Showing papers in "Journal of Micromechanics and Microengineering in 2022"
TL;DR: In this paper , a review summarizes the development of MEMS-based MOSs gas sensors in terms of the MEMS micro-hotplate, wafer-scale deposition and patterning methods for MOS materials, and several latest applications.
Abstract: With the growing demand for gas monitoring in various fields as the fast development of the internet of things, metal oxide semiconductors (MOSs) gas sensors based on the advanced microelectromechanical systems (MEMS) technology have achieved great developments in the past decades, especially in mainland China. This review summarizes the development of MEMS-based MOSs gas sensors in terms of the MEMS micro-hotplate, wafer-scale deposition and patterning methods for MOS materials, and several latest applications. Various designs of the micro-hotplates have been proposed, particularly, the suspended membrane type with low power consumption. By combining the ‘bottom up’ and the ‘top down’ strategies, MEMS provides a promising solution for wafer-scale fabrication process of MOSs based gas sensors, which have been successfully applied for the detection of ethanol, H2, H2S, toluene, HCHO, Freon etc. With the diversiform nano-structures of MOSs and emerging machine learning algorithm, great progress has been made recently on the aspects of the sensing performance, pulse heating and intelligent sensing systems.
15 citations
TL;DR: In this paper , a relationship between the printing speed, number of layers, and deformation value is formulated to model the performance of the microactuators based on these variables.
Abstract: This paper presents two novel large-stroke XY micropositioning stages that are fabricated completely using four-dimensional (4D) printed polylactic acid (PLA). The proposed designs do not require manual training to perform actuation. Instead, printing speed is used to achieve shape programming and manipulate the deformation and shrinking levels of the PLA microactuators that control the microstage. A relationship between the printing speed, number of layers, and deformation value is formulated to model the performance of the microactuators based on these variables. The same approach is then used to develop the two proposed designs in this work. One-way actuations in the x- and y-axes are achieved using PLA actuators that are printed at speeds in the range of 40–80 mm s−1, while the rest of the structure (passive part) is printed at a speed of 10 mm s−1 to minimize unwanted deformations. The microactuators are activated by immersing the designs in hot water at 85 °C. The maximum values of the x- and y-actuations are achieved when using the highest printing speed for the microactuators. Design 1 offers actuation values of 1.99 and 1.40 mm along the x- and y-axes, respectively, while these values are 1.76 and 2.30 mm when using Design 2. The proposed designs offer a cost-effective batch fabrication solution for micropositioning applications, where the weight of the PLA required for Design 1 and Design 2 is 48.37 g and 12.61 g, respectively, which respectively costs $0.65 and $0.17. The performance of the x- and y-axes actuations show repeatable results with standard deviation values of 0.062 and 0.050 for Designs 1, and 0.054 and 0.047 for Design 2, respectively. Moreover, the standard deviation of the reproducibility of the x- and y-axes actuations are 0.064 and 0.051 for Designs 1, and 0.054 and 0.048 for Design 2, respectively. In addition, the designs offer a promising performance compared to the currently available large-stroke micropositioning stages in terms of the simplicity of the fabrication process and the area ratio.
15 citations
TL;DR: In this article , the impact of the abnormal grains in the Sc0.15Al0.85N films on the performance of bulk acoustic wave resonators and filters is systematically evaluated by both simulations and measurements.
Abstract: Sc x Al1−x N is a promising piezoelectric material for radio frequency communication applications with excellent electro-acoustic properties. However, the growth of abnormally oriented grains is widely observed in the Sc doped AlN films deposited by sputtering. In this work, for the first time, the impact of the abnormal grains in the Sc0.15Al0.85N films on the performance of bulk acoustic wave resonators and filters is systematically evaluated by both simulations and measurements. The correlation between the device performance and the abnormal grain parameters, including the density, dimension, crystal orientation, growth height and the total volume of the abnormal grains, is evaluated and quantified. Simulation results show that the total volume of all abnormal grains in the whole device is the most critical factor among the parameters. Abnormal grains with randomly distributed parameters and around 6% total volume of the film can degrade the effective coupling coefficient of the resonator from 13.6% to 11%, leading to a 10.6% decrement of the filter bandwidth. Wafer-level device characterizations and measurements are performed, and the results are consistent with the simulations. This study provides a practical method for predicting the performance of the resonators and filters with abnormal grains, and a guideline for film quality evaluation.
