Micro-flow visualization (μ-FV) and computational fluid dynamics are complementarily performed to study the evolution of a single inkjet droplet ejected from a bend-mode piezoelectric inkjet printhead and the equilibrium film characteristics of the droplet deposition in microfabricated cavities. The numerical simulation is characterized by the coupled piezoelectric-structural- fluid solution procedure and verified by the μ-FV results. The numerical code is applied to investigate the influences of electric voltage, pulse shape, ink property (fluid viscosity μ and surface tension σ), and nozzle diameter Dn on the droplet volume, velocity, and configurations. Besides, by varying the droplet Weber number (We), droplet impact velocity Vd, sidewall contact angle (θs) of the microcavities, and microcavity length-to-width ratio (L / W) various deposition characteristics in microcavities are examined and the critical We (Wec) for filling microcavities with uniform ink films are identified. The computed results are found in good agreement with the experimental ones. For inkjet droplet evolution, new findings are to discover the critical ranges of electric waveform parameters, μ and σ outside which the phenomena of satellite droplets and puddle formation at the nozzle opening are absent. In addition, the imbedded physical rationales for these critical ranges are provided. The results are new in terms of the identifications of the critical σ and Dn for the reference of improving the droplet quality. For droplet deposition in microcavities, Wec have been found relating to the ability of the droplet to wet the side walls and fill a microcavity with a uniform film. The results are also new in terms of the identifications of the critical contact angle (θs)c and critical impact velocity (Vd)c. At (θs)c and at and beyond (Vd)c, the formation of an intact flat film in the cavity is fulfilled. The functional dependences between Wec and normalized θs as well as L / W are deduced for the first time. These correlations are believed to provide useful engineering references for operating inkjet printheads and fabricating uniform thin film coating on the bottom substrate of microcavities.

ABSTRACT i
ACKNOWLEDGEMENTS iii
LIST OF TABLES ix
LIST OF FIGURES xi
NOMENCLATURES xix
CHAPTER 1 INTRODUCTION 1
1-1 Research Motivation 1
1-2 Droplet Ejection from a Piezoelectric Inkjet Printhead 7
1-2-1 Literature Survey 7
1-2-2 Literature Summary 9
1-2-3 Research Objectives 10
1-3 Droplet Deposition in Microcavities 11
1-3-1 Literature Survey 11
1-3-2 Literature Summary 13
1-3-3 Research Objectives 13
CHAPTER 2 EXPERIMENTAL APPARATUS AND CONDITIONS 15
2-1 Description of the PIJ Printhead 15
2-2 Fabrication Process of Microcavities 16
2-3 Working Fluid Used and Contact Angle Measurement 17
2-4 Variation of θs and L / W of the Microcavities 18
2-5 μ-FV and IJP System 19
2-6 Variation of Droplet We 21
CHAPTER 3 MATHEMATICAL FORMULATION 23
3-1 Governing Equations 23
3-2 Boundary Conditions 27
3-3 Numerical Algorithm 28
3-4 Computational Grid System 29
CHAPTER 4 DROPLET EJECTION FROM A PIJ PRINTHEAD 32
4-1 □-FV of Inkjet Droplet Evolutions 32
4-2 Effects of Epp and Pulse Shape on Bd, Vd and Droplet Configurations 37
4-3 Effects of μ and σ on Bd, Vd, and Droplet Configurations 42
4-4 Effects of Dn on Bd, Vd, and Droplet Configurations 45
4-5 Summary 46
CHAPTER 5 DROPLET DEPOSITION IN MICROCAVITIES 49
5-1 Droplet Deposition in the Microcavities for θb = 35° 49
5-1-1 Micro-Flow Visualization of PEDOT Droplet Evolutions 49
5-1-2 Effects of We on Droplet Deposition in the Microcavities at Equilibrium 52
5-1-3 Effects of θs on Droplet Deposition Process in the Microcavities 54
5-1-4 Effects of Vd on Deposition Process in the Microcavities 58
5-2 Droplet Deposition in the Microcavities for θb = 65° 60
5-2-1 Effects of We on Droplet Deposition in the Microcavities at Equilibrium 60
5-2-2 Effects of θs on Droplet Deposition in the Microcavities at Equilibrium 63
5-2-3 Effects of L / W on Droplet Deposition in the Microcavities at Equilibrium 65
5-3 Summary 67
CHAPTER 6 CONCLUSIONS AND RECOMMANDATIONS 71
6-1 Conclusions 71
6-2 Future Recommendations 73
APPENDIX A: μ-PIV AND CFD STUDIES ON STEADY AND PERIODIC MICRO DIFFUSER FLOWS 75
A-1 Description of the Problem and Literature Survey 75
A-2 Experimental Apparatus and Conditions 78
A-3 Theoretical Formulation 80
A-4 Results and Discussion 84
A-4-1 Steady Flow in a Micro Diffuser Followed by a Sudden Expansion 84
A-4-2 Periodic Flow of a Piezoelcetric Inkjet Printhead 85
A-5 Conclusions 88
APPENDIX B: MICRODROPLET EVOLUTIOn ACTUATED BY A PIJ PRINTHEAD 90
B-1 Description of the Problem and Literature Survey 90
B-2 Theoretical Formulation 93
B-2-1 Geometry and Grid System 93
B-2-2 Governing Equations 94
B-3 Results and discussion 97
B-4 Conclusions 101
REFERENCES 104
TABLES 118
FIGURES 120
RESUME 178

