Wave profile and tide monitoring system for scalable implementation

Apresentação de Poster em conferência Nacional.Presentation of a wave profile and tide monitoring system, with low-cost and low-power pressure sensors connected to a datalogger in a wired or acustic network

Wave profile and tide monitoring system for scalable implementation

A versatile, miniaturized, cost-effective, low-power wave profile and tide monitoring system, capable of long-term and scalable deployment, was developed to integrate pressure and temperature sensors in an RS485 network, for standalone operation with organized memory or real-time shared data monitoring. The pressure and temperature sensors are controlled by low-power microcontrollers, that communicate the data periodically to a datalogger, that depending on the application, store it in a removable SD card or send it to a server via Wi-Fi. The data is then analyzed to compensate for the loss in amplitude sensitivity according to the sensor’s depth. The wave profile can be sampled at a maximum rate of 100 Hz, with a 1 cm resolution. The system was tested successfully in real-life conditions, in rivers Douro and Cávado, and off the coast of Viana do Castelo.João Rocha was supported by the doctoral Grant PRT/BD/154322/2023 financed by the Portuguese Foundation for Science and Technology (FCT), and with funds from Portuguese State Budget, European Social Fund (ESF) and Por_Norte, under MIT Portugal Program. This work is co-funded by the projects K2D: Knowledge and Data from the Deep to Space (POCI-01-0247-FEDER-045941), SONDA (PTDC/EME-SIS/1960/2020), ATLÂNTIDA (NORTE-01-0145-FEDER-000040) and CMEMS - UIDB/04436/2020 and UIDP/04436/2020

PtOEP–PDMS-based optical oxygen sensor

The advanced and widespread use of microfluidic devices, which are usually fabricated in polydimethylsiloxane (PDMS), requires the integration of many sensors, always compatible with microfluidic fabrication processes. Moreover, current limitations of the existing optical and electrochemical oxygen sensors regarding long-term stability due to sensor degradation, biofouling, fabrication processes and cost have led to the development of new approaches. Thus, this manuscript reports the development, fabrication and characterization of a low-cost and highly sensitive dissolved oxygen optical sensor based on a membrane of PDMS doped with platinum octaethylporphyrin (PtOEP) film, fabricated using standard microfluidic materials and processes. The excellent mechanical and chemical properties (high permeability to oxygen, anti-biofouling characteristics) of PDMS result in membranes with superior sensitivity compared with other matrix materials. The wide use of PtOEP in sensing applications, due to its advantage of being easily synthesized using microtechnologies, its strong phosphorescence at room temperature with a quantum yield close to 50%, its excellent Strokes Shift as well as its relatively long lifetime (75 µs), provide the suitable conditions for the development of a miniaturized luminescence optical oxygen sensor allowing long-term applications. The influence of the PDMS film thickness (0.1–2.5 mm) and the PtOEP concentration (363, 545, 727 ppm) in luminescent properties are presented. This enables to achieve low detection levels in a gas media range from 0.5% up to 20%, and in liquid media from 0.5 mg/L up to 3.3 mg/L at 1 atm, 25 °C. As a result, we propose a simple and cost-effective system based on a LED membrane photodiode system to detect low oxygen concentrations for in situ applications.This work was co-financed by national funds through FCT—Fundação para a Ciência e Tecnologia, I.P. under project SONDA (PTDC/EME-SIS/1960/2020), by Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER), Project NORTE-01-0145-FEDER-000032—NextSea, by the European Regional Development Fund (ERDF) through INTERREG V-A Spain-Portugal Programme (POCTEP) 2014–2020, Project N. 0591_FOODSENS_1_E and by FCT national funds, under the national support to R&D units grants, through the reference projects UIDB/04436/2020 and UIDP/04436/2020

