1,721,070 research outputs found
Piezoelectric Performance of Continuous Beam and Narrow Supported Beam Arrays for Artificial Basilar Membranes
No full textWe report an experimental assessment of the electrical performance of two piezoelectric beam arrays for artificial basilar membranes (ABMs): a continuous beam array (CBA) and a narrow-supports beam array (NSBA). Both arrays consist of piezoelectric beams of sequentially varying lengths that mimic the frequency selectivity of mammalian cochleae. The narrow supports of the NSBA resulted in lateral deformation of the beams, whereas the CBA beams were flat. The displacement and piezoelectric output of each beam were measured at the resonance frequency of each beam using a scanning laser-Doppler vibrometer (SLDV). Both ABM prototypes showed mechanical frequency selectivity that depended on the beam length. The CBA generated a piezoelectric output in the range 6.6–23.2 μV and exhibited electrical frequency separability, whereas the NSBA failed to generate sufficient electrical potential due to the lateral deformation of the piezoelectric beams. The CBA was found to be more effective as an ABM, with potential for use in cochlear implants. © 2014, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.1
Characterizing the Performance of a Resonance-Based MEMS Particle Sensor with Glass Beads
No full textFine dust measurement methods, such as weight change, beta ray measurement, light scattering, and resonance change, have been studied and used, but there is still room for improvement in terms of cost, system volume, and accuracy. In this study, we aimed to develop a low-cost, micro-scale, and highly accurate dust sensor using semiconductor processes. The sensor consists of a piezoelectric membrane with a diameter of 800µm and a thickness of 2.8µm. The resonance frequency and mode shape were measured and monitored using a Laser-Doppler-Vibrometer (LDV), and the resonance frequency shift was calculated based on the same mode shape. Vibration modes from (0,1) to (3,1) were observed within a 0–200kHz frequency bandwidth. Spherical glass beads were used to measure resonance frequency shift for additional mass ranging from 0.863 to 4.52µg. The first resonance mode (0,1) exhibited a clear proportional relationship between the resonance frequency shift and additional mass, while other modes exhibited non-proportional trends. Intriguingly, notable discrepancies in the resonance frequency shift emerged based on the spatial placement of the glass beads, even when the mass was the same. Additionally, we presented an approximate theoretical curve to portray the resonance frequency shift, which we subsequently validated against our measurement findings. This study presents a new attempt on the characterization method of piezoelectric mass sensors and provides a relatively simple and accurate analysis of the results. © 2023, The Author(s), under exclusive licence to Korean Society for Precision Engineering.FALSEsciescopuskc
Nano-patterned SU-8 surface using nanosphere-lithography for enhanced neuronal cell growth
No full textMimicking the nanoscale surface texture of the extracellular matrix can affect the regulation of cellular behavior, including adhesion, differentiation, and neurite outgrowth. In this study, SU-8-based polymer surfaces with well-ordered nanowell arrays were fabricated using nanosphere lithography with polystyrene nanoparticles. We show that the SU-8 surface with nanowells resulted in similar neuronal development of rat pheochromocytoma (PC12) cells compared with an unpatterned poly-L-lysine (PLL)-coated SU-8 surface. Additionally, even after soaking the substrate in cell culture medium for two weeks, cells on the nanowell SU-8 surface showed long-term neurite outgrowth compared to cells on the PLL-coated SU-8 surface. The topographical surface modification of the nanowell array demonstrates potential as a replacement for cell adhesive material coatings such as PLL, for applications requiring long-term use of polymer-based implantable devices. © 2016 IOP Publishing Ltd.1
Design and fabrication of a mems test socket with an attached tip for a ball-grid-array integrated circuit package
No full textMicroelectromechanical system (MEMS) test sockets with attached tips were developed for a ball-grid-array integrated circuit (BGA IC) package, using MEMS fabrication technology in conjunction with Ni-Co electroplating and XeF2 isotropic silicon etching. The electroplating process was used to create metal tips and thick metal cantilevers, which increased the contact reliability and conductivity. XeF2 isotropic silicon etching was used to release the cantilever array, which reduced the process cost and increased the mechanical stability. A finite element analysis (FEA) simulation was conducted to verify the force-deflection relationships of five types of cantilevers with attached tips. With an input deflection of 40 μm, the measured forces ranged from 12.55 to 26.14 mN, and matched the FEA results. The path resistance between a tip and the appropriate electrode pad was less than 3.49 Ω for all cantilevers when the tips were connected to the corresponding positions with more than 5 mN of contact force. The cantilever design with a length of 430 um and a tip height of 60 um (L430D60) showed the best performance in terms of the force-deflection relationship, a well as resistance. Therefore, the fabricated MEMS test sockets with tips are potentially applicable to actual BGA IC package tests. © 2014 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.1
Characterization and Modeling of an Acoustic Sensor Using AlN Thin-Film for Frequency Selectivity
No full textIn this study, a one-dimensional beam array acoustic sensor was built using microelectromechanical system technology to achieve mechanical frequency selectivity. The acoustic sensor contained 16 beams of various lengths. The frequency selectivity was evaluated with a scanning laser Doppler vibrometer, while applying an alternating current having various frequencies with 2 volts amplitude and 0 volt offset. The beams formed separate band-pass filters in the proximity of the corresponding resonance frequencies in the range of 3 kHz to 13 kHz. The first resonance frequencies of the beams were calculated using finite element analysis to simulate the frequency response. In the finite element analysis models, mode shapes were studied to understand the effect of the beam deformation caused by the residual stress generated during the MEMS fabrication. The measured and simulated first resonance frequencies of the beams provided solid evidence of the tonotopicity of the sensor. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.1