11 citations
10 citations
9 citations
TL;DR: In this paper , a cadmium oxide (CdO) was deposited using pulsed laser deposition approach on porous silicon wafer for visible light photodetector application, through which a series of devices were proposed as a function of the deposition energy.
Abstract: In this article, cadmium oxide (CdO) was deposited using pulsed laser deposition approach on porous silicon (Si) wafer for visible light photodetector application, through which a series of devices were proposed as a function of the deposition energy. The microstructural as well as optical characteristics of the prepared film/s were demonstrated, respectively, using x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and ultraviolet visible light spectroscopy (UV–Vis) analysis. In details, the UV–Vis analysis revealed the occurrence of optical band gaps within the range of 2.38–2.42 eV , while an average nanoparticle diameter was found to be 45 nm using FE-SEM technique. This in turn demonstrated a sound relation with the photoresponsive behavior of the attained photodetectors. A photoresponsivity and specific detectivity of 1.9 μAmW−1 and 1.21×109 Jones were attained using 700 mJ laser energy. In the meanwhile, the estimated response/recover time of the addressed laser energy was found to be 300 s and 340 s , respectively. The photo-responsive characteristics of the fabricated devices were found to be in positive linear correlation with the applied laser energy.
8 citations
TL;DR: In this paper, a simulation study of tin (Sn) and Pb mixed halide (MAPb0.5Sn 0.5I3, 1.22 eV) PSC was carried out to make a contribution in the development of lead-free or low lead content perovskite solar cells for future thin-film photovoltaic (PV) technology.
Abstract: Lead-free or low lead content perovskite materials are explored in photovoltaic devices to mitigate the challenges of toxic lead-based halides. However, the conversion efficiency from such materials is far below compared to its counterparts. Therefore, to make a humble contribution in the development of lead-free or low lead content perovskite solar cells (PSCs) for future thin-film photovoltaic (PV) technology, a simulation study of tin (Sn) and Pb mixed halide (MAPb0.5Sn0.5I3, 1.22 eV) PSC is carried out in this manuscript. The device is further optimized in terms of transport layer and thickness variation to get 15.1% conversion efficiency. Moreover, the optimized narrow bandgap halide (NBH) based device is further deployed in the monolithic tandem configuration with lead-free wide bandgap (1.82 eV) halide, i.e., Cs2AgBi0.75Sb0.25Br6, 1.82eV (WBH) PSC, to mitigate the thermalization as well as transparent Eg losses. Filtered spectrum, current matching, and construction of tandem J-V curve at the current matching point are utilized to design the tandem solar cell under consideration. Tandem device delivered short current density, JSC (15.21 mA.cm-2), open-circuit voltage, VOC (1.95 V), fill factor, FF (74.09 %) and power conversion efficiency, PCE (21.97%). The performance of the devices considered in this work is found to be in good approximation with experimental work.
7 citations
TL;DR: In this paper , a review of metal oxide (MO x ) based H2S gas sensors is presented, which aims at enlightening the various aspects of hydrogen sulfide gas sensing technology in an unpretentious yet comprehensive manner.
Abstract: The presence of hydrogen sulfide (H2S) determines the air quality of both indoor and outdoor environments. To measure H2S concentration levels in the environment, a variety of sensors have been developed. metal oxide (MO x ) based gas sensors are among the most interesting class of MEMS sensors, capable of producing highly sensitive, selective, and specific signals in a plethora of chemical and physical signals. Nonetheless, in the presence of moisture, they have poor selectivity and response. However, the sensing performance of MO x towards H2S gas is previously reported in a number of studies. Nanotechnology advancements are expected to lead to the progress of highly sensitive, stable, and selective MO x -based H2S gas sensors in the future. This review article aims at enlightening the various aspects of H2S gas sensing technology in an unpretentious yet comprehensive manner.
7 citations
TL;DR: In this paper , a flexible capacitive pressure sensor with high sensitivity was proposed by using engineered micro-patterned porous polydimethylsiloxane (PDMS) dielectric layer through an environmental-friendly fabrication procedure.
