水資源短缺因氣候變遷日益嚴重，根據聯合國統計全球近三分之一人口生活在「高度缺水」的狀況。現今主流的解方依賴海水淡化，又以薄膜技術的逆滲透取得主導地位。高壓操作、高成本的薄膜逆滲透並不適合缺水的貧窮國家，因此海水淡化將目光轉向其他新興技術。
海水淡化技術中，薄膜蒸餾 (membrane distillation, MD)有相當潛力取代逆滲透，其特色在較低操作壓力及溫度，並使用低品位能源減少額外能耗，達成熱整合。然而膜污染及膜潤濕的問題致使其應用於實際發展受到限制。因此，本研究致力開發能抵抗低表面張力物質潤濕及高含鹽液體的薄膜以提升薄膜蒸餾的泛用性。
全疏膜 (Omniphobic membranes)是一種具有低表面能的薄膜，兼具疏水及疏油特性，能增強薄膜的抗潤濕性能。本研究藉由生長二氧化鈦奈米棒於玻璃纖維基材上，創造分層奈米結構，再經兩步驟氟化，使膜表面能降低達到全疏的目標。使用電子顯微鏡及原子力顯微鏡確認生成二氧化鈦奈米棒，玻璃纖維外表呈杉葉狀。經由X射線光電子能譜儀及能量分散光譜儀確認薄膜表面含高濃度的氟，從接觸角測量儀證實薄膜的全疏性及膜具自潔特性與低表面能，所有待測液體接觸角大於90°，水的滑動角小於10°。
最後以直接接觸式薄膜蒸餾展現含界面活性劑進料鹽水的脫鹽效能。全疏膜於薄膜蒸餾呈現良好效能，具穩定的水通量且鹽阻擋率高達99.99%，可操作於界面活性劑濃度達2 mM的環境下2小時不被潤濕。高鹽濃度進料下，全疏膜可持續操作長達100小時；高鹽環境下添加界面活性劑後仍能操作25小時不會潤濕。
本研究成功開發抗潤濕之全疏膜，在薄膜蒸餾中具穩健之效能，提升薄膜蒸餾技術商業化的潛力。

Due to climate change, water scarcity is more and more severe. According to statistics from United Nations, nearly one-third of the world population experiences high water stress levels. Seawater desalination, particularly reverse osmosis (RO) with membrane, is the most widely used solution. However, the high-pressure operation and high cost make it unsuitable for water scarcity, impoverished countries, leading the focus of seawater desalination to shift towards other emerging technologies.
Membrane distillation (MD) is a promising alternative to reverse osmosis for seawater desalination, characterized by lower operational pressure and temperature. By utilizing low-grade energy, this technique effectively reduces additional energy consumption and achieves heat integrate. This makes it a potential candidate to replace reverse osmosis as the mainstream technology. However, the practical application of MD is limited by membrane fouling and wetting. Therefore, this study focuses on membranes that can resist wetting by low surface tension substances and highly saline solutions to enhance the versatility of MD.
Omniphobic membrane is a type of membrane with low surface energy, exhibiting hydrophobic and oleophobic properties at the same time. These characteristics enhance the membrane's anti-wetting performance. In this study, titanium dioxide nanorods are grown on a glass fiber substrate to create a hierarchical nanostructure. Then, the membrane surface is fluorinated in two steps to reduce surface energy and achieve omniphobicity. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are applied to comfirm the formation of titanium dioxide nanorods. Pine-needle-like nanorods grow on glass fiber. X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy (EDS) determine the high concentration of fluorine on the membrane surface. Contact angle measurement confirms the membrane's omniphobicity, self-cleaning property, and low surface energy. All contact angles of tested liquids are larger than 90°. The sliding angle of water is smaller than 10°.
Finally, direct contact membrane distillation is used to assess the desalination performance of saline solutions containing surfactant. The omniphobic membrane shows excellent performance in MD, maintaining stable water flux and achieving a salt rejection rate up to 99.99%. It operates for 2 hours in 2 mM surfactant concentration without wetting. Under high-salinity solution, the omniphobic membrane continues to operate for up to 100 hours without wetting. Even with the addition of surfactants in a high-saline environment, it can still operate for 25 hours without wetting.
