Development, physicochemical characterization, and optimization of self-powered electrochemical humidity sensor based on thin-film aluminum

Циљ дисертације је развој новог типа сензора влажности ваздуха. Развијени сензор има структуру интердигиталног кондензатора, израђеног од алуминијума, димензија реда величине 1 mm2 . Сензор је израђен фотолитографским процесом. Приказан је нови начин за активирање алуминијума, применом једносмерне струје. Оптичком и микроскопијом атомских сила су одређене морфолошке карактеристике структуре. Скенирајућом електронском микроскопијом са енергијски дисперзивном спектроскопијом верификована је геометрија структуре и извршена је елементна анализа. Рендгеноструктурном анализом је утврђено да алуминијум има поликристалну структуру. Инфрацрвеном спектроскопијом са Фуријеовом трансформацијом је утврђено да се приликом реакције формирају хидроксиди алуминијума. Извршен је и прорачун енергије адсорпције воде на алуминијуму. Електрохемијском импедансном спектроскопијом је одређено еквивалентно коло сензора. Показано је да се рад сензора заснива на корозији алуминијума. Електричним мерењима одређена је временска резолуција одзива сензора (време одзива је 10 ms, време опоравка је 55 ms). Показано је да је сигнал пропорционалан локалној влажности, у опсегу од 30 % - 70 %, уз температурску зависност. Закључено је да је зависност напона од температуре последица промене адсорпционе равнотеже. Показано је да је мерење релативне влажности ваздуха највероватније омогућено спрезањем радиофреквентних и електрохемијских сигнала. Приказани су начини мерења са бољим односом сигнал шум. Практична примена сензора приказана је у експерименту у којем је коришћен као уређај за праћење дисања. Најзначајнији допринос дисертације је развој самонапајајућег сензора влаге, односно уређаја који функционише без спољашњег напајања. Резултат дисертације је иновативан уређај, први пут публикован на светском нивоу.The aim of this dissertation is the development of a new type of humidity sensor. The sensor is designed as an interdigitated capacitor, made out of aluminum, dimensions are of the order of 1 mm2 . It was fabricated using a photolithographic process. A novel procedure for aluminum activation by applying direct current is presented. Morphological characteristics of the structure were revealed by optical and atomic force microscopy. By employing scanning electron microscopy with energy dispersive microscopy, geometry of the structure was verified and elemental analysis was performed. X-ray diffraction showed that aluminum has a polycrystalline structure. Fourier transform Infrared spectroscopy showed that aluminum hydroxides are formed during reaction. Adsorption energy was also calculated. The equivalent circuit of the sensor was revealed by electrochemical impedance spectroscopy. It was shown that working principle is based on corrosion of aluminum. The time response of the sensor was obtained by electrical measurements (response and recovery time were found to be 10 ms and 55 ms, respectively). It was shown that the response is proportional to the local humidity, in the range of 30 % to 70 % with temperature dependence. This dependence is a consequence of changes in the adsorption equilibrium. It was concluded that humidity measurement was provided by coupling RF and electrochemical signals. Measurement configurations for signal with a higher signal-to-noise ratio were presented. Practical application of sensor was demonstrated through its usage as human breath detection device. The most significant contribution is the development of a full self-powered humidity sensor. The result of the dissertation is a completely innovative device, published for the first time worldwide

Ultrafast humidity sensor based on liquid phase exfoliated graphene

Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation (LPE) followed by Langmuir-Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.Comment: 18 pages, 13 figure

Full-self-powered humidity sensor based on electrochemical aluminum–water reaction

A detailed examination of the principle of operation behind the functioning of the full-self-powered humidity sensor is presented. The sensor has been realized as a structure consisting of an interdigitated capacitor with aluminum thin-film digits. In this work, the details of its fabrication and activation are described in detail. The performed XRD, FTIR, SEM, AFM, and EIS analyses, as well as noise measurements, revealed that the dominant process of electricity generation is the electrochemical reaction between the sensor’s aluminum electrodes and the water from humid air in the presence of oxygen, which was the main goal of this work. The response of the sensor to human breath is also presented as a demonstration of its possible practical application

Aluminum-based self-powered hyper-fast miniaturized sensor for breath humidity detection

