925 research outputs found
Electrochemical Sensors and On-chip Optical Sensors
abstract: The microelectronics technology has seen a tremendous growth over the past sixty years. The advancements in microelectronics, which shows the capability of yielding highly reliable and reproducible structures, have made the mass production of integrated electronic components feasible. Miniaturized, low-cost, and accurate sensors became available due to the rise of the microelectronics industry. A variety of sensors are being used extensively in many portable applications. These sensors are promising not only in research area but also in daily routine applications.
However, many sensing systems are relatively bulky, complicated, and expensive and main advantages of new sensors do not play an important role in practical applications. Many challenges arise due to intricacies for sensor packaging, especially operation in a solution environment. Additional problems emerge when interfacing sensors with external off-chip components. A large amount of research in the field of sensors has been focused on how to improve the system integration.
This work presents new methods for the design, fabrication, and integration of sensor systems. This thesis addresses these challenges, for example, interfacing microelectronic system to a liquid environment and developing a new technique for impedimetric measurement. This work also shows a new design for on-chip optical sensor without any other extra components or post-processing.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201
Determination of Sugar Level and the Existence of Magic Sugar in Various Beverages using a Glucose Meter with Four-Point Probe and Electrochemical Impedance
Nowadays, people are being inconsiderate about the healthy lifestyle that might lead us to be unhealthy and be prone to developing tumors in the kidney due to some kind of sugar being used. In order to minimize these problems, the team will raise people awareness. Raising people awareness is not the same as telling them what to do. It is about giving them the knowledge to let them decide for themselves. This is why the team developed a device that can measure the sugar level and determine the existence of magic sugar in various beverages. The device is composed of two major parts: first is the circuit that will measure the impedance of a liquid sample and second, is a four-point probe, which includes a microcontroller that will display and interpret the results. The Four-point probe applies the concept of Wenner method and Electrochemical Impedance. After constructing the device, the team performed its calibration that requires different liquid samples. Based on its gathered data, different graphical representations were formulated and translated into mathematical equations in order to integrate it onto the microcontroller. Whenever the microcontroller encounters an unknown solution, it can determine the sugar level and classify the type of sugar being used
The EcoChip : a wireless multi-sensor platform for comprehensive environmental monitoring
This paper presents the EcoChip, a new system
based on state-of-the-art electro-chemical impedance (EIS)
technologies allowing the growth of single strain organisms
isolated from northern habitats. This portable system is a complete
and autonomous wireless platform designed to monitor and
cultivate microorganisms directly sampled from their natural
environment, particularly from harsh northern environments.
Using 96-well plates, the EcoChip can be used in the field for realtime monitoring of bacterial growth. Manufactured with highquality electronic components, this new EIS monitoring system is
designed to function at a low excitation voltage signal to avoid
damaging the cultured cells. The high-precision calibration
network leads to high-precision results, even in the most limiting
contexts. Luminosity, humidity and temperature can also be
monitored with the addition of appropriate sensors. Access to
robust data storage systems and power supplies is an obvious
limitation for northern research. That is why the EcoChip is
equipped with a flash memory that can store data over long
periods of time. To resolve the power issue, a low-power microcontroller and a power management unit control and supply all
electronic building blocks. Data stored in the EcoChipâs flash
memory can be transmitted through a transceiver whenever a
receiver is located within the functional transmission range. In this
paper, we present the measured performance of the system, along
with results from laboratory tests in-vitro and from two field tests.