Abstract: Highly sensitive soft sensors play key roles in flexible electronics, which therefore have attracted much attention in recent years. Herein, we report a flexible capacitive pressure sensor with high sensitivity by using engineered micro-patterned porous polydimethylsiloxane (PDMS) dielectric layer through an environmental-friendly fabrication procedure. The porous structure is formed by evaporation of emulsified water droplets during PDMS curing process, while the micro-patterned structure is obtained via molding on sandpaper. Impressively, this structure renders the capacitive sensor with a high sensitivity up to 143.5 MPa−1 at the pressure range of 0.068 ∼ 150 kPa and excellent anti-fatigue performance over 20 000 cycles. Meanwhile, the sensor can distinguish different motions of the same person or different people doing the same action. Our work illustrates the promising application prospects of this flexible pressure sensor for the security field or human motion monitoring area.
7 citations
TL;DR: This review focuses on various microfluidics techniques for isolating WBCs from blood with advantages such as low cost, ease to operate, compact in size, and requiring a lower sample volume.
Abstract: Selective isolation of human blood cells has numerous applications in disease diagnostic, prognostics, drug discovery, and drug delivery. In particular, isolation of white blood cells (WBCs) is required for the detection of various diseases such as leukemia, human immunodeficiency virus infection, Epstein–Barr virus (EBV), and cancers. Although the conventional methods of centrifugation and flow cytometry are broadly employed to isolate WBCs in clinical practice, they experience several limitations such as the requirement of the large volume of samples and reagents, trained personnel, large setup, and have an adverse effect on the quality of cells. In contrast, microfluidics-based methods have appeared as a superior approach of cells isolation with advantages such as low cost, ease to operate, compact in size, and requiring a lower sample volume. This review focuses on various microfluidics techniques for isolating WBCs from blood. Here, we have discussed the working mechanism of different microfluidics techniques, microdevice designs, and their performance parameters to isolate WBCs. In addition, a brief description of the numerous advantages and limitations of the existing microdevices and their future prospects aiming to develop an affordable, user-friendly point-of-care solution is provided.
7 citations
TL;DR: In this article , a dielectric modulated triple metal gate-oxide-stack Z-shaped gate horizontal source pocket tunnel field effect transistor (DM-TMGOS-ZHP-TFET) structure has been investigated for the application of label free-biosensor.
Abstract: In this article, a dielectric modulated triple metal gate-oxide-stack Z-shaped gate horizontal source pocket tunnel field-effect transistor (DM-TMGOS-ZHP-TFET) structure has been investigated for the application of label free-biosensor. This work explores the advantage of gate work function engineering along with the gate-oxide-stack approach for the ZHP-TFET for the first time. An asymmetric nano-cavity is created adjacent to the source-channel junction to immobilize the target biomolecules conjugation to the proposed device. The sensitivity of the device is thoroughly investigated in terms of average subthreshold swing (SS), threshold voltage (V th) and the switching ratio (I on/I off) of the proposed device with the variation of the dielectric constant value inside the nano-gap under the gate electrode. The device characteristics are investigated with different combinations of metal work functions to match the desired feature and sensitivity of the device. In addition, the sensitivity analysis of the proposed device is analyzed in the presence of both positive and negative charged biomolecules in the cavity region to study the charge effect on label-free detection of the device. A comparative study is conducted between a single metal gate (SMG) ZHP-DM-TFET biosensor with the DM-TMGOS-ZHP-TFET biosensor explores the advantage of gate-work function engineering with a gate-oxide-stack approach. Interestingly the DM-TMGOS-ZHP-TFET biosensor shows superior results with a high current ratio sensitivity of 103 which is ten times more than the SMG-ZHP-DM-TFET biosensor and this device also exhibits low subthreshold characteristics.
TL;DR: DC triboelectric nanogenerators (DC-TENG) have emerged as a direct powering solution, incorporating strategies like electrostatic breakdown, mechanical switching, and dynamic Schottky junction to generate a unidirectional current as mentioned in this paper .
Abstract: Rapid advancements in the Internet of things (IoT) have revolutionized the world by creating a proliferation of low-power wireless devices and sensor nodes. The issue of powering these devices remains a critical challenge as they require a regulated direct current (DC) supply for their operation. Mechanical energy scavenging mechanisms are viewed and promoted as renewable powering solutions for low-power electronics. However, a majority of these energy harvesting mechanisms generate alternating current (AC). Converting AC to DC is a critical issue as it involves using a rectifier, which is not a preferred option considering additional circuitry, power requirements, and the significant threshold voltage of even the most state-of-the-art diodes. DC triboelectric nanogenerators (DC-TENG) have emerged as a direct powering solution, incorporating strategies like electrostatic breakdown, mechanical switching, and dynamic Schottky junction to generate a unidirectional current. Based on these strategies, different topologies for DC-TENG devices have been developed by researchers over time. Since its inception in 2014, the study on DC-TENG has rapidly emerged and expanded. This article reviews the progress associated with DC-TENG mechanisms and topologies, presents a theoretical and comparative study of these mechanisms, and highlights their applications. This article also examines the challenges, recent advancements, and future research prospects in this domain.