An aluminum-based, self-powered, miniaturized sensor for breath humidity detection is presented. The sensor is designed as an interdigitated capacitor made out of sputtered aluminum 1 % silicon (Al 1 %Si) thin film, 700 nm thickness, with digits 1.5 mm long, 0.01 mm wide and 0.01 mm clearance between them. The voltage on the open end of the sensor is generated when the surface is covered with a thin layer of water vapor, for instance if a person blows on it. The voltage generated is up to 1.5 V. The voltage generation is based on an electrochemical process of interaction between aluminum, water and oxygen from air, similar to the operation of an aluminum-air battery. The rise time of the signal during water vapor (or breath) detection is as small as 10 ms which makes it one of the fastest humidity sensors reported to date. The relaxation time is in the range of 50 ms. To make detection possible, the sensor surface needs to be activated by native oxide removal with the help of electric current and de-mineralized water droplet. Usability of the sensor was demonstrated in the detection of human breathing, where the sensor managed to follow the cycles of inhaling and exhaling.This is the peer-reviewed version of the article: Boskovic MV, Sarajlic M, Frantlovic M, Smiljanic MM, Randjelovic DV, Zobenica KC, Radovic DV, Aluminum-based self-powered hyper-fast miniaturized sensor for breath humidity detection, Sensors and Actuators: B. Chemical (2020), doi: [https://doi.org/10.1016/j.snb.2020.128635]Published version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3678

Raman study of Ba-doped ceria nanopowders

A series of Ce1-xBaxO2-y (5 LT = x LT = 0.20) nanometric powders were synthesized by self-propagating room temperature synthesis. XRD and Raman scattering measurements were used to characterize the samples. at room temperature. All the samples are solid solutions with fluorite type structure with an average crystallite size about 5 nm. The redshift and asymmetric broadening of the Raman F g mode can be well explained with combined confinement and strain effects because of the nanocrystalline powders nature. The appearance of the additional peaks at similar to 560 cm(-1) and similar to 600 cm(-1), are attributed to extrinsic and intrinsic O2- vacancies in ceria lattice. Raman spectra of temperature treated Ce0.80Ba0.20O2-delta sample revealed the instability of this system

Development of a MEMS Multisensor Chip for Aerodynamic Pressure Measurements

The existing instruments for aerodynamic pressure measurements are usually built around an array of discrete pressure sensors, placed in the same housing together with a few discrete temperature sensors. However, this approach is limiting, especially regarding miniaturization, sensor matching, and thermal coupling. In this work, we intend to overcome these limitations by proposing a novel MEMS multisensor chip, which has a monolithically integrated matrix of four piezoresistive MEMS pressure-sensing elements and two resistive temperature-sensing elements. After finishing the preliminary chip design, we performed computer simulations in order to assess its mechanical behavior when measured pressure is applied. Subsequently, the final chip design was completed, and the first batch was fabricated. The used technological processes included photolithography, thermal oxidation, diffusion, sputtering, micromachining (wet chemical etching), anodic bonding, and wafer dicing.The 10th International Electronic Conference on Sensors and Application

Development, physicochemical characterization, and optimization of self-powered electrochemical humidity sensor based on thin-film aluminum

Циљ дисертације је развој новог типа сензора влажности ваздуха. Развијени сензор има структуру интердигиталног кондензатора, израђеног од алуминијума, димензија реда величине 1 mm2 . Сензор је израђен фотолитографским процесом. Приказан је нови начин за активирање алуминијума, применом једносмерне струје. Оптичком и микроскопијом атомских сила су одређене морфолошке карактеристике структуре. Скенирајућом електронском микроскопијом са енергијски дисперзивном спектроскопијом верификована је геометрија структуре и извршена је елементна анализа. Рендгеноструктурном анализом је утврђено да алуминијум има поликристалну структуру. Инфрацрвеном спектроскопијом са Фуријеовом трансформацијом је утврђено да се приликом реакције формирају хидроксиди алуминијума. Извршен је и прорачун енергије адсорпције воде на алуминијуму. Електрохемијском импедансном спектроскопијом је одређено еквивалентно коло сензора. Показано је да се рад сензора заснива на корозији алуминијума. Електричним мерењима одређена је временска резолуција одзива сензора (време одзива је 10 ms, време опоравка је 55 ms). Показано је да је сигнал пропорционалан локалној влажности, у опсегу од 30 % - 70 %, уз температурску зависност. Закључено је да је зависност напона од температуре последица промене адсорпционе равнотеже. Показано је да је мерење релативне влажности ваздуха највероватније омогућено спрезањем радиофреквентних и електрохемијских сигнала. Приказани су начини мерења са бољим односом сигнал шум. Практична примена сензора приказана је у експерименту у којем је коришћен као уређај за праћење дисања. Најзначајнији допринос дисертације је развој самонапајајућег сензора влаге, односно уређаја који функционише без спољашњег напајања. Резултат дисертације је иновативан уређај, први пут публикован на светском нивоу.The aim of this dissertation is the development of a new type of humidity sensor. The sensor is designed as an interdigitated capacitor, made out of aluminum, dimensions are of the order of 1 mm2 . It was fabricated using a photolithographic process. A novel procedure for aluminum activation by applying direct current is presented. Morphological characteristics of the structure were revealed by optical and atomic force microscopy. By employing scanning electron microscopy with energy dispersive microscopy, geometry of the structure was verified and elemental analysis was performed. X-ray diffraction showed that aluminum has a polycrystalline structure. Fourier transform Infrared spectroscopy showed that aluminum hydroxides are formed during reaction. Adsorption energy was also calculated. The equivalent circuit of the sensor was revealed by electrochemical impedance spectroscopy. It was shown that working principle is based on corrosion of aluminum. The time response of the sensor was obtained by electrical measurements (response and recovery time were found to be 10 ms and 55 ms, respectively). It was shown that the response is proportional to the local humidity, in the range of 30 % to 70 % with temperature dependence. This dependence is a consequence of changes in the adsorption equilibrium. It was concluded that humidity measurement was provided by coupling RF and electrochemical signals. Measurement configurations for signal with a higher signal-to-noise ratio were presented. Practical application of sensor was demonstrated through its usage as human breath detection device. The most significant contribution is the development of a full self-powered humidity sensor. The result of the dissertation is a completely innovative device, published for the first time worldwide

