Here we present the fabrication and the performance of a novel, wearable, robust, flexible and di... more Here we present the fabrication and the performance of a novel, wearable, robust, flexible and disposable micro-fluidic device which incorporates miniature optical components as a detection system, for wireless monitoring in real time mode of sweat pH during an exercise session. This micro-fluidic platform is completely non-invasive, with the great advantage of providing a continuous flow of fresh sweat for continuous real time analysis, ensuring immediate feedback regarding sweat composition to an athlete and/or coach. To the best of our knowledge, this is the first wearable and wireless micro-fluidic device suitable for real time analysis and reporting of the wearer's physiological state.
This paper presents the fabrication and the performance of a novel, wearable, robust, flexible an... more This paper presents the fabrication and the performance of a novel, wearable, robust, flexible and disposable microfluidic device which incorporates micro-Light Emitting Diodes (μ-LEDs) as a detection system, for monitoring in real time mode the pH of the sweat generated during an exercise period. Up to now sweat analysis has been carried out using awkward methods of collecting sweat followed by laboratory analysis. The approach presented here can provide immediate feedback regarding sweat composition to an athlete and coach. The great advantage of sweat analysis is the fact that it is a completely non-invasive means of analyzing the wearer's physiological state and ensuring their health and well-being.
Molecules with Multiple Personalities: How Switchable Materials Could Revolutionize Chemical Sensing
ECS Transactions, 2009
Worldwide, the demand for sensing devices that can conform with the requirements of large-scale w... more Worldwide, the demand for sensing devices that can conform with the requirements of large-scale wireless sensor network (WSN) deployments is rising exponentially. Typically, sensors should be very low cost, low power (essentially self-sustaining), yet very rugged and reliable. At present, functioning WSN deployments involve physical transducers only, such as thermistors, accelerometers, photodetectors, flow meters, to monitor quantities like temperature, movement, light level and liquid level/flow. Remote, widely distributed monitoring of molecular targets remains relatively unexplored, except in the case of targets that can be detected directly using 'non-contact' techniques like spectroscopy. This paper will address the issues inhibiting the close integration of chemical sensing with WSNs and suggest strategies based on fundamental materials science that may offer routes to new sensing surfaces that can switch between different modes of behaviour (e.g. active-passive, expa...
A novel photo-controllable micro-fluidic electroosmotic pump based on spiropyran monolithic polym... more A novel photo-controllable micro-fluidic electroosmotic pump based on spiropyran monolithic polymers is presented here for the first time. Photochromic monolithic scaffolds have been synthesised within poly(tetrafluoroethylene) coated fused silica capillaries. These monoliths have a photochromic spiropyran monomer incorporated in the bulk by thermally induced copolymerisation with a cross-linking agent (divinylbenzene) and were encased in micro-fluidic devices to function as photo-controllable electroosmotic pumps (EOPs). Due to the presence of the spiropyran the monolith can exist in two forms: a zwitterionic merocyanine (MC) form and an uncharged spiropyran (SP). As both forms bare a net overall zero charge, an acidic electrolyte was used to produce a stable anodic electroosmotic flow (EOF), while still retaining the ability to switch between the SP and the MC forms, which exhibit different charge distributions. It was confirmed that visible light, which produces the SP form, caused an increase in EOF while UV light, which generates the MC form, caused a decrease in EOF. In this way the EOF from the chip was modified by light and not by changing the electric field, temperature or buffer pH, some of the more common methods of altering the EOF.
Investigations into the extent of structuring present in phosphonium based ionic liquids were car... more Investigations into the extent of structuring present in phosphonium based ionic liquids were carried out using photochromic molecular probes. Three spiropyran derivatives containing hydroxyl (BSP-1), carboxylic acid (BSP-2) and aliphatic chain (C 14 H 29 ) (BSP-3) functional groups were analysed in a range of phosphonium based ionic liquids and their subsequent physico-chemical interactions were reported. It is believed that the functional groups locate the probe molecules into specific regions based upon the interaction of the functional groups with particular and defined regions of the ionic liquid. The existence of structuring resulted in varied thermodynamic, kinetic and solvatochromic parameters with responses directly related to the certain polar and non-polar domains. BSP-1 and BSP-2 were found to exhibit generally negative entropies of activation ranging from -50JK -1 mol -1 to -90JK -1 mol -1 implying relatively low solvent-solute interactions and possible anion interactions with the polar functional groups. Higher than expected activation energies of 60kJ.mol -1 to 100kJ.mol -1 for polar probes maybe be due to functional groups competing with the charge sites of the MC form for solvent interaction thus reducing MC stabilisation effects. Differences in thermal relaxation rate constants (2.5x10 -3 s -1 in BSP-1 and 3x10 -4 s -1 in BSP-2 in [P 6,6,6,14 ][dbsa]) implied that the polar probe systems were examining polar/charged regions but that each probe was examining slightly differing polar domains. BSP-3 entropies of activation were positive and between 30 JK -1 mol -1 to 66 JK -1 mol -1 . The association of the non-polar functional group was believed to locate the spiropyran moiety to the interface of polar and non-polar regions and thus the thermal relaxation of the MC form resulted in solvent reorientation to accommodate the molecule as it reverted to its closed form. Slow rate constants in contrast to high activation energies (5 x 10 -4 s -1 and 111.91 kJ.mol -1 respectively, for BSP-3 in [P 6,6,6,14 ][dbsa]) may have been due to steric effects due to proposed cavity formation of the alkyl chains in phosphonium based IL structuring.
