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    Piezoelectric micro-energy harvester integrated with CMOS energy extraction circuits : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Auckland, New Zealand. EMBARGOED until 5 November 2027.
    (Massey University, 2024-10-29) Elamana Marakkadath, Dalin
    Conventional pressure monitoring sensors used in biomedical applications, such as blood pressure and left ventricular systolic pressure measurements, have significant drawbacks, including high power consumption that shortens battery life and contributes to increased costs. A multifunctional piezoelectric transducer has been implemented for self-powered pressure sensing and energy harvesting (EH), eliminating the need for a separate transducer for pressure sensing and energy harvesting. This approach optimizes resources and reduces costs. The piezoelectric EH/sensor uses a lead-free, biocompatible, high-performance aluminum nitride (AlN) transducer. This article presents comprehensive physics-based mathematical modelling and numerical simulations that deliver optimized design parameters for a novel piezoelectric thin-film MEMS transducer energy-converter for improved pressure sensitivity and power density. The experimental results show a sensitivity of 0.06 V/kPa and a power density of 1.1 mW/cm³.--Shortened abstract
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    Development of an amperometric biosensor for the detection of alcohol: a thesis presented in partial fulfilment of the requirements for the degree of Masters in Science in Biochemistry at Massey University
    (Massey University, 1993) Large, Ruth
    The aim of the following work was to design a biosensor for the detection of ethanol. A biosensor is an analytical device in which a biological sensing element is connected to or integrated with a physical transducing element. Amperometric enzyme biosensors utilise one or more enzymes to convert a substance which cannot be measured electrochemically to one which can be. In the case of an alcohol biosensor one of two enzymes (alcohol dehydrogenase and alcohol oxidase) can be used to convert electrochemically stable alcohol to either hydrogen peroxide or NADH which can be oxidised. In the design of an alcohol biosensor there are three major variables to consider, these are; enzyme type, electrode material, and immobilisation technique. The goal was to select optimum conditions for the formulation of the desired sensor. In the present work the electrode materials used were platinum, carbon (foil and paste) and the conducting organic salt N-methyl phenazinium.Tetracyanoquinodimethane (NMP.TCNQ). The immobilisation techniques used were; adsorption, cross-linking to a protein matrix and covalent binding. Of the biosensors produced from a selected combination or these variables each was tested by one or more of the following; cyclic voltammetry, enzyme assay, and amperometry. The most promising approach appears to be that of conjugating enzyme to haemin and allowing the conjugate to bind irreversibly to platinum via the haemin group. An electrode made with the organic salt NMP.TCNQ looked promising also but because the salt is readily oxidised it is unstable and therefore not an ideal electrode material.
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    Enzyme chemical engineering and its application to biosensors : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University, Turitea, New Zealand
    (Massey University, 2001) Luo, Wen
    Enzyme chemical engineering is a fast growing area in biotechnology. It has been used to change the stability, solubility, activity and other properties of enzymes for more control over and wider application of enzymes. In this thesis, this technology is applied to another new and fast growing area of research: biosensors. Over the last decade, biosensors are gaining increasing awareness as a highly attractive analytical tool. One of the current challenges in this area is to identify a universal and scaleable way to produce sensitive, stable, instantaneous, and easy to prepare biosensors for mass production. In this study, enzyme chemical engineering is adopted as a new approach and glucose oxidase is served as a model to build a biosensor system in attempting to address the above challenge. In the study, glucose oxidase was used as the catalyst to chemically amplify the redox reaction of glucose. Haemin was employed as the bifunctional promoter to act as a "bridge" to connect glucose oxidase (GOD) and electrode. Haemin, similar to ferrocene also acts as a mediator to transfer electrons between the active center of the enzyme and the electrode. In the construction of a haemin-glucose oxidase biosensor, haemin was covalently bound with glucose oxidase. The haemin-glucose oxidase conjugate was then chemisorbed on to the platinum electrode to modify the electrode surface and form an "enzymatic redox center-bridge-electrode" system. The modification of the glucose oxidase with haemin comprised of two steps: converting the haemin carboxyl group to the reactive enol ester and then covalently bonding to an amino group of glucose oxidase. For chemisorption, the electrode was soaked in a solution of the haemin-glucose oxidase conjugate in phosphate buffer solution (pH 7.0) at 4°C for 16 hours. The same experiment was carried out by using unmodified glucose oxidase as a blank. The following facts proved that the covalently bound haemin-glucose oxidase system was formed successfully: 1) The large molecule fractions eluted from the Sephadex G-10 gel column had the enzyme activity and other characteristics of glucose oxidase. 2) The same fractions retained about 2/3 to 3/4 of the specific activity of original glucose oxidase. 3) The absorbance spectra of these fractions showed the peaks corresponding to both haemin and glucose oxidase. The following evidence suggests that the haemin-glucose oxidase conjugate was successfully chemisorbed on to the electrode surface: 1) The cyclic voltammogram of the electrode chemisorbed with conjugate was completely different from that adsorbed with glucose oxidase alone. 2) The cyclic voltammogram of the conjugate chemisorbed electrode in the solution with glucose was quite distinct from that without glucose. Thus a different species from either glucose oxidase or haemin was chemiabsorbed on to the electrode. Furthermore, the conjugate chemisorbed electrode showed linearity between current response and glucose concentration at a range from 0mM to 10mM. The ratio of the current response to glucose concentration was about 1.6µA/mM. However, the platinum electrode adsorbed by GOD alone had a poor response to glucose. The response time of the system of platinum electrode-haemin-glucose oxidase was very rapid at less than one minute, and the response fell initially but then remained stable over a period of 14 days. Thus the experimental data proved that the system of platinum electrode-haemin-glucose oxidase met the requirements for a glucose sensor in the factors of the sensitivity, linear response range, lifetime, ease of preparation, convenience of operation, non-toxicity and low cost. In other words, it demonstrated the characteristics of a glucose biosensor. Finally, using the preparation of this glucose biosensor as a model, the electrochemical mechanism of the biosensor system was proposed. The model was also used to suggest a systematic approach for constructing amperometric biosensors. The extension of this approach and the potential applications of this type of biosensor are also discussed.
