Title Page
Abstract
Contents
1. Introduction 13
1.1. Electrochemical biosensors 13
1.2. Flexible and transparent electrodes 14
1.3. Aptamer science 15
2. Devices 16
2.1. Materials 16
2.1.1. Electrodes 16
2.1.2. Aptamer 21
2.2. Equipments 23
2.3. Device structures 25
3. Experiments 27
3.1. Fabrication recipe 27
3.2. Main Fabrication 29
3.2.1. Photoresist image reversal and lift-off 29
3.2.2. Graphene wet transfer and in situ etching 33
3.3. Aptamer immobilization 34
3.4. Fabricated devices 36
3.5. Measurements 37
3.5.1. Raman spectroscopy 37
3.5.2. X-ray photoelectron spectroscopy (XPS) 39
3.5.3. Cyclic voltammatery(CV) 41
3.5.4. Electrochemical impedance spectroscopy (EIS) 41
3.5.5. Sheet resistance 43
3.5.6. Atomic force microscopy(AFM) 44
3.5.7. Field emission-scanning electron microscopy (FE-SEM) 45
3.5.8. UV-Vis spectrophotometer 46
3.6. Cortisol sensing 47
3.6.1. Methods of Measurement 47
4. Results 49
4.1. Device characteristics 49
4.1.1. Raman spectroscopy 50
4.1.2. X-ray photoelectron spectroscopy (XPS) 51
4.1.3. Cyclic voltammetry (CV) 56
4.1.4. Electrochemical impedance spectroscopy (EIS) 58
4.1.5. Sheet resistance 62
4.1.6. Atomic force microscopy (AFM) 63
4.1.7. Field emission-scanning electron microscopy (FE-SEM) 65
4.1.8. Transmittance 67
4.2. Cortisol sensing 68
5. Conclusion & Discussion 71
References 73
국문 초록 76
Table 1. Sheet resistance of various channels 62
Table 2. RMS of GP, PG electrodes 64
Table 3. Analysis of FE-SEM data of GP, PG electrodes 66
Table 4. Transmittance of various materials 67
Figure 1. Sequence of deposition of Parylene-C 17
Figure 2. (a) Molecular structure of graphene single layer, (b) Carbon 18
Figure 3. Molecular structure of PEDOT:PSS 20
Figure 4. Molecular structure of Cyclic Olefin Polymer 20
Figure 5. (a) Structure of cortisol aptamer (b) Symptoms of highh cortisol... 22
Figure 6. Fabrication equipments (a) parylene coater, (b) spin coater, (c) aligner,... 24
Figure 7. (a) Schematic image of device (b) and (c) Structures of PG, GP devices 26
Figure 8. Schematic image of fabrication process 28
Figure 9. Schematic image of overcut and undercut 29
Figure 10. Image reversal & lift-off process 32
Figure 11. Image of PG, GP devices 36
Figure 12. Confocal Raman Spectrometer 38
Figure 13. X-ray photoelectron spectroscopy 40
Figure 14. three electrode system 42
Figure 15. Keithley 2400 SMU 43
Figure 16. Atomic force microscope 44
Figure 17. Field emission-scanning electron microscope 45
Figure 18. UV-Vis spectrophotometer 46
Figure 19. Mechanism of aptamer-cortisol binding (a) before, (b) after 48
Figure 20. Graph of raman spectroscopy 50
Figure 21. C1s graphes. (a) PEDOT:PSS, (b) graphene, (c) GP, (d) PG 53
Figure 22. S2p graphes. (a) All, (b) PEDOT:PSS, (c) GP, (d) PG 55
Figure 23. CV graphs. (a) GP, (b) PG 57
Figure 24. EIS grapes (a) Week 1, (b) Week 2, (c) Week 3, (d) Week 4 61
Figure 25. Sheet resistance graph 62
Figure 26. Various channel materials on glass slices. 64
Figure 27. AFM image. (a) GP, (b) PG 64
Figure 28. FE-SEM images. (a) GP, (b) PG 66
Figure 29. Transmittance graph 67
Figure 30. (a) CV graph according to cortisol concentration (b) theory of mechanism 69
Figure 31. Sensitivity slope. (a) day 1, (b) day 7 70