The EcoChip has been utilized to collect bio-environemental data
in the field from the northern soils and ecosystems of
Kuujjuarapik and Puvirnituq, during two expeditions, in 2017 and
2018, respectively. We show that the EcoChip can effectively carry
out EIS analyses over an excitation frequency ranging from 750
Hz to 10 kHz with an accuracy of 2.35%. The overall power
consumption of the system was 140.4 mW in normal operating
mode and 81 ”W in sleep mode. The proper development of the
isolated bacteria was confirmed through DNA sequencing,
indicating that bacteria thrive in the EcoChipâs culture wells while
the growing conditions are successfully gathered and stored
Low power CMOS IC, biosensor and wireless power transfer techniques for wireless sensor network application
The emerging field of wireless sensor network (WSN) is receiving great attention due to the interest in healthcare. Traditional battery-powered devices suffer from large size, weight and secondary replacement surgery after the battery life-time which is often not desired, especially for an implantable application. Thus an energy harvesting method needs to be investigated. In addition to energy harvesting, the sensor network needs to be low power to extend the wireless power transfer distance and meet the regulation on RF power exposed to human tissue (specific absorption ratio). Also, miniature sensor integration is another challenge since most of the commercial sensors have rigid form or have a bulky size. The objective of this thesis is to provide solutions to the aforementioned challenges
Signal distortion from microelectrodes in clinical EEG acquisition systems
Many centers are now using high-density microelectrodes during traditional intracranial electroencephalography (iEEG) both for research and clinical purposes. These microelectrodes are FDA-approved and integrate into clinical EEG acquisition systems. However, the electrical characteristics of these electrodes are poorly described and clinical systems were not designed to use them; thus, it is possible that this shift into clinical practice could have unintended consequences. In this study, we characterized the impedance of over 100 commercial macro- and microelectrodes using electrochemical impedance spectroscopy (EIS) to determine how electrode properties could affect signal acquisition and interpretation. The EIS data were combined with the published specifications of several commercial EEG systems to design digital filters that mimic the behavior of the electrodes and amplifiers. These filters were used to analyze simulated brain signals that contain a mixture of characteristic features commonly observed in iEEG. Each output was then processed with several common quantitative EEG measurements. Our results show that traditional macroelectrodes had low impedances and produced negligible distortion of the original signal. Brain tissue and electrical wiring also had negligible filtering effects. However, microelectrode impedances were much higher and more variable than the macroelectrodes. When connected to clinical amplifiers, higher impedance electrodes produced considerable distortion of the signal at low frequencies (<60ĂÂŹĂąâŹÂ Hz), which caused significant changes in amplitude, phase, variance and spectral band power. In contrast, there were only minimal changes to the signal content for frequencies above 100ĂÂŹĂąâŹÂ Hz. In order to minimize distortion with microelectrodes, we determined that an acquisition system should have an input impedance of at least 1ĂÂŹĂąâŹÂ GĂ
âĂ©, which is much higher than most clinical systems. These results show that it is critical to account for variations in impedance when analyzing EEG from different-sized electrodes. Data from microelectrodes may yield misleading results unless recorded with high-impedance amplifiers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98632/1/1741-2552_9_5_056007.pd
Understanding the role of the anode on the polarization losses in high-temperature polymer electrolyte membrane fuel cells using the distribution of relaxation times analysis
To investigate the role of the anode on the polarization losses of a High-Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC), we analyzed impedance data using the Distribution of Relaxation Times (DRT) method. Thereby, we varied the operating conditions of the anode (humidification, nitrogen dilution, and carbon monoxide (CO) impurities) to study its impact on Nyquist plot and DRT spectrum. Humidification of the hydrogen was found to dilute phosphoric acid, which is visible in the DRT. Nitrogen dilution of the anode gas slightly increases the Mass Transport (MT) resistance. Furthermore, CO was added to anode gas fed and it impacts the impedance throughout the whole frequency range, specifically the medium and low-frequency range, typically assigned to ORR kinetics and oxygen MT. For a more detailed analysis of the impedance data, a reference electrode was employed to separate the overpotential caused by each electrode. The DRT spectrum of the anode exhibits only one peak at 1 kHz. In the presence of CO, a second peak arises corresponding to side-reactions occurring as the anodic half-cell potential increases. It was found that the cathode is affected by CO on the anode merely by the lowered cell potential and not by CO directly
Circuits and Systems for On-Chip RF Chemical Sensors and RF FDD Duplexers
Integrating RF bio-chemical sensors and RF duplexers helps to reduce cost and area in the current applications. Furthermore, new applications can exist based on the large scale integration of these crucial blocks. This dissertation addresses the integration of RF bio-chemical sensors and RF duplexers by proposing these initiatives.