Adachi, C., Baldo, M. A., Forrest, S. R., Lamansky, S., Thompson, M. E., and Kwong, R. C. (2001). "High-efficiency red electrophosphorescence devices." Applied Physics Letters, 78(11), 1622-4

Anders, K., Roth, N., and Frohn, A. (1993). "The velocity change of ethanol droplets during collision with a wall analyzed by image-processing." Experiments In Fluids, 15(2), 91-6

Antoniadis, H., Curtis, H., Moon, R. L., Roitman, D. B., and Sheats, J. R. (2003). "Method and apparatus for fabricating polymer-based electroluminescent displays." U. S. Pat. 6 582 756

Asai, A. (1992). "3-dimensional calculation of bubble-growth and drop ejection in a bubble jet printer." Journal Of Fluids Engineering-Transactions Of The Asme, 114(4), 638-41

Asai, A., Hara, T., and Endo, I. (1987). "One-dimensional model of bubble-growth and liquid flow in bubble jet printers." Japanese Journal Of Applied Physics Part 1-Regular Papers Short Notes & Review Papers, 26(10), 1794-801

Asai, A., Hirasawa, S., and Endo, I. (1988). "Bubble generation mechanism in the bubble jet recording process." Journal Of Imaging Technology, 14(5), 120-4

Bennett, R., and Albertalli, D. (2005). "Use of industrial inkjet printing in flat panel displays."

Bennett, R., Edwards, C., Lee, J., and Silz, K. (2003). "Precision industrial ink jet printing technology for full color pled display and tft-lcd manufacturing."

Bogy, D. B., and Talke, F. E. (1984). "Experimental and theoretical-study of wave-propagation phenomena in drop-on-demand ink jet devices." Ibm Journal Of Research And Development, 28(3), 314-21

Brackbill, J. U., Kothe, D. B., and Zemach, C. (1992). "A continuum method for modeling surface-tension." Journal Of Computational Physics, 100(2), 335-54

Braun, D., and Heeger, A. J. (1991). "Visible-light emission from semiconducting polymer diodes." Applied Physics Letters, 58(18), 1982-4

Burroughes, J. H., Bradley, D. D. C., Brown, A. R., Marks, R. N., Mackay, K., Friend, R. H., et al. (1990). "Light-emitting-diodes based on conjugated polymers." Nature, 347(6293), 539-41

Challinor, A. (2004). "Xaar launches new high-performance xj128 printhead xaar." http://www.xaar.co.uk/news_det.asp?art_id=5100&sec_id=2580

Chang, S. C., Bharathan, J., Yang, Y., Helgeson, R., Wudl, F., Ramey, M. B., et al. (1998). "Dual-color polymer light-emitting pixels processed by hybrid inkjet printing." Applied Physics Letters, 73(18), 2561-3

Chen, C. C., Chen, S. H., Chung, C. K., Chan, C. Y., and Liou, T. M. (2002). "3d flow simulation of a micro droplet generator study on actuator shape effect." J. Flow Visualization and Image Processing, 3, 963-8

Chen, P. H., Chen, W. C., Ding, P. P., and Chang, S. H. (1998). "Droplet formation of a thermal sideshooter inkjet printhead." International Journal Of Heat And Fluid Flow, 19(4), 382-90

Chen, P. H., Peng, H. Y., Liu, H. Y., Chang, S. L., Wu, T. I., and Cheng, C. H. (1999). "Pressure response and droplet ejection of a piezoelectric inkjet printhead." International Journal Of Mechanical Sciences, 41(2), 235-48

Chen, R. H., and Wang, H. W. (2005). "Effects of tangential speed on low-normal-speed liquid drop impact on a non-wettable solid surface." Experiments In Fluids, 39(4), 754-60

Crooks, R., and Boger, D. V. (2000). "Influence of fluid elasticity on drops impacting on dry surfaces." J. Rheol., 44, 973-96

Duineveld, P. C., Decre, M. M. J., and Nisato, G. (2007). "Electroluminescent display panel." U. S. Pat. 2007/0063640

Edwards, C., and Albertalli, D. (2001). "Application of polymer led materials using piezo ink-jet printing." SID 01 Digest, 1049-51

Elrod, S. A., Khuri-Yakub, B. T., and F., Q. C. (1997). "Stabilization of the free surface of a liquid." U. S. Patent, 5 629 724

Frohn, A., and Roth, N. (2000). "Dynamics of droplets."