Desenvolvimento de um sensor de oxigénio dissolvido para meio aquático

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de ComputadoresApesar do planeta Terra ser conhecido como planeta azul, em virtude das enormes massas de água que sustenta (cerca de 70%), apenas 3% deste volume é água doce e desta pequena parcela somente 0,06% está disponível para consumo humano. Dessa forma, ao longo da última década, os avanços científicos têm vindo a acentuar a elevada relevância de conservação, proteção e monitorização das massas de água disponíveis de forma a viabilizar a vida na Terra de uma forma sustentável. No entanto, os meios aquáticos não são estáticos e imutáveis, as suas características biológicas, químicas e físicas alteram-se não só pela ação antrópica (descargas, poluição atmosférica, agricultura, desflorestamento) mas também pelo curso natural das condições que influenciam o ciclo da água (erosão, solubilidade de minerais e químicos naturalmente presentes nas formações rochosas). Nos últimos anos tem-se tornado evidente uma crescente procura por meios eficientes e autónomos de monitorização de qualidade da água, nomeadamente, plataformas de gestão de recursos hídricos rigorosas e precisas que permitam avaliar as diversas propriedades de um determinado volume de água de forma a criar bases estatísticas e meios de prevenção com o objetivo de corrigir eventuais anomalias. Todavia, os desafios políticos, económicos e sociais constituem ainda um obstáculo aos avanços tecnológicos. Esta é uma área que envolve diversas adversidades eletrónicas, tais como desenvolvimento de sistemas real time, com baixo consumo elétrico, exigência de elevada precisão e exatidão, mas também dificuldades relacionadas com biofouling, interveniência de espécies químicas nas medições, entre outras. Em suma é uma temática que desafia a área da engenharia eletrónica e informática, química, biologia e física (hidráulica). O oxigénio dissolvido (OD) é um dos principais parâmetros de análise de qualidade de água, o seu estudo permite deduzir a taxa fotossintética aquática, a taxa de stress animal em tanques de aquacultura, processos aeróbicos e anaeróbicos, taxas DBO (demanda bioquímica de oxigénio) e DQO (demanda química de oxigénio) e consequentemente possíveis descargas. Ambos os sensores óticos e eletroquímicos foram propostos anteriormente, mas várias limitações ainda existem, principalmente na manutenção de uma estabilidade de longo prazo devido à degradação do sensor, bio-incrustação e custo. Filmes de polidimetilsiloxano (PDMS), dopado com Platina octaetilporfirina (PtOEP) são propostos nesta dissertação para a fabricação de um sensor ótico de oxigénio dissolvido. O PDMS tem ampla utilização na fabricação de dispositivos lab-on-chip e aplicações médicas. Possui um processo de fabricação simples, resultando em moldes confiáveis e facilmente replicáveis, utilizando técnicas de baixo custo. As suas excelentes propriedades mecânicas e químicas (alta permeabilidade ao oxigénio, características antibiofouling) resultam em membranas com sensibilidade superior em comparação com outros materiais de matriz. A PtOEP é amplamente utilizada em diversas aplicações tanto como sensor de oxigénio quanto como sensor de pressão, assim, o PtOEP é facilmente encontrado já sintetizado, sem a necessidade de procedimentos complicados. O fabrico nas membranas consiste na mistura de PtOEP num solvente adequado e posterior incorporação em PDMS resultando na formação de membranas luminescentes sensíveis ao oxigénio. É apresentada a influência da espessura do filme PDMS (0,1 − 2,5 mm) e da concentração (181, 363, 545, 727 ppm) nas propriedades luminescentes. No sensor proposto, a membrana é excitada por luz LED ultravioleta modulada de 385 nm, e a luminescência capturada por um fotodíodo filtrado de 647 nm e posteriormente processada por um amplificador de transimpedância. Dessa forma, é possível atingir baixos níveis de deteção, nomeadamente em meio gasoso é possível analisar numa gama de 0,5 − 20% de concentração e em meio líquido de 0,5 − 3,3 mg / L a 1 atm, 25 C. O presente documento propõe um sistema simples e de baixo custo baseado num sistema fotodíodo/LED para detetar baixas concentrações de oxigénio em aplicações situ.Planet Earth is known as the Blue Planet, due to the huge bodies of water it supports (about 70%), 3% of this volume is freshwater but only 0.06% of this small portion is available for human consumption. Over the last decade, scientific advances have been emphasizing the high relevance of conservation, protection, and monitoring of available water bodies to make life sustainable on Earth. Aquatic ecosystems are