A low power integrated LC-oscillator-based broadband dielectric spectroscopy (BDS) system is presented. The real relative permittivity Δâr is measured as a shift in the oscillator frequency using an on-chip frequency-to-digital converter (FDC). The imaginary relative permittivity Δâr increases the losses of the oscillator tank which mandates a higher dc biasing current to preserve the same oscillation amplitude. An amplitude-locked loop (ALL) is used to fix the amplitude and linearize the relation between the oscillator bias current and Δâr. The proposed BDS system employs a sensing oscillator and a reference oscillator where correlated double sampling (CDS) is used to mitigate the impact of flicker noise, temperature variations and frequency drifts. A prototype is implemented in 0.18 ”m CMOS process with total chip area of 6.24 mm^2 to operate in 1-6 GHz range using three dual bands LC oscillators. The achieved standard deviation in the air is 2.1 ppm for frequency reading and 110 ppm for current reading.
A tunable integrated electrical balanced duplexer (EBD) is presented as a compact alternative to multiple bulky SAW and BAW duplexers in 3G/4G cellular transceivers. A balancing network creates a replica of the transmitter signal for cancellation at the input of a single-ended low noise amplifier (LNA) to isolate the receive path from the transmitter. The proposed passive EBD is based on a cross-connected transformer topology without the need of any extra balun at the antenna side. The duplexer achieves around 50 dB TX-RX isolation within 1.6-2.2 GHz range up to 22 dBm. The cascaded noise figure of the duplexer and LNA is 6.5 dB, and TX insertion loss (TXIL) of the duplexer is about 3.2 dB. The duplexer and LNA are implemented in 0.18 ”m CMOS process and occupy an active area of 0.35 mm^2
Novel Current-Mode Sensor Interfacing and Radio Blocks for Cell Culture Monitoring
Since 2004 Imperial College has been developing the worldâs first application-specific
instrumentation aiming at the on-line, in-situ, physiochemical monitoring of adult stem
cell cultures. That effort is internationally known as the âIntelligent Stem Cell Culture
Systemsâ (ISCCS) project. The ISCCS platform is formed by the functional integration
of biosensors, interfacing electronics and bioreactors. Contrary to the PCB-level
ISCCS platform the work presented in this thesis relates to the realization of a miniaturized
cell culture monitoring platform. Specifically, this thesis details the synthesis and
fabrication of pivotal VLSI circuit blocks suitable for the construction of a miniaturized
microelectronic cell monitoring platform. The thesis is composed of two main parts.
The first part details the design and operation of a two-stage current-input currentoutput
topology suitable for three-electrode amperometric sensor measurements. The
first stage is a CMOS-dual rail-class AB-current conveyor providing a low impedancevirtual
ground node for a current input. The second stage is a novel hyperbolic-sinebased
externally-linear internally-non-linear current amplification stage. This stage
bases its operation upon the compressive sinhâ1 conversion of the interfaced current
to an intermediate auxiliary voltage and the subsequent sinh expansion of the same
voltage. The proposed novel topology has been simulated for current-gain values ranging
from 10 to 1000 using the parameters of the commercially available 0.8ÎŒm AMS
CMOS process. Measured results from a chip fabricated in the same technology are also
reported. The proposed interfacing/amplification architecture consumes 0.88-95ÎŒW. The second part describes the design and practical evaluation of a 13.56MHz frequency
shift keying (FSK) short-range (5cm) telemetry link suitable for the monitoring of incubated
cultures. Prior to the design of the full FSK radio system, a pair of 13.56MHz
antennae are characterized experimentally. The experimental S-parameter-value determination
of the 13.56MHz wireless link is incorporated into the Cadence Design
Framework allowing a high fidelity simulation of the reported FSK radio. The transmitter
of the proposed system is a novel multi-tapped seven-stage ring-oscillator-based
VCO whereas the core of the receiver is an appropriately modified phase locked loop
(PLL). Simulated and measured results from a 0.8ÎŒm CMOS technology chip are reported
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