本研究中設計了五組蝕刻深度為50 m的圖形，做為Leidenfrost液滴的加熱面，探討異丙醇/水混合系統之薄膜沸騰時液滴在加工表面上的運動與內流場型態，調配混合液的莫耳分率有0、0.05、0.2、0.4、0.6、0.7、0.8和1八種變化。實驗結果發現，蝕刻表面對液滴運動的影響主要在於中心圖形的大小，對於直徑約1000-2500 m的液滴，若表面之中心圖形直徑超過1000 m則可達到停留的效果，且在中心圖形最大為1600 m時，停留效果最為顯著。另外，液滴開始停留在蝕刻表面上的條件溫度幾乎等同於Leidenfrost溫度，但停留的狀態會隨著液滴的莫耳分率有不同的改變，其中莫耳分率0.2至0.4為最常見的運動區塊。
從液滴流場可視化實驗發現，液滴在一個穩定停留的運動靜止狀態時，會倚靠在加熱表面的邊壁達到穩定，其流場呈現快速且單一方向的旋轉狀態，液滴內的旋轉方向與液滴的行走方向有關；另一種流場型態為沿液滴壁面向上的對稱旋轉運動，通常出現在彈跳的液滴運動當中。
在異丙醇/水的二元混合系統中，Leidenfrost液滴的體積蒸發率隨時間的變化可分為三種型態，此三種型態的發生與液滴的莫耳分率有關。在異丙醇與水的二元混合液中，以莫耳分率0.4時，蒸發率隨時間的變化最為劇烈。
 

In this study, we design 5 different patterned surfaces to examine their influences in Leidenfrost droplet of 2-propanol/water mixture. The motion of Leidenfrost droplet, its inner flow field and the evaporation rate are investigated. The mole fraction of 2-propanol in water tested are 0 (pure water), 0.05, 0.2, 0.4, 0.6, 0.7, 0.8 and 1 (pure 2-propanol). The results show that to successful capture of droplet is the size of the central patterns. When the size of the central patterns exceeds 1000 m, which is equivalent to droplet diameter, highest capture percentage is achieved.
　　Moreover, the onset temperature of droplet capture is very close to the Leidenfrost temperature. The mode of droplet motion depends on the mole fractions. From the flow visualization result, we find a single-direction rotation when droplet resides on the patterned surface. On the other hand, a symmetric vortex pair emerges and fluid flows upward near the vapor-liquid interface when droplet bounces up and down.
　　For the 2-propanol/water mixtures, boiling can be classified into three types based on the evaporation rate of droplet. We find the variation of the evaporation depends on the mole fraction. From the result, rigorous variation of the evaporation rate occurs at the mole fraction of 0.4.

[1] J. D. Bernardin and I. Mudawar, "The Leidenfrost point: experimental study and assessment of existing models," Journal of Heat Transfer, vol. 121, pp. 894-903, 1999.
[2] T. Tran, H. J. Staat, A. Prosperetti, C. Sun, and D. Lohse, "Drop impact on superheated surfaces," Physical Review Letters, vol. 108, p. 036101, 2012.
[3] I. U. Vakarelski, N. A. Patankar, J. O. Marston, D. Y. C. Chan, and S. T. Sigurdur, "Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces," Nature, vol. 489, 2012.
[4] D. Arnaldo del Cerro, A. G. Marin, G. R. B. E. Romer, B. Pathiraj, D. Lohse, and A. J. Huis in ’t Veld, "Leidenfrost point reduction on micropatterned metallic surfaces," Langmuir, vol. 28, pp. 15106-15110, 2012.
[5] J. G. Leidenfrost, "On the fixation of water on diverse fire," International Journal of Heat and Mass Transfer, vol. 9, pp. 1209-1203, 1974.
[6] K. J. Baumeister, T. D. Hamill, and C. Lewis, "Creeping flow solution of the Leidenfrost phenomenon," National Aeronautics and Space Administration, Washington, D.C. TN D-3133, 1965.
