Surface and Structural Engineering of Ionovoltaic Device for Energy Harvesting and Sensing Applications

학위논문 (박사)-- 서울대학교 대학원 : 융합과학기술대학원 융합과학부(나노융합전공), 2019. 2. 김연상.최근 Ionovoltaic 변환기라 명명된, 액체와 고체 표면의 접촉에서 전기가 발생하는 현상을 이용한 전기 변환 장치에 관한 연구가 많은 관심을 받고 있다. 신재생 친환경 에너지 발전 장치에 관한 필요성이 커지고 수용액 기반에서 능동적으로 작동 할 수 있는 다양한 센서에 관한 요구가 꾸준히 증가하는 가운데, ionovoltaic 소자는 이러한 요구를 충족 시킬 수 있는 능동형 장치로서 주목받고 있다. 하지만 ionovoltaic 소자를 에너지 발전 소자와 능동적 센서로 실질적 활용과 적용을 하기에는 출력 에너지 밀도가 낮고, 공정이 복잡하다. 더욱이 충분히 밝혀지지 않은 소자의 구동 원리와 소자의 획일적인 재료 및 구조 연구는 소자의 다양한 활용 발전을 가로막고 있다. 여기, 이 학위 연구는 ionovoltaic 장치의 (i) 표면 개질과 (ii) 구조 공정 개선, 두 가지 연구를 통해 계면에서의 이온거동에 의한 전기 발생 현상을 보다 명확히 밝히며 이를 통해 센서와 에너지 수확장치로서의 폭 넓은 활용을 다룬다. 첫째, 기존에 사용되었던 불소 기반의 획일적인 소수성 표면 물질을 벗어나 표면 개질을 통한 새로운 전기적 특성을 갖는 소수성 표면 공정을 ionovoltaic 전환 소자에 적용하여 액체와 고체 계면에서의 이온 거동을 이용한 다양한 센싱 어플리케이션에 적용하였다. 음의 표면전위를 갖는 소수성 표면의 변환기와 양의 표면전위를 갖는 소수성 표면의 변환기를 개발하여 비교 분석 하였으며 이온 거동에 의한 전기신호 반전 효과를 처음으로 확인 하였다. 뿐만 아니라, 산, 염기에 민감한 표면 특성을 활용하여 pH 센서 및 요소(urea) 센서로서 활용성을 검증하였다. 둘째, 기존에 사용되었던 2 전극 시스템의 획일적인 소자의 구조를 탈피하고 새로운 형태의 소자 구조 공정을 통해 액체와 고체 표면의 접촉이 전기신호로 변환되는 원리 파악과 센싱 및 에너지 수확장치로서의 적용 가능성을 제시하였다. 소자의 전체적인 구조 공정과 전극 연구를 통해서 전기 신호의 발생 지속시간을 조절 할 수 있었으며 에너지밀도를 높일 수 있었다. 뿐만 아니라 투명하면서도 전기를 발생시킬 수 있는 고저항 ITO 전극 개발을 통해 건물이나 자동차의 외관 및 창문에 활용 될 수 있는 에너지 수확장치를 개발하여 ionovoltaic 장치의 폭넓은 활용가능성을 제시하였다.Recently, there has been a lot of interest in the research on the transducers using the phenomenon of electricity generation in the contact between the liquid and solid surface. In particular, transducers using EDL (electrical double layer) modulations, which named as ionovoltaic transducers are attracting attention because of their advantages in eco-friendly, simple drive systems and self-powered characteristics. With the growing need for renewable and eco-friendly energy generation devices and the increasing demand for a variety of sensors that can actively operate on an aqueous solution basis, the ionovoltaic devices can be utilized as a great candidate to solve these demands. However, the output energy density is low and the fabrication process is complicated to make practical use of the ionovoltaic device as the energy generating device and the active sensors. Moreover, the driving principle of the device which is not sufficiently clarified and the similar materials and structures research of the device are obstructing the various utilization development of the device. In this thesis clarifies the generation of electricity by the ionic behavior at the interface through two issues: (i) surface modification of ionovoltaic device and (ii) improvement of ionovoltaic device performance through the structural engineering. In addition, this study covers a wide range of applications as sensors and energy harvesting devices. First, applying a hydrophobic surface modification with novel electrical properties to the ionovoltaic device by engineering the hydrophobic layer, and applying