C - DTU Nanotech - Danmarks Tekniske Universitet

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22 3 Theoretical Considerations of Polymers for Bio-Microsystems 100µm 200µm Figure 3.5: Profile of a channel made by a CNC milling machine (the picture has been made by F. Bundgaard (MIC) using a scanning electron microscope)
4 Basic Principles of a Peltier Element In this Chapter the basic principles of Peltier cooling are illustrated. Peltier found in 1834 that, when an electric current passes through the junction between two different conductors, there is a heating or cooling effect, depending on the direction of the current [12]. The inversion of the Peltier effect is the Seebeck effect, that has been discovered in 1821: In an electric circuit of two different conductors and a temperature difference in the junction between them a voltage occurs at the opening of the circuit in one of the conductors [3]. Thus the Peltier effect is the basis of the thermoelectric refrigerator just as the Seebeck effect forms the basis of the thermoelectric generator [9, 12]. The basic principle of Peltier cooling is the transformation of electrical energy into thermal energy according to the following equation [25]: WP = ΠABIt (4.1) WP = Amount of heat ΠAB = Peltier coefficient I = Current t = Time For the Peltier effect, free movable electrons, which are not linked with atoms, and bonds lacking electrons are very important. Bonds lacking electrons behave like positive charged particles and are called holes. Holes are also free to move in a crystal. To built a ther- mocouple using the Peltier effect, a material with electrons and one with holes has to be connected via an electrical junction. Electrons and holes both carry positive kinetic energy. Energy is transported from a hole current in the same direction as the current, while an electron current will transport energy in the opposite direction to the current. By adjusting the polarity and type of current, heat can be transported to or from one side of a junction [22]. The Peltier coefficient ΠAB (for two materials A and B forming the junction) relates the current flux to the heat flux per junction. ΠAB is approximated for narrow temperature ranges by [22]: ΠAB ≈ (αA − αB)T (4.2) 23
Page 1: Danmarks Tekniske Universitet Insti
Page 5: Zusammenfassung Diese Arbeit besch
Page 8 and 9: 8 Contents 6 Development of a Bio-M
Page 10 and 11: 10 Nomenclature COC Cyclo-olefin co
Page 12 and 13: 12 1 Introduction sampling system w
Page 14 and 15: 14 2 Overview of Small-Scale Cultiv
Page 17 and 18: 3 Theoretical Considerations of Pol
Page 19 and 20: 100µm 3.2 Topas R○ and the CNC m
Page 21: 3.2 Topas R○ and the CNC micromil
Page 25: p-semiconductor p-semiconductor 4 B
Page 28 and 29: 28 5 Freezing Different Samples usi
Page 42 and 43: 42 6 Development of a Bio-Microreac
Page 64 and 65: 64 7 Concluding Remarks Reactor cha
Page 67 and 68: Appendix Freezing experiments with
Page 69: Experiments with 20 µl PBS-buffer
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72 List of Figures 6.8 Heat wire de
Page 75 and 76:
Bibliography [1] Arisawa, H.; Brill
Page 77 and 78:
Bibliography 77 [26] Mark, H. F.: E
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Bibliography 79 [50] Zimmermann, H.
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C - DTU Nanotech - Danmarks Tekniske Universitet

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