In this paper, we present a novel symbolic MEMS modeling methodology for devices with tapered beam geometries. Such beams are very common in piezoelectric energy harvesters. While a closed-form solution for the device model may be possible in cases without taper, it becomes increasingly difficult to obtain for tapered devices. In the latter cases, we show how a symbolic perturbation expansion with the taper angle as the perturbation parameter can be used to conjure up a closed-form approximation of the modal behavior of the device. A major contribution of our work is the development of a special library of symbolic processing modules in MATHEMATICA to help construct the perturbation expansion, set up a series of symbolic modal solutions of the tapered device, and ultimately, build an equivalent circuit model. Furthermore, a MATLAB script is used for the numerical evaluation of the symbolic model for any given perturbation order. Significant performance improvement is obtained with respect to the finite-element method with almost no loss in accuracy.
This paper presents the design and fabrication of two-state mechanical-contact type electrostatically-actuated MEMS switches for micro-wave band application. The switch designs presented in this paper are based on those presented in previous work, with further optimization: (i) to improve the switching off function of a one-way switch, thereby eliminating stiction in the ON-state, (ii) addition of another set of signal lines in order to achieve two-way functionality and (iii) signal line contact surface optimization having three different profiles in order investigate the contact surface profile effect on signal coupling. These lateral switches exhibit a simulated switching time of 0.90 µs, a pull-in voltage of 21 V, with a spring stiffness constant of 17.52 N/m. The proposed switch architectures were designed and fabricated utilizing the PiezoMUMPs MPW process. These switches can be integrated with piezo-actuated LBAW resonators to achieve the required frequency band switching.
In this paper, we present the design of a dual-chamber nozzle (DCN) for a newly developed concept of a printhead for Aerosol-on-Demand (AoD) jet-printing using fluid dynamic modelling and simulation. In this newly developed concept, the ink is atomized inside of the nozzle chamber by ultrasonic excitation. This enables on-demand operation of the printhead. Focusing is achieved by means of a sheath gas and the nozzle geometry. To achieve a collimated aerosol jet, a DCN is advantageous. Computational fluid dynamics (CFD) is used to perform the design layout of a DCN for AoD jet-printing, with the goal of finding a design-for-manufacture.
In this work, we designed and assembled a customized characterization bench for 2D micro scanners with an optical field of view (FoV) of up to 30deg. The optical characterization bench allows for short-, medium- and long-term characterizations under different humidity, gas atmospheres, temperature, or pressure conditions. The mechanical displacement of the mirror under test can be monitored optically and electronically. Fine assessments such as the characterization of nonlinearities or coupling between vibrational modes can be performed in a unique semi-automated setup capable of combining optical and environmental characterizations to assess Micro-Opto-Electromechanical systems (MOEMS) devices, in particular micro-scanners.
DC-40 GHz single pole double throw (SPDT) microelectromechanical (MEMS) switch designed and manufactured on top of high resistivity (HR) and advanced trap-rich (TR) silicon substrates have been characterized and compared. It has been shown that the passive devices designed on TR substrate sense an effective resistivity 10 times higher than the ones designed on HR substrate. The insertion loss on an SPDT implemented on TR is 0.39 dB lower than the one on HR at 10 GHz and 0.9 dB lower at 40 GHz. Moreover, in terms of device linearity, the level of the second harmonic H2 is 20 dB lower for TR than for HR substrate, demonstrating the high efficiency of trap-rich substrate. To the authors knowledge, this is the first MEMS on TR substrate used for radio-frequency applications.
The front-end electronics design for a MEMS microphone array is presented for aero-acoustic applications. It is compliant with the requirements of flight tests: 40 Hz – 10 kHz bandwidth, 130 dB dynamic range, compensated from ambient temperature change (95ºC) and pressure change (80 kPa) during the tests. A multiplexing approach is adopted to reduce the signals distribution of an 80 elements array with piezo-resistive microphones. Considerations for a digital output sensing system are included.
