Julian W. Gardner
University of Warwick, School of Engineering, Faculty Member
- Julian Gardner BSc PhD DSc FIET FREng is the Professor of Electronic Engineering at the University of Warwick, UK. He... moreJulian Gardner BSc PhD DSc FIET FREng is the Professor of Electronic Engineering at the University of Warwick, UK. He has published over 450 technical papers and is an author of 8 books. He was an Alexander von Humboldt Fellowship in Germany in 1994 and Fellow of the Institute of Technology in 1997. In addition to being professor of electronic engineering, he is Founder and Head of the Microsensors & Bioelectronics Laboratory; and co-director of the Centre for Cognitive & Neural Systems at Warwick. He was elected a Fellow of the Royal Academy of Engineering in 2006 and won the IET JJ Thompson Medal for Achievements in Electronics in 2007. He has been involved in the spin-out of three companies, with the latest “Cambridge CMOS Sensors Ltd” awarded Company of the Year in 2012 and 2015 at the Business Weekly Awards. His research interests are Microsensors & MEMS in general, and in particular Artificial Olfaction, Chemical Sensing, Smart Sensors, and Signal Processing Methods.edit
The increase in air pollution and its effect on human health, is highlighting a growing demand for ubiquitous low-cost air quality monitors. Acoustic resonators have significant potential to satisfy this need. Solidly mounted resonators... more
The increase in air pollution and its effect on human health, is highlighting a growing demand for ubiquitous low-cost air quality monitors. Acoustic resonators have significant potential to satisfy this need. Solidly mounted resonators (SMR) are of special interest, because they have the advantage of being small and can be integrated into smart CMOS systems for air quality monitoring. This paper presents a CMOS-based SMR with a resonant frequency of about 2 GHz and a Q-factor of ca 200. The device comprises an integrated microheater with multi-purpose potential for temperature frequency modulation, temperature control, enhanced device sensitivity, sensor self-cleaning and use of single sensor as a virtual sensor array.
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Monitoring particulate matter concentrations is of particular importance within the overall assessment of indoor and outdoor air quality and its impact on human health. Bulk acoustic wave (BAW) technology offers low cost, robust... more
Monitoring particulate matter concentrations is of particular importance within the overall assessment of indoor and outdoor air quality and its impact on human health. Bulk acoustic wave (BAW) technology offers low cost, robust alternative to widely employed optical measurements. However, due to its reasonably new application within the area of particulate measurements, an in-depth characterisation of this technology to temperature and humidity variations that are inevitably present within the indoor and outdoor environment is necessary step in order to determine its suitability for possible commercialisation. This work presents the characterisation of the temperature and humidity dependence of solidly mounted resonators for particulate matter sensing. Both theoretical results, obtained through modelling and simulation, and experimental result, obtained within the laboratory conditions, are analysed and compared. A 1.5 GHz resonator with a zinc oxide thin film is modelled using a one-dimensional equivalent circuit model, and finite-element methods based on both two-dimensional model and the three-dimensional model. The simulation results show that the temperature dependence of the resonator is strongly dependent on the material properties and crystal structure of the zinc oxide film. Our models estimate the temperature coefficient of frequency to be -30 to -40 ppm/Centigrade. This theoretical temperature dependence was comparable to experimentally measured value of ca. -49 ppm/Centigrade. In addition to temperature characterisation of discrete devices, the resonator was combined with read-out circuitry, which was also simulated and tested experimentally. The temperature coefficient of frequency in this case was found to be much higher at -220 ppm/Centigrade demonstrating the necessity for temperature control or temperature compensation within the complete system in practical applications. The effect of humidity was also investigated. The experimental mean resonant frequency shift per percent increase in relative humidity of the ambient air was found to be -3.8 kHz/%RH, while the models showed negligible sensitivity to humidity variations. Finally, preliminary experiments were conducted within the controlled lab environment showing promising result for possible application of this technology in particulate matter monitoring. The resonant frequency shift of approximately 300 kHz was measured after mass loading the sensing area of the resonator with estimated 24 ng of standard Arizona dust particles.