TL;DR: In this article , the authors used multiphysics finite element modeling validated by experimental analysis to better understand the dynamics of the membrane and key parameters that affect the vibration analysis and atomization process.
Abstract: Vibrating mesh atomizers (VMAs) are increasing in demand for various applications that require high quality droplet size distribution of aerosols. However, manufacturing limitations of metallic mesh atomizers have prevented researchers from investigating the dynamics and vibration analysis required to further enhance performance. Newly developed MEMS based VMAs allow these devices to be custom designed including varying aperture size, shape, and pitch as well as varying membrane dimensions. In this paper, a systematic vibration analysis of silicon-based MEMS based VMA was investigated to better understand the mechanisms of the atomization process and atomization rate. The MEMS atomizer consists of a microfabricated mesh on silicon membrane coupled with piezoelectric ring. The atomization process with this device is intricate to model due to combination of fluid transfer and dynamics of the membrane actuated by the piezoelectric ring. This paper uses multiphysics finite element modeling validated by experimental analysis to better understand the dynamics of the membrane and key parameters that affect the vibration analysis and atomization process. Resonance frequency, displacement, velocity, and mode shapes of the various dynamic modes of the atomizer were studied using finite element analysis and compared with the experimental results to validate the model. The results demonstrate a strong correlation between the modeled and experimental results of the resonant frequencies and atomization rates. The results can be used to design VMAs with enhanced performance for specific applications in the future.
TL;DR: In this article , the authors proposed a novel MEMS electric field sensor based on surface acoustic wave (SAW) technology, which is a delay line device with an interdigital transducer and a reflector.
Abstract: Existing microelectro mechanical systems (MEMSs) electric field sensors have movable parts and electronic components. The movable parts are susceptible to external vibration, and the electronic components distort the distribution of the measured electric field. Therefore, we proposed a novel MEMS electric field sensor based on surface acoustic wave (SAW) technology. The SAW electric field sensor is a delay line device with an interdigital transducer and a reflector. The substrate of the device is a ZnO/SiO2/Si multilayer structure. The ZnO piezoelectric layer is not only used as the propagation medium of SAW, but also used as the sensing film of the external electric field. Then, the external electric field could be detected by analyzing the change of the eigenfrequency of the SAW. The multilayer structure of the substrate was prepared by MEMS process. The interdigital transducer and the reflector are fabricated by the lift-off process. The SAW sensor is characterized at different external electric field strengths by a network analyzer. The sensitivity of the sensor was 0.23 kHz/(kV m−1) and the nonlinearity was 6.8%.
TL;DR: In this article, the authors presented a valve-based piezoelectric pump with an unfixed check valve, which greatly simplifies the assembly and improves the output performance.
Abstract: Piezoelectric pump, driven by piezoelectric actuator, is one of the most promising micropumps in compact system. However, the application of piezoelectric pump is limited by the check valve, which is not efficient enough and needs careful fixation. This work presents a novel design with unfixed check valve, which greatly simplifies the assembly of valve-based piezoelectric pump and improves the output performance. The valve is unfixed with a small gap to obtain variable stiffness at different working stages, making it open more quickly. The piezoelectric pumps with three different valve gaps were designed, fabricated, and tested. The pump with the unfixed valve shows a 25.6% flow rate improvement compared with the fixed check valve without reducing the output pressure. To reveal the mechanism of the flow rate improvement, we investigated the flow resistance and the volumetric efficiency of the piezoelectric pump. The results show that the unfixed valve increases the volumetric efficiency of the piezoelectric pump, which improves the flow rate. The prototype pump achieved the maximum output performance of 162 ml min−1 and 33 kPa. The power consumption was less than 100 mW, reaching a pump efficiency of 21.7%.
TL;DR: In this paper , a dielectric µ-bridge based on polymer microelectromechanical systems (MEMS) Pirani gauge is employed for hermetic characterization of packaged electronic sensors.