The Design and Optimization of a Compressive-Type Vector Sensor Utilizing a PMN-28PT Piezoelectric Single-Crystal
Full text linkUnderwater sensors that detect the distance and direction of acoustic sources are critical for surveillance monitoring and target detection in the water. Here, we propose an axial vector sensor that utilizes a small (~1 cm3) compressive-type piezoelectric accelerometer using piezoelectric single crystals. Initially, finite element analysis (FEA) was used to optimize the structure that comprised piezoelectric Pb(Mb1/3Nb2/3)O3-28%PbTiO3 single crystals on a tungsten seismic mass. The receiving voltage sensitivity (RVS) was enhanced through geometric optimization of the thickness and sensing area of the piezoelectric material and the seismic mass. The estimated maximum RVS of the optimized vector sensor was −212 dB. FEA simulations and practical measurements were used to verify the directivity of the vector sensor design, which exhibited a dipole pattern. The dipole beam pattern was used to obtain cardioid patterns using the simulated and measured results for comparison. The results clearly showed the feasibility of using the proposed piezoelectric single-crystal accelerometer for a compressive-type vector sensor
PZT Ferroelectric Synapse TFT With Multi-Level of Conductance State for Neuromorphic Applications
No full textTo fundamentally solve the bottleneck of Von Neumann’s computing architecture, a neuromorphic thin-film transistor (NTFT) employing Pb(Zr, Ti)O3 (PZT) was investigated. The indium gallium zinc oxide (IGZO) channel back gate TFT structure was chosen to solve the diffusion of atoms that form a channel layer during the annealing process for crystallization of PZT. A post-deposition process with IGZO after annealing PZT and using an oxide-based material as a channel structure can minimize the diffusion phenomenon of junction materials and oxygen together, which leads to a high and reliable performance of the NTFT. The basic operations of synapses short-term memory (STM) and long-term memory (LTM) were also analyzed to confirm the application of a neuromorphic device. The high dielectric constant and polarization properties of Pb(Zr, Ti)O3 (PZT) allow the power consumption of spike signals used in spike dependent plasticity change to be reduced to 10 pJ. Moreover, a wide dynamic range of Gmax / Gmin ≅ 1000 was obtained, and the channel conductance was maintained over 40000 seconds. The optimized pulse achieved multi-level states (>32), which made the learning process efficient. This study verified that the PZT-TFT structure has a high potential and merits for neuromorphic devices.1
A magnetically actuated microrobot for targeted neural cell delivery and selective connection of neural networks
Full text linkThere has been a great deal of interest in the development of technologies for actively manipulating neural networks in vitro, providing natural but simplified environments in a highly reproducible manner in which to study brain function and related diseases. Platforms for these in vitro neural networks require precise and selective neural connections at the target location, with minimal external influences, and measurement of neural activity to determine how neurons communicate. Here, we report a neuron-loaded microrobot for selective connection of neural networks via precise delivery to a gap between two neural clusters by an external magnetic field. In addition, the extracellular action potential was propagated from one cluster to the other through the neurons on the microrobot. The proposed technique shows the potential for use in experiments to understand how neurons communicate in the neural network by actively connecting neural clusters. Copyright © 2020 The Authors, some rights reserved.1
Integrated Piezoelectric AlN Thin Film with SU-8/PDMS Supporting Layer for Flexible Sensor Array
Full text linkThis research focuses on the development of a flexible tactile sensor array consisting of aluminum nitride (AlN) based on micro-electro-mechanical system (MEMS) technology. A total of 2304 tactile sensors were integrated into a small area of 2.5 × 2.5 cm2. Five hundred nm thick AlN film with strong c-axis texture was sputtered on Cr/Au/Cr (50/50/5 nm) layers as the sacrificial layer coated on a Si wafer. To achieve device flexibility, polydimethylsiloxane (PDMS) polymer and SU-8 photoresist layer were used as the supporting layers after etching away a release layer. Twenty-five mM (3-mercaptopropyl) trimethoxysilane (MPTMS) improves the adhesion between metal and polymers due to formation of a self-assembled monolayer (SAM) on the surface of the top electrode. The flexible tactile sensor has 8 × 8 channels and each channel has 36 sensor elements with nine SU-8 bump blocks. The tactile sensor array was demonstrated to be flexible by bending 90 degrees. The tactile sensor array was demonstrated to show clear spatial resolution through detecting the distinct electrical response of each channel under local mechanical stimulus
Noncytotoxic artificial bacterial flagella fabricated from biocompatible ORMOCOMP and iron coating
No full textMagnetic microrobots have potential use in biomedical applications such as minimally invasive surgery, targeted diagnosis and therapy. Inspired by nature, artificial bacterial flagella (ABFs) are a form of microrobot powered by magnetic helical propulsion. For the promise of ABFs to be realized, issues of biocompatibility must be addressed and the materials used in their fabrication should be carefully considered. In this work, we fabricate the helical bodies of ABFs from a commercially available biocompatible photoresist, ORMOCOMP, by subsequently coating them with Fe for magnetic actuation. 3-(4,5- Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays show that Fe-coated ORMOCOMP layers do not undermine the cell viability during 72 hours of incubation compared to control substrates. Cells exhibit normal morphology on ABF arrays and show good lamellipodial and filopodial interactions with the ABF surfaces. The swimming performance of Fe-coated ABFs is characterized using a three-pair Helmholtz coil arrangement. ABFs exhibit a maximum forward speed of 48.9 μm s-1 under a field of 9 mT at a frequency of 72 Hz. In summary, our Fe-coated ABFs exhibit little cytotoxicity and have potential for in vivo applications, especially those involving difficult to access regions within the human body. © 2014 The Royal Society of Chemistry.1
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