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Pollution by particulate matter (PM) poses a serious and growing risk to human health. Film Bulk Acoustic Resonators (FBARs) have been proposed as a low-cost way to monitor particle concentration. This paper presents particle detection by... more
Pollution by particulate matter (PM) poses a serious and growing risk to human health. Film Bulk Acoustic Resonators (FBARs) have been proposed as a low-cost way to monitor particle concentration. This paper presents particle detection by a 1.1 GHz aluminium nitride based FBAR designed and fabricated by SilTerra Malaysia. The FBARs are used in a differential configuration with one sensing and one reference device in a system comprising a microchannel with an electric microfan and a thermophoretic precipitator microhotplate array for improved sampling. A custom-built test chamber was designed to characterise the device at different levels of particulate matter concentration in air. The particle feed rate into the test chamber was varied between 9.5, 19, 43, 66 and <inline-formula> <tex-math notation="LaTeX">$94~\mu \text{g}/\text{m}^{3}\text{s}$ </tex-math></inline-formula>. The FBAR frequency was found to decrease with increasing particulate matter concentration in the test chamber air. The experiments were conducted with and without the microchannel and it was found that the sampling channel increased sensitivity of FBAR resonant frequency to particle concentration per cubic meter of air from 5 Hz/<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>gm<sup>−3</sup> to 20 Hz/<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>gm<sup>−3</sup>. The detection limit in this test was estimated at ca. <inline-formula> <tex-math notation="LaTeX">$50~\mu \text{g}/\text{m}^{3}$ </tex-math></inline-formula>, which is around current European limits for PM10 pollution. In addition, the use of the sampling microfan to aid cleaning of FBARs after particle measurement was also investigated and found to be feasible especially for lower particle concentration.
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Accurate air quality monitoring requires processing of multi-dimensional, multi-location sensor data, which has previously been considered in centralised machine learning models. These are often unsuitable for resource-constrained edge... more
Accurate air quality monitoring requires processing of multi-dimensional, multi-location sensor data, which has previously been considered in centralised machine learning models. These are often unsuitable for resource-constrained edge devices. In this article, we address this challenge by: (1) designing a novel hybrid deep learning model for hourly PM2.5 pollutant prediction; (2) optimising the obtained model for edge devices; and (3) examining model performance running on the edge devices in terms of both accuracy and latency. The hybrid deep learning model in this work comprises a 1D Convolutional Neural Network (CNN) and a Long Short-Term Memory (LSTM) to predict hourly PM2.5 concentration. The results show that our proposed model outperforms other deep learning models, evaluated by calculating RMSE and MAE errors. The proposed model was optimised for edge devices, the Raspberry Pi 3 Model B+ (RPi3B+) and Raspberry Pi 4 Model B (RPi4B). This optimised model reduced file size to ...
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Biosensors play a key role in medical diagnostics, and acoustic wave technology such as solidly mounted resonators (SMRs) applied to this field is one of the latest developments with great potential. This study seeks to explore the... more
Biosensors play a key role in medical diagnostics, and acoustic wave technology such as solidly mounted resonators (SMRs) applied to this field is one of the latest developments with great potential. This study seeks to explore the potential application of SMRs to detect and quantify prostate-specific antigen (PSA) for the screening and diagnosis of prostate cancer. The primary results show promising frequency shift of SMR sensors coated with Polydimethylsiloxane (PDMS) to different liquids. The SMR frequency is 1.082, 1.084 and 1.088 GHz, respectively, to air, deionized water and toluene (liquid) presence. These sensors have great potential as an accurate, low-cost method for measuring PSA and biomarkers for cancer and other diseases.