This study successfully develops omniphobic membranes with anti-wetting property. The membranes achieve robust performance in membrane distillation and enhance commercialized potential of MD in the future.

[1] 經濟部水利署, 自來水生活用水量統計, 2023.
[2] 經濟部水利署, 110 年工業用水量統計報告, 2023, pp. B-23.
[3] U.N.D.o. Economic, S. Affairs, The sustainable development goals report 2023, UN2023.
[4] S. Gorjian, B. Ghobadian, Solar desalination: A sustainable solution to water crisis in Iran, Renewable and Sustainable Energy Reviews 48 (2015) 571-584. https://doi.org/https://doi.org/10.1016/j.rser.2015.04.009.
[5] M. Sharifikia, Environmental challenges and drought hazard assessment of Hamoun Desert Lake in Sistan region, Iran, based on the time series of satellite imagery, Natural Hazards 65(1) (2013) 201-217. https://doi.org/10.1007/s11069-012-0353-8.
[6] J.K. Cooley, The War over Water, Foreign Policy (54) (1984) 3-26. https://doi.org/10.2307/1148352.
[7] 閻亢宗, 大喜馬拉雅水資源危機與中印水戰爭風險, 問題與研究 52(4) (2013) 1-31. https://doi.org/10.30390/isc.201312_52(4).0001.
[8] D. Meißner, B. Klein, B. Frielingsdorf, Implementing Hydrological Forecasting Services Supporting Waterway Management and Transportation Logistics Relating to Hydroclimatic Impacts, Atmosphere, 2022.
[9] C. Schwaller, Y. Keller, B. Helmreich, J.E. Drewes, Estimating the agricultural irrigation demand for planning of non-potable water reuse projects, Agricultural Water Management 244 (2021) 106529. https://doi.org/https://doi.org/10.1016/j.agwat.2020.106529.
[10] S.s.n.w.a. PUB, Our Water, Our Future, Water and the Future of Humanity: Revisiting Water Security (2016) 7.
[11] A. Tal, Addressing Desalination’s Carbon Footprint: The Israeli Experience, Water, 2018.
[12] 賴君義, 薄膜科技概論 Introduction to membrane science and technology, 五南圖書出版股份有限公司, 臺北市, 2019.
[13] L. Francis, F.E. Ahmed, N. Hilal, Electrospun membranes for membrane distillation: The state of play and recent advances, Desalination 526 (2022) 115511. https://doi.org/https://doi.org/10.1016/j.desal.2021.115511.
[14] T. Ni, J. Lin, L. Kong, S. Zhao, Omniphobic membranes for distillation: Opportunities and challenges, Chinese Chemical Letters 32(11) (2021) 3298-3306. https://doi.org/10.1016/j.cclet.2021.02.035.
[15] B.R. Bodell, Silicone rubber vapor diffusion in saline water distillation, US, 1963.
[16] P.K. Weyl, Recovery of demineralized water from saline waters, Google Patents, 1967.
[17] M.E. Findley, Vaporization through porous membranes, Industrial and Engineering Chemistry Process Design and Development 6(2) (1967) 226-230. https://doi.org/10.1021/i260022a013.
[18] C.A. Quist-Jensen, F. Macedonio, E. Drioli, Integrated Membrane Desalination Systems with Membrane Crystallization Units for Resource Recovery: A New Approach for Mining from the Sea, Crystals, 2016.
[19] W. Ni, Y. Li, J. Zhao, G. Zhang, X. Du, Y. Dong, Simulation Study on Direct Contact Membrane Distillation Modules for High-Concentration NaCl Solution, Membranes, 2020.
[20] M. Yao, L.D. Tijing, G. Naidu, S.-H. Kim, H. Matsuyama, A.G. Fane, H.K. Shon, A review of membrane wettability for the treatment of saline water deploying membrane distillation, Desalination 479 (2020) 114312. https://doi.org/https://doi.org/10.1016/j.desal.2020.114312.
[21] Z. Wang, Y. Chen, S. Lin, Kinetic model for surfactant-induced pore wetting in membrane distillation, Journal of Membrane Science 564 (2018) 275-288. https://doi.org/https://doi.org/10.1016/j.memsci.2018.07.010.