Fromm, J. E. (1984). "Numerical-calculation of the fluid-dynamics of drop-on-demand jets." Ibm Journal Of Research And Development, 28(3), 322-33

Fu, C., and Huang, H. (2007). "Different methods for the fabrication of uv-liga molds using su-8 with tapered de-molding angles." Microsystem Technologies-Micro-And Nanosystems-Information Storage And Processing Systems, 13(3-4), 293-8

Fuller, S. B., Wilhelm, E. J., and Jacobson, J. A. (2002). "Ink-jet printed nanoparticle microelectromechanical systems." Journal Of Microelectromechanical Systems, 11(1), 54-60

Gupta, R. (2005). "Post processing of films to improve film quality." U. S. Pat. 2005/0276910

Hamaguchi, M., and Yoshino, K. (1996). "Color-variable electroluminescence from multilayer polymer films." Applied Physics Letters, 69(2), 143-5

Hammad, K. J., Ötügen, M. V., and Arik, E. B. (1999). "A piv study of the laminar axisymmetric sudden expansion flow." Exp. Fluids, 266-72

Hayes, D. J., Wallace, D. B., and Cox, W. R. (1999). "Microjet printing of solder and polymers for multi-chip modules and chip-scale packages." in Proc. IMAPS int. Conf. on High Density Packaging and MCMs, 242-7

Hebner, T. R., Wu, C. C., Marcy, D., Lu, M. H., and Sturm, J. C. (1998). "Ink-jet printing of doped polymers for organic light emitting devices." Applied Physics Letters, 72(5), 519-21

Holmes, R. J., Forrest, S. R., Tung, Y. J., Kwong, R. C., Brown, J. J., Garon, S., et al. (2003). "Blue organic electrophosphorescence using exothermic host-guest energy transfer." Applied Physics Letters, 82(15), 2422-4

"Ieee standard on piezoelectricity." (1996). Ieee Transactions On Ultrasonics Ferroelectrics And Frequency Control, 43(5), A1-A54

Khosla, P. K., and Rubin, S. G. (1974). "A diagonally dominant second-order accurate implicit scheme." Computers & Fluids, 2, 207-9

Knupp, P., Margolin, L. G., and Shashkov, M. (2002). "Reference jacobian optimization-based rezone strategies for arbitrary lagrangian eulerian methods." Journal Of Computational Physics, 176(1), 93-128

Le, H. P. (1998). "Progress and trends in ink jet printing technology." J. Imaging Sci. and Tec., 42, 49-62

Lee, Y. T., Chen, R. H., Pu, J. Y., and Lin, T. H. (2002). "Effects of excitation waveforms on the breakup of liquid jets." Int. Symp. on Exp. Mech. (Taipei, Taiwan)

Liou, T. M., Chan, C. Y., Fu, C. C., and Shih, K. C. (2008). "Effects of impact inertia and surface characteristics on deposited polymer droplets in microcavities." Journal Of Microelectromechanical Systems, 17(2), 278-87

Macagno, E. O., and Hung, T. (1967). "Computational and experimental study of a captive annular eddy." J. of Fluid Mech., 28, 43-64

Macler, M., and Nelson, C. (2005). "Surface characteristic apparatus and method." U. S. Patent, 6 938 986

Mao, T., Kuhn, D. C. S., and Tran, H. (1997). "Spread and rebound of liquid droplets upon impact on flat surfaces." Aiche Journal, 43(9), 2169-79

Meinhart, C. D., and Zhang, H. S. (2000). "The flow structure inside a microfabricated inkjet printhead." Journal Of Microelectromechanical Systems, 9(1), 67-75

Muzaferija, S. (1994). "Adaptive finite volume method for flow prediction using unstructured meshes and multigrid approach."

Muzaferija, S., and Perić, M. (1998). "Computation of free-surface flows using interface-tracking and interface-capturing methods." Nonlinear water wave interaction

Pak, Y. E. (1992). "Linear electroelastic fracture-mechanics of piezoelectric materials." International Journal Of Fracture, 54(1), 79-100

Pan, F. X., Kubby, J., and Chen, J. K. (2002). "Numerical simulation of fluid-structure interaction in a mems diaphragm drop ejector." Journal Of Micromechanics And Microengineering, 12(1), 70-6

PasandidehFard, M., Qiao, Y. M., Chandra, S., and Mostaghimi, J. (1996). "Capillary effects during droplet impact on a solid surface." Physics Of Fluids, 8(3), 650-9

Patankar, S. V. (1980). "Numerical heat transfer and fluid flow."