it to various sensing applications using ionic behaviors at the solid-liquid interface. The ionovoltaic transducers with a negative / a positive surface potentials were developed and compared, and the effect of reversing the electrical signal by ionic behavior was confirmed for the first time. In addition, the modified ionovoltaic transducer has proven its applicability as a pH sensor and urea (bio)sensor by utilizing a pH-sensitive surface. Secondly, we identified the principle that the contact between the liquid and the solid surface is converted into the electric signal through the new type of device through the structural engineering and to apply it as the sensing and energy harvesting device. In addition, through electrode studies, we have understood the conduction mechanism and investigated the effect of resistance on ionovoltaic device performance. Through the whole structural engineering of the ionovoltaic device and the electrode modification, it was possible to control the generation time of the electric signal and to increase the energy density. Moreover, we have developed an energy harvester that can be used for the exterior and windows of buildings or automobiles through the development of high-resistance ITO mono- electrodes using the sputtering system, suggesting wide application possibilities of ionovoltaic devices.List of figures 9 Chapter 1 Introduction 16 1.1 Overview 16 1.2 Reference 19 Chapter 2 Fundamental and Literature Review 20 2.1 Working mechanism of ionovoltaic device 20 2.2 Components of ionovoltaic device 23 2.2.1. Surface of ionovoltaic devices 26 2.2.2. Structure of Ionovoltaic devices 29 2.4 References 31 Chapter 3 Surface Modification of Ionovoltaic Device and Applications 32 3.1 Introduction 32 3.2 Fabrication of pH-sensitive surface 34 3.3 Device performances and working mechanism 37 3.4 Application of ionovoltaic device as a pH sensor 48 3.4.1 pH sensing device performance and working principle 48 3.5 Application of ionovoltaic device as a urea detector 54 3.5.1 Fabrication method 55 3.5.2 Device performance and working mechanism 58 3.5.3 Possibility of ionovoltaic urea detector as a biosensor 72 3.6 Conclusion 74 3.6 Experimental details 76 3.7. Reference 79 Chapter 4 Structural Engineering of Ionovoltaic Device and Applications 85 4.1 Introduction 85 4.2 Fluidic ionovoltaic device 85 4.2.1 Fabrication method and device performance 87 4.2.2 Application of ionovoltaic device as an air-slug sensor 96 4.3 ITO mono-electrode based ionovoltaic device 100 4.3.1 Fabrication of ITO mono-electrode and ionovoltaic device 103 4.3.2 Influence of sputtering parameters on a characteristics of ITO mono-electrode based ionovoltaic device. 106 4.3.3 Application and advantages of ITO based ionovoltaic device 116 4.4 Conclusion 118 4.5 Experimental details 119 4.6 References 122 Chapter. 5 Conclusion 129 List of publications 132 요 약 (국문초록) 134Docto