[22] M. Rezaei, D.M. Warsinger, J.H. Lienhard V, M.C. Duke, T. Matsuura, W.M. Samhaber, Wetting phenomena in membrane distillation: Mechanisms, reversal, and prevention, Water Research 139 (2018) 329-352. https://doi.org/https://doi.org/10.1016/j.watres.2018.03.058.
[23] N.G.P. Chew, S. Zhao, C.H. Loh, N. Permogorov, R. Wang, Surfactant effects on water recovery from produced water via direct-contact membrane distillation, Journal of Membrane Science 528 (2017) 126-134. https://doi.org/https://doi.org/10.1016/j.memsci.2017.01.024.
[24] R.N. Wenzel, Resistance of solid surfaces to wetting by water, Industrial & engineering chemistry 28(8) (1936) 988-994.
[25] A. Cassie, S. Baxter, Transactions of the Faraday Society, Transactions of the Faraday Society 40 (1944) 546-551.
[26] K.J. Lu, Y. Chen, T.-S. Chung, Design of omniphobic interfaces for membrane distillation – A review, Water Research 162 (2019) 64-77. https://doi.org/https://doi.org/10.1016/j.watres.2019.06.056.
[27] M.H. Kwon, H.S. Shin, C.N. Chu, Fabrication of a super-hydrophobic surface on metal using laser ablation and electrodeposition, Applied Surface Science 288 (2014) 222-228.
[28] C. Boo, J. Lee, M. Elimelech, Omniphobic Polyvinylidene Fluoride (PVDF) Membrane for Desalination of Shale Gas Produced Water by Membrane Distillation, Environmental Science & Technology 50(22) (2016) 12275-12282. https://doi.org/10.1021/acs.est.6b03882.
[29] M.S. El-Bourawi, Z. Ding, R. Ma, M. Khayet, A framework for better understanding membrane distillation separation process, Journal of Membrane Science 285(1) (2006) 4-29. https://doi.org/https://doi.org/10.1016/j.memsci.2006.08.002.
[30] S. Zhao, L. Wardhaugh, J. Zhang, P.H.M. Feron, Condensation, re-evaporation and associated heat transfer in membrane evaporation and sweeping gas membrane distillation, Journal of Membrane Science 475 (2015) 445-454. https://doi.org/https://doi.org/10.1016/j.memsci.2014.11.002.
[31] Y. Zhang, X. Wang, Z. Cui, E. Drioli, Z. Wang, S. Zhao, Enhancing wetting resistance of poly(vinylidene fluoride) membranes for vacuum membrane distillation, Desalination 415 (2017) 58-66. https://doi.org/https://doi.org/10.1016/j.desal.2017.04.011.
[32] B.S. Lalia, V. Kochkodan, R. Hashaikeh, N. Hilal, A review on membrane fabrication: Structure, properties and performance relationship, Desalination 326 (2013) 77-95. https://doi.org/https://doi.org/10.1016/j.desal.2013.06.016.
[33] H. Cho, Y. Choi, S. Lee, Effect of pretreatment and operating conditions on the performance of membrane distillation for the treatment of shale gas wastewater, Desalination 437 (2018) 195-209. https://doi.org/https://doi.org/10.1016/j.desal.2018.03.009.
[34] Y.C. Woo, Y. Kim, M. Yao, L.D. Tijing, J.-S. Choi, S. Lee, S.-H. Kim, H.K. Shon, Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique, Environmental Science & Technology 52(4) (2018) 2186-2196. https://doi.org/10.1021/acs.est.7b05450.
[35] S. Meng, Y. Ye, J. Mansouri, V. Chen, Crystallization behavior of salts during membrane distillation with hydrophobic and superhydrophobic capillary membranes, Journal of Membrane Science 473 (2015) 165-176. https://doi.org/10.1016/j.memsci.2014.09.024.
[36] J.A. Kharraz, A.K. An, Patterned superhydrophobic polyvinylidene fluoride (PVDF) membranes for membrane distillation: Enhanced flux with improved fouling and wetting resistance, Journal of Membrane Science 595 (2020) 117596. https://doi.org/https://doi.org/10.1016/j.memsci.2019.117596.