Due to their enhanced piezoelectric coefficient, aluminum scandium nitride thin films have been a promising piezoelectric material for MEMS, in particular for RF filters applications. Resonators based on this material present strong microfabrication challenges, especially in applications where partial etching of the piezoelectric AlScN is necessary, such as hybrid SAW/BAW devices. This work compares different AlScN etching techniques, with the aim of achieving smooth fully or partially etched surfaces, nearly vertical sidewalls, and high selectivity towards the mask material.
This paper proposes an automatic generation system of capacitive MEMS accelerometers. In the system, capacitance of MEMS accelerometers is calculated by using a computational model without computationally heavy simulation. We fabricated MEMS accelerometers according to the generated parameters to evaluate the proposed system. Unfortunately, small change in differential capacitances of fabricated MEMS sensors was observed when acceleration was applied because of some failures during fabrication process. However, we believe that the results of this study can be exploited in the automatic generation system to automatically generate parameters for accelerometers that can be used for actual measurements.
This paper reports a Silicon (Si)-based, multiple Fourier-horn ultrasonic nebulizer (MFHUN) which was fabricated through femtosecond laser structuring of Si to reduce sample preparation time and study the effectiveness of this manufacturing process for Si-resonating structures. The system showed better transfer characteristics than what is reported in literature, giving the presented nebulizer the advantage of higher power efficiency and lower individual sample preparation costs.
Thermal actuators are useful for precise and reliable control in various applications such as flow control, MEMS, robotics, and biology. However, existing actuators often suffer from large power consumption, slow response, and limited scalability, which limits their application particularly in underwater systems. Herein, we present the design and fabrication of SU-8 based thermal bimorph actuators having fast response and large out-of-plane deflection at low power levels, making them an ideal candidate for underwater applications. The time response and deflection of the thermal actuators were optimized by carefully tailoring the actuator geometry. We have verified the effectiveness of proposed actuators via computational and experimental results, which indicate that more than 60 μm out-of-plane deflection could be obtained at around 35 mW input power, with actuation time as low as 200 ms.
The ever-increasing demand for low-cost air quality sensors paved the way for miniaturized photoacoustic spectroscopy (PAS) gas sensors. We present a sophisticated system model to predict the optical output of a critical component of a PAS sensor—the infrared (IR) emitter, suited to optimize the overall system stability further. It consists of validated sub-models of the microheater, the optical filter, and the optical path in between. It is verified by measurements of the emitter output for a wide range of gas concentrations below 10.000 ppm inside the emitter.
This paper presents the design, fabrication, and characterization of five CMOS-compatible microstrip patch antennas on high-resistivity silicon substrate (HRSi) in two different configurations: (i) a classical patch antenna designed to work at 10 GHz and used as a reference; (ii) the same patch antenna but with different numbers of unit cells (i.e., one, three, five, and nine) in the back reflector, each cell being a complementary split ring resonator (CSRR). The simulation results show an improvement of the CSRR-based antenna in comparison with the reference patch antenna, in terms of both gain G and radiation efficiency η: at 7.5 GHz, G increases from -6.29 dB to 1.87 dB and η is 7× times higher, while at 8 GHz G increases from -2.81 dB to 2.33 dB and η is 3× times higher. The experimental results of the CSRR-based antennas, in comparison with the reference one, demonstrate the following: (i) a gain performance improvement with more than 17 dB at 8.2 GHz, (ii) a reduction of the resonant frequency with almost 26% at 8 GHz, (iii) a multiband antenna working in the large frequency range 7.5-12 GHz with improved bandwidth in comparison with the reference antenna, i.e., 1365 MHz instead of 35 MHz.
