Microelectromechanical Systems Technology Research Articles

A high-resolution area-change-based capacitive MEMS tilt sensor

Tilt sensors have been widely used in many applications, such as instrumentation leveling, oil drilling and structural health monitoring. With the rapid development of the micro-electromechanical system (MEMS) technology, MEMS accelerometer-based high-performance tilt sensors are capable of replacing conventional tilt sensors in most of application fields. High-sensitivity MEMS resonant accelerometers (MRAs) are fully qualified for tilt sensing. However, MRA chips have to be vacuum packaged and require complex circuits; therefore, they are difficult to be miniaturized and commercialized. In this case, this paper introduces a commercial-oriented capacitive MEMS accelerometer for tilt sensing with both high-resolution and compact size. The proposed MEMS sensor utilizes simplified fabrication processes, the area-change-based capacitive displacement transducer and the capacitance-to-voltage conversion application specific integrated circuit (ASIC) for low-cost, high-sensitivity, low power consumption and miniaturization. The developed MEMS sensor has a package dimension of 14 mm × 14 mm × 3.6 mm with a single +5 V power supply and analog voltage output. Several evaluation experiments have been conducted with the results showing that the developed MEMS tilt sensor has a full measurement range of ±180°, a linear measurement range of ±30° with a nonlinearity of ±2.8%, a sensitivity of 33.6 mV/°, a noise floor of 2 × 10−4°/√Hz, a bandwidth of 100 Hz and an angle resolution of 7 × 10−4° with an integral time of 0.5 s. Compared with other commercial MEMS tilt sensors, the proposed sensor has a better resolution, a lower noise floor, a larger bandwidth, a lower power consumption and a smaller package. The simplified fabrication process and high performance suggest the developed MEMS tilt sensor is promising to be competitive in the market.

RETRACTED ARTICLE: A new structure and modeling of a three-axis MEMS capacitive accelerometer with high dynamic range and sensitivity

In this paper, a three-axis capacitor accelerator has been analyzed, modeled and optimized using micro-electromechanical systems technology. In the proposed structure, acceleration measurements are carried out on all three axes simultaneously using a mass and spring system, which makes it possible to achieve a high sensitivity at a low occupancy level without losing other accelerator factors. In this structure, it is shown that each axis acceleration has a very low impact on the acceleration of the other two axes. If any external factor (e.g., electromagnetic waves) changes the value of a single capacitor, the original output of the capacitor does not change for detecting acceleration. In this paper, first the model is extracted for the proposed accelerometer structure and then to prove the validity of the model, the proposed structure is simulated using Intellisuite software. Moreover, a multi-objective genetic optimization algorithm which is made of NSGA2 and SPEA algorithms has been used to determine the dimensions of the constituents of the spring and the weight. This algorithm is implemented in MATLAB software. This study covers a dynamic range up to 1000 g and an operating frequency up to 20 kHz. The accelerometer sensitivity is 4fF/g in the z axis direction while it is 9fF/g in the x and y axes directions.

MEMS-on-fiber ultrasonic sensor with two resonant frequencies for partial discharges detection.

A novel fiber optic extrinsic Fabry-Perot interferometric (EFPI) ultrasonic sensor with two resonant frequencies for detecting the partial discharges (PDs) in switchgear is demonstrated. The key sensing element consists of two 5-µm-thickness and beam-supported silicon diaphragms, whose natural frequencies are designed differently to enable the sensor to achieve the resonant responses at two different frequencies, thus obtaining a broadened frequency response. The sensing element is fabricated by employing the microelectromechanical systems (MEMS) technology on a silicon-on-insulator (SOI) wafer. The experimental results show that the sensor possesses two resonant frequencies of 31 kHz and 63 kHz, and obviously, shows a highly sensitive frequency response over a broader range compared with the approach composed of a single sensing diaphragm with only one resonant frequency. The noise-limited minimum detectable ultrasonic pressure (MDUP) reaches 251 µPa/Hz1/2@ 31 kHz and 316 µPa/Hz1/2@ 63 kHz, respectively.