[37] S. Dong, Y. Yun, M. Wang, C. Li, H. Fu, X. Li, W. Yang, G. Liu, Superhydrophobic alumina hollow ceramic membrane modified by TiO2 nanorod array for vacuum membrane distillation, Journal of the Taiwan Institute of Chemical Engineers 117 (2020) 56-62. https://doi.org/https://doi.org/10.1016/j.jtice.2020.11.030.
[38] H.-C. Yang, J. Hou, V. Chen, Z.-K. Xu, Janus Membranes: Exploring Duality for Advanced Separation, Angewandte Chemie International Edition 55(43) (2016) 13398-13407. https://doi.org/https://doi.org/10.1002/anie.201601589.
[39] Z. Huang, G. Yang, J. Zhang, S. Gray, Z. Xie, Dual-layer membranes with a thin film hydrophilic MOF/PVA nanocomposite for enhanced antiwetting property in membrane distillation, Desalination 518 (2021) 115268. https://doi.org/https://doi.org/10.1016/j.desal.2021.115268.
[40] D. Cheng, J. Zhang, N. Li, D. Ng, S.R. Gray, Z. Xie, Antiwettability and Performance Stability of a Composite Hydrophobic/Hydrophilic Dual-Layer Membrane in Wastewater Treatment by Membrane Distillation, Industrial & Engineering Chemistry Research 57(28) (2018) 9313-9322. https://doi.org/10.1021/acs.iecr.8b02027.
[41] S. Kalam, A. Dutta, X. Du, X. Li, T. Tong, J. Lee, A non-substrate-specific technique of antifouling and antiwetting Janus membrane fabrication for membrane distillation, Desalination 573 (2024) 117195. https://doi.org/https://doi.org/10.1016/j.desal.2023.117195.
[42] G. Yang, D. Ng, Z. Huang, J. Zhang, S. Gray, Z. Xie, Janus hollow fibre membranes with intrusion anchored structure for robust desalination and leachate treatment in direct contact membrane distillation, Desalination 551 (2023) 116423. https://doi.org/https://doi.org/10.1016/j.desal.2023.116423.
[43] Y. Jia, K. Guan, P. Zhang, Q. Shen, Z. Li, T. Istirokhatun, H. Matsuyama, Asymmetric superwetting Janus structure for fouling- and scaling-resistant membrane distillation, Journal of Membrane Science 657 (2022) 120697. https://doi.org/https://doi.org/10.1016/j.memsci.2022.120697.
[44] P. Zhang, S. Xiang, R.R. Gonzales, Z. Li, Y.-H. Chiao, K. Guan, M. Hu, P. Xu, Z. Mai, S. Rajabzadeh, K. Nakagawa, H. Matsuyama, Wetting-and scaling-resistant superhydrophobic hollow fiber membrane with hierarchical surface structure for membrane distillation, Journal of Membrane Science 693 (2024) 122338. https://doi.org/https://doi.org/10.1016/j.memsci.2023.122338.
[45] L.-H. Chen, A. Huang, Y.-R. Chen, C.-H. Chen, C.-C. Hsu, F.-Y. Tsai, K.-L. Tung, Omniphobic membranes for direct contact membrane distillation: Effective deposition of zinc oxide nanoparticles, Desalination 428 (2018) 255-263. https://doi.org/https://doi.org/10.1016/j.desal.2017.11.029.
[46] S.A. Alftessi, M.H.D. Othman, M.R. Adam, T.M. Farag, A. Mustafa, T. Matsuura, J. Jaafar, M.A. Rahman, A.F. Ismail, Omniphobic surface modification of silica sand ceramic hollow fiber membrane for desalination via direct contact membrane distillation, Desalination 532 (2022) 115705. https://doi.org/https://doi.org/10.1016/j.desal.2022.115705.
[47] J. Doshi, D.H. Reneker, Electrospinning process and applications of electrospun fibers, Journal of Electrostatics 35(2) (1995) 151-160. https://doi.org/https://doi.org/10.1016/0304-3886(95)00041-8.
[48] N.S. Prasanna, N. Choudhary, N. Singh, K. Raghavarao, Omniphobic membranes in membrane distillation for desalination applications: A mini-review, Chemical Engineering Journal Advances 14 (2023) 100486. https://doi.org/https://doi.org/10.1016/j.ceja.2023.100486.
