A Sub-500 mu W Interface Electronics for Bionic Ears

This paper presents an ultra-low power current-mode circuit for a bionic ear interface. Piezoelectric (PZT) sensors at the system input transduce sound vibrations into multi-channel electrical signals, which are then processed by the proposed circuit to stimulate the auditory nerves consistently with the input amplitude level. The sensor outputs are first amplified and range-compressed through ultra-low power logarithmic amplifiers (LAs) into AC current waveforms, which are then rectified through custom current-mode circuits. The envelopes of the rectified signals are extracted, and are selectively sampled as reference for the stimulation current generator, armed with a 7-bit user-programmed DAC to enable patient fitting (calibration). Adjusted biphasic stimulation current is delivered to the nerves according to continuous inter-leaved sampling (CIS) stimulation strategy through a switch matrix. Each current pulse is optimized to have an exponentially decaying shape, which leads to reduced supply voltage, and hence similar to 20% lower stimulator power dissipation. The circuit has been designed and fabricated in 180nm high-voltage CMOS technology with up to 60 dB measured input dynamic range, and up to 1 mA average stimulation current. The 8-channel interface has been validated to be fully functional with 472 mu W power dissipation, which is the lowest value in the literature to date, when stimulated by a mimicked speech signal

Thin-Film PZT based Multi-Channel Acoustic MEMS Transducer for Cochlear Implant Applications

AuthorThis paper presents a multi-channel acoustic transducer that works within the audible frequency range (250-5500 Hz) and mimics the operation of the cochlea by filtering incoming sound. The transducer is composed of eight thin film piezoelectric cantilever beams with different resonance frequencies. The transducer is well suited to be implanted in middle ear cavity with an active volume of 5 mm × 5 mm × 0.62 mm and mass of 4.8 mg. Resonance frequencies and piezoelectric outputs of the beams are modeled with Finite Element Method (FEM). Vibration experiments showed that the transducer is capable of generating up to 139.36 mVpp under 0.1 g excitation. Test results are consistent with the FEM model on frequency (97%) and output voltage (89%) values. Device was further tested with acoustic excitation on an artificial tympanic membrane and flexible substrate. Under acoustic excitation, 50.7 mVpp output voltage generated under 100 dB Sound Pressure Level (SPL). Output voltages observed in acoustical and mechanical characterizations are the highest values reported to the best of our knowledge. Finally, to assess the feasibility of the transducer in daily sound levels, it was excited with a speech sample and output signal was recovered. Time-domain waveforms of the recorded and recovered signals showed close patterns

A Compact Electromagnetic Vibration Harvesting System with High Performance Interface Electronics

A compact vibration-based electromagnetic (EM) energy harvesting system utilizing high performance interface electronics, has been presented. The energy harvester module consists of an AA-battery sized cylinder tube with an external coil winding, a fixed magnet at the bottom of the tube, and a free magnet inside. The transducer is able to operate at low external vibration frequencies between 9.5 and 12 Hz. The generated AC voltage is converted to DC using a custom rectifier circuit that utilizes a gate cross coupled (GCC) input stage. This decreases the effective threshold voltage of the utilized diodes, while increasing the DC output power delivered to the load. The autonomous system, composed of an EM energy harvester module and a 0.35 mu m CMOS IC, delivers 11.6 mu W power to a 41 mu A load at an external vibration frequency of 12 Hz. The volume of the total system is 4.5 cm(3), and the overall system power density is 2.6 mu W/cm(3)

Multi-slice CT findings in COVID-19 pneumonia: A cross-sectional multicenter study

In this cross-sectional study of 278 patients, patients diagnosed with COVID-19 per their clinical features, laboratory, and thorax computed tomography (CT) findings were evaluated in terms of the most common characteristic findings. The lesions were classified according to the disease stage. The most common findings for each phase were investigated. The typical CT results included ground glass opacity (GGO), unilateral involvement, and single lesions in the early stages, as well as bilateral involvement, and multiple lesions in the progressive and peak phases. Additionally, vascular dilatation was the most common finding after GGO. Basal segment dominance and peripheral-intraparenchymal-basal segment involvement were mostly seen in the peak-phase patients. Thus, we think that this finding is an essential key to determining that the disease is in the advanced stages. The crazy-paving pattern was also a typical finding in the early-stage patients. Cavitary lesions, pulmonary nodules, and mediastinal lymph nodes were not observed in the lungs

Modeling and fabrication of electrostatically actuated diaphragms for on-chip valving of MEMS-compatible microfluidic systems