We have compared the rate of thermal reversion of Spirooxazine (SO) from its merocyanine (MC) for... more We have compared the rate of thermal reversion of Spirooxazine (SO) from its merocyanine (MC) form within ionic liquids and molecular solvents. E t (30) and Kamlet-Taft parameter studies indicate ILs are comparable to polar protic and aprotic solvents. The observed reversion kinetics within the ionic liquids were slower than that of molecular solvents with similar polarity, indicating a greater degree of interactions between the ionic liquid ions and the zwitterionic MC isomer, which led to increased lifetimes for the MC-ion complexes. Pre-metathesis cleaning of precursor salts was found to be necessary in order to obtain spectroscopic grade ILs for physiochemical analysis using solvatochromic probe dyes. 85 nitrocycloexanone 12 and multiparameter studies using the Kamlet-Taft parameters . Solvatochromic methods are based on the fact that these dyes interact with the solvent into which they are added and the extent of these interactions is 2 | Journal Name, [year], [vol], 00-00
The concept of 'Internet-Scale' sensing requires a massive scale-up in sensor numbers. While ther... more The concept of 'Internet-Scale' sensing requires a massive scale-up in sensor numbers. While there has been considerable activity in transducer-based 'sensornets', there has been virtually no corresponding deployments of chemo/biosensor networks. Considerable advances in materials science will be required before largescale deployments can be realised 'Sensornets' are large-scale distributed sensing networks comprised of many small sensing devices equipped with memory, processors, and short-range wireless communications capabilities . These devices, known as 'Motes' can gather and share sensor data from multiple locations through in-built wireless communications capabilities. The vision of incorporating chemical and biological sensing dimensions into these platforms is very appealing, and the potential applications in areas critical to society are truly revolutionary . For example,
Journal of Photochemistry and Photobiology A: Chemistry, 2009
Switchable materials have tremendous potential for application in sensor development that could b... more Switchable materials have tremendous potential for application in sensor development that could be applied to many fields. We are focusing on emerging area of wireless sensor networks due to the potential impact of this concept in society. Spiropyran-based sensors are probably the most studied type of photoswitchable sensing devices. They suffer from many issues but photofatigue, insufficient selectivity and lack of sensitivity are probably the most important characteristics that hinder their wider application. Here, we are address these issues and demonstrate that covalent attachment of modified spiropyran into a polymeric film significantly reduces photodegradation. The observed signal loss after 12 th cycle of switching between the spiropyran and merocyanine forms is only about 27% compared to the loss of 57% of the initial signal in an equivalent experiment based on nonimmobilized spiropyran. This has enabled us to demonstrate at least 5 reversible cycles of detection of an ion of interest (in our case H + ) with minimal signal loss. Furthermore, we demonstrate that the sensitivity can be increased by incorporation of additional binding groups in the parent spiropyran molecule. Using molecular modeling to calculate the relevant bond lengths as a measure of interaction between MC and H + , the calculated increase of H-bond strength is approximately an order of magnitude for a derivative containing a methoxy group incorporated in the o-position of the parent spiropyran in comparison to the equivalent unsubstituted phenol. This theoretical result was found to correspond very well with experimental observation. As a result, we have increased the sensitivity to H + by approximately one order of magnitude.
We report an enzymatic sensor based on an organic electrochemical transistor that uses a room tem... more We report an enzymatic sensor based on an organic electrochemical transistor that uses a room temperature ionic liquid as an integral part of its structure and as an immobilization medium for the enzyme and the mediator.
Solid-contact Ion Selective Electrodes (SC-ISEs) for the detection of lead are prepared on screen... more Solid-contact Ion Selective Electrodes (SC-ISEs) for the detection of lead are prepared on screen printed substrates in order to have low-cost and disposable sensors which may be useful in long-term environmental monitoring. It is shown that the materials used as solid contact layer, the deposition techniques and their thickness affect greatly the performances of the sensors. Poly(3-octylthiophene-2,5-diyl) (POT) and poly-3,4-ethylenedioxithiophene (PEDOT) are employed in this investigation. A trend showing an optimum is found for sensors prepared with POT as the batch reproducibility depends on the amount drop-cast, i.e., thickness. In case of PEDOT which is grown amperometrically the trend is more complex but an optimum for the batch reproducibility is again found depending on the current density. In the latter case, the film thickness and the overoxidation degree of the polymer probably concur in determining a more complex relationship.