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A key challenge in building machine learning models for time series prediction is the incompleteness of the datasets. Missing data can arise for a variety of reasons, including sensor failure and network outages, resulting in datasets... more
A key challenge in building machine learning models for time series prediction is the incompleteness of the datasets. Missing data can arise for a variety of reasons, including sensor failure and network outages, resulting in datasets that can be missing significant periods of measurements. Models built using these datasets can therefore be biased. Although various methods have been proposed to handle missing data in many application areas, more air quality missing data prediction requires additional investigation. This study proposes an autoencoder model with spatiotemporal considerations to estimate missing values in air quality data. The model consists of one-dimensional convolution layers, making it flexible to cover spatial and temporal behaviours of air contaminants. This model exploits data from nearby stations to enhance predictions at the target station with missing data. This method does not require additional external features, such as weather and climate data. The result...
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Encyclopedia of Sensors is the first encyclopedia ever published in the field of sensors. The multivolume encyclopedia will provide a complete coverage of most recent advances and emerging new sensor technologies in the fields of science,... more
Encyclopedia of Sensors is the first encyclopedia ever published in the field of sensors. The multivolume encyclopedia will provide a complete coverage of most recent advances and emerging new sensor technologies in the fields of science, engineering and medicine. Although there are many books focused on sensors however no encyclopedic reference work has been published as of today. This encyclopedia will cover all aspects of sensor science and technology dealing with all types of sensor materials, their synthesis and spectroscopic characterization, sensor designs, fabrication and manufacturing techniques, sensor probes, features, physical, chemical and biosensors, their applications in electronics, photonic and optoelectronic industries, medicine, surface sensing, food industry, environmental engineering and nanotechnology. It is written for a wide range of audience from non-scientists to active scientists and engineers, professionals and experts working in the field of sensors.
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In this paper we present for the first time a Gallium Nitride-on-Silicon (GaN-on-Si) anenometric flow sensor based on a gold (Au) thermoresistive hot-wire. The device was fabricated in a custom GaN process, with an etching process to... more
In this paper we present for the first time a Gallium Nitride-on-Silicon (GaN-on-Si) anenometric flow sensor based on a gold (Au) thermoresistive hot-wire. The device was fabricated in a custom GaN process, with an etching process to release a membrane made of the GaN stack. This membrane thermally isolates the hot-wire, increasing its thermal efficiency, which was measured to be 1.04°C/mW. Testing was performed at mass flow rates from 0-4 SLPM using a custom gas rig. The sensitivity of the device, driven in a constant current mode at 3 different zero-flow temperatures, was compared showing an increase in peak sensitivity of 67% at 250°C compared to 150°C.
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Gas sensors fabricated using conventional silicon microtechnology can suffer from a number of significant disadvantages when compared with commercially available thick-film, screen-printed devices. For example, platinum gate MOSFET... more
Gas sensors fabricated using conventional silicon microtechnology can suffer from a number of significant disadvantages when compared with commercially available thick-film, screen-printed devices. For example, platinum gate MOSFET devices normally operate only at a temperature of up to 180 degree(s)C and this limits the catalyst activity, and hence their sensitivity and response time. In addition, the fabrication of an integrated, resistive heater poses interesting problems; thus whilst polysilicon heaters are CMOS compatible, they tend to suffer from non-linearity, poor reproducibility and stability; whereas platinum resistive heaters are incompatible with a CMOS process and thus difficult and expensive to manufacture. Here we propose the use of SOI technology leading to a new generation of high-temperature, silicon smart gas sensors (patent pending). Numerical simulations of an n-channel MOSFET structure on a thin SOI membrane have been performed in non- isothermal conditions using a MEDICI simulator. Our results demonstrate that SOI-based devices can operate at temperatures of up to 350 degree(s)C without causing a problem for neighboring CMOS I.C. circuitry. The power consumption of our SOI-based designs may be as low as ca. 10 mW at 300 degree(s)C and so compares favorably with previously reported values for non-SOI based silicon micromachined gas sensors. In conclusion, SOI technology may be used to fabricate novel high-temperature, micropower resistive and catalytic-gate MOSFET gas/odor sensors. These devices can be fabricated in a standard SOI CMOS process at low unit cost and should offer an excellent degree of reproducibility. Applications envisaged are in air quality sensors for the automotive industry and odor sensors for electronic noses.
