京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21783号 / 工博第4600号 / 新制||工||1717(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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The convergence of the digital and physical world encourages advances in high-speed telecommunication and fifth generation technology. Two-phase heat transfer systems are common engineering solutions. However, due to the large frequency spectra in 5G, the systematic heat generation increases requiring more efficient thermal management. The surface characteristics of solid materials in these systems is vital making micro-architectured materials a novel pathway to improve heat transfer. The coefficient of thermal expansion and thermal conductivity of the Schoen-Gyroid, a triply periodic minimal surface structure is studied along with a classical cylindrical porous structure. Graphite and graphene are considered as materials with excellent thermal and mechanical properties and are thus the base materials considered in this project. A comprehensive manufacturability study was conducted in order to gain knowledge regarding different graphite/graphene options and it was concluded that commercially available isotropic graphite was the best suited material for the purpose of this project. A decoupled thermo-mechanical analysis of the coefficient of thermal expansion and thermal conductivity of said structures as a function of volume fraction was conducted using computational homogenization with finite element analysis. A linearly elastic constitutive material model in COMSOL Multiphysics was used. As expected, the homogenized effective material is governed by linear constitutive model. Moreover, the results displayed a linear dependency on the porosity for both the CTE and thermal conductivity. The mechanical FEM model was validated using an analytical model derived by Gibson and Ashby and the thermal conductivity FEM model was validated using experimental data.

Compared to other instruments for chemical analyses, electrochemical analyzers are relatively simple, inexpensive, easy to miniaturize and require little-to-no maintenance. However, like all commercially available instruments, commercial electrochemical analyzers like potentiostats primarily operate as black boxes with manufacturers providing little or no information about internal circuitry and programming. This practice can limit a researcher’s ability to develop new techniques or adapt an instrument for applications outside its typical use. In contrast, creators of open-source instruments release all the necessary information for reproduction of the hardware and software – minimizing such barriers to innovation in chemical analyses. Here, we report a low-cost, compact potentiostat based on an open-source Arduino microcontroller capable of performing electrochemical analyses such as cyclic and linear sweep voltammetry with an operating range of ± 208 𝜇A and ± 2.5 V. Performance of the potentiostat is investigated with low-cost pencil graphite electrodes and compared to a commercial potentiostat.

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No description available.

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Electrochemical measurements are utilized in various fields, including healthcare (e.g., potentiometric measurements for electrolytes in blood and blood gas, amperometric biosensing of glucose as in blood glucose meters), water quality (e.g., pH measurement, voltammetric analyses for heavy metals), and energy. Much of the appeal of electrochemical analyses can be attributed to the relative simplicity, low cost and lack of maintenance associated with electrochemical instruments, along with techniques that can exhibit high sensitivity and selectivity, wide linear dynamic range, and low limits of detection for many analytes. While commercial electrochemical analyzers are less expensive than many other instruments for chemical analyses and are available from various manufacturers, versatility and performance often coincide with added expense. Recently, the development of low-cost, adaptable, open-source chemical instruments, including electrochemical analyzers, has emerged as a topic of great interest in the scientific community. In contrast to commercial instruments, for which schematics and underlying operation details are often obscured – severely limiting modifications and improvements, creators of open-source instruments release all the necessary information for reproduction of the hardware and software. As a result, open-source instruments not only serve as excellent teaching tools for novices to gain experience in electronics and programming, but also present opportunity to design and develop low-cost, portable instruments, which have particular significance for point-of-care sensing applications, use in resource-limited settings, and the rapidly developing field of on-body sensors. In this work, we report the design of a low-cost, compact electrochemical analyzer based on an open-source Arduino microcontroller. The instrument is capable of performing electrochemical analyses such as cyclic and linear sweep voltammetry with an operating range of ± 138 ��A and ± 1.65 V. Performance of the platform is investigated with low-cost pencil graphite electrodes and results compared to commercial potentiostats.

Abstract Electrochemical sensors are simple, fast, accurate, and low-cost analytical devices. They are especially important to the field of healthcare since they enable measurement of important indicators of patient health such as electrolytes and glucose in blood. Continued development and improvements in electrochemical sensors can result in more accessible, affordable, and effective diagnoses and treatment strategies. Electrochemical sensors employ electrodes, usually modified with a recognition agent specific for the analyte (the biomolecule of interest). The presence of the analyte at the electrode surface is typically measured through an electrochemical reaction that generates a signal in the form of an electric current or difference in electric potential. As an alternative, electrochemiluminescence, a phenomenon whereby an electrochemical reaction generates a product in an electronically excited state that is capable of emitting light, has great benefits due to its high sensitivity, selectivity, and extremely low background signal. Here we employ a camera equipped with a complementary metal-oxide semiconductor (CMOS) detector that is interfaced with a simple zoom lens to measure ECL generated at low-cost pencil graphite electrodes and small electrode arrays using tris(2,2′- bipyridyl) dichlororuthenium(II) hexahydrate ([Ru(bpy)3]2+) with tri-n-propylamine (TPA) as the coreactant. ECL signals produced at pencil graphite working electrodes were linear with respect to [Ru(bpy)3]2+ concentrations for 45–450μM [Ru(bpy)3]2+. The detection limit was found to be 2µM using the CMOS camera with exposure time set at 10s. This proof-of-concept work suggests the pencil graphite electrode with simple imaging system platform can be applied for ECL-based biosensing strategies.