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    The development of amperometric biosensors for the detection of glucose, lactate and ethanol : a thesis presented in partial fulfilment for the degree of Master of Science in Biochemistry at Massey University
    (Massey University, 1996) Goh, Leong Peng
    Amperometric biosensors, also commonly known as enzyme sensors or enzyme electrodes, are a growing and very progressive area of research. Biosensors are analytical devices that contain a biological sensing element connected to a physical transducing element. The physical transducer "senses" the change in the biological element as it undergoes a chemical reaction. The physical transducer then converts chemical equivalents from the enzyme reaction in a dependent relationship to electrical equivalents that can be measured. Biosensors combine the power of electrochemistry with the specificity of enzymes to produce sensors that are specific to particular enzyme substrates. Some have wide specificities and others are quite narrow. Considering the wide range of enzymes available, the choice depends on the end use of these sensors. The aim of the current study was to design biosensors for the detection of glucose, lactate and ethanol. The method for attaching enzymes to electrodes was based on the carbodiimide method. The carbodiimide method activates haeme which then is able to be covalently attached to enzymes. Enzyme-haeme conjugates were then allowed to absorb onto platinum electrodes by exploiting the knowledge that haeme can bind irreversibly to platinum by sharing pi-electrons with the d-orbitals of platinum. The enzymes involved were glucose oxidase, lactate dehydrogenase and alcohol dehydrogenase. The use of flow injection analysis for evaluating biosensors was desenbed and was found to be a fast, efficient method and the results were highly reproducible. In testing electrodes, the results of the present study showed it was possible to obtain current response that was dependent on the concentration of substrate when these enzyme electrodes were used. A particularly significant result in this study was the achievement of current responses that were dependent on substrate concentration in the absence of NAD+ for lactate and alcohol dehydrogenases using the substrates lactate and ethanol respectively. There is however much work to be done to improve the success rate of making these enzyme electrodes. Several factors were found to cause variable results whilst making and using these enzyme electrodes, such as the absorption of unbound enzyme to the sensing surface of the electrode that may produce significant current response, the formation of aggregated haeme during the enzyme-haeme conjugation process and most importantly, and the ability to make successful enzyme-haeme conjugates to be absorbed onto the sensing surface of the electrodes.
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    Biosensors for fertility and pregnancy in cattle : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Palmerston North, New Zealand
    (Massey University, 2013) Hsu, Yu-Ting
    This project is focused on progesterone sensing, using both surface plasmon resonance (SPR) and lateral flow immunoassay (LFIA) methods with a new progesterone (P4) sensing material to develop cost effective assays for progesterone sensing in bovine serum and milk samples. P4-PEG-OVA was synthesised, characterised and used for P4 detection. The P4-PEG-OVA sensor surface showed an improvement in surface response compared with two shorter ligand 4TP-P4-OVA and 4TPH-P4-OVA in SPR studies. An analysis method has been developed and modified for bovine serum and milk analyses. The results indicated the P4-PEG-OVA ligand allowed sensitive P4 detection in SPR sensing and allowed bovine P4 cycle profiling. The SPR analysed data was compatible with the ECLIA and ELISA independent analyses and the P4 cycle of each of the three bovine milk samples showed a very similar trend and the extraction level was also consistent. The P4-PEG-OVA ligand was used to develop a LFIA sensor strip, and the inhibition assay for bovine serum and milk analyses established. The results indicated that, after appropriate sample pre-treatment, the bovine estrous cycle profile could be detected. The LFIA method can be a potentially quick, easy and cost effective semi-quantitative P4 analysis for serum and milk samples. A new material, polyhydroxyalkanoate (PHA) granules has been investigated for the possibility of developing a new surface biosensor. From the surface studies, the results indicated that the 3GNZZPhaC beads have the potential to become an alternative binding material for SPR sensing due to its unique gold binding property. A flow cell was designed, constructed, and tested on 3GNZZPhaC beads prior the preliminary SPR investigations. The ZZPhaC beads also showed the gold binding property and ZZPhaC beads were used for SPR studies. The results suggested a possible application for them as a new SPR binding material for antibody detection.
