Marina Cole

Development of smart tongue devices for measurement of liquid properties

In this paper, we describe the design and characterization of shear horizontal surface acoustic wave devices for the analysis of liquid samples. Devices were fabricated on both 36/spl deg/ rotated Y-cut X-propagating LiTaO/sub 3/ and LiNbO/sub 3/ substrates. The design consists of a dual delay-line configuration where one delay line is metallized and shielded, while the other is left electrically active. Experiments to characterize the devices in terms of sensitivity, temperature dependence, and mass loading have been conducted and the results presented. Different liquid samples, i.e., water, orange juice, and milk, are 100% linearly separable using principal components analysis. In addition, it is possible to measure the fat content (/spl plusmn/0.1%) as well as the freshness of full (whole) milk.

Polymeric resistive bridge gas sensor array driven by a standard cell CMOS current drive chip

Gas sensitive micro-bridge devices, fabricated with four conducting polymer resistive elements, have been characterised using a standard cell CMOS current drive chip and precision linear analogue circuitry. Poly(anilene)(PAN) types of polymers were used to create the four resistive elements, while two opposite arms of the micro-bridge were passivated by a protective coating of either epoxy resin or nafion. The nafion coated bridges exhibited a substantially reduced sensitivity to ambient humidity and, rather surprisingly, a positive temperature coefficient.

Enhanced infra-red emission from sub-millimeter microelectromechanical systems micro hotplates via inkjet deposited carbon nanoparticles and fullerenes

In this paper, we demonstrate a micro-inkjet printing technique as a reproducible post-process for the deposition of carbon nanoparticles and fullerene adlayers onto fully CMOS compatible micro-electro-mechanical silicon-on-insulator infrared (IR) light sources to enhance their infrared emission. We show experimentally a significant increase in the infrared emission efficiency of the coated emitters. We numerically validate these findings with models suggesting a dominant performance increase for wavelengths <5.5 μm. Here, the bimodal size distribution in the diameter of the carbon nanoparticles, relative to the fullerenes, is an effective mediator towards topologically enhanced emittance of our miniaturised emitters. A 90% improvement in IR emission power density has been shown which we have rationalised with an increase in the mean thickness of the deposited carbon nanoparticle adlayer.

Investigations on an electronic tongue with polymer microfluidic cell for liquid sensing and identification

Design and experimental results of a surface acoustic wave (SAW) microsensor with polymer microfluidic cell for the sensing and identification of liquids is presented in this paper. This microsensor, which is a part of a smart tongue–nose system, uses a horizontally polarized SAW (SH-SAW) for the detection and identification of liquids. The SH-SAW microsensors are fabricated on 36°-rotated Y-cut X-propagating LiTaO3 (36YX.LT) substrate. This design consists of a dual-delay-line configuration in which one line is free and other one is metallized and shielded. Polymer microfluidic cells were designed and fabricated on top of it using a microstereolithography system to avoid dielectric loading of the IDTs by liquid which leads to unwanted dielectric sensitivity to the sensor. Due to the high electromechanical coupling of the 36YX.LT substrate, it could detect differences in electrical properties and hence distinguish different liquids. It is clear from these results that the microsensor based on 36YX.LT is an effective liquid identification system for the electronic tongue application.

Parametric model of a polymeric chemoresistor for use in smart sensor design and simulation

Abstract A novel parametric model of a polymeric chemoresistor is proposed for application in the design and simulation of smart gas sensors. The model has been implemented using Cadence™ software and enables the simulation of both the static and dynamic response of a chemoresistor to a mixture of different gases. It also takes into account parametrically the effects of ambient temperature, humidity and sensor noise. The layout design and a schematic symbol have also been generated in Cadence -thus creating a resistive polymeric cell that can be used in the general design of smart ASIC based systems. The top cell comprises several sub-cells allowing versatility and adaptability in implementation through its modular structure. By changing the values of the simulation parameters and/or the mathematical model of the sub-cell that evaluates the gas sensor response, it is possible to extend its application to the design and simulation of chemoresistors in different configurations and with different gas sensitive materials. Here we illustrate our model in the design and simulation of resistive sensors employing carbon-black polymer composite films as the class of gas sensitive material.

