61 research outputs found
Novel Current-Mode Sensor Interfacing and Radio Blocks for Cell Culture Monitoring
Since 2004 Imperial College has been developing the world’s 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 ‘Intelligent Stem Cell Culture
Systems’ (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 sinh−1 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 0.8μm AMS
CMOS process. Measured results from a chip fabricated in the same technology are also
reported. The proposed interfacing/amplification architecture consumes 0.88-95μW. 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 0.8μm CMOS technology chip are reported
CMOS Hyperbolic Sine ELIN filters for low/audio frequency biomedical applications
Hyperbolic-Sine (Sinh) filters form a subclass of Externally-Linear-Internally-Non-
Linear (ELIN) systems. They can handle large-signals in a low power environment under half
the capacitor area required by the more popular ELIN Log-domain filters. Their inherent
class-AB nature stems from the odd property of the sinh function at the heart of their
companding operation. Despite this early realisation, the Sinh filtering paradigm has not
attracted the interest it deserves to date probably due to its mathematical and circuit-level
complexity.
This Thesis presents an overview of the CMOS weak inversion Sinh filtering
paradigm and explains how biomedical systems of low- to audio-frequency range could
benefit from it. Its dual scope is to: consolidate the theory behind the synthesis and design of
high order Sinh continuous–time filters and more importantly to confirm their micro-power
consumption and 100+ dB of DR through measured results presented for the first time.
Novel high order Sinh topologies are designed by means of a systematic
mathematical framework introduced. They employ a recently proposed CMOS Sinh
integrator comprising only p-type devices in its translinear loops. The performance of the
high order topologies is evaluated both solely and in comparison with their Log domain
counterparts. A 5th order Sinh Chebyshev low pass filter is compared head-to-head with a
corresponding and also novel Log domain class-AB topology, confirming that Sinh filters
constitute a solution of equally high DR (100+ dB) with half the capacitor area at the expense
of higher complexity and power consumption. The theoretical findings are validated by
means of measured results from an 8th order notch filter for 50/60Hz noise fabricated in a
0.35μm CMOS technology. Measured results confirm a DR of 102dB, a moderate SNR of
~60dB and 74μW power consumption from 2V power supply
ENABLING HARDWARE TECHNOLOGIES FOR AUTONOMY IN TINY ROBOTS: CONTROL, INTEGRATION, ACTUATION
The last two decades have seen many exciting examples of tiny robots from a few cm3 to less than one cm3. Although individually limited, a large group of these robots has the potential to work cooperatively and accomplish complex tasks. Two examples from nature that exhibit this type of cooperation are ant and bee colonies. They have the potential to assist in applications like search and rescue, military scouting, infrastructure and equipment monitoring, nano-manufacture, and possibly medicine.
Most of these applications require the high level of autonomy that has been demonstrated by large robotic platforms, such as the iRobot and Honda ASIMO. However, when robot size shrinks down, current approaches to achieve the necessary functions are no longer valid. This work focused on challenges associated with the electronics and fabrication. We addressed three major technical hurdles inherent to current approaches: 1) difficulty of compact integration; 2) need for real-time and power-efficient computations; 3) unavailability of commercial tiny actuators and motion mechanisms. The aim of this work was to provide enabling hardware technologies to achieve autonomy in tiny robots.
We proposed a decentralized application-specific integrated circuit (ASIC) where each component is responsible for its own operation and autonomy to the greatest extent possible. The ASIC consists of electronics modules for the fundamental functions required to fulfill the desired autonomy: actuation, control, power supply, and sensing. The actuators and mechanisms could potentially be post-fabricated on the ASIC directly. This design makes for a modular architecture.
The following components were shown to work in physical implementations or simulations: 1) a tunable motion controller for ultralow frequency actuation; 2) a nonvolatile memory and programming circuit to achieve automatic and one-time programming; 3) a high-voltage circuit with the highest reported breakdown voltage in standard 0.5 μm CMOS; 4) thermal actuators fabricated using CMOS compatible process; 5) a low-power mixed-signal computational architecture for robotic dynamics simulator; 6) a frequency-boost technique to achieve low jitter in ring oscillators. These contributions will be generally enabling for other systems with strict size and power constraints such as wireless sensor nodes
Bioimpedance sensors: a tutorial
Electrical bioimpedance entails the measurement of the electrical properties of tissues as a function of frequency. It is thus a spectroscopic technique. It has been applied in a plethora of biomedical applications for diagnostic and monitoring purposes. In this tutorial, the basics of electrical bioimpedance sensor design will be discussed. The electrode/electrolyte interface is thoroughly described, as well as methods for its modelling with equivalent circuits and computational tools. The design optimization and modelling of bipolar and tetrapolar bioimpedance sensors is presented in detail, based on the sensitivity theorem. Analytical and numerical modelling approaches for electric field simulations based on conformal mapping, point electrode approximations and the finite element method (FEM) are also elaborated. Finally, current trends on bioimpedance sensors are discussed followed by an overview of instrumentation methods for bioimpedance measurements, covering aspects of voltage signal excitations, current sources, voltage measurement front-end topologies and methods for computing the electrical impedance
Charge-Modulated Field-Effect Transistor: technologies and applications for biochemical sensing
The research activity described in the attached dissertation focused on the development, fabrication and characterization of field-effect transistor-based biochemical sensor (bioFET) developed in different technologies. Such a research field has been attracting a significant interest in the last decades, as electronic sensors can represent as valuable, portable and low cost alternative to the bulk, expensive laboratory instrumentation. Among the biochemical reactions, genetic processes have been thoroughly investigated in literature: in particular, DNA hybridization detection represents a basic biological reaction for several, more sophisticated analysis in medical, pharmaceutical and forensic fields.
