Ph.D. Thesis Biomimetic functional surfaces with tailored wettability for water harvesting and anti-icing applications Nguyen Thanh Binh Nano-Mechatronics UNIVERSITY OF SCIENCE AND TECHNOLOGY February 2019 Biomimetic functional surfaces with tailored wettability for water harvesting and anti-icing 2019 Nguyen Thanh Binh applications Biomimetic functional surfaces with tailored wettability for water harvesting and anti-icing applications Nguyen Thanh Binh A Dissertation Submitted in Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy / Master February 2019 UNIVERSITY OF SCIENCE AND TECHNOLOGY Major of Nano-Mechatronics Supervisor Hyuneui LIM We hereby approve the Ph.D. thesis of Nguyen Thanh Binh. February 2019 Dr. Seungchul PARK Chairman of Thesis Committee Dr. Wandoo KIM Thesis Committee Member Dr. Changdae PARK Thesis Committee Member Dr. Junhee LEE Thesis Committee Member Dr. Hyoungsoo KIM Thesis Committee Member Dr. Youngdo JUNG Thesis Committee Member Dr. Hyuneui LIM Thesis Committee Member / Supervisor UNIVERSITY OF SCIENCE AND TECHNOLOGY ACKNOWLEDGEMENT This study is the result of my PhD thesis carried out at Nature-Inspired Nanoconvergence Systems Department – Nano - Convergence Mechanical Systems Research Division – Korea Institute of Machinery and Materials, Korea with tremendous amount of support. First, I would like to express my sincere gratitude to my advisor, Professor Hyuneui. Lim, for giving me the opportunity to become her student at Nano- mechatronics Department (UST), for giving me all the support, encouragement and advice over past six and half years, and for spending long hours editing this thesis. Her insightful guidance will be great inspiration for my future work in my university afterwards. I would like to thank Dr. Wandoo Kim for his valuable advice and encouragement during my Ph.D’s degree. I would like to convey my great gratefulness to the members of my dissertation defense committee, Dr. Changdae Park, Dr. Junhee Lee, Dr. Hyoungsoo Kim, Dr. Youngdo Jung for giving me all valuable comments and suggestions. Specifically, I would like to thank Dr. Seungchul Park for his honest advice, valuable support and i encouragement, who served as Chairman of my thesis committee. I am also thankful to Dr. Duckgyu Lee for assistance regarding experiment process and theoretical support when I started my PhD’s degree. A special thank should be given to all my laboratory members, Dr. Sunjong Oh, Dr. Cholong Jung, Dr. Seonggi Kim, Cheonji Lee, Gyuhyeon Han for their enthusiastic support. Finally, I dedicate this thesis to my parents, my wife and my daughter for their sincere love, outstanding support, for always beside and encouragement during my PhD’s degree. This would have been impossible without them. ii ABSTRACT iii Biomimetic functional surfaces with tailored wettability for water harvesting and anti-icing applications * Biomimetic or Biomimicry refers to an approach that imitates nature’s time- proved models, elements and strategies to solve sustainability human challenges. In this study, we proposed the fabrication and investigation process on several bio- inspired functional surfaces with tunable wettability towards solving specific problems: water harvesting and anti-icing. Water condensation is a phenomenon which refers to the changing physical state of a matter from gaseous into liquid phase. The simplest process can be imagined is water condensation on objects near earth’s surfaces such as: fog, dew, frost, etc. In this work, we will focus on optimizing suitable surface morphology for durable and high efficiency water harvesting performance. Several geometries and surface energies will have been conducted on Aluminum (Al) plates in order to maximize harvesting efficiency. On the other hand, icing phenomenon refers to a process when liquid transferring its physical state to solid phase. Ice accumulation on functional surfaces had illustrated many bizarre effects and disadvantages in aviation, industry and human activities. Several passive approaches including water iv repellency, Slippery Liquid-Infused Porous Surfaces (SLIPS) and unique design structure in order to optimize anti-icing performance will be introduced throughout this study. Totally, we propose different physicochemical processes which arm to manipulate surface wettability towards solving specific problems including water condensation and anti-icing. The understanding about mechanism and fabrication process is useful for designing water harvesting system and icephobic applications. _________________________________ *A thesis submitted to committee of the University of Science and Technology in a partial fulfillment of the requirement for the degree of Doctor of Science conferred in February, 2019. 