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In this paper we describe the design of a smart calorimetric solid-state gas sensor based on SOI technology and featuring a thin membrane realised through post-process back etching. Micro-heaters are produced from active CMOS elements... more
In this paper we describe the design of a smart calorimetric solid-state gas sensor based on SOI technology and featuring a thin membrane realised through post-process back etching. Micro-heaters are produced from active CMOS elements (i.e. n- or p-channel MOSFETs) and isolated in a thin SOI membrane in order to permit high temperature operation (up to ca. 300 degreesC). Thermodiodes are placed on and off the micro-hotplates to measure operating and ambient temperatures. The device can be operated as a microcalorimeter when one microheater is coated with an active catalytic layer and the other with an inert material. The differential signal is then simply related to the concentration of a combustible gas in air. Full simulations of the I-V device characteristics; temperature of the membrane and transducer circuit have been carried out. The device has been fabricated at IMEC (via Europractice) employing 0.8 mum TEMIC Matra MHS D-MILL BiCMOS technology. These smart sensors feature very low power consumption, high sensitivity and low fabrication cost achieved through full CMOS integration.
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In this paper we present a thermal conductivity gas sensor with improved sensitivity by adding holes in the thin-film membrane. A numerical model is created and validated against the reference CMOS MEMS thermal conductivity sensor. The... more
In this paper we present a thermal conductivity gas sensor with improved sensitivity by adding holes in the thin-film membrane. A numerical model is created and validated against the reference CMOS MEMS thermal conductivity sensor. The numerical model is used to investigate the advantages of having isolating holes through the membrane, located on either side of the heating resistor. These holes increase robustness and minimise catastrophic failure caused by pressure difference whilst simultaneously increasing sensitivity by enhancing convective interaction. The electro-thermal efficiency is shown to increase by 16% whilst the sensitivity to measuring percentage CO2 increases by 39.2%. It is also shown that increasing the width of the holes does not have significant effect on these sensitivities; thus, small holes can be incorporated, leaving room for multiple resistors across the membrane for different measuring techniques. This paper serves as proof that membrane holes can be used to optimise thermal conductivity sensors and will serve as a reference when these designs are fabricated and tested, leading to a new low-power, high-sensitivity gas sensor.
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Non-dispersive-infra-red (NDIR) sensors are believed to be one of the most selective and robust solutions for CO2 detection, though cost prohibits their broader integration. In this paper we propose a commercially viable... more
Non-dispersive-infra-red (NDIR) sensors are believed to be one of the most selective and robust solutions for CO2 detection, though cost prohibits their broader integration. In this paper we propose a commercially viable silicon-on-insulator (SOI) complementary metal-oxide (CMOS) micro-electro-mechanical (MEMS) technology for an IR thermal emitter. For the first time, vertically aligned multi walled carbon nanotubes (VA-MWCNTs) are suggested as a possible coating for the enhancement of the emission intensity of the optical source of a NDIR system. VA-MWCNTs have been grown in situ by chemical vapour deposition (CVD) exclusively on the heater area. Optical microscopy, scanning electron microscopy and Raman spectroscopy have been used to verify the quality of the VA-MWCNTs growth. The CNT-coated emitter demonstrated an increased response to CO2 of approx. 60%. Furthermore, we show that the VA-MWCNTs are stable up to temperatures of 500°C for up to 100 hours. © 2013 IEEE
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In this paper we report synthesis of Au-SnO2 nanocomposites, and their integration on micro-hotplates through dip pen nano-lithography to realize a resistive acetone sensor device. The devices are power efficient (8.2°C temperature... more
In this paper we report synthesis of Au-SnO2 nanocomposites, and their integration on micro-hotplates through dip pen nano-lithography to realize a resistive acetone sensor device. The devices are power efficient (8.2°C temperature increase requires for 1 milli watt of power). The devices were characterized exposing acetone in presence of both dry and humid (40% RH) air. The response varies between 3.8 times (with 250 ppm) and 5.5 times (1000 ppm), and did not show much deterioration in presence of humidity.