In this study, we investigate the conditions of bonding by implementing Transient Liquid Phase of the metal technique in order to secure a flexible polyimide sheet to different semiconductor substrates (Si, SOI, InP). We test the TLP bonding using Ni and Sn as filler and parental metals at low thicknesses (from 300 nm/600 nm to 1.5 μm/3 μm, for Ni/Sn respectively). At these conditions, we highlight a discrepancy with the expected behavior, especially above 280°C.
Triangular resonators re-shaped with the Sierpinski geometry have been designed, implementing them with single-pole-double-through (SPDT) RF MEMS switches to provide fine-tuning for potential applications in the K-Band. Prototypes of band-stop filters working at 20 GHz and 26 GHz, for RADAR and satellite communications have been studied in coplanar waveguide (CPW) configuration. The tuning was obtained by switching between two device branches loaded with different resonators. As a result, dual-band operation can be obtained depending on the choice of the resonator. The studied filters belong to the more general group of devices inspired by the metamaterial design.
We report a new method to extend the frequency bandwidth of MEMS vibrational energy harvester. By increasing the potential voltage used to charge the electret film, the bandwidth expands to almost half of the center frequency of resonance, making it possible to effectively generate power from minute mechanical vibrations of 0.1 G or less. As a result, the harvester becomes capable of generating power from frequencies off the resonance.
Aluminium Nitride (AlN) as a piezoelectric material has certain advantages compared to PZT, like linearity, inherent polarity and the absence of lead as a potentially hazardous substance. Its weaker piezoelectric coefficient can partially be compensated by a higher driving voltage, as AlN usually has a high dielectric strength. Yet, while developing our quasistatic MEMS micro mirrors based on AlN, we frequently encountered dielectric breakdowns between 30V and 80 V, while expecting reliable operation up to 150 V. By means of lock-in thermography, we were able to localize hot spots at the border of the top electrode that would lead to breakdown events. A cumulation of such hot spots was examined by focused ion beam (FIB) slicing and we discovered AlN voids close to the border. An inspection of the Pt bottom electrode by SEM and dark field microscopy showed no significant defect density in this process stage. Our explanation for the failure is therefore a diffusion of ions into the AlN layer that would be mobilized by the electric field across the piezo layer and lead to heating and dielectric breakdown. To conclude the study, we plan further analysis by TEM and EDX.
This article analyses noise measurement on a tuning fork micro-electromechanical sensor (MEMS) gyroscope with the sense mode operated in open loop. It considers the impact of noise on drive displacement through the mechanical coupling, which to our best knowledge has only one mention in the literature. A model for this noise and its parameters estimation based on experiments is proposed. Models for other noise sources and the sensor, mainly based on literature, are developed. The expected noise power spectral density (PSD) at the sensor output is compared with experiments. It was found successful to predict the main behaviours of measured noise. Moreover, noise resulting from mechanical coupling is found to be an important contributor in low frequencies.
This paper presents the design procedure, fabrication process, and experimental results of a high-sensitivity 100 N force sensor used as a weighing load cell. It incorporates MEMS semiconductor strain gauges that are bonded to a buckling lamella. A stainless steel single-point test body bears the force load, and its deflection causes the lamella to buckle. Due to the higher gauge factor of the silicon strain gauges, this sensor has a rated output four times higher than commercial load cells equipped with metallic strain gauges. This increased sensitivity enables the detection of force variations as low as 0.01% of the rated output.
Piezoelectric sensors are moving rapidly toward commercialization. The issue of robustness and mechanical characterization has become an important consideration in device design and manufacturing. This paper explores experiments and an in-depth analysis of surface acoustic waves (SAW) manufactured on AT-cut quartz substrate with gold transducers and with biocompatible and hydrophobic parylene C (poly(2-chloro-p-xylylene)) coating layer. We discuss different experimental techniques that use electrical and interferometric measurements to analyze the performance of SAW sensors. The present study highlights several approved SAW device characterization techniques and methods, the ways in which they can be optimized, and the ways in which they can be used to enhance SAW device performances.
