A robust sensing mechanism requires a high sensitivity, fast response, and good fabrication compatibility. A surface acoustic wave (SAW) device possesses such properties, which make it suitable for gas sensing. This paper reported on the design, fabrication, characterization and measurement of a two-port SAW device built on an ST-cut quartz piezoelectric substrate. In order to develop a reliable SAW device, some performance parameters should be considered, such as the quality factor and electromechanical coupling coefficient. There are several possible ways to increase the quality factor of a SAW device such as by varying the number of interdigitated electrode (IDT) pairs as well as by using different IDT wavelengths. The devices were fabricated using three different numbers of IDTs $(\mathrm{N}=24,48$ , and 72) and two different IDT wavelengths $(\lambda=20\ \mu \mathrm{m}$ and 80 $\mu \mathrm{m})$ . The calculated quality factor, Q, confirmed that increasing the number of IDTs and reducing the value of the IDT wavelength would lead to a higher quality factor. The optimized SAW device with 72 IDTs and an IDT wavelength of 20 $\mu \mathrm{m}$ showed the highest quality factor of 306.58 at a resonance frequency of 248.33 MHz. The results of this study suggest that the ST-cut quartz SAW device with a high number of IDTs and small wavelength can be a better candidate for a surface acoustic wave device for sensing applications such as gas sensing.

This paper presents the current progress towards a lab-on-chip biosensor for early dengue detection, consisting of an integrated sensor with dual-function working electrode that enables in-situ measurements of both electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM) enclosed in a miniaturized 3D-printed package equipped with electrical contacts and sample fluid delivery to the quartz biosensor array. The sensors consist of an array of three 10 MI-lz IEQCM biosensors on a single quartz substrate. Early validation is performed for future dengue sensing application. We report the design, optimisation, and fabrication of the sensors, as well as early optimisation and validation of surface bioconjugation of antibodies. This lab-on-chip has the potential to provide accurate dengue detection due to its high sensitivity and dynamic range, as well as providing rapid and early dengue detection in point-of-care settings.

Dengue is an infectious mosquito-borne viral disease that affects approximately 50 million people annually worldwide and is prevalent mostly in the tropics. Severe cases of dengue can be fatal, making early detection and fast diagnosis crucial towards improving patient care and survival rates. Currently, early detection can be achieved through detection of NS1 protein, using ELISA technique. Unfortunately, ELISA is an expensive method, making it unsuitable as a screening technique, especially in low-resource settings. In this work, we present a prototype device and its early validation studies, of an integrated electrochemical and mass-sensor for dengue NS1 antigen. The sensor is connected to open source mass-sensing software and hardware, OpenQCM which makes it easily portable. Having dual-measurement capabilities (mass and impedance) increases the sensitivity of the sensor. Preliminary studies suggest that the prototype could achieve ultralow limit of detection as low as 10 ng mL-1, dual-sensing cross-validation capability, portable size, sample-toanalysis time of less than 30 minutes, and parallelization of multiple assays. This work could lead to early and accurate dengue detection in routine point-of-care settings.

Quartz Crystal Microbalance (QCM) is a device that allows non-destructive measurements of r in situ reaction activities. In this article, an array comprising of six 3MHz QCM sensors in an array were characterized using a vector network analyzer and OpenQCM, a portable measuring instrument that measures change in resonance frequency. Measurements of S21 transmission characteristics using the vector network analyzer provides the resonance frequency and can also be used to derive the RLC equivalent electrical circuit values of a resonant two-port network based on the Butterworth-Van Dyke model. In this work, Rm, Lm, Cm and Co were obtained via curve-fitting of the measurement results to the simulated results. Measurements were done in triplicates to verify reproducibility for all 6 sensors. For comparison, measurements were also done using a portable, open-source instrument, OpenQCM. The OpenQCM instrument directly measures changes in resonance frequencies, making it ideal for biosensing experiments, which correlate changes in mass with changes in resonance frequencies. Comparison between resonance frequency measurements using VNA and OpenQCM exhibit low percentage difference 0.2%. This QCM sensor array has the potential of conducting real-time, point-of-care analyses for detection of biological molecules.

A compact planar inverted-F antenna (PIFA) has been designed, fabricated, and characterized to work either for receiving or transmitting applications. The antenna center frequency can be tuned from 1.52 up to 2.25 GHz, using switched auxiliary strips. Ohmic contact radio frequency microelectromechanical system (RF-MEMS) switches are used to connect and disconnect the auxiliary strips, maintaining both efficiency and antenna linearity (power handling capability). The measured PIFA efficiency for all states in an anechoic chamber is between 52% and 95%. The antenna linearity has also been measured using an adjacent channel power ratio test bench, showing 42-dB dynamic range up to 28-dBm input power.