0446 A Novel System for Enabling High-Density EEG Recordings in a Mouse

Abstract Introduction Recent advances in micro-electromechanical system (MEMS) technology have promoted the development of microelectrode arrays (MEA) that allow high resolution recordings in neuroscience research. However, applying MEA in studies in freely moving mice remains very challenging due to the large number of electrical connections required in this type of studies. The use of commutators for a large number of connections is not practical, and headmounts/loggers placed on the animal head are too heavy for small animals such as mice. Therefore, there is a need for a better compact system for using MEA in mice. Herein, we designed such a system and successfully recorded high-density-EEG in freely moving mice. Methods We designed a system in which forty flexible ultrathin wires are connected to the headstage enclosed in a container held close to the mouse. The container also houses a logger and battery connected to the headstage. This recording system allows minimizing weighted pressure on the animal using a counterbalance, so that the animal can freely move in the cage. Results We tested the system using a signal generator and mouse EEG arrays (NeuroNexus). When potentials produced by the signal generator were recorded via the wires, recorded traces were indistinguishable from the traces that were recorded when the signal generator was connected directly to the logger. We then implanted mice with EEG electrode arrays under surgical anesthesia. The high-density EEG recordings were performed one and four weeks after the surgery. High-quality EEG signals were observed in all the channels of the 32-channel logger (SpikeGadgets) in freely moving mice. Conclusion We successfully developed and tested a novel system for enabling high-density EEG recordings in freely moving mice. We expect that this system will be useful for recording biopotentials from different types of MEA in freely moving mice. Support NIH 1R43OD023231 (LG), NIH 1RF1AG061774 (DG), and NIH 5R21NS106406 (DG)

Sensor Technologies for Automobiles and Robots

AbstractThis paper reviews various sensor technologies with application in automobiles and robots. Several automotive sensors have been developed using the micro‐electromechanical systems (MEMS) technology. The technologies related to combustion pressure sensors, yaw rate sensors, acceleration sensors, and optical scanners are described here. The combustion pressure sensors are used for engine control, while the yaw rate sensors of quartz and silicon crystals and the acceleration sensors are applied for vehicle motion control. Optical scanners are developed for autonomous driving. Several automotive sensors have been significantly reduced in size and cost, and their performance has been improved dramatically by MEMS technology. The inertial force‐sensing system with yaw rate and acceleration sensors enabled the assistant and partner robots to stand on two legs, walk, or invert and move on two wheels. Because the robots are required to have a variety of sensors, a nerve‐net sensing system was developed. This sensing system has three layers: the host, relay, and sensor nodes. The sensor node is a special large‐scale integration called a ‘nerve‐net chip.’ A triaxial force tactile sensor integrated with the nerve‐net chip was developed as a 2.8‐mm square surface‐mountable chip. A force and thermal tactile sensor was also developed, which detected heat flows and discriminated the materials of contacted objects. The heat flow sensor was thinned with thin‐film technology. The sensor technologies will be used for eco cars and autonomous vehicles. Next‐generation robots are also supported by several automotive sensor technologies. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Enhancement of condensation heat transfer on a microstructured surface with wettability gradient

Micro- and nanoscale phase-change phenomena are becoming increasingly important for heat transfer owing to the rapid development of microelectromechanical system (MEMS) technology in the fields of microsystems such as in advanced electronics or biomedical devices. In particular, many studies on dropwise condensation have been conducted based on progress of material science for hydrophobic or hydrophilic surfaces. Although majority of these studies achieved high heat transfer performance under low subcooling conditions, the heat transfer coefficient decreased as subcooling increased because of condensate removal limitations. Our previous study using a bi-philic surface with microgrooved structures failed in terms of flooding wherein several patterns were covered by a large liquid film because of poor drainage ability. In microsystems, gravity or vapor shearing forces are ineffective in enhancing droplet departure from the condensing surface as the spaces of the microsystem are limited. Thus, to enhance condensation heat transfer, the flooding and plugging phenomena need to be considered, and therefore, a novel condensing surface needs to be fabricated to remove the growing droplets from the condensing surface. Herein, we introduced a wettability gradient by gradually changing the pattern widths of the hydrophobic and hydrophilic surfaces. The groove width of the hydrophilic part was designed to increase as the condensate flowed downstream. The experiments were conducted under low steam pressure conditions; we found that the size of the droplets could be controlled by modifying the pattern width and the wettability gradient could be used to remove large droplets. The flooding was suppressed, and the heat transfer coefficient was enhanced by three times compared with the results of the microstructured condensing surface with a straight pattern. These results showed that the wettability gradient effectively enhanced condensation heat transfer.

