Fabrication and Characterization of Annular-Shaped Piezoelectric Micromachined Ultrasonic Transducer Mounted with Pb(Zr,Ti)O3-Based Monocrystalline Thin Film

In this study, we propose an annular-shaped piezoelectric micromachined ultrasonic transducer (pMUT) based on a Pb(Zr,Ti)O3-based monocrystalline thin film. This pMUT is expected to increase the resonance frequency while maintaining displacement sensitivity, making it superior to an island-shaped pMUT, which is a conventional design. To demonstrate the validity of this assumption, annular- and island-shaped pMUTs with a 60-μm-diameter diaphragm were prototyped and characterized. As a result, the annular-shaped pMUT exhibited a resonance frequency of 11.9 MHz, a static displacement sensitivity of 2.35 nm/V and a transmitting figure-of-merit (FOM) of 28 nm∙MHz/V. On the other hand, the island-shaped pMUT exhibited a resonance frequency of 9.6 MHz and a static displacement of 2.5 nm/V and an FOM of 24 nm∙MHz/V. Therefore, the annular-shaped pMUT was experimentally demonstrated to provide a higher FOM compared to the island-shaped pMUT. In addition, the annular-shaped pMUT with the optimal dimensions is found to be able to keep a relatively large fabrication margin. This is an advantageous point for the practical device fabrication. We believe this design has a potential to become a standard design for high-performance pMUT devices.

Giant Displacement Sensitivity Using Push-Pull Method in Interferometry

We present a giant sensitivity displacement sensor combining the push-pull method and enhanced Vernier effect. The displacement sensor consists in two interferometers that are composed by two cleaved standard optical fibers coupled by a 3 dB coupler and combined with a double-sided mirror. The push pull-method is applied to the mirror creating a symmetrical change to the length of each interferometer. Furthermore, we demonstrate that the Vernier effect has a maximum sensitivity of two-fold that obtained with a single interferometer. The combination of the push-pull method and the Vernier effect in the displacement sensors allows a sensitivity of 60 ± 1 nm/μm when compared with a single interferometer working in the same free spectral range. In addition, exploring the maximum performance of the displacement sensors, a sensitivity of 254 ± 6 nm/μm is achieved, presenting a M-factor of 1071 and MVernier of 1.9 corresponding to a resolution of 79 pm. This new solution allows the implementation of giant-sensitive displacement measurement for a wide range of applications.

Design and analysis of a displacement sensor-integrated compliant microgripper based on parallel structure

This study evaluates the displacement sensitivity of a new compliant microgripper. The microgripper is designed based on a four-bar mechanism and the concept of a compliant mechanism. The effects of the width of the right circular hinge, the thickness of microgripper, and the material properties on the dis-placement sensitivity are considered via using the finite element method. In the beginning, the stress and deformation of the compliant microgripper are evaluated. Subsequently, the displacement of the microgripper is then analyzed. The results showed that the design parameter and the displacement sensitivity have a close relationship. To increase the grasping reliability and measure the displacement or force, a micro-displacement sensor is integrated with the proposed microgripper. Finally, the modeling and analysis of the proposed sensor are conducted.

Performance of compliant mechanisms applied to a modified shape accelerometer of single and double layer

<span>Accelerometers are widely used in several mechanisms of high sensitivity. They are employed for example in tilt-control in spacecraft, inertial navigation, oil exploration, seismic monitoring, etc. In order to improve the sensitivity of the measurements, implementation of Displacement-amplifying Compliant Mechanisms (DaCMs) in a capacitive accelerometer have been reported in the literature. In this paper, a system composed of two elements; capacitive accelerometer with extended beams (CAEB) and a DaCM geometry, of single and souble layer, are analysed. Three materials were considered, in the case, for the second layer. The DaCM implementation improves the operation frequency and displacement sensitivity, under different proportions, at the same time. Furthermore, three sweeps were performed: a range of thickness from 25 µm up to 30 µm (to determine the appropriate silicon mass value, using SOI technology), a range of second layer thickness (to choose the more appropriate material and its thickness) and a range of gravity values (to determine the maximum normal stress in the beams, which defines the superior value of the g operation range). The in-plane mode (y-axis) was considered in all analysed cases. This characterization was developed using the Finite Element Method. Structural and modal analysis responses were under study.</span>