초록 v 자연모사 기능성 표면을 이용한 맞춤형 수분수집 및 방빙 응용 연구 자연모사 및 자연모방은 이미 자연의 진화에 의하여 증명된 문제해결법을 이 용하여 지속 가능한 인류의 도전과제를 해결하는 접근방식입니다. 본 연구는 표면의 젖음성을 제어할 수 있는 자연모사 기능성 표면의 제작 및 이에 대한 구체적인 적용인 수분수집 및 방빙의 응용을 제안합니다. 수분 응축이란 공기중의 수분이 기체 상태에서 액체 상태로 변화하는 현상을 말합니다. 이는 안개, 이슬, 서리 등과 같이 지구 표면에서 물이 응축되는 것 을 통해 손쉽게 확인이 가능합니다. 본 연구에서는 고내구성 및 고효율의 수 분수집을 위한 표면 구조 최적화에 집중을 하였습니다. 수분수집 효율 극대화 를 위한 다양한 형상 및 다양한 표면에너지를 가지는 알루미늄 기판을 제작하 였습니다. 또한, 빙결현상은 물이 액체 상태에서 고체상태로 변화하는 과정을 말합니다. 기능성 표면에 얼음이 쌓이는 현상의 경우 항공, 산업 및 사람들의 활동에 많 은 문제를 야기합니다. 본 연구에서는 발수특성 유도, 미끄러운 유체가 주입된 다공성 표면 (SLIPS) 및 독특한 구조 등 다양한 수동적인 접근방식을 연구하 였습니다. 따라서, 본 연구에서는 수분응축 및 방빙 등의 구체적인 현안을 해결하기 위 한 표면 젖음성 제어에 기반한 다양한 물리화학적 공정을 제안합니다. 이러한 메커니즘 및 공정과정에 대한 기반지식은 수분수집 및 방빙 관련 응용이 가능 합니다. TABLE OF CONTENTS ACKNOWLEDGMENTS………………………………………………....i vi ABSTRACT……………………………………………………...……....iii ABSTRACT (KOREAN)………………………………………...…….....v TABLE OF CONTENTS….………………..……………………………vi LIST OF FIGURES………………………..……………………………...x LIST OF TABLE……………………………………………...…..........xvii 1. INTRODUCTION..……..………………………..…...…………......1 1.1 Bio-Inspired Surfaces.……………………….…..….……….1 1.2 Water Harvesting……….….…..….………………..…..........4 1.3 Icing and Anti-icing …………………………....…………...8 2 . BASIC THEORY…………...…………….....……….....……..........12 2.1 Wettability ………………..…………………..………….....12 2.1.1 Surface Tension………................……………..…….13 2.1.2 Superhydrophobic Surface………….…..…………...16 2.1.2.1 Wenzel State………….……………...……..17 2.1.2.2 Cassie-Baxter State……………….....…….…20 vii 2.1.3 Transition from Wenzel to Cassie-Baxter state…...…21 2.2 Nucleation Phenomenon…...…..……....…………………….23 2.2.1 Homogeneous Condensation……...………..………..25 2.2.2 Heterogeneous Condensation…….………………….27 2.3 Water Condensation………………………...………………..30 2.4 Icing and Anti-icing…………………………….………..…..33 2.4.1 Freezing Time…………………………....…………..37 2.4.2 Adhesion Strength……………………….…………..38 3 . RESEARCH ON WATER HARVESTING……………….………...42 3.1 Current Research ………………..………….……………...42 3.2 Experimental methods………………………………..…...52 3.3 Results and Discussion………………..……..…….………..55 3.4 Conclusion ..............................................................................70 4 . RESEARCH ON ANTI-ICING……………....…………..…………71 4.1 Current Research…………………………….………………71 viii 4.2 Effects of Morphology Parameters on Anti-icing Performance of SH Surfaces………………………………………………82 4.2.1 Experimental methods……………………………….82 4.2.2 Results and Discussion………………………………86 4.2.3 Conclusion………………………………...…………96 4.3 Anti-icing on Slippery Liquid-Infused Porous Surface (SLIPs)……………………………………………………....97 4.3.1 Experimental methods……………………………….97 4.3.2 Results and Discussion……………………..………103 4.3.3 Conclusion……………………….………………....114 4.4 Unique Structure for Multi-Functional Surface………...….115 4.4.1 Experimental methods……………..………..…….116 4.4.2 Results and Discussion……………..…..…………119 4.4.3 Conclusion………………………...……..…………131 5. CONCLUSION.………...………………………..……...……...….133 ix REFERENCES .…………………………..….…………..........…….…136 LIST OF FIGURES Figure 1.1 Summarization of bio-inspired functional surfaces and our approaches in this study…………………………………………………...………...….......1 x Figure 1.2 Cactus spines (Donald Erickson), Spider web (Alberto Ghizzi Panizza) and Stenocara beetle (Wikimedia commons).....................................................…5 Figure 1.3 Dew harvesting system in Morocco (Fadel Senna/AFP photo) and Dehumidifier (LG.com)…………………………………..……………………...6 Figure 1.4 Water condensation behaviors on Bare and Hybrid Al………….…7 Figure 1.5 Ice accumulation on aircraft (aircraft.sewaro.us) and De-icing in process (aviationtroubleshooting.blogspot.com) ………………...…………….…8 Figure 1.6 Superhydrophobic surface for anti-icing…………………………..10 Figure 1.7 Penguin feather (Steve Gschmeissner), pitcher plant (Britannica.com) and Inspired Slippery Liquid – Infused Porous surface ……………………….11 Figure 2.1 Molecule at surface misses its half attractive inter-across actions and always tends to move inward………………………………………………….13 Figure 2.2 Surface tension determines the formation of liquid . (a) In air and (b) in contact with solid (glass) wall………………………....………...….……..…14 Figure 2.3 Schematic of liquid drop showing the quantities of Young equation..16 Figure 2.4 Wenzel wetting regime……............................................................…18 Figure 2.5 Geometry when liquid droplet moves an unit area dASL..…………19 Figure 2.6 Cassie-Baxter wetting regime……………..……………………….21 xi Figure 2.7 Apparent contact angle exhibits as a function of Young’s angle via predicted theoretical…………………………………………….