Abstract: The paper introduces a SU-8 dielectric µ-bridge based polymer microelectromechanical systems (MEMS) Pirani gauge which can be employed for hermetic characterization of packaged electronic sensors. The µ-bridge structure is adopted due to its simplicity in fabrication and lower footprint, which makes it feasible for heterogeneous integration. Further, the integration of SU-8 polymer with the active thermistor offers superior thermal isolation from the substrate and extends the dynamic range. Before fabricating the actual device, the SU-8 based µ-bridge is optimized for stress-free release. A stress engineering is performed and thermal processing of SU-8 is optimized. The measurement results reveal that the removal of quenching from the baking steps leads to the successful fabrication of freely suspended µ-bridge with SU-8 polymer as a structural layer. A quantitative comparison of the proposed gauge is established by comparing the gauge performance with conventional dielectric materials like silicon dioxide (SiO2), silicon nitride (Si3N4), and aluminum oxide (Al2O3). The fabricated SU-8 polymer-based MEMS Pirani gauge with a 40 µm × 7 µm footprint can be used for hermetic characterization from 30 Pa to 105 Pa and is an ideal candidate for heterogeneous integration.
TL;DR: The fabrication and experimental study of a flexible bi-layer microfluidic device for blood oxygenation, mimicking the thin alveolar exchange barrier constituting a lung, using a facile technique by sandwiching a thin polymeric membrane as the gas exchange layer between two flexible microchannels.
Abstract: We report the fabrication and experimental study of a flexible bi-layer microfluidic device for blood oxygenation, mimicking the thin alveolar exchange barrier constituting a lung. A facile technique is employed to fabricate the device by sandwiching a thin polymeric membrane as the gas exchange layer between two flexible microchannels. A numerical model coupling the mass, momentum, and species transport equations, is used to simulate oxygen diffusion between the blood and oxygen channels across the gas exchange membrane. The oxygen saturation is experimentally measured at different locations in the blood channel along the flow direction and compared against the simulation results, which show a very good agreement. The effect of blood and oxygen flow rates, channel height, and membrane thickness on the variations in oxygen concentration in the blood and oxygen channels and the diffusion membrane are studied. The outcome of the present study may find relevance in the development of organ-on-chip devices for blood oxygenation.
TL;DR: In this paper , the bipolar resistive switching behavior of a 2D material such as Graphene Oxide (GO):poly(4-vinylphenol) (PVP) based bilayer in ReRAM devices is demonstrated.
Abstract: In this paper, firstly, some recently explored promising materials and processes for resistive random access memory (ReRAM) devices with bipolar switching mechanism along with their performance are discussed. Further, resistive switching behaviour of TiO x /graphene oxide (GO):poly(4-vinylphenol) (PVP) based bilayer in ReRAM devices is demonstrated. It was found that bipolar resistive switching behaviour is significantly enhanced by embedding 2D material such as GO in the organic polymer acting as switching layer. ReRAM devices with Ag/PVP:GO/TiO x /fluorine doped tin oxide (FTO) structure exhibited high ON/OFF current ratio (>103), low voltage operation, and high retention time. Bipolar resistive switching from these engineered active layers will have great potential for future large area and sustainable electronics.
TL;DR: In this article , the authors investigate the nonlinear properties of a microcantilever resonator and their control by nonlinear feedback and show that the response amplitude and corresponding response frequency can be controlled by cubic nonlinear velocity feedback and cubic non-linear displacement feedback, respectively.
Abstract: Abstract It is well known that the micro scale deviations of mechanical properties of a sample can be detected by measurement methods that use microcantilever as resonators. Those methods use the natural frequency shift of a resonator, thus we need to recognize the frequency shift caused by the effects of a sample on a resonator with high sensitivity and accuracy. Experimental approaches based on self-excited oscillation enable the detection of these shifts even when the resonator is immersed in a high-viscosity environment. In the present study, we experimentally and theoretically investigate the nonlinear characteristics of a microcantilever resonator and their control by nonlinear feedback. We show that the steady-state response amplitude and the corresponding response frequency can be controlled by cubic nonlinear velocity feedback and cubic nonlinear displacement feedback, respectively. Furthermore, the amplitude and frequency of the steady-state self-excited oscillation can be controlled separately. These results will expand application of measurement methods that use self-excited resonators.
