Modified screen printed electrodes for electrochemical sensing applications in food and beverage analysis

Electrochemical sensor technology has the potential to revolutinise analytical measurements in food analysis by providing a cheap, easy to use and portable alternative to traditional chromotography and mass spectrometry based techniques. In this thesis two such sensors are developed - one for the detection of caffeine and other for the detection of the mycotoxin, deoxynivalenol. These sensors are developed from both a food safety and quality control point of view. The majority of sensor development has been for the medical point of care sector, however apart from blood glucose sensing, commerical successes have been limited. Regulatory barriers are not as significant in the food industry compared to the medical industry and hence, real world applications should be more feasible. Chapter 1 provides a general introduction to sensor technology for food analysis with an emphasis on electrochemical transducers and modified electrodes in particular. Background theory is outlined for both fundamental electrochemistry and immunoassay development and previously published work in electrochemical sensors for food analysis is summarised. In Chapter 2 a number of electrochemical pretreatment techniques are compared with multiwall carbon nanotubes (MWCNT) and reduced graphene oxide (RGO) modified screen printed electrodes in the development of an electrochemical immunosensor for mouse IgG detection. It was found that a MWCNT/Nafion modified electrode had the most promising analytical characteristics with an LOD of 0.2 ppm, IC50 value of 0.3 ppm, linear range of 0.04 - 2.7 ppm and R 2 value of 0.9286. Subsequent to the optimisation of an electrode material for this model analyte (mouse IgG), an electrochemical immunosensor for deoxynivalenol was developed in Chapter 3. Firstly, an ELISA protocol was developed with a LOD of 0.534 ppm and linear range of 0.9 - 53 ppm, followed by the transfer of this protocol onto the MWCNT/Nafion electrode. A limit of detection of 0.95 ppm and IC50 value of 2 ppm were found. These values are promising considering that the EU maximum residue limit (MRL) for DON in wheat samples is 1.75 ppm. However, the developed sensor was unable to detect DON in wheat samples suggesting that a more sophisticated sample pretreatment method would need to be investigated. In Chapter 4, a number of different approaches for electrochemical caffeine detection are investigated namely electrochemically pretreated, nafion modified and screen printed graphene electrodes. It was found that the nafion modified electrode was the most suitable in energy drinks samples. This sensor had a LOD of 8 µM and linear range of 10 - 128 µM. Finally, in Chapter 5 some suggestions are given to future directions for electrochemical sensor development

On-Line Realtime Water Quality Monitoring and Control for Swimming Pools

Effective swimming pool water quality monitoring and control systems are important to safeguard public health and for bather comfort. Most Irish swimming pool monitoring systems rely heavily on manual methods for sampling, testing and data recording of important parameters. Microbiological testing is infrequent and results can often take days. The goal of this research is to develop a water quality monitoring and control system with real time data logging, automatic data analysis, remote monitoring and control, microbiological sampling capabilities and online connectivity. National Instruments hardware and its software package LabView form the basis of the monitoring and control system. Several sensors measure the main water parameters affecting disinfection and overall water balance: temperature, pH level, total dissolved solids, turbidity, chlorine level and redox potential. Water hardness is measured manually due to the prohibitive cost of an automatic system. The LabView package and related hardware controls the chemical dosing of the pool in order to maintain these parameters within their recommended optimum levels. An investigation is also being carried out into the development of a biosensor to detect E. coli, as it is the best indicator of faecal contamination in water. The flexibility of the technology used in this research means that it has numerous other potential applications, such as: drinking water treatment, waste water treatment, industrial process control, environmental study and monitoring

Monolayer doping of Si with improved oxidation resistance

In this article, the functionalization of planar silicon with arsenic- and phosphorus-based azides was investigated. Covalently bonded and well-ordered alkyne-terminated monolayers were prepared from a range of commercially available dialkyne precursors using a well-known thermal hydrosilylation mechanism to form an acetylene-terminated monolayer. The terminal acetylene moieties were further functionalized through the application of copper-catalyzed azide–alkyne cycloaddition (CuAAC) reactions between dopant-containing azides and the terminal acetylene groups. The introduction of dopant molecules via this method does not require harsh conditions typically employed in traditional monolayer doping approaches, enabling greater surface coverage with improved resistance toward reoxidation. X-ray photoelectron spectroscopy studies showed successful dialkyne incorporation with minimal Si surface oxidation, and monitoring of the C 1s and N 1s core-level spectra showed successful azide–alkyne cycloaddition. Electrochemical capacitance–voltage measurements showed effective diffusion of the activated dopant atoms into the Si substrates

Systematic literature review of hand gestures used in human computer interaction interfaces

Gestures, widely accepted as a humans' natural mode of interaction with their surroundings, have been considered for use in human-computer based interfaces since the early 1980s. They have been explored and implemented, with a range of success and maturity levels, in a variety of fields, facilitated by a multitude of technologies. Underpinning gesture theory however focuses on gestures performed simultaneously with speech, and majority of gesture based interfaces are supported by other modes of interaction. This article reports the results of a systematic review undertaken to identify characteristics of touchless/in-air hand gestures used in interaction interfaces. 148 articles were reviewed reporting on gesture-based interaction interfaces, identified through searching engineering and science databases (Engineering Village, Pro Quest, Science Direct, Scopus and Web of Science). The goal of the review was to map the field of gesture-based interfaces, investigate the patterns in gesture use, and identify common combinations of gestures for different combinations of applications and technologies. From the review, the community seems disparate with little evidence of building upon prior work and a fundamental framework of gesture-based interaction is not evident. However, the findings can help inform future developments and provide valuable information about the benefits and drawbacks of different approaches. It was further found that the nature and appropriateness of gestures used was not a primary factor in gesture elicitation when designing gesture based systems, and that ease of technology implementation often took precedence