Perić, M., and Ferziger, J. H. (1996). "Computational methods for fluid dynamic."

Pozrikidis, C. (1990). "The deformation of a liquid-drop moving normal to a plane wall." Journal Of Fluid Mechanics, 215, 331-63

Sayama, T., and Yonekubo, S. (1998). "Device for driving inkjet print head." U. S. Patent 6 074 033

Sen, A. K., and Darabi, J. (2007). "Droplet ejection performance of a monolithic thermal inkjet print head." Journal Of Micromechanics And Microengineering, 17(8), 1420-7

Shield, T. W., Bogy, D. B., and Talke, F. E. (1987). "Drop formation by dod ink-jet nozzles - a comparison of experiment and numerical-simulation." Ibm Journal Of Research And Development, 31(1), 96-110

Sikalo, S., Tropea, C., and Ganic, E. N. (2005). "Impact of droplets onto inclined surfaces." Journal Of Colloid And Interface Science, 286(2), 661-9

Sun, R. G., Wang, Y. Z., Wang, D. K., Zheng, Q. B., Kyllo, E. M., Gustafson, T. L., et al. (2000). "High luminescent efficiency in light-emitting polymers due to effective exciton confinement." Applied Physics Letters, 76(5), 634-6

Tseng, F. G., Kim, C. J., and Ho, C. M. (2002). "A high-resolution high-frequency monolithic top-shooting microinjector free of satellite drops - part i: Concept, design, and model." Journal Of Microelectromechanical Systems, 11(5), 427-36

Wang, Y. Z., Gebler, D. D., Fu, D. K., Swager, T. M., and Epstein, A. J. (1997a). "Color variable bipolar/ac light-emitting devices based on conjugated polymers." Applied Physics Letters, 70(24), 3215-7

Wang, Y. Z., Gebler, D. D., Spry, D. J., Fu, D. K., Swager, T. M., MacDiarmid, A. G., et al. (1997b). "Novel light-emitting devices based on pyridine-containing conjugated polymers." Ieee Transactions On Electron Devices, 44(8), 1263-8

Wang, Y. Z., Sun, R. G., Meghdadi, F., Leising, G., and Epstein, A. J. (1999a). "Multicolor multilayer light-emitting devices based on pyridine-containing conjugated polymers and para-sexiphenyl oligomer." Applied Physics Letters, 74(24), 3613-5

Wang, Y. Z., Sun, R. G., Wang, D. K., Swager, T. M., and Epstein, A. J. (1999b). "Polarity- and voltage-controlled color-variable light-emitting devices based on conjugated polymers." Applied Physics Letters, 74(18), 2593-5

Wijshoff, H. (2004). "Free surface flow and acousto-elastic interaction in piezo inkjet." Proc. of Nanotech, 2, 215-8

Wolk, M. B., Baude, P. F., McCormick, F. B., and Hsu, Y. (2001). "Thermal transfer element and process for forming organic electroluminescent devices." U. S. Pat. 6 194 119

Wu, C. L., Torniainen, E. D., and Taylor, M. S. (2008). "Hydrophobic nozzle exit with improved micro fluid ejection dynamics." U. S. Patent, 7 377 620

Wu, H. C., Hwang, W. S., and Lin, H. J. (2004). "Development of a three-dimensional simulation system for micro-inkjet and its experimental verification." Materials Science And Engineering A-Structural Materials Properties Microstructure And Processing, 373(1-2), 268-78

Yamazaki, S., Yamamoto, K., and Arai, Y. (2004). "Electro-optical device and manufacturing method thereof." U. S. Pat. 6 830 494

Yang, A. S., Yang, J. C., and Hong, M. C. (2006). "Droplet ejection study of a picojet printhead." Journal Of Micromechanics And Microengineering, 16(1), 180-8

Yang, Y., Chang, S. C., Bharathan, J., and Liu, J. (2000). "Organic/polymeric electroluminescent devices processed by hybrid ink-jet printing." Journal Of Materials Science-Materials In Electronics, 11(2), 89-96

Yeh, J. T. (2001). "A vof-fem and coupled pled inkjet simulation." Proc. of ASME Fluids Engineering Division Summer Metting (New Orleans, USA), 1-5

Yu, G., Srdanov, G., Stainer, M., Innocenzo, J. G., and Sun, R. G. (2007). "Methods for producing full-color organic electroluminescent devices." U. S. Pat. 7 226 799