TL;DR: In this article , a 2D flexible printed circuit board (FPCB) micromirror and a scanning 3D light detection and ranging (LIDAR) based on it were integrated with a single point LIDAR.
Abstract: This paper presents a 2D flexible printed circuit board (FPCB) micromirror and a scanning 3D light detection and ranging (LIDAR) based on it by integrating the 2D FPCB micromirror with a commercially available single point LIDAR. The 2D FPCB micromirror retains the benefits of previously developed 1D FPCB micromirrors, i.e. large aperture and low cost while providing rotation of the mirror plate about two orthogonal axes to be able to scan a laser beam about both vertical and horizontal axes to achieve 2D scanning. One 2D FPCB micromirror is integrated with a single point LIDAR to achieve a 3D scanning LIDAR, which, in comparison to the previously developed 1D FPCB micromirror based 3D LIDAR, achieved more compact structure and easier fabrication/assembly due to no strict requirement on the alignment between two micromirrors while only one 2D micromirror rather than two 1D micromirrors used. Prototypes of the 2D FPCB micromirror and the 3D LIDAR based on it are fabricated and tested. The test results demonstrate that the 2D FPCB micromirror based 3D LIDAR achieved a volume reduction over the previous 1D FPCB micromirror based 3D LIDAR from 1042 cm3 to 754 cm3 with a field of view of 40°× 24° at 150 Hz horizontal scanning and 2 Hz vertical scanning.
TL;DR: In this paper , an integrated flexible microfluidics-Laser-Induced Gated Polyamide (LIG)-based electrochemical biosensor was developed for point-of-source applications in conjunction with a custom 3D printed peristaltic pump.
Abstract: By providing a facile and scalable alternative to otherwise complex and resource-intensive synthesis of graphene, laser-induced graphene (LIG) is spearheading the translation of graphene-based propositions to deployable technologies for societal benefit. LIG is a versatile and economical synthesis approach which is being used on a variety of substrates and in a multitude of applications—including miniaturized sensing systems. One aspect that has not been addressed thoroughly in LIG-based miniaturized sensing systems is its successful integration with microfluidics and its possible use in point-of-care settings. To further diversify the applications of LIG with integrated microfluidics, this work reports on the development of an integrated flexible microfluidics-LIG based electrochemical biosensor. The work describes the methodology to develop a polydimethylsiloxane-LIG scribed polyamide microfluidic device in a leakage-free flexible application. In view of the excellent electrical and electrochemical properties of LIG, such device has been employed for electrochemical biosensing. The biosensing capabilities of the microfluidic device were validated via sensing of cardiac troponin I—a gold standard cardiac biomarker for early identification of acute myocardial infarction (AMI). The developed biosensor demonstrated a detection and quantification limit of 45.33 pg ml−1 and 151.10 pg ml−1 respectively, which are in clinically significant ranges for diagnosis of AMI. The µ-fluidic biosensor was also analyzed for stability and interference with other cardiac biomarkers. The developed integrated µ-fluidic electrochemical biosensor was evaluated for possible point-of-source applications in conjunction with a custom 3D printed peristaltic pump and smartphone-enabled miniaturized potentiostat.
TL;DR: This work shows that the top surface of centimetric parallelepipedic PDMS blocks, molded on a rigid plate, deviates from its expected flatness, the amplitude of the deviation being dependent on the crosslinking protocol, and identifies a suitable two-steps protocol which eliminates those replication errors.
Abstract: PolyDiMethylSiloxane (PDMS) is an elastomer increasingly used to produce soft objects by replication, in a variety of fields including soft electronics, microfluidics, tribology, biomechanics and soft robotics. While PDMS replication is usually considered faithful at all scales, down to nanoscales, detailed quantitative comparisons between the geometric features of the mold and the replicated object are still required to further ground this commonly accepted view. Here, we show that the top surface of centimetric parallelepipedic PDMS blocks, molded on a rigid plate, deviates from its expected flatness, the amplitude of the deviation being dependent on the crosslinking protocol. As a practical solution, we identify a suitable two-steps protocol which eliminates those replication errors. Using finite element simulations, we show that the effect originates from a thermal contraction when the sample cools from the curing temperature down to the operating temperature. This phenomenon actually applies at any length scale, and finely depends on the sample’s aspect ratio and boundary conditions. Our results should help mitigating replication errors in all applications where a well-defined sample geometry is required.
