlap between the field of the resonant mode and the analyte (0.76) and low group velocity of PCRR modes consequence into enhance sensitivity for gas sensing.

We present the design of a microfluidic pumping device based on the effect of boundary layer driven acoustic streaming. One wall of the channel is made from a flexible material and hosts a flexural travelling wave, which induces a directed flow of the fluid inside the channel. A flexible printed circuit board was chosen as the oscillating wall, which makes the manufacturing process easy and could potentially enable the fabrication of low-cost disposable devices for the use in e.g. biomedical applications. Numerical studies based on an approach utilizing perturbation theory were conducted, where a comparison with the result of a time-dependent simulation of the full Navier-Stokes equations is provided. Based on the numerical analysis, a quadratic dependency of the flow velocity on the deflection amplitude of the membrane was identified. A ring-shaped membrane and channel were considered to be most practical for the experimental setup, where the idea and design process will be discussed. The flow velocity was measured using particle tracking velocimetry and the results show the same quadratic dependency of the flow velocity, which is in agreement with the theory.

Photonics has been extensively exploited in the visible and near-infrared spectral ranges. Sensing of liquids and gases is a promising area for advancing of the photonics also in the mid-infrared spectral range (MIR). Of particular interest is the realization of Si-based MIR devices and their integration on a single chip. In this paper, the fundamental material challenges for the fabrication of photonic and opto-electronic devices in the mid-infrared are discussed. An approach for development, characterization, and integration of numerous photonic components for the spectral range λ = 4–6 μm is presented. Using Si, SiOx, and Si3N 4 as a material base, it is illustrated that fully Si-compatible active and passive devices are possible, which can be readily integrated onto a silicon chip. Finally, a compact mathematical model is provided for evanescent sensing of fluids with rib and photonic crystal waveguides.