In recent decades the development of technologies capable to offer highly localized and precise temperature control has received increasing attention due to their relevance and applicability in numerous engineering fields. Multiple scientific papers have been written that focus on the enhancement of the performance of thermoelectric materials and micro-devices.
This Ph.D. thesis in the field of Mechanical Engineering pursues three main research goals regarding electrothermal phenomena: (1) To provide an optimization design strategy for micro-thermoelectric coolers by analyzing the interplay between electrical and thermal fluxes during device operation. (2) To analyze the suitability of a device, based on micro-thermoelectric coolers, for controlling the thermal environment in microbiological systems. (3) To develop an experimental technique, based on optical pump-probe thermal imaging, to extract the thermal conductivity anisotropy of thin films. For this purpose, numerical simulations and experiments were carried out.
The results show, that the design of micro-thermoelectric devices must take into account the impact of parameters that are typically neglected in the construction of macro scale devices. Poorly designed parameters, such as the metallic contacts, the distance between thermoelectric elements and their interaction with the substrate, carry severe reductions of the performance of micro-thermoelectric devices. It is demonstrated that the optimal performance is achieved when the thermoelectric legs are properly dimensioned, so that a balance of the Fourier and Joule fluxes is reached.
Numerical analyses prove that micro-thermoelectric coolers offer a feasible alternative to overcome the current spatial and temperature limitations of conventional technologies and therefore enable to investigate the thermal environment of biological systems at the micro-scale. Guidelines for the implementation of the experimental platform are provided.
The evaluation of the numerical and experimental data proves that optical pump-probe thermal imaging is suitable to characterize both the in-plane and the through-plane thermal conductivity of thin films. The experimental conditions to extract the anisotropy of the sample under study are determined.
The outcome of this work yields new insights into electrothermal phenomena at the micro-scale and thus creates new routes in the design, fabrication and characterization of micro- thermoelectric materials and devices.:Acknowledgements IV
Erklärung der Urheberschaft VI
Summary VII
Zusammenfassung VIII
Table of content IX
List of figures XI
List of tables XIV
Abbreviations and symbols XV
1 Introduction 1
1.1 Motivation 1
1.2 Outline of the thesis 4
1.2.1 Chapter 2 - Fundamentals 4
1.2.2 Chapter 3 - Design guidelines of micro-thermoelectric coolers 4
1.2.3 Chapter 4 - Development of a platform for biological systems experimentation 4
1.2.4 Chapter 5 - Development of a technique for thermal transport characterization in thin films 5
1.2.5 Chapter 6 - Main conclusion and future research 5
1.3 Main research objectives 5
2 Fundamentals 7
2.1 Thermoelectric phenomena 7
2.2 Performance estimation of micro-thermoelectric coolers 10
2.3 Finite element modelling 12
2.3.1 Introduction to finite element modelling 12
2.3.2 Finite element modelling of thermoelectric phenomena 17
2.4 Thermoreflectance imaging microscopy 19
3 Design guidelines of micro-thermoelectric coolers 26
3.1 Introduction 26
3.2 Micro-thermoelectric coolers: an alternative for thermal management 28
3.3 Analysis approach 29
3.3.1 Input current optimization 31
3.3.2 Metallic contacts 32
3.3.3 Leg pair geometry 35
3.3.4 Fill factor 38
3.3.5 Experimental characterization of µTECs 41
3.4 Summary 44
4 Development of a platform for biological systems experimentation 46
4.1 Introduction 46
4.2 Thermal analysis on biological systems 48
4.3 Platform conceptual proposal 50
4.4 Analysis approach 52
4.4.1 Input current optimization 52
4.4.2 Fill material 54
4.4.3 Thermotaxis 55
4.4.4 Top material 56
4.4.5 Cold spot optimization 58
4.5 Experimental platform construction 59
4.6 Summary 62
5 Development of a technique for thermal transport characterization in thin films 64
5.1 Introduction 64
5.2 Thermal anisotropy characterization in thin films 65
5.3 Experimental apparatus 66
5.4 Experimental measurements 69
5.5 Analysis approach 72
5.5.1 Thermal conductivity anisotropy analysis 76
5.5.2 Effect of the laser power on the temperature distribution 79
5.5.3 Enhancement of the system sensitivity 80
5.6 Summary 83
6 Main conclusion and future research 85
6.1 Main conclusion 85
6.2 Outlook 88
7 References 89
8 Scientific output 97
8.1 Publications in peer review journals 97
8.2 Selected conference abstracts 98
9 Curriculum vitae 99
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:74206 |
| Date | 19 March 2021 |
| Creators | Lara Ramos, David Alberto |
| Contributors | Nielsch, Kornelius, Beitelschmidt, Michael, Woias, Peter, Schierning, Gabi, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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