TL;DR: In this article , a cost-effective position sensing method for 2D scanning mirrors is presented, which uses only one 1D PSD (position sensitive detector) located at the backside of the 2D scan mirror plate to retrieve 2D rotation angle about the two axes separately in real time.
Abstract: This paper presents a cost-effective position sensing method for 2D scanning mirrors. The method uses only one 1D PSD (position sensitive detector) located at the backside of the 2D scanning mirror plate to retrieve the 2D rotation angle about the two axes separately in real time. Any 2D scanning mirror with resonant vibration about one axis and quasi-static vibration such as sinusoidal, saw tooth, triangular oscillation about the other axis can use this method. The two vibration axes are orthogonal to each other to form the scanning patterns, which are most desired in scanning 3D LiDAR systems. 3D scanning LiDAR is the targeted application for this research. The method uses timing measurement to measure the resonant vibration angle and Lagrange interpolation polynomial approximation to retrieve the quasi-static vibration angle. A prototype has been built to measure the 2D rotation angle of a 2D micromirror. The measured angle using the proposed method was verified using a 2D PSD. The largest errors for the vertical/horizontal angles were 9.6% and 5.36% respectively. The position sensing mechanism is also integrated to a scanning 2D micromirror based LiDAR system to demonstrate it as real time capability.
TL;DR: In this article , a micro-sized cold plasma jet generator is presented and its characteristics are analyzed, which mainly consists of two concentric silicone tubes with the inner one acting as the gas channel and the outer layer acting as insulating layer of heat and high voltage.
Abstract: Atmospheric cold plasma jets with various configurations have drawn intense interests in diverse applications, such as surface modification and endoscopic applications. In this paper, a long and ultra-flexible micro-sized cold plasma jet generator is presented and its characteristics are analyzed. The generator mainly consists of two concentric silicone tubes with the inner one acting as the gas channel and the outer one acting as insulating layer of heat and high voltage. Gold thin film was sputtered on the circular surface of inner tube to work as the electrode as well as separation layer of ultraviolet radiation. Electrical, optical and thermal characteristics of this generator were investigated. Cold microplasma jet can be generated and ejected to the ambient air with the length varied from 0.1 m to 2.5 m, and it can impact on the finger without electric and heat sensation. Optical emission spectra analysis indicated that reactive species like OH and O atoms were generated in the plasma. This device exhibits ultra-flexible property which can be arbitrarily bent and plugged into complex and deep environment. Localized internal surface modification of polyvinyl chloride tube using this microplasma jet was also demonstrated and the result showed that surface wettability can be greatly improved after plasma treatment. This generator shows great potential for internal surface processing, plasma endoscopic and maskless lithography applications.
TL;DR: In this paper , a Lamb mode aluminum nitride piezoelectric resonator with enhanced quality factors (Q) was proposed to reduce the anchor loss while retaining size compactness and mechanical robustness.
Abstract: This work presents a novel ultra-high frequency Lamb mode Aluminum nitride piezoelectric resonator with enhanced quality factors (Q). With slots introduced in the vicinity of the tether support end, the elastic waves leaking from the tether sidewalls can be reflected, which effectively reduces the anchor loss while retaining size compactness and mechanical robustness. Comprehensive analysis was carried out to provide helpful guidance for obtaining optimal slot designs. For various resonators with frequencies ranging from 630 MHz to 1.97 GHz, promising Q enhancements up to 2 times have all been achieved. The 1.97 GHz resonator implemented excellent f × Q product up to 6.72 × 1012 and low motional resistance down to 340 Ω, which is one of the highest performances among the reported devices. The devices with enhanced Q values as well as compact size possess potential application in advanced radio frequency front end transceivers.
TL;DR: In this article , an etchant consisting of a standard solution of sulphuric acid and phosphoric acid (96 vol% H2SO4: 85 vol% h3PO4, 3:1 vol%) at 180 °C is utilized.