Industrial inspection using Gaussian functions in a colour space

This paper presents an original method of modelling the colour distributions of images using 2D Gaussian functions and its application to flaw detection in industrial inspection. 2D Gaussian functions are used to model the colours that appear in the non-flawed images in an unsupervised manner. Pixels under test are compared to the colour distribution from training images. 140 images have been tested and the results are given. This method has a wide range of applications for detecting colour separable objects in images. It also has great potential in industrial inspection due to its speed, accuracy and unsupervised training

Poly(ethylene glycol)-Based Hyperbranched Polymer from RAFT and Its Application as a Silver-Sulfadiazine-Loaded Antibacterial Hydrogel in Wound Care

A multifunctional branched copolymer was synthesized by Reversible Addition−Fragmentation Chain Transfer polymerization (RAFT) of poly(ethylene glycol) diacrylate (PEGDA Mn = 575) and poly(ethylene glycol) methyl methacrylate (PEGMEMA Mn = 500) at a feed molar ratio of 50:50. Proton nuclear magnetic resonance spectros- copy (1HNMR) confirmed a hyperbranched molecular structure and a high degree of vinyl functionality. An in situ cross-linkable hydrogel system was generated via a "click" thiol−ene-type Michael addition reaction of vinyl functional groups from this PEGDA/PEGMEMA copolymer system in combination with thiol-modified hyaluronic acid. Furthermore, encapsulation of antimicrobial silver sulfadiazine (SSD) into the copolymer system was conducted to create an advanced antimicrobial wound care dressing. This hydrogel demon- strated a sustained antibacterial activity against the bacterial strains Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli in comparison to the direct topical application of SSD. In addition, in vitro toxicology evaluations demonstrated that this hydrogel?with low concentrations of encapsulated SSD-supported the survival of embedded human adipose derived stem cells (hADSCs) and inhibited growth of the aforementioned pathogens. Here we demonstrate that this hydrogel encapsulated with a low concentration (1.0% w/v) of SSD can be utilized as a carrier system for stem cells with the ability to inhibit growth of pathogens and without adverse effects on hADSCs

The neural correlates of ideation in product design engineering practitioners

In product design engineering (PDE), ideation involves the generation of technical behaviours and physical structures to address specific functional requirements. This differs from generic creative ideation tasks, which emphasise functional and technical considerations less. To advance knowledge about the neural basis of PDE ideation, we present the first fMRI study on professional product design engineers practising in industry. We aimed to explore brain activation during ideation, and compare activation in open-ended and constrained tasks. Imagery manipulation tasks were contrasted with ideation tasks in a sample of 29 PDE professionals. The key findings were: (1) PDE ideation is associated with greater activity in left cingulate gyrus; (2) there were no significant differences between open-ended and constrained tasks; and (3) a preliminary association with activity in the right superior temporal gyrus was also observed. The results are consistent with existing fMRI work on generic creative ideation, suggesting that PDE ideation may share a number of similarities at the neural level. Future work includes: functional connectivity analysis of open-ended and constrained ideation to further investigate potential differences; investigating the effects of aspects of design expertise/training on processing; and the use of novelty measures directly linked to the designer’s internal processing in fMRI analysis

A novel user-based gesture vocabulary for conceptual design

Research into hand gestures for human computer interaction has been prolific recently, but within it research on hand gestures for conceptual design has either focused on gestures that were defined by the researchers rather than the users, or those that were heavily influenced by what can be achieved using currently available technology. This paper reports on the study performed to identify a user elicited vocabulary of gestures for conceptual design, disassociated from the currently available technology, and its subsequent evaluation. The study included 44 product design engineering students (3rd, 4th year and recent graduates) and identified 1772 gestures that were analysed to build a novel gesture consensus set of vocabulary of hand gestures for conceptual design. This set is then evaluated by 10 other professionals, in order to generalise this set for a wider range of users and possibly reduce the need for training. The evaluation has shown that majority of gestures added to the vocabulary were easy to perform and appropriate for the activities, but that at the implementation stage the vocabulary will require another round of evaluation to account for the technology capabilities. The aim of this work is to create a starting point for a potential future system that could adapt to individual designers and allow them to use non-prescribed gestures that will support rather than inhibit their conceptual design thinking processes, akin to the developments that happened in hand writing recognition or predictive texting

Extending the structural alignment model to similarity judgements of design concepts

Similarity is an important facet of many aspects of human behavior. Similarity has also been identified as an important factor in combinatorial design creativity, specifically analogical reasoning (Chan et al. 2011) and combination of pairs of stimuli (Nagai et al. 2009). Analogical transfer occurs via a cognitive process of structural alignment (Gentner & Markman 1997) and the same is assumed to be true in a design context. Conceptual combination and similarity judgements, however, are both thought to operate via two independent processes of structural alignment and scenario creation (Wisniewski 1997). A number of authors have proposed metrics for similarity in design, however none appear to be supported by human perceptions of similarity. Investigation of the role of similarity in the combination of design concepts requires an understanding of the cognitive mechanisms by which designers perceive similarity. To wards such an understanding, an experiment is conducted to test the applicability of structural alignment as a model of design concept similarity judgement

Natural and intuitive gesture interaction for 3D object manipulation in conceptual design

Gesture interaction with three-dimensional (3D) representations is increasingly explored, however there is little research present on the nature of the gestures used. A study was conducted in order to explore gestures designers perform naturally and intuitively while interacting with 3D objects during conceptual design. The findings demonstrate that different designers perform similar gestures for the same activities, and that their interaction with a 3D representation on a 2D screen is consistent with that which would be expected if a physical object were suspended in air in front of them