[7] K. J. Baumeister and F. F. Simon, "Leidenfrost temperature: its correlation for liquid metals, cryogens, hydrocarbons, and water," Journal of Heat Transfer, vol. 95, pp. 166-173, 1973.
[8] W. S. Bradfield, "Liquid-solid contact in stable film boiling," Industrial & Engineering Chemistry Fundamentals, vol. 5, pp. 200-204, 1966.
[9] P. R. Chappidi, F. S. Gunnerson, and K. O. Pasamehmetoglu, "A simple forced convection film boiling model," International Communications in Heat and Mass Transfer, vol. 17, pp. 259-270, 1990.
[10] N. Nagai and S. Nishio, "Leidenfrost temperature on an extremely smooth surface," Experimental Thermal and Fluid Science, vol. 12, pp. 373-379, 1996.
[11] T. G. Myers and J. P. F. Charpin, "A mathematical model of the Leidenfrost effect on an axisymmetric droplet," Physics of Fluids, vol. 21, pp. 063101-8, 2009.
[12] S. C. Yao and K. Y. Cai, "The dynamics and Leidenfrost temperature of drops impacting on a hot surface at small angles," Experimental Thermal and Fluid Science, vol. 1, pp. 363-371, 1988.
[13] V. Bertola, "An experimental study of bouncing Leidenfrost drops: Comparison between Newtonian and viscoelastic liquids," International Journal of Heat and Mass Transfer, vol. 52, pp. 1786-1793, 2009.
[14] Y. Ge and L. S. Fan, "Three-dimensional simulation of impingement of a liquid droplet on a flat surface in the Leidenfrost regime," Physics of Fluids, vol. 17, p. 027104, 2005.
[15] R. Jeschar and H. Griebel, Influence of gases dissolved in cooling water on heat transfer during stable film boiling vol.67, Dusseldorf: Stahleisen, 1996.
[16] Y. M. Qiao and S. Chandra, "Experiments on adding a surfactant to water drops boiling on a hot surface," Mathematical, Physical and Engineering Sciences, vol. 453, pp. 673-689, 1997.
[17] H. Linke, B. J. Aleman, L. D. Melling, M. J. Taormina, M. J. Francis, C. C. Dow-Hygelund, V. Narayanan, R. P. Taylor, and A. Stout, "Self-propelled Leidenfrost droplets," Physical Review Letters, vol. 96, p. 154502, 2006.
[18] G. Dupeux, M. Le Merrer, G. Lagubeau, C. Clanet, S. Hardt, and D. Quere, "Viscous mechanism for Leidenfrost propulsion on a ratchet," Europhysics Letters, vol. 96, p. 58001, 2011.
[19] G. Lagubeau, M. Clanet, Christophe, and D.Quere, "Leidenfrost on a ratchet," Natual Physics, vol. 7, p. 3, 2011.
[20] T. R. Cousins, R. E. Goldstein, J. W. Jaworski, and A. I. Pesci, "A ratchet trap for Leidenfrost drops," Journal of Fluid Mechanics, vol. 696, pp. 215-227, 2012.
[21] A. G. Marin, D. A. del Cerro, G.R. Romer, B. Pathiraj, A. H. Veld, and D. Lohse, "Capillary droplets on Leidenfrost micro-ratchets," Physics of Fluids, vol. 24, pp. 122001-10, 2012.
[22] M. Elbahri, D. Paretkar, K. Hirmas, S. Jebril, and R. Adelung, "Anti-lotus effect for nanostructuring at the Leidenfrost temperature," Advanced Materials, vol. 19, pp. 1262-1266, 2007.
[23] N. A. Patankar, "Supernucleating surfaces for nucleate boiling and dropwise condensation heat transfer," Soft Matter, vol. 6, pp. 1613-1620, 2010.
[24] I. U. Vakarelski, J. O. Marston, D. Y. C. Chan, and S. T. Thoroddsen, "Drag reduction by Leidenfrost vapor layers," Physical Review Letters, vol. 106, p. 214501, 2011.
[25] P. J. Magalhaes, M.D. Abramoff, and S.J. Ram, "Image processing with ImageJ," Biophotonics international, vol. 11, pp. 36-42, 2004.