Metamaterials – from fundamentals and MEMS tuning mechanisms to applications

Abstract Metamaterials, consisting of subwavelength resonant structures, can be artificially engineered to yield desired response to electromagnetic waves. In contrast to the naturally existing materials whose properties are limited by their chemical compositions and structures, the optical response of metamaterials is controlled by the geometrics of resonant unit cells, called “meta-atoms”. Many exotic functionalities such as negative refractive index, cloaking, perfect absorber, have been realized in metamaterials. One recent technical advance in this field is the active metamaterial, in which the structure of metamaterials can be tuned to realize multiple states in a single device. Microelectromechanical systems (MEMS) technology, well-known for its ability of reconfiguring mechanical structures, complementary metal-oxide-semiconductor (CMOS) compatibility and low power consumption, is perfectly suitable for such purpose. In the past one decade, we have seen numerous exciting works endeavoring to incorporate the novel MEMS functionalities with metamaterials for widespread applications. In this review, we will first visit the fundamental theories of MEMS-based active metamaterials, such as the lumped circuit model, coupled-mode theory, and interference theory. Then, we summarize the recent applications of MEMS-based metamaterials in various research fields. Finally, we provide an outlook on the future research directions of MEMS-based metamaterials and their possible applications.

High Sensitive Detection of Volatile Organic Compounds Using Tin Oxide Semiconductor Sensors with Hot-Wire-Type Structures

Introduction Detection of VOCs (volatile organic compounds) has been required because it is detrimental to human health. In particular, in working environment with organic solvents, the need for VOC detectors has grown to reduce the damage to workers. For this purpose, we have developed SnO2 semiconductor sensors with hot-wire-type structures.The hot-wire-type semiconductor sensor can detect ppm concentration gas with a simple structure suitable for mass-production, resulting in practical use in various applications [1]. In this work, we have achieved high sensitivity and selectivity for VOCs by optimizing SnO2 loaded with several metal oxides. Moreover, the newly developed VOC sensor has excellent durability against the poisonous siloxane, leading to commercial products thanks to these advantageous characteristics.To improve convenience for portable use of VOC detectors, we have developed VOC sensors fabricated by micro electro mechanical systems (MEMS) technology to save power consumption [2]. The power consumption of the MEMS VOC sensor was greatly reduced in comparison with conventional hot-wire-type sensors, without sacrificing high sensitivity to VOCs. The low power consumption of the MEMS sensor makes it possible to extend the battery life, which would lead to further spread use of the VOC detectors. Experimental Figure 1 shows the structure of a hot wire semiconductor sensor, which consists of a platinum wire coil and a sintered SnO2 bead. A solution containing several metals was dropped and immersed in the sintered SnO2. Thereafter, metal oxides were supported on SnO2 by current heating to fabricate a hot-wire semiconductor VOC sensor. The coil served as both a heater and electrodes for the semiconductor bead; the total resistance of the sensor (Rs) was approximated by a parallel electric circuit consisting of the coil resistance and the semiconductor one (Fig.2). For the evaluation of the characteristics, the sensor output voltage (V s) was obtained by incorporating the sensor into a bridge circuit and applying a voltage. The operating temperature of the VOC sensor was controlled to be approximately 450 ℃. The sample gas sensitivity was calculated as difference between V s in mixture of air and sample gas (V s gas) and V s in clean air (V s air).Figure 3 shows a cross-sectional schematic of the MEMS VOC sensor. In the MEMS sensor, a Pt micro-heater/electrodes, patterned by using photolithography, was constructed on about 100 μm square insulating membrane cross-linked to the Si substrate. A sensitive layer of SnO2 with thickness of a few tens µm was deposited on the Pt micro-heater by thick film technology. After sintering the SnO2 thick film on the platinum pattern, several metal oxides were added. Results and Conclusions Figure 4 shows the typical gas sensitivity characteristics of the fabricated hot-wire-type semiconductor sensor to various VOCs. The sensor showed high sensitivity for vapors such as acetone, ethyl acetate, and toluene in a concentration range that affects human health. On the other hand, the sensor showed low sensitivity to interfering gases such as methane and hydrogen. These results demonstrate that the sensors have sufficient selectivity for practical use. Optimization of loaded metal oxides successfully controlled oxidation activity of SnO2 optimally, resulting in improved VOC sensitivity and further reduced interfering gas sensitivity. Furthermore, the sensor showed significantly better durability against toxic siloxane gas than the conventional one, resulting in long-life use in real field. The improved durability against siloxane poisoning is attributable to the controlled oxidation activity of SnO2 by loaded metal oxides. The developed sensor is useful for monitoring VOC as a practical detector that can measure in real time.Next, we investigated the MEMS VOC sensors. Quick thermal response owing to the miniaturized structure enabled us to achieve working temperatures (~500 °C) of the sensor only in 30 milliseconds. Thus, we could operate the MEMS sensor in a pulsed voltage mode, in which averaged power consumption was less than 1 mW. We confirmed that the MEMS sensors, even with the pulsed voltage operation, reproduced high sensitivity to VOCs obtained in the conventional sensor. In addition, the MEMS sensor exhibited long term stability for more than two years. The MEMS VOC sensor would contribute to the improvement of working environment with the spread use of VOC detectors.In conclusion, we have successfully developed hot-wire-type semiconductor VOC sensors ready for commercial use. We have also developed VOC sensors fabricated by MEMS technology to save power consumption.