Most commercial quartz crystal microbalance (QCM) sensors are fabricated as a single AT quartz crystal device and are used for biosensor applications. This limits the sensor's ability to perform detection of multiple targets at a single time. To overcome this we propose in this work, the design, optimization and simulation of a MEMS quartz mass (QCM) sensor array. A circular mass sensor placed in an array of four sensors with working electrode radius, r = 100μm and centre to centre distance between electrodes, s=2.5mm was designed. Based on COMSOL simulations, resonance frequency of 10.40MHz and mass sensitivity of 0.223 Hz.cm 2 .ng −1 in liquids was obtained. Simulations indicate the best placement of the quadruple MEMS sensors in an array such that their signals do not interfere with each other. Low degradation of resonance frequency up to 40 kHz was observed based on simulation results.

The increase in frequency spectrum for wireless communication system has led to the growing interest in thin film electroacoustic technology that scales favorably upon miniaturization. Non-ferroelectric piezoelectric thin films such as Zinc Oxide is one of the most promising material for Complementary Metal Oxide Semiconductor-Microelectromechanical system (CMOS-MEMS) integration due to its silicon compatibility and good piezoelectric properties. This paper compares ZnO and Al doped ZnO (AZO) thin films performance characteristics when applied as CMOS-based surface acoustic wave (SAW) resonators. The interdigitated electrodes were fabricated using 0.35 μm CMOS technology followed by piezoelectric thin film deposition and probe pad patterning. Pure ZnO and AZO with 2 wt% Al2O3 have been prepared by pulse laser deposition and RF magnetron sputtering respectively. Both deposited ZnO and AZO thin films exhibited preferential crystalline growth in 002 direction. EDS analysis confirmed the incorporation of aluminium in zinc oxide thin films. High frequency electrical measurement results revealed that the devices with AZO thin film have enhanced performances as compared to devices based on ZnO thin film. It is shown that the insertion loss for AZO thin film was reduced from −65.1 to −53.5 dB and the quality factor was enhanced from 11.33 to 25.81. More significantly, the electromechanical coupling coefficient and piezoelectric coefficient were enhanced from κ = 0.044–0.069% and d 31  = 5.00 to 5.41 pm/V for AZO devices compared to those based on ZnO devices, respectively. One possible explanation of these enhanced piezoelectric properties comes from the almost ideal c-axis orientation of AZO thin film as compared to pure ZnO thin films. Our results suggest that the AZO thin film can be a better candidate for surface acoustic wave resonator using the CMOS-MEMS platform.

This paper introduces a new fabrication process for the realization of cavity resonators and band pass filters, using additive micro fabrication. 3D air-filled structures with a 195 μm thickness are obtained by using successive electroplating. Thanks to this fabrication process, a 140 GHz cavity resonator with an unloaded quality factor of 511 has been fabricated. A four-pole band pass filter at 140 GHz is presented, with a 3.1% bandwidth at -3 dB, and measured 3.7 dB in-band loss. Measurements are in good agreement with HFSS simulations without any post-processing tuning.

A new additive micro fabrication process for cavity resonator and band-pass filters is presented. 195 μm thick 3D air-filled components are fabricated operating at 38 GHz cavity resonator and two-pole band-pass filter. This paper presents a complete characterization of these components, with accurate simulation models. These models can be used to compute the losses in the component, and next improve them.

This paper presents a new planar miniaturized micromachined 5 pole bandpass dual-mode cross-slot filter at 19.82 GHz. A 5 pole filter is presented with 2 dB of insertion losses with a fractional bandwidth of 400 MHz and a high rejection (40 dB) at 19.1 GHz. A thermal study was also achieved to ensure the structure is ready for space conditions.

This paper presents new planar micromachined 5 pole bandpass filter topologies with narrow bandwidth and moderate insertion losses at 150 GHz. A 5 pole narrow band filter is presented at 150 GHz with 5 6 dB of insertion losses with a fractional bandwidth of 2% and high rejection (≫40 dB).

