Analysis of MEMS Piezoelectric Hydrophone at High Sensitivity for underwater application

Micro-electromechanical systems (MEMS), is a technology that is used to design small integrated devices that combines both electrical (voltage, resistance) and mechanical components (stress, displacement). These devices are assembled using integrated circuit batch processing methods and their size can vary from Micrometers (μm) to Millimeters (mm). MEMS devices have the capability to sense and control the environment. These devices are fabricated using System Integrated chip technology and micro-level segments are manufactured using silicon. To remove the selective parts of silicon i.e. extra silicon parts, Processes such as back etching, high-aspect-ratio micromachining are used to remove selective parts of silicon or to add the extra layers to form the electromechanical components. The study is concerned to design a T- Shape vector Hydrophone using MEMS Technology and to analyses mechanical properties like induced stresses, deformation and to analyses the piezoelectric hydrophone characteristics like frequency response, sensitivity and Voltage to achieve improved sensitivity. MEMS Directional Hydrophone PZT is simulated. Both the structure resembles the fish lateral line and auditory cilia system which converts acoustic pressure into voltage. © 2017 Elsevier Ltd

Characterization and modeling of CMOS-compatible acoustical particle velocity sensors for applications requiring low supply voltages

Acoustic particle velocity sensors have been obtained applying simple low resolution micromachining steps to chips fabricated using a standard microelectronic process. Each sensor consists of four silicided polysilicon wires, suspended over cavities etched into the substrate, and connected to form a heatstone bridge. Full compatibility of the micromachining procedure with the original process is demonstrated by integrating a simple pre-amplifier on the same chip as the sensors and showing that both blocks are functional. Proper design of the sensing structures allows them to operate with a single 3.3 V power supply. Sensitivity and noise measurements, performed to estimate the sensor detection limit, are described. Excess noise with a flicker-like behavior, not ascribable to the amplifier, is found when the bridges are biased in working conditions. In addition, the dependence of the sensitivity on the dc bias voltage of the bridges is investigated, comparing the experimental data with the results of a simple analytical model and finite element method simulations

Deep-Sea Model-Aided Navigation Accuracy for Autonomous Underwater Vehicles Using Online Calibrated Dynamic Models

In this work, the accuracy of inertial-based navigation systems for autonomous underwater vehicles (AUVs) in typical mapping and exploration missions up to 5000m depth is examined. The benefit of using an additional AUV motion model in the navigation is surveyed. Underwater navigation requires acoustic positioning sensors. In this work, so-called Ultra-Short-Baseline (USBL) devices were used allowing the AUV to localize itself relative to an opposite device attached to a (surface) vehicle. Despite their easy use, the devices\u27 absolute positioning accuracy decreases proportional to range. This makes underwater navigation a sophisticated estimation task requiring integration of multiple sensors for inertial, orientation, velocity and position measurements. First, error models for the necessary sensors are derived. The emphasis is on the USBL devices due to their key role in navigation - besides a velocity sensor based on the Doppler effect. The USBL model is based on theoretical considerations and conclusions from experimental data. The error models and the navigation algorithms are evaluated on real-world data collected during field experiments in shallow sea. The results of this evaluation are used to parametrize an AUV motion model. Usually, such a model is used only for model-based motion control and planning. In this work, however, besides serving as a simulation reference model, it is used as a tool to improve navigation accuracy by providing virtual measurements to the navigation algorithm (model-aided navigation). The benefit of model-aided navigation is evaluated through Monte Carlo simulation in a deep-sea exploration mission. The final and main contributions of this work are twofold. First, the basic expected navigation accuracy for a typical deep-sea mission with USBL and an ensemble of high-quality navigation sensors is evaluated. Secondly, the same setting is examined using model-aided navigation. The model-aiding is activated after the AUV gets close to sea-bottom. This reflects the case where the motion model is identified online which is only feasible if the velocity sensor is close to the ground (e.g. 100m or closer). The results indicate that, ideally, deep-sea navigation via USBL can be achieved with an accuracy in range of 3-15m w.r.t. the expected root-mean-square error. This also depends on the reference vehicle\u27s position at the surface. In case the actual estimation certainty is already below a certain threshold (ca. <4m), the simulations reveal that the model-aided scheme can improve the navigation accuracy w.r.t. position by 3-12%