Developments of MEMS Gas Sensors Based on Tin Oxide semiconductors: Application to Battery-Powered Household Gas Alarms

Developments of MEMS Gas Sensors Based on Tin Oxide semiconductors: Application to Battery-Powered Household Gas Alarms

Dissolved Oxygen MEMS Sensor With Enhanced Sensing Current

A new approach is proposed to enhance sensing amperometric current in three-electrode Clark dissolved oxygen (DO2) Microelectromechanical systems (MEMS) sensors. In the proposed approach, the counter electrode (CE) in a conventional concentric three-electrode sensor is modified to admit a large ratio of static electric current in an electrochemical solution. The typically large CE of a conventional sensor is replaced with an array of narrow-width electrodes. The modified CE is expected to reduce the inductive coupling and simultaneously increase the capacitive coupling of the structure. The overall changes of inductive and capacitive couplings are shown to enhance the sensing amperometric current of the sensor. Two μ-sensors are developed and fabricated based on MEMS technology including a conventional, as the reference and a new modified μ-sensors. The experimental results confirm an enhancement of 3.2:1 (0.352 μA:0.112 μA for 23% of DO2) in the sensing amperometric current of the developed MEMS μ-sensor compared to the conventional same-sized counterpart.

TiO2/airgap-based polarizing beam splitter: design, simulation, and fabrication based on MEMS technologies

In this paper, we introduce a new thin-film polarizing beam splitter (PBS) based on air as a layer with a low refractive index (L) and titanium dioxide (TiO2) as a material with a high refractive index (H). A cube-type PBS presents an active area of approximately 1.0 × 1.0 mm2, and the airgap layer in conjunction with TiO2 thin-films provides an extremely high refractive index contrast (1.2). The PBS cube is projected onto a borosilicate glass substrate and the multiple layers obtained through TFCalcTM simulations, expressed in multiples of a quarter-wavelength optical thickness, are 1.6H L 1.1H 1.5L 1.1H L 1.6H. The projected structure ensures the separation of the polarizing states of light (transmission of the p-polarization and reflection of the s-polarization) from the visible to near infrared spectral range, over a bandwidth higher than 170 nm. This is the minimal working bandwidth obtained for visible range (centered at 550 nm), considering a polarization degree higher than 0.95. The projected PBS is fabricated based on conventional microelectromechanical systems (MEMS) technologies, namely, thin-film deposition, annealing, and etching processes. Finally, the fabricated PBS was experimentally characterized, with the measured transmittance of the fabricated structure reaching close to the expected TFCalcTM simulation result. This characterization is the final validation of the structure since, theoretically, reflection is the complement of transmission in a dielectric thin-film multilayer.