This paper presents an analytical model to estimate the actuation potential of an electrostatic parylene-C diaphragm, processed on a glass wafer using standard microelectromechanical systems (MEMS) process technology, and integrable to polydimethylsiloxane (PDMS) based lab-on-a-chip systems to construct a normally-closed microvalve for flow manipulation. The accurate estimation of the pull-in voltage of the diaphragm is critical to preserve the feasibility of integration. Thus, we introduced an analytical model, in a good agreement with the finite element method (FEM), to extend the solution of the pull-in instability by including the effect of nonlinear stretching for multilayered circular diaphragms. We characterized the operation of fabricated diaphragms with a 300 mu m radius for the parameters, including pull-in voltage (221 V on average), opening and closing response times (in microseconds), repeatability (more than 50 times), and touch area (25.3% +/- 2.6% at pull-in potential). The experimental pull-in voltage shows close accuracy with the predicted results. Moreover, the diaphragm, sealed with a PDMS microchannel, was tested under fluid flow to prove the applicability of microfluidic integration. The hybrid fabrication method enables the realization of optically transparent and durable electrostatic microvalves for complex functioning of polymer-based microfluidic systems, as the extended analytical formulation permits accurate modeling of operation.This paper presents an analytical model to estimate the actuation potential of an electrostatic parylene-C diaphragm, processed on a glass wafer using standard microelectromechanical systems (MEMS) process technology, and integrable to polydimethylsiloxane (PDMS) based lab-on-a-chip systems to construct a normally-closed microvalve for flow manipulation. The accurate estimation of the pull-in voltage of the diaphragm is critical to preserve the feasibility of integration. Thus, we introduced an analytical model, in a good agreement with the finite element method (FEM), to extend the solution of the pull-in instability by including the effect of nonlinear stretching for multilayered circular diaphragms. We characterized the operation of fabricated diaphragms with a 300 µm radius for the parameters, including pull-in voltage (221 V on average), opening and closing response times (in microseconds), repeatability (more than 50 times), and touch area (25.3% ± 2.6% at pull-in potential). The experimental pull-in voltage shows close accuracy with the predicted results. Moreover, the diaphragm, sealed with a PDMS microchannel, was tested under fluid flow to prove the applicability of microfluidic integration. The hybrid fabrication method enables the realization of optically transparent and durable electrostatic microvalves for complex functioning of polymer-based microfluidic systems, as the extended analytical formulation permits accurate modeling of operation

The improved inverted AlGaAs/GaAs interface: its relevance for high-mobility quantum wells and hybrid systems

Two dimensional electron gases (2DEGs) realized at GaAs/AlGaAs single interfaces by molecular-beam epitaxy (MBE) reach mobilities of about 15 million cm^2/Vs if the AlGaAs alloy is grown after the GaAs. Surprisingly, the mobilities may drop to a few millions for the identical but inverted AlGaAs/GaAs interface, i.e. reversed layering. Here we report on a series of inverted heterostructures with varying growth parameters including temperature, doping, and composition. Minimizing the segregation of both dopants and background impurities leads to mobilities of 13 million cm^2/Vs for inverted structures. The dependence of the mobility on electron density tunes by a gate or by illumination is found to be the identical if no doping layers exist between the 2DEG and the respective gate. Otherwise, it differs significantly compared to normal interface structures. Reducing the distance of the 2DEG to the surface down to 50nm requires an additional doping layer between 2DEG and surface in order to compensate for the surface-Schottky barrier. The suitability of such shallow inverted structures for future semiconductor-superconductor hybrid systems is discussed. Lastly, our understanding of the improved inverted interface enables us to produce optimized double-sided doped quantum wells exhibiting an electron mobility of 40 million cm^2/Vs at 1K.Comment: 19 pages, 9 figure

A High Throughput Lab-On-A-Chip System for Label Free Quantification of Breast Cancer Cells under Continuous Flow

This paper presents an LOC system combining microfluidic DEP channel with a CMOS image sensor for label and lens free detection and real-time counting of MCF-7 cells under continuous flow. Trapped and then released MCF-7 cells are accurately detected and counted under flow with a CMOS image sensor integrated underneath the DEP channel, for the first time in the literature. CMOS image sensor can capture 391 frames per second (fps) that allows detection of the released cells flowing through the channel with a flow rate up to 130 mu l/min (0.468 m/s). Therefore, the proposed system is able to detect the cells under high flow where conventional techniques for cell quantification such as fluorescent tagging become unusable. Detected cells are automatically counted with a computer program and the counting accuracy of the whole system is 95%. (C) 2016 The Authors. Published by Elsevier Ltd

A microfluidic device enabling drug resistance analysis of leukemia cells via coupled dielectrophoretic detection and impedimetric counting

© 2021, The Author(s).We report the development of a lab-on-a-chip system, that facilitates coupled dielectrophoretic detection (DEP-D) and impedimetric counting (IM-C), for investigating drug resistance in K562 and CCRF-CEM leukemia cells without (immuno) labeling. Two IM-C units were placed upstream and downstream of the DEP-D unit for enumeration, respectively, before and after the cells were treated in DEP-D unit, where the difference in cell count gave the total number of trapped cells based on their DEP characteristics. Conductivity of the running buffer was matched the conductivity of cytoplasm of wild type K562 and CCRF-CEM cells. Results showed that DEP responses of drug resistant and wild type K562 cells were statistically discriminative (at p = 0.05 level) at 200 mS/m buffer conductivity and at 8.6 MHz working frequency of DEP-D unit. For CCRF-CEM cells, conductivity and frequency values were 160 mS/m and 6.2 MHz, respectively. Our approach enabled discrimination of resistant cells in a group by setting up a threshold provided by the conductivity of running buffer. Subsequent selection of drug resistant cells can be applied to investigate variations in gene expressions and occurrence of mutations related to drug resistance