This present work reports on the study of controllable aluminium doped zinc oxide (AZO) patterning by chemical etching for MEMS application. The AZO thin film was prepared by RF magnetron sputtering as it is capable of producing uniform thin film at high deposition rates. X-Ray diffraction (XRD) and atomic force microscopy (AFM) characterization were done to characterize AZO thin film. The sputtered AZO thin film shows c-axis (002) orientation, low surface roughness and high crystalline quality. To pattern AZO thin film for MEMS application, wet etching was chosen due to its ease of processing with few controlling parameters. Four etching solutions were used namely: 10 % Nitric acid, 10 % Phosphoric acid, 10 % Acetic acid and Molybdenum etch solutions. For the first time, chemical etching using Molybdenum etch that consist of a mixture of CH3COOH, HNO3 and H3PO4 was characterized and reported. The effect of these acidic solutions on the undercut etching, vertical and lateral etch rate were studied. The etched AZO were characterized by scanning electron microscopy (SEM) and stylus profilometer. The investigations showed that the Molybdenum etch has the lowest undercut etching of 7.11 µm, and is highly effective in terms of lateral and vertical etching with an etch ratio of 1.30. Successful fine patterning of AZO thin films was demonstrated at device level on a surface acoustic wave resonator fabricated in 0.35 μm CMOS technology. The AZO thin film acts as the piezoelectric thin film for acoustic wave generation. Patterning of the AZO thin film is necessary for access to measurement probe pads. The working acoustic resonator showed resonance peak at 1.044 GHz at 45.28 dB insertion loss indicating that the proposed Molybdenum etch method does not adversely affect the device's operating characteristics.

In this paper, we present an additive microfabrication process for the realization of millimeter-wave and near terahertz components. The fabrication of 3D air-filled components like air-filled cavity filters is possible with this technique. The demonstrated fabrication process can be used at Ka band.

This paper reports on the design, simulation, fabrication, and test results of ZnO-based contour-mode micro-resonators integrating piezoelectric zinc oxide (ZnO) layers. The inter-digitated (IDT) type micro-resonators are fabricated on ZnO films and suspended top of 2 μm thick silicon membranes using silicon-on insulator technology. We analyze several possibilities of increasing the quality factor (Q) and the electromechanical coupling coefficient (kt2) of the devices by varying the numbers and lengths of the IDT electrodes and using different thicknesses of the ZnO layer. We designed and fabricated IDTs of different finger numbers (n = 25, 40, 50, and 80) and lengths (L = 100/130/170/200 μm) for three different thicknesses of ZnO films (200, 600, and 800 nm). The measured Q factor confirms that reducing the length and the number of IDT fingers enables us to reach better electrical performances at resonant frequencies around 700 MHz. The extracted results for an optimized micro-resonator device having an IDT length of 100 μm and 40 finger electrodes show a Q of 1180 and a kt2 of 7.4%. We demonstrate also that the reduction of the ZnO thickness from 800 nm to 200 nm increases the quality factor from 430 to 1600, respectively, around 700 MHz. Experimental data are in very good agreement with theoretical simulations of the fabricated devices

The design, simulation, fabrication and test results of micro-resonators integrating piezoelectric zinc oxide (ZnO) layers are reported in this paper. Interdigitated electrodes are used to excite the thin piezoelectric layer. These micro-resonators are built on top of 2μm silicon membranes of SOI wafers. To improve the quality factor Q and the electromechanical coupling coefficient k t 2 of the proposed devices different numbers and different lengths of inter-digitated (IDTs) electrodes have been tested.

(001)-epitaxial thin films of pure and Mn-doped lead-free Na0.5Bi0.5TiO3 (NBT) were grown on (00l) LaAlO3 single crystals, by pulsed laser deposition. The determination of the microwave dielectric permittivity, from interdigitated capacitance values treated using the combination of two previously developed analytical models, constitutes the backbone of this work. In the 3-5 GHz frequency range, constant er values of similar to 485 and similar to 515 for the pure and Mn-doped layers, respectively, were extracted and found in good agreement with literature data for pure NBT bulk ceramics, thus underlining the relevance of the approach. These permittivity values were re-injected in a second step into an electromagnetic simulation of the equivalent electrical circuit. Smith charts revealed the good matching between experimental and simulated data, proving that the employed method appears meaningful. Mn doping seems to lead to a small permittivity increase and clearly to a moderate reduction of the dielectric losses in the 3-5 GHz interval. Finally, the variation of the capacitance versus temperature testifies to the ferroelectric nature of the samples. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This letter describes the design, fabrication and characterization of surface micro-machined micro-coaxial transmission lines. The fabrication process relies on successive deposition of sacrificial polymer layers and metal electroplating. Transmission lines with a cross-section of 88 μm × 42 μm have been fabricated on a fused silica substrate, with various shapes. These lines are very well suited for applications above 50 GHz, where propagation in air minimizes both loss and dispersion. The measured lines have good performances with measured insertion losses of -0.33 dB/mm @ 127 GHz and return loss better than -15 dB.