C - DTU Nanotech - Danmarks Tekniske Universitet

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30 5 Freezing Different Samples using Peltier Cooling Table 5.1: CO2–laser settings for design I to IV and for the top cover Velocity [m/s] Power [%] Passes Shape 400 50 26 I Vessel 400 30 2 Screw bores 400 50 25 Shape 400 50 26 II Vessel 400 8 7 Screw bores 400 50 25 III Shape 400 50 26 and Vessel 400 50 25 IV Screw bores 400 50 25 Top cover Shape 400 50 26 part Vessel 400 7 7 1 Screw bores 400 50 25 Top cover Shape 400 50 26 part Vessel – – – 2 Screw bores 400 50 25 vessels was measured with a caliper. Design III and IV In III and IV the vessel was first created as a hole in the PMMA plate by laser ablation (laser settings and WinMarkPro drawing are shown in Tab. 5.1 and Fig. 5.2). In III a piece of aluminium foil was glued with vacuum grease to the laser machined PMMA plate to form the bottom of the vessel. For creating a bottom in design IV, a piece of PMMA foil was fixed together with the laser machined PMMA plate between two steel blocks with a screw clamp, and was placed in an oven for 1 h at 108 ◦ C. This process is called thermal bonding. The pressure for thermal bonding of PMMA plates depends on the task. In a separate ex- periment the pressure was checked for two different tasks: To bond two plates to each other, and to bond small wires between two PMMA plates. The force onto the plates was measured with an electrical force sensor and thus the pressure was calculated. Top cover Two different top covers were fabricated for the freezing chambers. Part 1 of the top cover was equivalent to freezing chamber II and part 2 had the same shape as all freezing chambers but no vessel (laser setup is shown in Tab. 5.1). Part 1 and 2 were thermally bonded in the oven for 1 h at 108 ◦ C. By thermally bonding part 1 and 2 together, a top cover with an air gap was created. An air gap was preventing the sample, which could be loaded into the
5.1 Materials and Methods 31 freezing chamber, to touch the top cover (further described in section 5.2.2). Part 2 could be used as top cover also, but this top cover had no air gap. 5.1.2 Freezing experiments with PBS–buffer relating to the freezing chamber design Chemicals (Vwr) • 10 mmol PBS–buffer 8 g/l NaCl, 0.2 g/l KCl, 1 g/l Na2HPO4 and 0.2 g/l KH2PO4 in double distilled water (pH = 7.2) Equipment • Pressurized air • Ice • Cooling block • Freezing chambers I–IV • Power supply IPS2303DD Iso–Tech • Peltier element TEC 1–1703 Nippon India • Heat sink grease Circuitworks Chemtronics Method Experimental setup (Fig. 5.3): The Peltier element was placed beneath the freezing chamber, to cool the vessel bottom. On both sides of the element heat sink grease was used for a better heat conduction. The resulting heat from the Peltier element was dissipated to a cooling block, which was immersed in ice. The dissipation process was supported by pressurized air from an air gun, which flowed around the cooling block. A sample at room–temperature was pipetted into the vessel. In the most experiments the freezing chamber was closed with a top cover, which had an air gap. The top cover and the freezing chamber were screwed onto the cooling block, thus the Peltier element was pressed with its cool side to the freezing chamber and with its hot side to the cooling block. In the experiments with design I first no top cover, no pressurized air and no ice layer was used. Additionally the two top covers were tested (see section 5.1.1). The following experiments were performed:
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 and 22: 3.2 Topas R○ and the CNC micromil
Page 23 and 24: 4 Basic Principles of a Peltier Ele
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
Page 72 and 73: 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
Page 79: Bibliography 79 [50] Zimmermann, H.

C - DTU Nanotech - Danmarks Tekniske Universitet

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