This work describes the synthesis and characteristics of a novel electrochromic ionic liquid (IL)... more This work describes the synthesis and characteristics of a novel electrochromic ionic liquid (IL) based on a phosphonium core tethered to a viologen moiety. When integrated into a solid-state electrochromic platform, the viologen modified IL behaved as both the electrolyte and the electrochromic material. Platform fabrication was achieved through in situ photo-polymerization and encapsulation of this novel IL within a hybrid sol-gel. Important parameters of the platform performance, including its coloration efficiency, switching kinetics, and optical properties were characterised using UV-vis spectroscopy and cyclic voltammetry in tandem. The electrochromic platform exhibits a coloration efficiency of 10.72 cm 2 C -1 and a varied optical output as a function of the incident current. Despite the rather viscous nature of the material, the platform exhibited approximately 2 orders of magnitude faster switching kinetics (221 s to reach 95 % absorbance) when compared to previously reported electrochromic ILs (18 000 s).
This overview aims to summarize the existing potential of "Ionogels" as a platform to develop sti... more This overview aims to summarize the existing potential of "Ionogels" as a platform to develop stimuli responsive materials. Ionogels are a class of materials that contain an Ionic Liquid (IL) confined within a polymer matrix. Recently defined as "a solid interconnected network spreading throughout a liquid phase", the ionogel therefore combines the properties of both its solid and liquid components. ILs are low melting salts that exist as liquids composed entirely of cations and anions at or around 100 °C. Important physical properties of these liquids such as viscosity, density, melting point and conductivity can be altered to suit a purpose by choice of the cation/anion. Here we provide an overview to highlight the literature thus far, detailing the encapsulation of IL and responsive materials within these polymeric structures. Exciting applications in the areas of optical and electrochemical sensing, solid state electrolytes and actuating materials shall be discussed.
ESI- An electrochromic ionic liquid: design, characterisation and performance in a solid-state platform
Complete list of the materials and instrumentation used throughout this work; 1H and 31P NMR spec... more Complete list of the materials and instrumentation used throughout this work; 1H and 31P NMR spectra of all starting and intermediate materials and the final synthesised IL; DSC and TGA thermal analyses of intermediate and final synthesised ILs; electrochromic device thickness analysis; and electro- chemical impedance spectroscopy of oxidized and reduced forms of the electrochromic IL. This material is available free of ■charge via the Internet at http://pubs.acs.org.
2010 International Conference on Body Sensor Networks, 2010
This paper presents the fabrication, characterization and the performance of a wearable, robust, ... more This paper presents the fabrication, characterization and the performance of a wearable, robust, flexible and disposable barcode system based on novel ionic liquid polymer gels (ionogels) for monitoring in real time mode the pH of the sweat generated during an exercise period. Up to now sweat analysis has been carried out using awkward methods of collecting sweat followed by laboratory analysis. The approach presented here can provide immediate feedback regarding sweat composition. The great advantage of sweat analysis is the fact that it is a completely non-invasive means of analyzing the wearer's physiological state and ensuring their health and wellbeing.
Molecular photoswitches have been used to investigate the possibility of nano-structured polar an... more Molecular photoswitches have been used to investigate the possibility of nano-structured polar and non-polar domains in ionic liquids (ILs). Two photochromic compounds, spiropyran (BSP) and spirooxazine (SO) were added to imidazolium based ionic liquids containing the anion [NTf2]and their photochromic behaviour was monitored with increasing side chain length (C 2-C 12) of the imidazolium cation. Increasing side-chain length was found to have only minor effects on the rate of thermal relaxation of the merocyanine form of spiropyran (MC BSP) and spirooxazine (MC SO) to BSP and SO, respectively. BSP was found to be a suitable optical probe as linear correlations in parameters were observed for this compound. This is believed to be because BSP-IL interactions are based on hydrogen bonding between the MC BSP and the ionic liquid cations, compared to MC SO , which is limited to electrostatic interactions. Hence, the sensitivity of MC BSP is enhanced in the charged polar regions of the IL. Increasing the side-chain of the cation results in slight increases in MC BSP to BSP relaxation activation energy from 96.93 kJ.mol-1 in [C 4 mIm][NTf 2 ] to 105.27 kJ.mol-1 in [C 12 mIm][NTf 2 ]. MC BSP to BSP relaxation ΔS ‡ and ΔH ‡ values also increase with increasing side-chain. The ability for spirocyclic compounds to switch between polar and non-polar forms appears to allow polar and non-polar regions in ILs to be probed dynamically using a single probe dye. It appears that the value of the ground state equilibrium constant, K e , is dominated by the non-polar regions of the IL while the equilibrium constant of activation, K ‡ , is dominated by the polar regions. A correlation of side chain length to equilibrium constant of activation is believed to be because polar regions are possibly expanding 2 due to increasing influence of non-polar side chain interactions and compound insertion upon the overall solvent structure. The result of such reordering and dispersion of polar regions reduces solvent-solute interactions which increases the rate of MC BSP to BSP relaxation.
Uploads
Papers by Robert Byrne