not static and immutable, their biological, chemical, and physical characteristics are altered not only by anthropic action (discharges, air pollution, agriculture, deforestation) but also by the natural conditions that influence the water cycle (erosion, minerals solubility, and chemicals naturally present in rock formations). In recent years, increasing demand for efficient and autonomous ways to monitor water quality has become evident, and precise water resource management platforms that allow the evaluation of the different properties of a volume of water to create statistical bases and means of prevention to correct any anomalies. However, political, economic, and social challenges are still an obstacle to technological advances. This is an area that involves several electronic adversities, such as the development of realtime systems, with low electrical consumption, high precision, and accuracy, but also difficulties related to biofouling, intervening of chemical species in measurements, among others. In short, it is a theme that challenges the area of electronic and computer engineering, chemistry, biology, and physics (hydraulics). Dissolved oxygen (DO) is one of the main parameters of water quality analysis, its study allows to deduce the aquatic photosynthetic rate [4], the animal stress rate in aquaculture tanks, aerobic and anaerobic processes, biochemical oxygen demand (BOD) rates, and dissolved oxygen concentration (DOC) and consequently possible discharges. Both optical and electrochemical sensors have been proposed previously, but several limitations still exist, mainly in maintaining long-term stability due to sensor degradation, biofouling, and cost. Platinum octaethylporphyrin (PtOEP) doped polydimethylsiloxane (PDMS) films are proposed here for the manufacture of an optical DO sensor. PDMS is used in the manufacture of lab-on-chip devices and medical applications. It has a simple manufacturing process, it takes place in qualified and easily replicable molds, using low-cost techniques. As its excellent mechanical and composite properties (high oxygen permeability, anti-biofouling characteristics) result in membranes with superior sensitivity compared to other matrix materials. A PtOEP is used in several applications both as an oxygen sensor and as a pressure sensor, thus, the PtOEP is easily found already synthesized, without the need for complicated procedures. The manufacture in the membranes consists of the mixture of PtOEP in a suitable solvent and later incorporation in PDMS obtaining in the formation of luminescent membranes sensitive to oxygen. The entry of the thickness of the PDMS film (0.1-2.5 mm) and the concentration (181,363,545,727 ppm) in the luminescent properties. In the proposed sensor, the membrane is excited by 385 nm ultraviolet modulated LED light, and the luminescence captured by a filtered photodiode of 647 nm and later processed by a transimpedance amplifier. Thus, it is possible to achieve low levels of detection, namely in a gaseous medium, it is possible to analyze the range of 0.5-20% concentration and in liquid medium of 0.5 -3.3 mg / L at 1 atm, 25 °C. This document proposes a simple and low-cost system based on a photodiode / LED system to detect application losses in situ applications.Este trabalho foi cofinanciado por fundos nacionais através da FCT - Fundação para a Ciência e Tecnologia, I.P. pelo Programa Operacional Regional do Norte (NORTE2020), por meio do Fundo Europeu de Desenvolvimento Regional (FEDER), Projeto NORTE-01-0145-FEDER-000032 - NextSea

Low cost, portable in-situ spectral analysis sensor for monitoring water contamination

Protecting water resources is essential for mitigating the impacts of global warming. Preserving hydrological basins and implementing sustainable practices in water use plays a critical role in maintaining natural ecosystems. In-situ sensors are a highly valuable tool for continuously monitoring these resources. They provide essential information that enables responsible authorities to act promptly and minimize the impact of any issues. We propose a sensor that aims to analyse water quality by detecting possible contaminations, considering variations in colour and turbidity. It consists of an optical transmission setup with eleven different excitation wavelengths ranging from 365 nm to 940 nm and a corresponding detection system. The system uses a GSM antenna to transmit realtime information and alarms to a big data server.This work is co-funded by the projects River2Ocean project (NORTE-01-0145- FEDER-000068), PLASTISENSOR (PTDC/EAM-OCE/6797/2020) and CMEMS - UIDB/04436/2020 and UIDP/04436/202