Showing papers by "Aoife Morrin published in 2017"

Biomedical Diagnostics Enabled by Integrated Organic and Printed Electronics.

Abstract: Organic and printed electronics integration has the potential to revolutionize many technologies, including biomedical diagnostics. This work demonstrates the successful integration of multiple printed electronic functionalities into a single device capable of the measurement of hydrogen peroxide and total cholesterol. The single-use device employed printed electrochemical sensors for hydrogen peroxide electroreduction integrated with printed electrochromic display and battery. The system was driven by a conventional electronic circuit designed to illustrate the complete integration of silicon integrated circuits via pick and place or using organic electronic circuits. The device was capable of measuring 8 μL samples of both hydrogen peroxide (0–5 mM, 2.72 × 10–6 A·mM–1) and total cholesterol in serum from 0 to 9 mM (1.34 × 10–8 A·mM–1, r2 = 0.99, RSD < 10%, n = 3), and the result was output on a semiquantitative linear bar display. The device could operate for 10 min via a printed battery, and display th...

Probing skin physiology through the volatile footprint: Discriminating volatile emissions before and after acute barrier disruption.

Abstract: Volatile organic compounds emitted by human skin were sampled before and after acute barrier disruption of the volar forearm to investigate the significance of this approach to skin physiology research. A small wearable housing integrating a solid-phase micro-extraction fibre permitting rapid enclosed headspace sampling of human skin volatiles is presented, enabling non-invasive sample collection in 15 minutes, in a comfortable wearable format. Gas chromatography-mass spectrometry was utilised to separate and identify the volatile metabolites. A total of 37 compounds were identified, with aldehydes (hexanal, nonanal, decanal), acids (nonanoic, decanoic, dodecanoic, tetradecanoic and pentadecanoic acids) and hydrocarbons (squalane, squalene) predominant within the chemical profile. Acute barrier disruption was achieved through tape stripping (TS) of the stratum corneum to determine the impact on the volatile signature. Principle component analysis demonstrated there to be a discriminating volatile signature before and after TS. The dysregulation of significant features was examined. Several compounds derived from sebaceous components and their oxidation products were altered following barrier disruption, including squalane, squalene, octanal and nonanal. The upregulation of glycine was also observed, which may indicate a perturbation to the skin's natural moisturising factor production. TS impacted the hydro-lipid film that functions within the skin barrier, resulting in a differing volatile signature from affected skin. This provides a valuable non-invasive approach for scientific and clinical studies in dermatology, particularly around dermatological disorders associated with compromised barrier function.

Impedance spectroscopy for monosaccharides detection using responsive hydrogel modified paper-based electrodes.

Abstract: Herein we present a novel sensor for the detection of monosaccharides (e.g. glucose, fructose) in solution, using electrical impedance spectroscopy. The sensor is based on carbon interdigitated electrodes, printed on paper using screen printing. The surface of the electrodes was modified with a thin layer of hydrogel containing acrylamide copolymerised with 20 mol% 3-(Acrylamido)phenylboronic acid (PBA). It was observed that the hydrogel layers containing 20 mol% PBA swell considerably in the presence of glucose and fructose. This in turn changes the measured impedance across the electrodes, making it a suitable sensor for the quantitative detection of saccharides. We investigated the impedance and capacitance variations with different concentrations of glucose and fructose (0–5 mM) in aqueous phosphate buffer solutions. Variations in impedance were attributed to changes in the dielectric properties of the hydrogel under an applied electric field, due to swelling of the hydrogel layer induced by uptake and binding of sugar molecules to the boronate species within the gel. Impedance measurements at 1 kHz demonstrated that hydrogel swelling leads to an increased mobility of ions within the swollen hydrogel layer. The impedance decreased with increasing sugar concentration and the relative capacitance curves are markedly different for fructose and glucose, as the hydrogel exhibits greater swelling in the presence of fructose than glucose over the same concentration range. As the proposed sensor was shown to be suitable for the detection of glucose at concentration levels found in human sweat, future work will focus on the incorporation of these modified paper-based electrodes into wearable skin patches for non-invasive sugar monitoring in sweat.

Screen‐printed Tattoo Sensor towards the Non‐invasive Assessment of the Skin Barrier

Abstract: The development and characterisation of a screen-printed tattoo sensor for the non-invasive assessment of the skin barrier is presented. A screen-printed silver tattoo sensor comprising two concentric circle electrodes was fabricated and applied and characterised initially on a soft tissue mimic. It was shown that the tattoo was capable of tracking changes in water content in the soft tissue mimic using impedance spectroscopy. The tattoo sensors were then applied to porcine and human skins and impedance spectroscopy was used to interrogate the skin at the outer stratum corneum (SC). The SC is a layer of great interest from a dermatological point of view since it plays a critical role in the barrier function of the skin by protecting underlying tissue from infection, dehydration, chemical irritants and mechanical stress. Hydration changes were tracked in the skin using the impedance approach and validated against a tissue dielectric constant (TDC) measurement taken with the MoistureMeterD (MMD, Delfin Technologies). The impedimetric results obtained using the tattoo sensor were modelled into proposed circuit models representative of the systems measured. From this study, the potential of using wearable tattoo electrodes coupled with impedance spectroscopy as a transduction technique, to investigate skin barrier status offers considerable promise towards the monitoring and self-management of skin health.