Laser-Induced Carbonisation for Biosensing

Das Internet of Things hat das Ziel, ein globales Netz von Geräten zur Überwachung einer Vielzahl von Parametern aufzubauen, um z.B. Gefahren in verschiedenen Bereichen vorzubeugen und Risiken für Menschenleben, Infrastrukturen und die Umwelt zu verringern. Zu den am schnellsten wachsenden Themen in diesem sich entwickelnden Bereich gehören biomedizinische Point-of-Care-Geräte, die rechtzeitig Hilfe für Menschen leisten, die sich in einer persönlichen oder externen Gefahr befinden. Sie werden in Form von Sensorfeldern entwickelt, die hauptsächlich aus flexibler Elektronik bestehen und in der Lage sind, spezielle Analyten zu erkennen. Diese neuen Geräte sollten die folgenden Kriterien erfüllen: Sie sollten einfach herzustellen und wirtschaftlich umsetztbar sein und einen geringen ökologischen Fußabdruck aufweisen. Von der Vielzahl der entwickelten Sensoren zeichnen sich die kohlenstoffbasierten Geräte durch ihre Robustheit, hohe Biokompatibilität, hervorragende Reaktionseffizienz und chemische Inertheit aus. Die neuartige Herstellungsmethode, die durch die laserinduzierte Karbonisierung von Polymervorläufern ermöglicht wird, erlaubt im Vergleich zu pyrolytischen Standardmethoden eine schnelle Herstellung von kohlenstoffreichen porösen Filmen, die direkt in flexible Substrate eingebaut werden, und erfüllt alle gesetzten Ziele. Dieses neuartige Material, das mit halbindustriellen Lasersystemen hergestellt wird, ist noch relativ unerforscht. Diese hier durchgeführte Untersuchung wird an zwei weit verbreiteten Polymervorläufern umgesetzt, die in industriellen Anwendungen verwendet werden, nämlich Kapton und Nomex. Das thermische Modell für die Karbonisierung und Entwicklung des Vorläufers wurde modifiziert und auf einen breiten Bereich der getesteten Lasereingangsparameter angewendet. Die wichtigsten Erkenntnisse über die Entwicklung des Laserkohlenstofffilms stimmen mit den simulierten Ergebnissen überein. Das Modell liefert eine gute Annäherung an die Karbonisierung, erfordert aber noch Verbesserungen bei der Darstellung der volumetrischen Parameter, die durch den Anstieg der Porosität beeinflusst werden. Die Laser-Kohlenstoff-Filme wurden auf ihre kristallinen und oberflächenchemischen Eigenschaften hin untersucht, die sich für die Analyse von Grenzflächen eignen und mit nachvollziehbaren Methoden für den selektiven Nachweis der spezifischen Analyten eingestellt werden können. Auf diese Weise wurden biomedizinische Sensoren für den passiven Nachweis von Harnstoff über eine Chitosan-Zwischenschicht für das Enzym Urease und aktive nicht-enzymatische Sensoren, die über ein Cu/CuO-Komposit für den spezifischen Nachweis von Glukose verankert sind, entwickelt. Dies ebnet den Weg für die Herstellung abgestimmter Biosensoren und chemischer Sensoren in einem halbindustriellen Maßstab, der mit Rolle-zu-Rolle-Verfahren kompatibel ist

Biosensors

A biosensor is defined as a detecting device that combines a transducer with a biologically sensitive and selective component. When a specific target molecule interacts with the biological component, a signal is produced, at transducer level, proportional to the concentration of the substance. Therefore biosensors can measure compounds present in the environment, chemical processes, food and human body at low cost if compared with traditional analytical techniques. This book covers a wide range of aspects and issues related to biosensor technology, bringing together researchers from 11 different countries. The book consists of 16 chapters written by 53 authors. The first four chapters describe several aspects of nanotechnology applied to biosensors. The subsequent section, including three chapters, is devoted to biosensor applications in the fields of drug discovery, diagnostics and bacteria detection. The principles behind optical biosensors and some of their application are discussed in chapters from 8 to 11. The last five chapters treat of microelectronics, interfacing circuits, signal transmission, biotelemetry and algorithms applied to biosensing

Investigation of light-addressable potentiometric sensors for electrochemical imaging based on different semiconductor substrates

PhDLight-addressable potentiometric sensors (LAPS) and scanning photo-induced impedance microscopy (SPIM) have been extensively applied as chemical sensors and biosensors. This thesis focuses on the investigation of LAPS and SPIM for electrochemical imaging based on two different semiconductor substrates, silicon on sapphire (SOS) and indium tin oxide (ITO) coated glass. Firstly, SOS substrates were modified with 1,8-nonadiyne self-assembled organic monolayers (SAMs), which served as the insulator. The resultant alkyne terminals provided a platform for the further functionalization of the sensor substrate with various chemicals and biomolecules by Cu(I)-catalyzed azide alkyne cycloaddition (CuAAC) ‘click’ reactions. The CuAAC reaction combined with microcontact printing (μCP) was successfully used to create chemical patterns on alkyne-terminated SOS substrates. The patterned monolayers were found to be contaminated with the copper catalyst used in the click reaction as visualized by LAPS and SPIM. Different strategies for avoiding copper contamination were tested. Only cleaning of the silicon surfaces with an ethylenediaminetetraacetic acid tetrasodium salt (EDTA) solution containing trifluoroacetic acid after the ‘click’ modification proved to be an effective method as confirmed by LAPS and SPIM results, which allowed, for the first time, the impedance of an organic monolayer to be imaged. Furthermore, the 1,8-nonadiyne modified SOS substrate was functionalized and patterned with an RGD containing peptide, which was used to improve the biocompatibility of the substrate and cell adhesion. By seeding cells on the peptide patterned sensor substrate, cell patterning was achieved. Single cell imaging using LAPS and SPIM was attempted on the RGD containing peptide modified SOS substrate Finally, an ITO coated glass substrate was used as a LAPS substrate for the first time. The photocurrent response, the pH response, LAPS and SPIM imaging and its lateral resolution using ITO coated glass without any modification were investigated. Importantly, single cell images were obtained with this ITO-based LAPS systemChina Scholarship Council and Queen Mary University of Londo