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© 2017 by Taylor & Francis Group, LLC. All rights reserved. This chapter focuses on the development of sensors and sensor systems for harsh environments. Among various applications with high commercial impact, combustion optimisation... more
© 2017 by Taylor & Francis Group, LLC. All rights reserved. This chapter focuses on the development of sensors and sensor systems for harsh environments. Among various applications with high commercial impact, combustion optimisation and emission control in small-scale boilers is considered as an illustrative application which can ben efit from the employment of a multimeasurand sensor system able to cope with harsh environment conditions. More specifically, silicon on insulator (SOI) is proposed as common technology platform for the realisation of a diode temperature sensor, a thermal flow sensor, a capacitive humidity sen sor, a chemiresistive oxygen sensor, a diode ultraviolet (UV) photosensor, and a non-dispersive-infra-red (NDIR) carbon dioxide sensor. Considerations regarding circuitry, packaging and system integration and testing are also included, along with a detailed analysis of each single sensing device.
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For the first time, we demonstrate the detection of carbon dioxide (CO2) using a non-dispersive infra-red (NDIR) technique that does not require an expensive CMOS-incompatible optical filter. This is achieved by employing a differential... more
For the first time, we demonstrate the detection of carbon dioxide (CO2) using a non-dispersive infra-red (NDIR) technique that does not require an expensive CMOS-incompatible optical filter. This is achieved by employing a differential IR thermopile detector with micro-engineered (plasmonic) optical properties, fabricated in a commercially available standard CMOS MEMS process. The proof of concept demonstrated here represents a milestone in low-cost gas sensing spectroscopy, and has the potential to impact profoundly in the entire IR field; many consumer electronics applications (wearables, smartphones, tablets and portable medical devices) will become viable, leading to high volume commercial applications for plasmonic devices.
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This paper summarizes the outcome of the EC FP7 project MSP - Multi Sensor Platform for Smart Building Management (Grant Agreement No. 611887). The MSP consortium comprising 17 partners from 6 European countries developed a full... more
This paper summarizes the outcome of the EC FP7 project MSP - Multi Sensor Platform for Smart Building Management (Grant Agreement No. 611887). The MSP consortium comprising 17 partners from 6 European countries developed a full manufacturing chain for 3D system integration, which has never been realized before. It enables 3D-integration of highly sophisticated components and sensor devices on a CMOS electronic platform chip. The final multi-sensor system comprises a variety of gas sensors as well as optical sensors for ultraviolet, visible and infrared light. The MSP demonstrator system implemented in a wearable wristband device integrates a total of 57 sensors – this is a worldwide unique sensor system.
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The gas sensor market is growing fast, driven by many socioeconomic and industrial factors. Mid-infrared (MIR) gas sensors offer excellent performance for an increasing number of sensing applications in healthcare, smart homes, and the... more
The gas sensor market is growing fast, driven by many socioeconomic and industrial factors. Mid-infrared (MIR) gas sensors offer excellent performance for an increasing number of sensing applications in healthcare, smart homes, and the automotive sector. Having access to low-cost, miniaturized, energy efficient light sources is of critical importance for the monolithic integration of MIR sensors. Here, we present an on-chip broadband thermal MIR source fabricated by combining a complementary metal oxide semiconductor (CMOS) micro-hotplate with a dielectric-encapsulated carbon nanotube (CNT) blackbody layer. The micro-hotplate was used during fabrication as a micro-reactor to facilitate high temperature (>700 $$^{\circ }$$ ∘ C) growth of the CNT layer and also for post-growth thermal annealing. We demonstrate, for the first time, stable extended operation in air of devices with a dielectric-encapsulated CNT layer at heater temperatures above 600 $$^{\circ }$$ ∘ C. The demonstrated...