….…………22 Figure 2.8 Cluster free energy of formation against cluster radius (r)……….26 Figure 2.9 Energy barriers for homogeneous and heterogeneous nucleation.......29 Figure 2.10 Condensation process in term of heterogeneous nucleation……..30 Figure 2.11 Normalized nucleation energy barrier and nucleation rate for water heterogeneous nucleation (Varanasi, 2010)........………………………………..32 Figure 2.12 Icing phenomenon…………….…………………………...……….34 Figure 2.13 The freezing time definition……………………………………..38 Figure 2.14 The difference between adhesion and cohesion……….......…39 Figure 2.15 Cohesion and adhesion force in case of water and ice..……….40 Figure 2.16 Adhesion strength (in term of shear stress) in our experiment……..41 Figure 3.1 Dew and Fog collector in Morocco (Neil Hall – dailymail.co.uk) and Warka Warka tower for water harvesting in India (Warka Water Inc.).……….43 Figure 3.2 (a) Surface of water capture behavior discovered by Parker (2001) and (b) Further investigation conducted by Thomas Norgaard (2010) ……………45 Figure 3.3 Water collection on spider silk (Lei Jang, 2010) and Opuntia xii microdasys catus spines (Jie Ju, 2012)………………………………………….46 Figure 3.4 (a) Hybrid pattern investigated by Garrod(2007) and (b) water formation in Dorrer model(2008)……………..……...…………………………48 Figure 3.5 Hierarchical structure for enhancing water collection performance using (a) cylinder micropillars (Chen C-H, 2007) and (b) pyramidal structure (Chen Xuemei, 2011)…………………...………………………………….....…49 Figure 3.6 Water harvesting via dewing (Anna Lee, 2012)……………………51 Figure 3.7 Fabrication process of Al surface…………………………...……….53 Figure 3.8 Our design inspired from Stenocara beetle’s back morphology (a) and shadow masks with different spot sizes used in our work……………………54 Figure 3.9 Experimental setup (a) and environmental chamber (b)…….…….55 Figure 3.10 Condensation process on different wettability by the time….……56 Figure 3.11 Prior evolution direction of new form nucleus on different wetting states…………………………………………………………………………...58 Figure 3.12 Condensation rate by the time on surfaces with different wettability……………………………………………………….………………60 Figure 3.13 Water condensation performances on different hybrid samples…....63 xiii Figure 3.14 Water droplet formation on hybrid samples (a) and (b) our experiment to determine receding and advancing contact angles ……...……….65 Figure 3.15 (a) Water droplet formation on hybrid samples and (b) our experiment to determine receding and advancing contact angles ……...………..67 Figure 3.16 Condensation rate with different pattern size...………….....………69 Figure 4.1 Model of water impact with initial dynamic energy conducted by Bahadur (2010) and Mischenko (2011)…………………...………………….....73 Figure 4.2 Spontaneous jumping behavior as a removal method. Experiments conducted by (a) Boreyko (2009) and Chen C-H (2009)……………....…74 Figure 4.3 (a) Ice adhesion measurement custom-built equipment proposed by Kulinich and (b) ice adhesion summarization conducted by Adam (2010)….....76 Figure 4.4 Freezing time delaying conducted by (a) Cao (2009) and (b) Li(2014)…...…………………………………………………………………….77 Figure 4.5 (a) Superhydrophobic may not always reduce adhesion strength (Jing Chen, 2012) and (b) extend freezing time (Stefan Jung, 2011)………………..79 Figure 4.6 (a) Nepenthes pitcher and peristome morphology (Holger F.Bohn. 2004) and (b) design of SLIPs (Wong, 2011) …………………...….……......…80 Figure 4.7 (a) Fabrication process of quartz nanopillars and (b) SEM images of xiv different top size with corresponded contact angles………………………….....83 Figure 4.8 Experimental setup for adhesion strength and freezing time measurement…………………………………………………………………….84 Figure 4.9 Schematic of nanopillar morphology and areal fraction f…..............86 Fi gur e 4.10 Adhesi on str engt h and areal fracti on … .………....…90 Figure 4.11 Icing evolution on surfaces with different morphologies….....92 Figure 4.12 Adhesion strength and areal fraction…...…………….……....…93 Figure 4.13 Height effects in anti-icing performance…………………...….....94 Figure 4.14 Schematic of parameters contributing on anti-icing performance in term of contact area and height………………………………………………95 Figure 4.15 Schematic of fabrication process …………………...….....98 Figure 4.16 (a) Surface roughness and 3D mapping images of samples before and after lubricant coating using a confocal microscope and (b) SEM images of sides and top view of etched Al……………………………………………………. 100 Figure 4.17 Interfacial surface tension measurement using tensiometer (a) and phenomena description (b)………………………………………………….....102 Figure 4.18 Experimental setup for measuring ice adhesion strength ………..102 xv