[49] N.M.A. Omar, M.H.D. Othman, Z.S. Tai, A.O.A. Amhamed, E. Yuliwati, M.H. Puteh, T.A. Kurniawan, M.A. Rahman, J. Jaafar, A.F. Ismail, Robust omniphobic ceramic hollow fibre membrane with leaf-like copper oxide hierarchical structure by membrane distillation, Desalination 564 (2023) 116816. https://doi.org/https://doi.org/10.1016/j.desal.2023.116816.
[50] W. Zhang, Z. Wang, B. Li, Omniphobic membrane with nest-like re-entrant structure via electrospraying strategy for robust membrane distillation, Journal of Membrane Science 640 (2021) 119824. https://doi.org/https://doi.org/10.1016/j.memsci.2021.119824.
[51] M.H. Abd Aziz, M.H. Dzarfan Othman, N.H. Alias, T. Nakayama, Y. Shingaya, N.A. Hashim, T.A. Kurniawan, T. Matsuura, M.A. Rahman, J. Jaafar, Enhanced omniphobicity of mullite hollow fiber membrane with organosilane-functionalized TiO2 micro-flowers and nanorods layer deposition for desalination using direct contact membrane distillation, Journal of Membrane Science 607 (2020) 118137. https://doi.org/https://doi.org/10.1016/j.memsci.2020.118137.
[52] X. Li, W. Qing, Y. Wu, S. Shao, L.E. Peng, Y. Yang, P. Wang, F. Liu, C.Y. Tang, Omniphobic Nanofibrous Membrane with Pine-Needle-Like Hierarchical Nanostructures: Toward Enhanced Performance for Membrane Distillation, ACS Applied Materials & Interfaces 11(51) (2019) 47963-47971. https://doi.org/10.1021/acsami.9b17494.
[53] X. Du, M. Alipanahrostami, W. Wang, T. Tong, Long-Chain PFASs-Free Omniphobic Membranes for Sustained Membrane Distillation, ACS Appl Mater Interfaces (2022). https://doi.org/10.1021/acsami.2c01499.
[54] M. Asadolahi, H. Fashandi, Creating Nature-Inspired Surface Roughness and Modifying Surface Chemistry of PVDF Electrospun Fibers Using Low-Pressure Plasma towards Omniphobic Membrane for Long-term Distillation, Separation and Purification Technology 330 (2024). https://doi.org/10.1016/j.seppur.2023.125442.
[55] W. Qing, Y. Wu, X. Li, X. Shi, S. Shao, Y. Mei, W. Zhang, C.Y. Tang, Omniphobic PVDF nanofibrous membrane for superior anti-wetting performance in direct contact membrane distillation, Journal of Membrane Science 608 (2020). https://doi.org/10.1016/j.memsci.2020.118226.
[56] E.F. Hare, E.G. Shafrin, W.A. Zisman, Properties of Films of Adsorbed Fluorinated Acids, The Journal of Physical Chemistry 58(3) (1954) 236-239. https://doi.org/10.1021/j150513a011.
[57] X. Huang, C. Li, K. Zuo, Q. Li, Predominant Effect of Material Surface Hydrophobicity on Gypsum Scale Formation, Environmental Science & Technology 54(23) (2020) 15395-15404. https://doi.org/10.1021/acs.est.0c03826.
[58] Y. Xu, Y. Yang, X. Fan, Z. Liu, Y. Song, Y. Wang, P. Tao, C. Song, M. Shao, In-situ silica nanoparticle assembly technique to develop an omniphobic membrane for durable membrane distillation, Desalination 499 (2021) 114832. https://doi.org/https://doi.org/10.1016/j.desal.2020.114832.
[59] Y. Zhao, M. Huo, J. Huo, P. Zhang, X. Shao, X. Zhang, Preparation of silica-epoxy superhydrophobic coating with mechanical stability and multifunctional performance via one-step approach, Colloids and Surfaces A: Physicochemical and Engineering Aspects 653 (2022) 129957. https://doi.org/https://doi.org/10.1016/j.colsurfa.2022.129957.
[60] L. Deng, H. Ye, X. Li, P. Li, J. Zhang, X. Wang, M. Zhu, B.S. Hsiao, Self-roughened omniphobic coatings on nanofibrous membrane for membrane distillation, Separation and Purification Technology 206 (2018) 14-25. https://doi.org/https://doi.org/10.1016/j.seppur.2018.05.035.