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Introduction Thermal conductivity gas sensors are used in a multitude of fields where identifying concentrations of certain gasses within mixtures is important, such as in exhaust emission monitoring, chemical process control to name some... more
Introduction Thermal conductivity gas sensors are used in a multitude of fields where identifying concentrations of certain gasses within mixtures is important, such as in exhaust emission monitoring, chemical process control to name some examples. There is also a growing demand to be able to place sensors in more extreme environments closer to the source of the reaction/emissions. Traditionally, silicon-on-insulator (SOI) is the material of choice for MEMS for use in harsh environments, however SOI has a limit of around 300°C before it can no longer reliably sense [1]. In this work, we present a Gallium Nitride-on-Silicon (GaN-on-Si) thermal conductivity calorimetric gas sensor. Depending on the specific process, devices fabricated from GaN can survive temperatures up to 1000°C [2] [3]. As a wide band-gap semiconductor, GaN devices do not suffer the adverse effects of excessive carrier generation that silicon-based devices do [4]. Using GaN, it is possible to fabricate heterogenous...
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Abstract This chapter addresses both the challenges and benefits of fabricating gas sensors using complementary metal oxide semiconductor (CMOS) technology and the integration of associated circuitry onto a single silicon chip. The main... more
Abstract This chapter addresses both the challenges and benefits of fabricating gas sensors using complementary metal oxide semiconductor (CMOS) technology and the integration of associated circuitry onto a single silicon chip. The main objective described here is, specifically, the development of ultra-low power (∼mW) resistive and calorimetric gas sensors that can operate at high temperatures (up to 600 °C) on a thin (∼μm) CMOS platform. Compatibility with standard CMOS technology permits high volumes of production (>100k dies per annum) at very low unit cost (
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Biosynthetic infochemical communication is an emerging scientific field employing molecular compounds for information transmission, labelling, and biochemical interfacing; having potential application in diverse areas ranging from pest... more
Biosynthetic infochemical communication is an emerging scientific field employing molecular compounds for information transmission, labelling, and biochemical interfacing; having potential application in diverse areas ranging from pest management to group coordination of swarming robots. Our communication system comprises a chemoemitter module that encodes information by producing volatile pheromone components and a chemoreceiver module that decodes the transmitted ratiometric information via polymer-coated piezoelectric Surface Acoustic Wave Resonator (SAWR) sensors. The inspiration for such a system is based on the pheromone-based communication between insects. Ten features are extracted from the SAWR sensor response and analysed using multi-variate classification techniques, i.e., Linear Discriminant Analysis (LDA), Probabilistic Neural Network (PNN), and Multilayer Perception Neural Network (MLPNN) methods, and an optimal feature subset is identified. A combination of steady sta...
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We report on the integration of inkjet-printed graphene with a CMOS micro-electro-mechanical-system (MEMS) microhotplate for humidity sensing. The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl... more
We report on the integration of inkjet-printed graphene with a CMOS micro-electro-mechanical-system (MEMS) microhotplate for humidity sensing. The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer. We formulate inks with different graphene concentrations, which are then deposited through inkjet printing over predefined interdigitated gold electrodes on a CMOS microhotplate. The graphene flakes form a percolating network to render the resultant graphene-PVP thin film conductive, which varies in presence of humidity due to swelling of the hygroscopic PVP host. When the sensors are exposed to relative humidity ranging from 10-80%, we observe significant changes in resistance with increasing sensitivity from the amount of graphene in the inks. Our sensors show excellent repeatability and stability, over a period of several weeks. The location specific deposition of functional g...
Research Interests: Materials Science, Graphene, Nanotechnology, Medicine, Gas Sensors, and 3 moreQC, Conductive Ink, and T
Here we report on the mask-less deposition of Au-SnO2 nanocomposites with a silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) micro electro mechanical system (MEMS) platform through the use of dip pen... more
Here we report on the mask-less deposition of Au-SnO2 nanocomposites with a silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) micro electro mechanical system (MEMS) platform through the use of dip pen nanolithography (DPN) to create a low-cost ethanol sensor. MEMS technology is used in order to achieve low power consumption, by the employment of a membrane structure formed using deep reactive ion etching technique. The device consists of an embedded tungsten micro-heater with gold interdigitated electrodes on top of the SOI membrane. The tungsten micro-heater is used to raise the membrane temperature up to its operating temperature and the electrodes are used to measure the resistance of the nanocomposite sensing layer. The CMOS MEMS devices have high electro-thermal efficiency, with 8.2 °C temperature increase per mW power of consumption. The sensing material (Au-SnO2 nanocomposite) was synthesised starting from SnO nanoplates, then Au nanoparticles were att...