The development of the research activity was centered on a specific biosensor, namely Charge-Modulated Field-Effect Transistor (CMFET), originally proposed in 2005 by the Electronic Department at the University of Cagliari. In particular, the aim of the activity was to make a significant step forward with respect to the results already presented in literature for DNA hybridization detection, employing two different technologies: CMOS process and organic electronics.
As regards CMOS process, the activity mainly focused on the testing of a Lab-on-a-Chip (LoC), hosting several CMFET structures, developed and fabricated before but never tested. The activity carried out allowed to develop a precise electrical model of the device, validated by actual measurements, by which the basic performances of the device were derived. Subsequently, the application of the LoC for DNA hybridization detection was demonstrated: a reliable biochemical protocol for the modification of the chip surface with DNA strands was developed, as well as a precise measurement procedure. A complete evaluation of the sensitivity and selectivity of the device with respect to DNA hybridization was obtained; from the obtained results, several consideration about the relationship between the chip layout and the performances of the device were inferred. In conclusion, a road-map for the development of a new chip, customized for the application as DNA hybridization sensor, was developed.
As regards the Organic CMFET (OCMFET), the activity comprised design, fabrication and testing of devices particularly conceived as disposable DNA hybridization sensors for field-measurement kits. Such a task required the development of innovative technological processes for the fabrication of high-performances organic transistors, i.e. transistors capable to be operated at low voltages (about 1 V) with quasi-ideal electrical performances. In particular, a highly reliable fabrication process, compatible with plastic electronics and easily up-scalable to an industrial size, was determined. Consequently, novel OCMFET were fabricated and tested. World record results in terms of sensitivity and selectivity among the organic transistor-based DNA sensors were reproducibly obtained. Thanks to the reliability of the results, the performances of the OCMFET were carefully studied, and design rules for the optimization of the device were inferred; an optimized, low voltage OCMFET allowed to further enhance the result, determining final performances even better than the one of silicon-based sensors. Finally, thanks to an innovative analysis on the influence of the device polarization to the characteristics of the bioreceptor layer at a micro-nanometrical size, a physical effect related to a tilting of the DNA molecules with respect to the surface was observed. This feature, possibly related to the CMFET working principle, can allow to overcome a general limitation of the bioFET technologies that have limited so far the application of these devices in vivo, thus opening novel possible applications for the CMFET working principle beyond the measurements in vitr
NASA Tech Briefs, December 1990
Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences
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Accuracy problems in weighing vehicles during motion
The objective of this study is to help solving some of the measurement accuracy and reliability problems of present WIM systems. The theoretical part of the study is focused on vehicle dynamic effects since they have long been identified as one of the major causes of error in high speed dynamic vehicle weighing.
A detailed system analysis describes the functionality of the basic elements of the WIM process - vehicle suspension dynamics, sensor system, and signal processing. In the metrological analysis the standard measurement categories accuracy, repeatability, reproducibility etc., are defined for the technique, and the main sources of measurement errors are identified. Mathematical models are presented of the vehicle suspension/tyres, and a rigid sensor platform with its ground foundation, which are later used in a series of vehicle - roadsurface dynamic interaction computer simulations. A locally developed interactive modelling package is used to run the simulations. Two major sets of simulations are performed - 1) vehicle interaction with road profiles of deterministic shapes, 2) vehicle interaction with road surfaces of stochastic description. The effects of different factors influencing the outcome of the measurement, e.g. vehicle speed, platform protrusion level, vehicle physical parameters, etc., are investigated.
As part of the experimental work a concept for a capacitive sensor is proposed in line with the trend of developing low-cost, easy to install WIM systems. Finite element modelling is used to derive the optimal sensor strip profile. Finally a frequency modulated capacitance measurement circuit incorporating frequency drift compensation is developed and tested with good results.
Most of the study results are presented in both tabular and graphical form. The corresponding conclusions are drawn on the basis of the obtained data, regarding the design, installation and usage of WIM equipment
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