Development of an Ultra-Sensitive and Flexible Piezoresistive Flow Sensor Using Vertical Graphene Nanosheets

© 2020, © 2020, The Author(s). This paper suggests development of a flexible, lightweight, and ultra-sensitive piezoresistive flow sensor based on vertical graphene nanosheets (VGNs) with a mazelike structure. The sensor was thoroughly characterized for steady-state and oscillatory water flow monitoring applications. The results demonstrated a high sensitivity (103.91 mV (mm/s)−1) and a very low-velocity detection threshold (1.127 mm s−1) in steady-state flow monitoring. As one of many potential applications, we demonstrated that the proposed VGNs/PDMS flow sensor can closely mimic the vestibular hair cell sensors housed inside the semicircular canals (SCCs). As a proof of concept, magnetic resonance imaging of the human inner ear was conducted to measure the dimensions of the SCCs and to develop a 3D printed lateral semicircular canal (LSCC). The sensor was embedded into the artificial LSCC and tested for various physiological movements. The obtained results indicate that the flow sensor is able to distinguish minute changes in the rotational axis physical geometry, frequency, and amplitude. The success of this study paves the way for extending this technology not only to vestibular organ prosthesis but also to other applications such as blood/urine flow monitoring, intravenous therapy (IV), water leakage monitoring, and unmanned underwater robots through incorporation of the appropriate packaging of devices.[Figure not available: see fulltext.

Development and Characterization of Polymer-based Magnetoelectric Nanofibers

With the rapid development of bionics, where biological systems meet electronics, there is an interest in polymer-based electrode systems that are soft, flexible, easily processed and fabricated. In this research area, magnetoelectric (ME) composites bring new and exciting opportunities, including contactless or “wireless” electrical stimulation, less-invasive integration in the form of dispersible, injectable nanoelectrodes, and applications as biodegradable sensors and bioenergy harvesters in the biomedical field. When ME composites are exposed to a magnetic field, a magnetostrictive (MS) component transfers strain to a piezoelectric (PE) component that generates an output voltage. In doing so, ME composites have the ability to enable magnetic-to-electrical conversion and thus can be utilized to power devices or electrically stimulate tissues or cells from a remote magnetic stimulus. To date, ceramic materials have mostly been applied in nanostructured ME composites, however, these may become fragile and cause deleterious reactions at the interface regions, leading to low electrical resistivity and high dielectric losses and ultimately low output voltage. To overcome these shortcomings, polymer-based ME composites offer new solutions to develop softer, contactless electrodes, without electrical connections, for easier and unique fabrication approaches (e.g. incorporation into soft gels). Their strain-mediated ME effect in large scale devices has been thoroughly studied both experimentally and theoretically. Polymer-based ME composites have almost exclusively used the PE polymer, poly (vinylidene fluoride) (PVDF), due to its high PE coefficient and as such developments in exploring other types of PE polymers have not been forthcoming. For example, other PE polymers such as poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and poly (lactic acid) (PLA) have yet to be investigated though have the potential to bring added-value and function to polymer-based ME composites. Compared to PVDF and its copolymer P(VDF-TrFE), the piezoelectricity of another copolymer, P(VDF-HFP), is less-well understood. As a biocompatible polymer, PLA has been extensively investigated for applications in drug delivery and tissue engineering. Instead of being used only as a biodegradable and bioactive thermoplastic material, PLA is promising as a PE polymer, which has potential to mimic PE functions of tissues. Thus, in addition to PVDF, the thesis investigates the PE properties of P(VDF-HFP) and PLA and aims to develop ME composite nanofibers based on these polymers