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A new signal processing technique has been developed for resistive metal oxide (MOX) gas sensors to enable high-bandwidth measurements and enhanced selectivity at PPM levels (<5 PPM VOCs). An embedded micro-heater is thermally pulsed... more
A new signal processing technique has been developed for resistive metal oxide (MOX) gas sensors to enable high-bandwidth measurements and enhanced selectivity at PPM levels (<5 PPM VOCs). An embedded micro-heater is thermally pulsed from a temperature of 225 to 350 °C, which enables the chemical reaction kinetics of the sensing film to be extracted using a fast Fourier transform. Signal processing is performed in real-time using a low-cost microcontroller integrated into a sensor module. Three sensors, coated with SnO2, WO3 and NiO respectively, were operated and processed at the same time. This approach enables the removal of long-term baseline drift and is more resilient to changes in ambient temperature. It also greatly reduced the measurement time from ~10 s to 2 s or less. Bench-top experimental results are presented for 0 to 200 ppm of acetone, and 0 ppm to 500 ppm of ethanol. Our results demonstrate our sensor system can be used on a mobile robot for real-time gas sensing.
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In this paper we present a temperature-modulated graphene oxide (GO) resistive humidity sensor that employs complementary-metal-oxide-semiconductor (CMOS) micro-electro-mechanical-system (MEMS) micro-hotplate technology for the monitoring... more
In this paper we present a temperature-modulated graphene oxide (GO) resistive humidity sensor that employs complementary-metal-oxide-semiconductor (CMOS) micro-electro-mechanical-system (MEMS) micro-hotplate technology for the monitoring and control of indoor air quality (IAQ). GO powder is obtained by chemical exfoliation, dispersed in water and deposited via ink-jet printing onto a low power micro-hotplate. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) show the typical layered and wrinkled morphology of the GO. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red (FTIR) spectroscopy indicate that the GO flakes possess a significant number of oxygen containing functional groups (epoxy, carbonyl, hydroxyl) extremely attractive for humidity detection. Electro-thermal characterisation of the micro-hotplates shows a thermal efficiency of 0.11 mW per °C, resulting in a sensor DC power consumption of only 2.75 mW at 50 °C....
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ABSTRACT
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The wealth of information concealed in a single human breath has been of interest for many years, promising not only disease detection, but also the monitoring of our general well-being. Recent developments in the fields of nano-sensor... more
The wealth of information concealed in a single human breath has been of interest for many years, promising not only disease detection, but also the monitoring of our general well-being. Recent developments in the fields of nano-sensor arrays and MEMS have enabled once bulky artificial olfactory sensor systems, or so-called "electronic noses", to become smaller, lower power and portable devices. At the same time, wearable health monitoring devices are now available, although reliable breath sensing equipment is somewhat missing from the market of physical, rather than chemical sensor gadgets. In this article, we report on the unprecedented rise in healthcare problems caused by an increasingly overweight population. We first review recently-developed electronic noses for the detection of diseases by the analysis of basic volatile organic compounds (VOCs). Then, we discuss the primary cause of obesity from over eating and the high calorific content of food. We present the ne...
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An infra-red (IR) device comprising a dielectric membrane formed on a silicon substrate comprising an etched portion; and at least one patterned layer formed within or on the dielectric membrane for controlling IR emission or IR... more
An infra-red (IR) device comprising a dielectric membrane formed on a silicon substrate
comprising an etched portion; and at least one patterned layer formed within or on the
dielectric membrane for controlling IR emission or IR absorption of the IR device, wherein
the at least one patterned layer comprises laterally spaced structures.
comprising an etched portion; and at least one patterned layer formed within or on the
dielectric membrane for controlling IR emission or IR absorption of the IR device, wherein
the at least one patterned layer comprises laterally spaced structures.