Coherent Optical Transduction of Suspended Microcapillary Resonators for Multi-Parameter Sensing Applications

Characterization of micro and nanoparticle mass has become increasingly relevant in a wide range of fields, from materials science to drug development. The real-time analysis of complex mixtures in liquids demands very high mass sensitivity and high throughput. One of the most promising approaches for real-time measurements in liquid, with an excellent mass sensitivity, is the use of suspended microchannel resonators, where a carrier liquid containing the analytes flows through a nanomechanical resonator while tracking its resonance frequency shift. To this end, an extremely sensitive mechanical displacement technique is necessary. Here, we have developed an optomechanical transduction technique to enhance the mechanical displacement sensitivity of optically transparent hollow nanomechanical resonators. The capillaries have been fabricated by using a thermal stretching technique, which allows to accurately control the final dimensions of the device. We have experimentally demonstrated the light coupling into the fused silica capillary walls and how the evanescent light coming out from the silica interferes with the surrounding electromagnetic field distribution, a standing wave sustained by the incident laser and the reflected power from the substrate, modulating the reflectivity. The enhancement of the displacement sensitivity due to this interferometric modulation (two orders of magnitude better than compared with previous accomplishments) has been theoretically predicted and experimentally demonstrated.

Considerations for ultrasound exposure during transcranial MR acoustic radiation force imaging

The aim of this study was to improve the sensitivity of magnetic resonance-acoustic radiation force imaging (MR-ARFI) to minimize pressures required to localize focused ultrasound (FUS) beams, and to establish safe FUS localization parameters for ongoing ultrasound neuromodulation experiments in living non-human primates. We developed an optical tracking method to ensure that the MR-ARFI motion-encoding gradients (MEGs) were aligned with a single-element FUS transducer and that the imaged slice was prescribed at the optically tracked location of the acoustic focus. This method was validated in phantoms, which showed that MR-ARFI-derived displacement sensitivity is maximized when the MR-ARFI MEGs were maximally aligned with the FUS propagation direction. The method was then applied in vivo to acquire displacement images in two healthy macaque monkeys (M fascicularis) which showed the FUS beam within the brain. Temperature images were acquired using MR thermometry to provide an estimate of in vivo brain temperature changes during MR-ARFI, and pressure and thermal simulations of the acoustic pulses were performed using the k-Wave package which showed no significant heating at the focus of the FUS beam. The methods presented here will benefit the multitude of transcranial FUS applications as well as future human applications.

Design Guidelines for MEMS Optical Accelerometer based on Dependence of Sensitivities on Diaphragm Dimensions

This work deals in specifying the design considerations while constructing a Micro Electro Mechanical Systems (MEMS) optical accelerometer working on capacitive sensing technique. Sensitivity is one of the most demanded characteristics of any sensor. The sensor considered is a MEMS capacitive accelerometer in which both displacement and capacitance are the primary sensing characteristics. This differential capacitive accelerometer causes change in displacement due to applied acceleration and further produces change in capacitance. So, the main focus in this work is to improve or select the suitable diaphragm dimensions of the differential capacitor in order to get optimal capacitive and displacement sensitivity. This is done for an Optical MEMS (MOEMS) based sensor where slight change has a large-scale impact. The electrical signal is converted to optical by adding an Optical Interferometer. Mach–Zehnder Interferometer (MZI) is used to carry out the intensity modulation which also gives protection in inflammable surroundings. This makes the system suitable for working in high temperature regions.

Fertilizer monitoring using micromachined cantilever

In this study, we will create a grid of micro electro-mechanical (MEMS) sensors, which will measure the contents of soil, especially urea. This will inform the farmers about the condition of soil in real time, and thus allowing them to know how much fertilizer they need to add. MEMS sensor is placed in the soil to measure the soil content by chemical reaction with the fertilizers; its accuracy can be improved if these sensors are placed on multiple points, i.e., they are placed in a grid. In the present study, we designed micro-cantilever based gas detectors, to detect ammonia present in the fertilizers. Several designs were proposed to find the best fit for this purpose. Numerical studies have been carried out on the proposed designs, to evaluate the displacement sensitivity and the voltage developed in the piezoelectric layer, and the triangular cantilever was found to be the most sensitive cantilever for that purpose.