Touching on elements for a non-invasive sensory feedback system for use in a prosthetic hand

Hand amputation results in the loss of motor and sensory functions, impacting activities of daily life and quality of life. Commercially available prosthetic hands restore the motor function but lack sensory feedback, which is crucial to receive information about the prosthesis state in real-time when interacting with the external environment. As a supplement to the missing sensory feedback, the amputee needs to rely on visual and audio cues to operate the prosthetic hand, which can be mentally demanding. This thesis revolves around finding potential solutions to contribute to an intuitive non-invasive sensory feedback system that could be cognitively less burdensome and enhance the sense of embodiment (the feeling that an artificial limb belongs to one’s own body), increasing acceptance of wearing a prosthesis.A sensory feedback system contains sensors to detect signals applied to the prosthetics. The signals are encoded via signal processing to resemble the detected sensation delivered by actuators on the skin. There is a challenge in implementing commercial sensors in a prosthetic finger. Due to the prosthetic finger’s curvature and the fact that some prosthetic hands use a covering rubber glove, the sensor response would be inaccurate. This thesis shows that a pneumatic touch sensor integrated into a rubber glove eliminates these errors. This sensor provides a consistent reading independent of the incident angle of stimulus, has a sensitivity of 0.82 kPa/N, a hysteresis error of 2.39±0.17%, and a linearity error of 2.95±0.40%.For intuitive tactile stimulation, it has been suggested that the feedback stimulus should be modality-matched with the intention to provide a sensation that can be easily associated with the real touch on the prosthetic hand, e.g., pressure on the prosthetic finger should provide pressure on the residual limb. A stimulus should also be spatially matched (e.g., position, size, and shape). Electrotactile stimulation has the ability to provide various sensations due to it having several adjustable parameters. Therefore, this type of stimulus is a good candidate for discrimination of textures. A microphone can detect texture-elicited vibrations to be processed, and by varying, e.g., the median frequency of the electrical stimulation, the signal can be presented on the skin. Participants in a study using electrotactile feedback showed a median accuracy of 85% in differentiating between four textures.During active exploration, electrotactile and vibrotactile feedback provide spatially matched modality stimulations, providing continuous feedback and providing a displaced sensation or a sensation dispatched on a larger area. Evaluating commonly used stimulation modalities using the Rubber Hand Illusion, modalities which resemble the intended sensation provide a more vivid illusion of ownership for the rubber hand.For a potentially more intuitive sensory feedback, the stimulation can be somatotopically matched, where the stimulus is experienced as being applied on a site corresponding to their missing hand. This is possible for amputees who experience referred sensation on their residual stump. However, not all amputees experience referred sensations. Nonetheless, after a structured training period, it is possible to learn to associate touch with specific fingers, and the effect persisted after two weeks. This effect was evaluated on participants with intact limbs, so it remains to evaluate this effect for amputees.In conclusion, this thesis proposes suggestions on sensory feedback systems that could be helpful in future prosthetic hands to (1) reduce their complexity and (2) enhance the sense of body ownership to enhance the overall sense of embodiment as an addition to an intuitive control system

Analysis, Design and Fabrication of Micromixers, Volume II

Micromixers are an important component in micrototal analysis systems and lab-on-a-chip platforms which are widely used for sample preparation and analysis, drug delivery, and biological and chemical synthesis. The Special Issue "Analysis, Design and Fabrication of Micromixers II" published in Micromachines covers new mechanisms, numerical and/or experimental mixing analysis, design, and fabrication of various micromixers. This reprint includes an editorial, two review papers, and eleven research papers reporting on five active and six passive micromixers. Three of the active micromixers have electrokinetic driving force, but the other two are activated by mechanical mechanism and acoustic streaming. Three studies employs non-Newtonian working fluids, one of which deals with nano-non-Newtonian fluids. Most of the cases investigated micromixer design