Silicon Multi-Pass Gas Cell for Chip-Scale Gas Analysis by Absorption Spectroscopy.

Semiconductor and micro-electromechanical system (MEMS) technologies have been already proved as strong solutions for producing miniaturized optical spectrometers, light sources and photodetectors. However, the implementation of optical absorption spectroscopy for in-situ gas analysis requires further integration of a gas cell using the same technologies towards full integration of a complete gas analysis system-on-chip. Here, we propose design guidelines and experimental validation of a gas cell fabricated using MEMS technology. The architecture is based on a circular multi-pass gas cell in a miniaturized form. Simulation results based on the proposed modeling scheme helps in determining the optimum dimensions of the gas cell, given the constraints of micro-fabrication. The carbon dioxide spectral signature is successfully measured using the proposed integrated multi-pass gas cell coupled with a MEMS-based spectrometer.

A Design and Optimization of a New, Three-Axis MEMS Capacitive Accelerometer with High Dynamic Range and Sensitivity

In this paper a three-axis capacitor accelerator has been designed, analyzed and optimized using micro-electromechanical systems technology. The accelerometers are generally divided into three categories of single axis, two axes, and three axes in terms of their ability to measure acceleration. In the suggested structure, acceleration measurements are carried out on all three axes simultaneously using a mass and spring system, which makes it possible to achieve a high sensitivity at a low occupancy level without losing other accelerator factors. By taking difference in this structure, it is shown that each axis acceleration has a very low impact on the measured acceleration of the other two axes. If any external factor changes the value of a single capacitor, the original output of the capacitor does not change for detecting acceleration. In other words, the acceleration of any of these three axes, due to its designing features, does not influence the other two axes and the system performance cannot be disrupted by external factors. The other important characteristics of the accelerometers are dynamic range, operating frequency and sensitivity. This study covers a dynamic range up to 1000g and an operating frequency up to 20 kHz. The accelerometer sensitivity is 4fF/g in the z axis direction while it is 9fF/g in the x and y axes directions. In this paper, the simulation of the structure is performed using Intellisuite software. Moreover, a multi-objective genetic optimization algorithm has been used to determine the dimensions of the constituents of the spring and the weight.

Special Issue on MEMS for Robotics and Mechatronics

MEMS (Micro Electro Mechanical Systems) is a technology that is used to incorporate sensors, actuators, microstructures, and circuits on chips by using a combination of various technologies with semiconductor process. MEMS are also used in robotics and mechatronics since they can provide compact, low-cost functional components that play crucial roles in their respective systems. We would like to elaborate on the history of MEMS technology, whose initial development started around 1970. In 1960s, Dr. Isemi Igarashi of Toyota Central R&D Labs., Inc. in Japan developed a semiconductor pressure sensor of piezo-resistance type. In 1980s, the pressure sensors were used to control automobile engines to clear exhaust gas regulations and thus contributed to solving environmental issues. In 1990s, semiconductor acceleration sensors were used for passive safety technologies to detect collision of automobiles and activate air bags, which resulted in decrease in traffic fatalities. In 2000s, an active safety system with gyro sensors was developed to detect and control spinning of a vehicle. In future, space recognition sensors with optical scanners to measure light propagation time and detect distance to an object will be used for autonomous driving. For smartphones, a microphone, an acceleration sensor, and a gyro sensor are used in user interface, and a film bulk acoustic wave resonator (FBAR) is used in a wireless communication filter. For projectors, the built-in circuit of a mirror array system is used to move mirrors placed in an array. After the development of projectors, films have not been used in movie theaters. MEMS are also widely used in medical and biological fields, such as blood pressure measurement. Esashi began research on a semiconductor ion sensor ISFET (ion sensitive field effect transistor) in 1971. ISFET detects ion concentration in electrolyte by exposing the insulating film of an insulated gate transistor to the liquid. He set up a prototyping facility when he was a graduate student and wrote only one paper on this research, although the prototyping facility was used afterwards. The ion sensor was certified under the Pharmaceutical Affairs Law after a 12-year application process and was used as catheter-type pH sensor to diagnose reflux esophagitis. MEMS are widely used for minimally invasive medical treatment, which causes minimum damage to human body. Moreover, MEMS are used as disposable sensors to prevent infection or as implanted devices. In addition, MEMS are used for production inspection and scientific instrument, including scanning probe microscopes (SPMs), which observe atoms using extremely small nano-probes, and probe cards that simultaneously test several integrated circuits on a wafer using aligned probes. When he was an associate professor, Esashi improved the prototyping facility that he made when he was a student and made a large scale integrated circuit (LSI). After he became a professor, he accepted researchers from more than 130 companies and developed MEMS using the prototyping facility to develop a product through the academia-industry collaboration. He realized integrated MEMS by combining LSI and MEMS. This includes a system of many tactile sensors attached on the body surface of a safe robot for real-time detection of contact through packet communication. After he retired from the university, he developed a “prototype coin laundry,” which enables companies to do develop without having their own prototyping facility. The prototype coin laundry is a system where engineers can use the prototyping facility to develop devices, and the system has been managed by successors. Unlike integrated circuits for which standardization is easy, standardization of MEMS is challenging because of difficulty in development. It is necessary to access various knowledge for the development of MEMS, and he has made efforts to provide the knowledge. Finally, we would like to thank authors who submitted papers to this Special Issue on MEMS for Robotics and Mechatronics as well as those who were involved in editing and reviewing the papers. We sincerely hope for further development in this field of research.