Fabrication and testing of smart tongue devices for liquid sensing

In this paper we describe the design and characterisation of shear horizontal surface acoustic wave (SH-SAW) devices for the analysis of liquid samples. Devices were fabricated on both 36/spl deg/ rotated Y-cut X-propagating LiTaO/sub 3/ and LiNbO/sub 3/ substrates. The design consists of a dual delay line configuration where one delay line is metallized and shielded and the other is left electrically active. Experiments to characterise the devices in terms of sensitivity, temperature dependence and mass loading have been conducted and results presented. Discrimination between different liquid samples, i.e. water, orange juice and milk are 100%, using principal component analysis. In addition, experiments on the discrimination of milk samples with different fat content have also been performed as well as freshness of full (whole) milk. Finally the integration of electronic nose and smart tongue devices has been proposed.

Design and simulation of a smart ratiometric ASIC chip for VOC monitoring

This paper reports on the design and simulation of a novel ratiometric application specific integrated circuit (ASIC) chip for the monitoring of volatile organic compounds (VOCs) or gases. The design integrates two polymeric chemoresistors in a ratiometric configuration, together with smart circuitry, into a single chip fabricated through a standard silicon CMOS process. The circuit provides automatic compensation of signal from variations in both supply voltage and ambient temperature. On-chip control of the operating temperature of the sensors is also an option. The response of the ratiometric set of polymeric chemoresistors to different concentrations of gases at different temperatures and humidities was simulated with the aid of a novel parametric Cadence model. Simulations confirm that the ratiometric configuration is less sensitive to temperature variations and that it also has a better performance in terms of humidity dependence when compared to an individual chemoresistor. These features, together with its ability to compensate for a large range in values of polymer resistance, make us believe that the circuit offers relevant smart capabilities at a very low-cost and so it can be used as the main component for the mass production of a self-calibrating, programmable, palm-top instrument.

Dual high-frequency Surface Acoustic Wave Resonator for ultrafine particle sensing

This paper describes the development of a low-cost robust Surface Acoustic Wave Resonator (SAWR) micro sensor capable of detecting sub-micron size particles below 1 ng. The device comprises two 262 MHz Rayleigh wave SAW resonators fabricated on ST-cut quartz where one is used for particle sensing and the other as a reference channel. Electro-acoustic detection of different particles (including carbon, gold, sucrose, silicon, and PTFE) with different diameters was studied. The mass sensitivity of the SAWR was found to be typically 275 Hz/ng or 4 pg/Hz for the detection of 750 nm diameter gold particles. We believe that the device could be used as a low-cost and low power microsensor for the real-time and ubiquitous monitoring of airborne particulate matter. In particular, our SAWR sensor can be used to detect the typical levels of ultrafine particulate pollutants (PM2.5) found in city air today.

Design and Implementation of a Modular Biomimetic Infochemical Communication System

We describe here the design and implementation of a novel biomimetic infochemical communication system that employs airborne molecules alone to communicate over space and time. The system involves the design and fabrication of a microsystem capable of producing and releasing a precise mix of biosynthetic compounds and a sensor system capable of detecting and decoding the ratiometrically encoded chemical information. The research inspired by biology has been based upon the biosynthetic pathways of infochemical production and information processing within the insect world. In this novel approach, the functional equivalents of the nanoscale biological machinery are implemented by combining the latest advances and convergence of expertise in the fields of biochemistry, molecular biology, neuroscience, micro- and nanofabrication, materials science, and smart sensor and microcircuit design. The biomimetic system comprises a micromachined bio-reactor mimicking the sex gland of the female insect that releases a blend of pheromones in precisely controlled ratios, together with a cell-based biosensor system, mimicking the antennae of the male insect. The signals from the biosensors are classified and ratios decoded using a field-programmable gate array implementation of a neuromorphic model of the antenna lobe of the insect. We believe that this novel, smart infochemical communication system, inspired by the insects behavior, could eventually be implemented in VLSI technology at low cost and low power with possible application in the fields of automatic identification and data capturing, product labeling, search and rescue, environmental monitoring, and pest control

Efficient and Effective VLSI Architecture for a Wavelet-based Broadband Sonar Signal Detection System

A compact and fast hardware architecture using a digital approximation and current VLSI technology as a field- programmable gate array (FPGA) structure has been developed for applications in broadband sonar signal detection. The VLSI implementation is sought to maximize the speed of a hybrid algorithm developed previously for the underwater active sonar echolocation system. It consists of two parts: discrete wavelet transform (DWT) filtering bank, and continuous wavelet transform (CWT) convolver. The DWT filtering bank is employed to minimize the unwanted sonar channel characteristics thus enhancing the signal received from the target. The output of the DWT denoising block is then processed by the CWT convolver in order to estimate targets motion parameters. Simulation results obtained have clearly demonstrated the capability of the VLSI architecture in providing the very efficient and accurate solution in sonar signal detection.