Microreactor system with immobilized enzyme on polydimethylsiloxane (PDMS) polymers

Microsystems, specifically microreactors, open the gate to new, improved analytical techniques while offering many advantages for a large number of applications in chemical engineering, pharmacy, medicine, and biotechnology. This study explored the feasibility of fabrication of microreactors using polydimethylsiloxane (PDMS) as a support for enzyme immobilization. Urease enzyme was used for catalyzing the conversion of urea to ammonia. PDMS (polydimethylsiloxane) is a silicone-based elastomeric polymer. Traditional micromanufacturing technology was employed for reactor mold fabrication. The mold was fabricated based on photolithography techniques, and SU-8 photoresist was used to construct reactor structure templates. The resulting silicon-wafer based reactor molds were then used repeatedly to generate PDMS microreactors. One advantage of using an immobilized enzyme system is that the bio-catalyst is retained within the reactor system and enables high concentrations to be maintained. Two enzyme immobilization methods were explored for use with PDMS microreactor systems. One used CMC (1-cyclohexyl-3-(2-morpholineoeethyl) carbodiimide metho-p-tolunensulfonate) as a crosslinker for covalently binding the enzyme to the PDMS microreactor surface. The other employed directly incorporating the enzyme into the uncured polymer. The latter method provided a higher urease activity and was used for most microreactor studies. To allow an examination of reactor path length, two different reactor templates were applied for evaluation: straight- and wave-channel microreactors. The reactors were tested with different enzyme loadings, feed flowrates, channel lengths, and different operation environments. The wave-channel reactors exhibited considerably high urea conversions at relatively higher flowrates compared with the straight-channel reactors. Urea conversion was about 90% in wave-channel reactor with 0.001 ml/min flowrate and 0.01 g/g PDMS urease loading, whereas for straight-channel reactor, it is only about 10% urea conversion. A mathematical model was developed for the microreactors tested. The predicted results were consistent with the experiment results for the straight-charnel reactors with short-channels. For the wave-channel reactors, the model showed large deviation from experimented results. The longer the channel length, the greater the deviation. Several assumptions were considered to account for the deviations: channel structure, ammonium ion inhibition, and reactive surface estimation

Nanostructured Metal Oxide-Based Microfluidic Biosensors for Point-of-Care Diagnostics

The potential research on microfluidic devices for detection of biomolecules has recently intensified due to its application in point-of-care (POC) diagnostics for global health care. Early detection plays an imperative role to determine predisposition to disease (prevention) or the outcome of disease (monitoring and prognosis). There is a significant need for POC diagnostics devices as perceived from biohazard threats, the spread of infectious disease, home testing and monitoring. The POC diagnostics can provide a convenient and immediate response to a patient test sample. The POC diagnostics can be attained via use of transportable, portable, and handheld instruments such as blood glucometer, cholesterol meter etc. and test kits. It includes testing of blood or urine for pathogens, glucose, cholesterol, blood gas, coagulation, biomarkers, hemoglobin, pregnancy etc. Cheaper, smaller, faster, and smarter devices are the main merits of POC diagnostics for detection of various target analytes. A number of clinical biochemical studies such as blood gas, glucose/lactate/cholesterol, nucleic acid sequence analysis, proteins/peptides, combinatorial synthesis, toxicity monitoring, immunoassays, and forensic analysis are also focused areas for developing microfluidic biochips