A colorimetric method for use within portable test kits for nitrate determination in various water matrices

Abstract: A method using zinc powder in conjunction with the common Griess assay was developed for the detection of nitrate in water. This method is applicable to portable water test kits and allows for the accurate determination of nitrate in freshwater. The linear range for the method was shown to be 0.5–45 mg L−1 NO3− and the limit of detection (LOD) was 0.5 mg L−1 NO3−. The proposed method was validated over a five-day period and acceptable recovery and uncertainties were achieved when analysing freshwater matrices. The performance of the developed method was compared to an ISO-accredited ion chromatographic (IC) method by carrying out blind sample analysis. A good agreement between the two methods was achieved as comparable concentrations were determined using each method. In addition, the Zn method was compared to the performance of a novel solid-phase reagent method, previously developed within the group. The most accurate performance was demonstrated by the Zn powder method when analysing freshwater samples. The novel solid-phase reagent method demonstrated the greater accuracy when analysing seawater samples.

Non-Invasive Assessment of Skin Barrier Properties: Investigating Emerging Tools for In Vitro and In Vivo Applications

Abstract: There is increasing interest in the development of non-invasive tools for studying the properties of skin, due to the potential for non-destructive sampling, reduced ethical concerns and the potential comparability of results in vivo and in vitro. The present research focuses on the use of a range of non-invasive approaches for studying skin and skin barrier properties in human skin and human skin equivalents (HSE). Analytical methods used include pH measurements, electrical sensing of the epidermis and detection of volatile metabolic skin products. Standard probe based measurements of pH and the tissue dielectric constant (TDC) are used. Two other more novel approaches that utilise wearable platforms are also demonstrated here that can assess the electrical properties of skin and to profile skin volatile species. The potential utility of these wearable tools that permit repeatability of testing and comparability of results is considered through application of our recently reported impedance-based tattoo sensors and volatile samplers on both human participants and HSEs. The HSE exhibited a higher pH (6.5) and TDC (56) than human skin (pH 4.9–5.6, TDC 29–36), and the tattoo sensor revealed a lower impedance signal for HSEs, suggesting the model could maintain homeostasis, but in a different manner to human skin, which demonstrated a more highly resistive barrier. Characterisation of volatiles showed a variety of compound classes emanating from skin, with 16 and 27 compounds identified in HSEs and participants respectively. The continuing development of these tools offers potential for improved quality and relevance of data, and potential for detection of changes that are undetectable in traditional palpable and visual assessments, permitting early detection of irritant reactions.

Inducing macroporosity in hydrogels using hydrogen peroxide as a blowing agent

Abstract: A new gas blowing method to induce a macroporous structure in pH-responsive hydrogel materials with basic functional groups is reported by a new technique that generates oxygen bubbles via hydrogen peroxide decomposition to template the polymer. This overcomes pH limitations associated with the more traditional approach of using a carbon dioxide gas blowing agent. This new approach is shown to effectively induce a macroporous structure which overcomes the diffusional limitation of bulk hydrogels and, as a result, dramatically increases swelling rates. The hydrogel comprises an aliphatic diamine, Jeffamine®, cross-linked with polyethylene glycol diglycidyl ether (PEGDGE) in a single simple polymerisation step, generating a polymeric network with pendant basic groups. This cross-linking reaction requires protonation of the amine groups, which precludes it from being compatible with the carbon dioxide gas blowing method as this requires a low pH for the decomposition of carbonate. To overcome this, the production of oxygen bubbles in situ via a catalytic decomposition of hydrogen peroxide on silver nanoparticles is used to induce a macroporous structure in the hydrogel. This method was shown to successfully induce a macroporous structure whereby interconnected pores from sub-micron up to 0.5 mm diameter are created within the hydrogel. This new method of inducing macroporosity is described here in terms of the hydrogel polymerisation conditions and the nature of the porosity is characterised in terms of its ability to overcome the diffusional limitations of bulk hydrogels. Finally, rapid, reversible pulsatile pH-sensing is demonstrated using these hydrogels.

CHAPTER 1:Reactive Inkjet Printing—An Introduction

Abstract: ‘Reactive inkjet (RIJ) printing’, or ‘reactive inkjet’ is a type of inkjet technique whose history in the research literature has been documented for less than ten years. Despite its recent beginnings, it has attracted much attention as a cost-effective and highly controllable method to fabricate patterns, where it elegantly combines the processes of material deposition and chemical reaction. This chapter introduces the reader to what is meant by this term and surveys the various types of inkjet printing (such as piezo and thermal), as well as describing droplet ejection mechanisms and ink considerations.