Development of MEMS Tactile Sensation Device for Haptic Robot

A tactile sensation device using micro-electromechanical system (MEMS) has been developed. This device is integrated with a haptic sensation robot for use as fingers. The tactile device must be miniaturized to enable attachment of the actuator mechanism to the fingers. Therefore, we used MEMS technology for this device. The device is composed of an interface part fabricated by 3D printing, pins, and MEMS cantilever-type actuators. It has the ability to stimulate the mechanoreceptors of the fingertips. The device and robot can display not only high-resolution images of the fingertips but also the repulsion force during finger operations such as tool holding and rotation. We have not yet achieved the final device because of fabrication problems. In this paper, we explain the details, progress of development, and results of trials on the prototype device.

3D Printed MEMS Technology-Recent Developments and Applications.

Microelectromechanical systems (MEMS) are of high interest for recent electronic applications. Their applications range from medicine to measurement technology, from microfluidics to the Internet of Things (IoT). In many cases, MEMS elements serve as sensors or actuators, e.g., in recent mobile phones, but also in future autonomously driving cars. Most MEMS elements are based on silicon, which is not deformed plastically under a load, as opposed to metals. While highly sophisticated solutions were already found for diverse MEMS sensors, actuators, and other elements, MEMS fabrication is less standardized than pure microelectronics, which sometimes blocks new ideas. One of the possibilities to overcome this problem may be the 3D printing approach. While most 3D printing technologies do not offer sufficient resolution for MEMS production, and many of the common 3D printing materials cannot be used for this application, there are still niches in which the 3D printing of MEMS enables producing new structures and thus creating elements for new applications, or the faster and less expensive production of common systems. Here, we give an overview of the most recent developments and applications in 3D printing of MEMS.

Effects of flexural vibration and thickness vibration on receiving characteristics of a diaphragm-type PZT resonator

The piezoelectric micromachined ultrasonic transducer (PMUT) is increasingly being used in medical applications with the development of microelectromechanical system technology. The PMUT generates flexural vibration depending on its structure, but there is also thickness vibration depending on the film thickness of the resonator. This paper clarifies the effect of each vibration on the PMUT reception characteristics. Two approaches that may weaken flexural vibration are investigated in finite element simulation. One is thickening the support layer to increase the damping function. The other is increasing the thickness vibration by thickening the lead zirconate titanate (PZT) layer. Results reveal that flexural vibration is strongly related to ringing in the received waveform, owing to flexural vibration generating rapid phase changes in the frequency domain. Meanwhile, thickness vibration, the degree of which depends on the thickness of the PZT layer, is confirmed to affect the pulse width but be less relevant to ringing.

An 8-element Tx/Rx array utilizing MEMS detuning combined with 6 Rx loops for 19 F and 1 H lung imaging at 1.5T.