Advanced Electrochemical Biosensors

With the progress of nanoscience and biotechnology, advanced electrochemical biosensors have been widely investigated for various application fields. Such electrochemical sensors are well suited to miniaturization and integration for portable devices and parallel processing chips. Therefore, advanced electrochemical biosensors can open a new era in health care, drug discovery, and environmental monitoring. This Special Issue serves the need to promote exploratory research and development on emerging electrochemical biosensor technologies while aiming to reflect on the current state of research in this emerging field

Investigation of ZnO nanorods as chemical and biological sensors

PhD thesisZinc oxide (ZnO) is a metal-oxide semiconductor with a direct wide band gap and high exciton binding energy at room temperature. It has been applied to many applications such as solar cells, light emitting diodes, nano-generators and chemical sensors. In this thesis, a solution phase synthesis method has been used to produce ZnO nanorods on conductive substrates at low cost. By controlling the growth conditions, ZnO nanorods with an aspect ratio of 51 in a single step was achieved. The morphology, crystallisation, optical properties, band structures and carrier lifetime were analysed. Chemical sensors such as gas sensors play a very important role in our life and in industry. ZnO nanorods have been investigated as a sensing material to detect harmful gases such as NO2 and NH3. However, such a traditional sensing platform only works at high operating temperatures, which limits its application to portable devices or wireless devices. In order to decrease the working temperature, a Schottky diode was assembled by evaporating a gold layer on the top of the ZnO nanorods. Gas sensing results showed that this diode had good responses to NH3 gas at room temperature. It also displayed high selectivity to NH3 over acetone, CO2, CO and ethanol. Long-term tests demonstrated good stability over 7-weeks. ZnO nanorods are also a suitable sensing material for light-addressable potentiometric sensors (LAPS) that are designed to detect pH, redox ions and characterise cells and tissue. In contrast to the traditional electrolyte-insulator-semiconductor (EIS) structures, ZnO nanorods without an insulator were applied in LAPS and showed a spatial resolution of 3 μm. LAPS based on ZnO nanorods were used as a disposable biosensor for the detection of α-chymotrypsin. The effect of the ZnO morphology on the spatial resolution was also investigatedChina Scholarship CouncilQueen Mary University of Londo

“Enhancement of Sensitivity and Selectivity of Chemical Sensors Through Thin Film Coatings and Surface Modifications

Chemical sensors have become major analytical tools for how we monitorand obtain information about the chemical nature of ourselves and oursurroundings. Two characteristics of chemical sensors that are under constantdevelopment and improvement are their selectivity and their sensitivity.Selectivity is a concern of any chemical sensor, without it the signal obtained bya chemical sensor cannot be related to the target species concentration with anyconfidence. With chemical sensors the selectivity is generally created by theused of a chemical recognition layer such as a permeable membrane, or a thinchemical film. The sensitivity of a chemical sensor is a concern, as with anyquantitative analytical method, so that small differences in analyte concentrationare distinguishable and trace analysis can be performed. In this work theselectivity and sensitivity of two distinctly different devices used as chemicalsensors are investigated. The first device combines a scintillation fiber with aselective polymer coating to create a chemical sensor selective for 137Cs. Boththe selectivity and sensitivity of the scintillation fiber are improved with theaddition of the chemical recognition layer. The second device investigated is amicrocantilever sensor. Microcantilevers have been used to monitor chemicalspresent in both air and liquid environments. However, in moving frommeasurements made in air to measurements made in liquids, a great deal ofsensitivity is lost due to differences in the interfacial energies of thevmicrocantilevers in these two different environments. To overcome this limitationsurface modification of the microcantilevers was investigated to improve thesensitivity of these devices. Surfaces of the microcantilevers were modified byseveral different methods, the binding of gold nanobeads to the surface, creationof a roughened dealloyed surface, and the physical milling and chemical etchingof grooves into the surface of the microcantilevers, each of these surfacemodifications was shown to enhance the sensitivity of microcantilever chemicalsenors over microcantilever chemical sensors with smooth surfaces