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    Investigation of a biosensor for DNA detection : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Electronic Engineering at Massey University, School of Engineering and Advanced Technology (SEAT), Auckland, New Zealand
    (Massey University, 2011) Alipour, Massoud
    The aim of this project was to design a fully electronic sensor to detect hybridized DNA. In this study an integrated circuit for measuring capacitance of the sensor has been designed, which uses DNA as dielectric between the fingers of the sensor. Nowadays, bio-sensors are widely used in electrical sensing where, most of these sensors use the conversion of capacitance for sensing. Some of the benefits of capacitive sensors are: high resolution, high sensitivity, low power dissipation, the ability to be integrated with other circuits, good stability and near zero thermal factors in heat exposure. Capacitive sensors are not affected by magnetic disturbances from electrical fields. The first challenge in this study was bonding Single-strand DNA (ssDNA) to the sensor, which has been explained in chapter 2. After bonding ssDNA, the sample ssDNA will connect to their pairs on the sensor in the process called hybridization and the bonded addition then changes the capacitance of the sensor. To measure the change of the sensor‟s capacitance it is necessary to use interface circuits called “readout circuits”. These circuits convert every change in the capacitive value to electrical changes such as current, voltage, frequency or pulse bandwidth to make the processing easier. Changes in the signal are very small, making factors such as noise and offset very important. There are different methods available in measuring the changes in capacitance, which are discussed in this thesis and their advantages and disadvantages are described. After considering the best choice in DNA sensor, a suitable circuit for measuring the capacitance changes has been designed and simulated. Considerations for reducing noise and offset is also built in to the design of the circuit, Correlated Double Sampling (CDS) and Chopper Stabilisation (CHS) methods are used. Also, to achieve optimum results, these two methods are combined in this thesis. From the results of simulations, it is concluded that CDS and CDS&CHS methods are best suited for our design. In chapter four, at first, two methods for detection of the capacitance in the sensors are demonstrated in the form of block diagrams, and then the advantages and disadvantages of these methods are discussed. After choosing the better method, every part of that method was implemented separately, as an integrated circuit. After linking the different parts, an analogue integrated circuit was designed that turned the capacitive variations to time period variations. Then a digital circuit was designed in order to turn the period time variations to a digital output. The analogue part of the circuit was simulated using 0.25μm technology parameters Investigation of biosensor for DNA detection in Tanner software and the digital part was simulated with VHDL software. The results of these simulations are presented in chapter five. This study succeeded in reaching an accuracy of 0.7fF (Femto Farad, 10-15) capacitor variations. In the summary some suggestions for further research in this field were given.
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    Development of digital instrumentation for bond rupture detection : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand
    (Massey University, 2009) Van der Werff, Matthew John
    In the medical world the precise identification of a disease can take longer than it is safe to wait to start treatment so there is a need for faster and more precise biosensors. Bond Rupture is a new sensor technique that maybe able to improve disease detection. It does this by inducing bonds to rupture from the surface, and also measuring the point at which this rupture occurs this enables the forces to be measured on the surface. Specifically, this project has focused on the application of Bond Rupture to detecting antigens when bound to a surface using their specific antibodies, and the idea that the rupture force of these antigens can also be measured. The sensor that this project is based around is the Quartz Crystal Microbalance (QCM), which oscillates horizontally when a voltage is applied, and can also be used to measure mass change on its surface via change in resonant frequency. The aim of this project was to investigate possible Bond Rupture detection methods and techniques and has involved the development of a high speed digital electronics system, for the purposes of inducing and detecting Bond Rupture. This has involved the development of a FPGA based high speed transceiver board which is controlled by a Digital Signal Processor (DSP), as well as the development of various graphical user interfaces for end user interaction. Bond rupture testing was carried out by rupturing beads from the surface of a QCM in an experiment taking as little as 20 seconds. The Bond Rupture effect has been observed via the high accuracy measurement of the frequency change while inducing Bond Rupture on the sensor, proving that the Bond Rupture effect indeed exists. The research performed is believed to be a world first in terms of the method used and accuracy acquired.