Metoda za posmatranje i analizu protoka fluida u Si-Pyrex staklo opto-mikrofluidnim platformama

Ovo tehničko rešenje predstavlja razvoj metode za posmatranje i analizu protoka fluida u silicijum-Pyrex staklo opto-mikrofluidnim platformama. Metoda se zasniva na snimanju video zapisa pomoću metalografskog mikroskopa sa digitalnom kamerom dok se špric pumpama (syringe pump) definisano zadaje protok fluida kroz izrađenu platformu. Platforma se sastoji od mikrokanala koji su izrađeni procesima mikromašinstva, odnosno vlažnog hemijskog nagrizanja, i anodnog bondovanja silicijuma i Pyrex stakla. Kroz staklo platforme se posmatraju i snimaju protoci različitih fluida sa ili bez čestica u mikrokanalima. Mikrokanali mogu biti različitog dizajna i definisani u silicijumu i/ili Pyrex staklu. Validacija funkcije izrađene platforme (mikromiksera ili separatora čestica) vrši se analizom fotografija ili frejmova video zapisa pomoću odgovarajućih softverskih paketa, na primer ImageJ

Synthesis and characterization of the nanometric Pr-doped ceria

In this paper nanometric powders of solid solution of the host compound ceria (CeO(2)) with Pr dopant in the lattice were synthesized by self-propagating room temperature (SPRT) synthesis with composition (Ce(0.9)Pr(0.1)O(2-delta)). Powder properties such as specific surface area crystallite and particle size and lattice parameters have been studied. BET, TEM, X-ray diffraction (XRD) analysis and Raman scattering measurements were used to characterize the samples at room temperature. Obtained solid solution exhibits a fluorite-type crystal structure. The average crystallite size is about 3-4 nm. Williamson-Hall plots were used to separate the effect of the size and strain in the nanocrystals. It is noticed the redshift and asymmetric broadening of the Raman F(2g) mode which is explained with nanocrystalline nature of powders. Color characters of solid solution depending on calcinations temperature and their position in the chromaticity diagram were studied by UV-vis spectrophotometry (diffuse reflectance). (C) 2010 Elsevier B.V. All rights reserved

Self-Powered Wearable Breath-Monitoring Sensor Enabled by Electromagnetic Harvesting Based on Nano-Structured Electrochemically Active Aluminum

Self-powered sensors are gaining a lot of attention in recent years due to their possible application in the Internet of Things, medical implants and wireless and wearable devices. Human breath detection has applications in diagnostics, medical therapy and metabolism monitoring. One possible approach for breath monitoring is detecting the humidity in exhaled air. Here, we present an extremely sensitive, self-powered sensor for breath humidity monitoring. As a power source, the sensor uses electromagnetic energy harvested from the environment. Even electromagnetic energy harvested from the human body is enough for the operation of this sensor. The signal obtained using the human body as a source was up to 100 mV with an estimated power of 1 nW. The relatively low amount of energy that could be harvested in this way was producing a signal that was modulated by an interdigitated capacitor made out of electrochemically activated aluminum. The signal obtained in this way was rectified by a set of Schottky diodes and measured by a voltmeter. The sensor was capable of following a variety of different respiration patterns during normal breathing, exercise and rest, at the same time powered only by electromagnetic energy harvested from the human body. Everything happened in the normal environment used for everyday work and life, without any additional sources, and at a safe level of electromagnetic radiation