Abstract: In this paper a processing technique for sapphire is presented which combines laser-induced amorphization and subsequent selective wet etching of amorphized sapphire as well as anisotropic wet etching of single-crystalline sapphire (α-Al2O3). Using this technique, microstructures can be realized on the surface and in the bulk of sapphire substrates. By focusing ultra-short laser pulses inside sapphire, its structure can be transformed from crystalline into amorphous. The modified material can be selectively removed using etchants, such as hydrofluoric acid or potassium hydroxide (KOH), solely dissolving the amorphized part. In this work, however, an etchant consisting of a standard solution of sulphuric acid and phosphoric acid (96 vol% H2SO4: 85 vol% H3PO4, 3:1 vol%) at 180 °C is utilized. This method allows the realization of structures which are impossible to achieve when using conventional etchants which solely dissolve the amorphized sapphire. Ultrashort pulsed laser irradiation (230 fs) is used in this study as starting point for the subsequent anisotropic etching to form microstructures on the surface or in the bulk of sapphire that are terminated by characteristic crystal planes. In particular, the appearance of etching-induced patterns formed by stacks of rhombohedra is shown for structures below the surface, whereas triangular pits are achieved in surface processing.
TL;DR: In this paper , the effect of the lamination structure on the static and dynamic characteristics of a laminated film vibrator was evaluated. And the results confirmed that the resonant frequency of the vibrator depends on the film structure.
Abstract: This paper describes fabrication of a laminated film vibrator that uses an ultra-thin micro-electric mechanical system (MEMS) and the effect of lamination on the actuator. The thickness of the ultra-thin MEMS actuator fabricated by ultra-thin MEMS technology was 7.26 µm, making it especially flexible. The vibrator was actuated by applying voltage on a lead zirconate titanate (PZT) thin film. Then, we applied a lamination method to package the actuator. However, the lamination structure influenced the mechanical characteristics of the vibrator. Therefore, we evaluated the effect of the lamination structure on the static and dynamic characteristics of the laminated film vibrator. Four types of laminated film vibrators with different layer structures were prepared, and their displacements and velocity were measured when DC and AC voltages were applied. The maximum displacement of the cantilevers constructed from the laminated film vibrator (PZT: 11 mm × 11 mm) was 113.3 µm at 40 V DC. This result is in good agreement with the calculated result. Furthermore, the dynamic characteristics from both the experimental and simulated results confirmed that the resonant frequency of the laminated film vibrator depends on the film structure. This means the dynamic characteristics can be adjusted to suit the application. Applications of this laminated film actuator include use as a flexible hybrid electronics haptic device for monitoring vital signs.
TL;DR: In this article , a review of the recent trends of valveless actuator-driven piezoelectric pump in structural and application is presented, which attempts to guide the researchers with different professional backgrounds that can solve current problems through cross-disciplinary approaches.
Abstract: Piezoelectric actuator-driven valveless pump has been studied for a long time in theory and structure for the features of high precision, fast response, low power consumption, compact size, reliability for long-term use and high performance. The pump has a remarkable significance for drug delivery, biological application, chemical analysis, high precision gluing, solder paste, lubrication system and electronic chip cooling system, etc. However, a higher requirement on the control circuit and power supply for the pump is raised, also, the driving voltage of the pump should be further reduced. In this review, the piezoelectric pump with and without valve is analyzed in working principle. Then, the recent trends of valveless pump in different structures are discussed. The representative structural designs in different thinking are introduced in the working media, driven voltage, frequency, flow rate, pressure, and the efficiency of the pump, the performance of different pumps are also compared. Afterwards, the application of the pump for different purposes with featured structures are presented. Next are the limitations and the outlook of the pump, which provides some potential research points for subsequent studies, and ended with a summary. This review concludes the recent trends of valveless piezoelectric pump in structural and application, attempts to guide the researchers with different professional backgrounds that can solve current problems through cross-disciplinary approaches.
TL;DR: In this paper , an acoustic sensor with polydimethylsiloxane film sandwich structure is proposed, which has a good response at frequencies from 0.1 to 10 kHz, and has a sensitivity of 0.92 mV Pa−1 at 1 kHz acoustic frequency.
Abstract: An acoustic sensor packaged with polydimethylsiloxane film sandwich structure is proposed in this paper. The sensor uses a flat glass with a square hole in the middle as the substrate structure. The cavity length of the microfiber knot resonator is significantly changed by the applied acoustic pressure, which is ultimately manifested as a change in the strength of the sensor signal. The sensor has a good response at frequencies from 0.1 to 10 kHz, and has a sensitivity of 0.92 mV Pa−1 at 1 kHz acoustic frequency. The sensor studied in this paper has the advantages of wide frequency band, small size and low cost, and has a good application prospect in the field of acoustic signal detection.