Paper-based bateries as key enablers for self-powered conductivity sensing

Abstract

[eng] This thesis presents the development of different self-powered devices that allow the conductivity measurement of liquid samples, from different types of water samples to biological fluids. The devices have been developed with the aim of offering robust single-use systems following the criteria dictated by the WHO for Point of Care (PoC) devices, the ASSURED criteria (Affordable, Sensitive, Specific, User-friendly, Rapid and robust , Without equipment and deliverable to end users). For the development of these devices, three technological drivers have been used, such as printed electronics, paper microfluidics and self-powered systems. With the combination of these three technologies, three very different prototypes have been developed for the conductivity analysis of different samples, proving a digital and unequivocal result. In the first chapter, an introduction about the motivation for the development of ASSURED devices and how the use of the three technological drivers allows obtaining fully functional single-use devices is done. For this, the state of the art on the three technological drivers and their integration for the development of ASSURED self-powered digital devices is evaluated. The second chapter delves into the basic unit that allows devices to be self-powered, a paper-based conductivity battery-sensor. This chapter explains the bases that allow this battery to be sensitive to the conductivity of the electrolyte introduced into its paper core and how a signal directly related to the conductivity of the electrolyte can be extracted from the battery. Finally, the battery is tested with different liquids, demonstrating its suitability for the analysis of biological samples. In the third chapter, the first self-powered device for measuring different types of water is developed. It contains two interconnected conductivity battery-sensor that allow the measurement of the conductivity of the electrolyte, a hybrid circuit manufactured by inkjet printing were discrete electronic components have been hybridized and an electrochromic indicator that shows the value of the conductivity of the electrolyte in a scale-bar. In the fourth chapter, a medical device in the form of a skin patch is manufactured for the screening of Cystic Fibrosis. The patch has been designed following the standards dictated by the Cystic Fibrosis Foundation and the CLSI (Clinical and Laboratory Standards Institute) for the development of a screening device. The patch also contains two connected conductivity battery-sensor, a printed circuit hybridized with electronic components and two electrochromic indicators, which indicate whether or not the disease is present. The performance of the patch was validated using samples of artificial sweat samples at the threshold conductivity of Cystic Fibrosis patients and at -20% of the threshold conductivity. Finally, the fifth chapter presents the first steps in the development of a patch capable of storing the sweat of athletes for the subsequent analysis with the conductivity battery-sensor. First, the design of the patch was validated in a local race where two patches were placed on different participants and then the conductivity was measured, obtaining very similar results (coefficient of variation of less than 10% in the 75% of the subjects). Next, different conductivity sensor battery structures were evaluated to obtain the best possible performance in terms of dynamic range of measurement, sensitivity and linearity. Once the best battery structure was decided, its performance was compared to that of a commercial conductivity meter using real sweat samples. From this study, it was observed that the conductivity values provided by the battery differ from the commercial conductometer in less than 10% in 68% of the cases, between 10 and 20% in 21% of the cases and more than 20% in 11% of cases, thus concluding the effectiveness of our battery measurement in 68%.

[spa] Esta tesis presenta el desarrollo de diferentes dispositivos autoalimentados que permiten la medida de la conductividad de muestras líquidas, desde diferentes tipos de aguas a fluidos biológicos. Los dispositivos se han desarrollado con el objetivo de ofrecer sistemas robustos de un solo uso siguiendo los criterios dictados por la OMS para dispositivos Point of Care (PoC), los criterios de ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free and Deliverable to end-users). Para el desarrollo de estos dispositivos se han utilizado tres impulsores tecnológicos como son la utilización de la electrónica impresa, de la microfluídica en papel y de sistemas autoalimentados. Con la combinación de estas tres tecnologías se han desarrollado tres prototipos muy diferentes para el análisis de la conductividad de diferentes muestras, proporcionando un resultado digital e inequívoco. En el primer capítulo se hace una introducción sobre la motivación del desarrollo dispositivos ASSURED y de cómo la utilización de los tres impulsores tecnológicos permite la obtención de dispositivos de un solo uso completamente funcionales. Seguidamente, en el segundo capítulo se profundiza en la unidad básica que permite la autoalimentación de los dispositivos, una batería sensora de conductividad basada en papel, consiguiéndose con ella la medida de la conductividad diferentes líquidos, dejando patente su idoneidad para el análisis de muestras biológicas. Luego, en el tercer capítulo se desarrolla el primer dispositivo autoalimentado para la medida de la conductividad de diferentes tipos de aguas. En el cuarto capítulo se fabrica un dispositivo médico en forma de parche para la piel para el cribado de la Fibrosis Quística, validando su funcionamiento con muestras de sudor artificial ajustadas a valores de conductividad positivos y negativos de la enfermedad. Finalmente, en el quinto capítulo se presentan los primeros pasos del desarrollo de un parche capaz de almacenar el sudor de deportistas para su posterior análisis con la batería sensora de conductividad. Durante toda el desarrollo de la tesis se ha enfatizado la idoneidad en la utilización de los tres impulsores tecnológicos como elementos clave para la obtención de dispositivos acabados completamente funcionales.