To firstly improve the attainable image SNR of 19 F and 1 H C3 F8 lung imaging at 1.5 tesla using an 8-element transmit/receive (Tx/Rx) flexible vest array combined with a 6-element Rx-only array, and to secondly evaluate microelectromechanical systems for switching the array elements between the 2 resonant frequencies. The Tx efficiency and homogeneity of the 8-element array were measured and simulated for 1 H imaging in a cylindrical phantom and then evaluated for in vivo 19 F/1 H imaging. The added improvement provided by the 6-element Rx-only array was quantified through simulation and measurement and compared to the ultimate SNR. It was verified through the measurement of isolation that microelectromechanical systems switches provided broadband isolation of Tx/Rx circuitry such that the 19 F tuned Tx/Rx array could be effectively used for both 19 F and 1 H nuclei. For 1 H imaging, the measured Tx efficiency/homogeneity (mean ± percent SD; ) was comparable to that simulated ( ). The 6 additional Rx-only loops increased the mean Rx sensitivity when compared to the 8-element array by a factor of 1.41× and 1.45× in simulation and measurement, respectively. In regions central to the thorax, the simulated SNR of the 14-element array achieves ≥70% of the ultimate SNR when including noise from the matching circuits and preamplifiers. A measured microelectromechanical systems switching speed of 12 µs and added minimum 22 dB of isolation between Tx and Rx were sufficient for Tx/Rx switching in this application. The described single-tuned array driven at 19 F and 1 H, utilizing microelectromechanical systems technology, provides excellent results for 19 F and 1 H dual-nuclear lung ventilation imaging.

Micro-machined respiratory monitoring system development for artificial ventilator in animal experiment

We developed a respiratory monitoring system to evaluate elasticity on the lungs of small animals by the positive-pressure airflow under artificial ventilation during experiments. The system consists of a tube-type thermal flow sensor fabricated using microelectromechanical systems (MEMS) technology and commercially available Si-MEMS pressure sensors. We first used a small spherical balloon having an inner volume of 0.68 cc as a simulated lung. We evaluated the balloon elasticity from the supplied flow volume and pressure inside the balloon and confirmed that our system can detect balloon elasticity from the gradient under both static and cyclic airflow. We evaluated our system in terms of the lung elasticity of a rat and obtained a flow volume vs. pressure curve showing the lung elasticity under artificial ventilation. The changes in the flow rate and pressure waveforms due to airway contraction with drug administration were detected with our system in real time.

The Influence of Soccer Playing Surface on the Loading Response to Ankle (P)Rehabilitation Exercises.

Contemporary synthetic playing surfaces have been associated with an increased risk of ankle injury in the various types of football. Triaxial accelerometers facilitate in vivo assessment of planar mechanical loading on the player. To quantify the influence of playing surface on the PlayerLoad elicited during footwork and plyometric drills focused on the mechanism of ankle injury. Repeated-measures, field-based design. Regulation soccer pitches. A total of 15 amateur soccer players (22.1 [2.4]y), injury free with ≥6 years competitive experience. Each player completed a test battery comprising 3 footwork drills (anterior, lateral, and diagonal) and 4 plyometric drills (anterior hop, inversion hop, eversion hop, and diagonal hop) on natural turf (NT), third-generation artificial turf (3G), and AstroTurf. Global positioning system sensors were located at C7 and the mid-tibia of each leg to measure triaxial acceleration (100Hz). PlayerLoad in each axial plane was calculated for each drill on each surface and at each global positioning system location. Analysis of variance revealed a significant main effect for sensor location in all drills, with PlayerLoad higher at mid-tibia than at C7 in all movement planes. AstroTurf elicited significantly higher PlayerLoad in the mediolateral and anteroposterior planes, with typically no difference between NT and 3G. In isolated inversion and eversion hopping trials, the 3G surface also elicited lower PlayerLoad than NT. PlayerLoad magnitude was sensitive to unit placement, advocating measurement with greater anatomical relevance when using microelectromechanical systems technology to monitor training or rehabilitation load. AstroTurf elicited higher PlayerLoad across all planes and drills and should be avoided for rehabilitative purposes, whereas 3G elicited a similar mechanical response to NT.