[61] L.-F. Ren, F. Xia, V. Chen, J. Shao, R. Chen, Y. He, TiO2-FTCS modified superhydrophobic PVDF electrospun nanofibrous membrane for desalination by direct contact membrane distillation, Desalination 423 (2017) 1-11. https://doi.org/https://doi.org/10.1016/j.desal.2017.09.004.
[62] M. Qtaishat, D. Rana, M. Khayet, T. Matsuura, Preparation and characterization of novel hydrophobic/hydrophilic polyetherimide composite membranes for desalination by direct contact membrane distillation, Journal of Membrane Science 327(1) (2009) 264-273. https://doi.org/https://doi.org/10.1016/j.memsci.2008.11.040.
[63] Z. Pan, X. Zhu, H. Jiang, Y. Liu, R. Chen, Flexible hierarchical Pd/SiO2-TiO2 nanofibrous catalytic membrane for complete and continuous reduction of p-nitrophenol, Journal of Experimental Nanoscience 16(1) (2021) 62-80. https://doi.org/10.1080/17458080.2021.1904137.
[64] H. Zhou, H. Wang, H. Niu, A. Gestos, T. Lin, Robust, Self-Healing Superamphiphobic Fabrics Prepared by Two-Step Coating of Fluoro-Containing Polymer, Fluoroalkyl Silane, and Modified Silica Nanoparticles, Advanced Functional Materials 23(13) (2013) 1664-1670. https://doi.org/https://doi.org/10.1002/adfm.201202030.
[65] Z. Li, P. Zhang, Y.-H. Chiao, K. Guan, R.R. Gonzales, P. Xu, Z. Mai, G. Xu, M. Hu, T. Kitagawa, T. Yoshioka, H. Matsuyama, Improvement of anti-wetting and anti-scaling properties in membrane distillation process by a facile fluorine coating method, Desalination 566 (2023) 116936. https://doi.org/https://doi.org/10.1016/j.desal.2023.116936.
[66] Y.-H. Huang, M.-J. Wang, T.-S. Chung, Development of multifunctional membranes via plasma-assisted nonsolvent induced phase separation, Nature Communications 15(1) (2024) 1092. https://doi.org/10.1038/s41467-024-45414-9.
[67] H. Huang, L. Pan, C.K. Lim, H. Gong, J. Guo, M.S. Tse, O.K. Tan, Hydrothermal Growth of TiO2 Nanorod Arrays and In Situ Conversion to Nanotube Arrays for Highly Efficient Quantum Dot-Sensitized Solar Cells, Small 9(18) (2013) 3153-3160. https://doi.org/https://doi.org/10.1002/smll.201203205.
[68] Q. Wang, H. Ren, Y. Zhao, X. Xia, F. Huang, G. Cui, B. Dong, B. Tang, Facile and mild preparation of brookite-rutile heterophase-junction TiO2 with high photocatalytic activity based on a deep eutectic solvent (DES), Journal of Materials Chemistry A 7(24) (2019) 14613-14619. https://doi.org/10.1039/C9TA02500F.
[69] C. Sun, N. Wang, S. Zhou, X. Hu, S. Zhou, P. Chen, Preparation of self-supporting hierarchical nanostructured anatase/rutile composite TiO2 film, Chemical Communications (28) (2008) 3293-3295. https://doi.org/10.1039/B805072D.
[70] L.E. Macevele, K.L.M. Moganedi, T. Magadzu, Investigation of Antibacterial and Fouling Resistance of Silver and Multi-Walled Carbon Nanotubes Doped Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composite Membrane, Membranes, 2017.
[71] L. Liu, Z. Xiao, Y. Liu, X. Li, H. Yin, A. Volkov, T. He, Understanding the fouling/scaling resistance of superhydrophobic/omniphobic membranes in membrane distillation, Desalination 499 (2021) 114864. https://doi.org/https://doi.org/10.1016/j.desal.2020.114864.
[72] L. Chen, P. Xu, H. Wang, Interplay of the Factors Affecting Water Flux and Salt Rejection in Membrane Distillation: A State-of-the-Art Critical Review, Water, 2020.