Novel Bottom-Up Sub-Micron Architectures for Advanced
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NOVEL BOTTOM-UP SUB-MICRON ARCHITECTURES FOR ADVANCED FUNCTIONAL DEVICES by CHIARA BUSA’ A thesis submitted to the University of Birmingham for the degree of DOCTOR OF PHILOSOPHY Supervisor: Dr Pola Goldberg-Oppenheimer Department of Chemical Engineering College of Engineering and Physical Sciences University of Birmingham May 2017 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract This thesis illustrates two novel routes for fabricating hierarchical micro-to-nano structures with interesting optical and wetting properties. The co-presence of asperities spanning the two length scales enables the fabrication of miniaturised, tuneable surfaces exhibiting a high potential for applications in for instance, waterproof coatings and nanophotonic devices, while exploiting the intrinsic properties of the structuring materials. Firstly, scalable, superhydrophobic surfaces were produced via carbon nanotubes (CNT)-based electrohydrodynamic lithography, fabricating multiscale polymeric cones and nanohair-like architectures with various periodicities. CNT forests were used for manufacturing essential components for the electrohydrodynamic setup and producing controlled micro-to-nano features on a millimetre scale. The achieved high contact angles introduced switchable Rose- to-Lotus wetting regimes. Secondly, a cost-effective method was introduced as a route towards plasmonic bandgap metamaterials via electrochemical replication of three-dimensional (3D) DNA nanostructures as sacrificial templates. A range of sub-30nm 3D DNA polyhedrons, immobilised onto conductive and insulating surfaces, were replicated with gold via electrochemical deposition and sputtering. Microscopic characterisation revealed detailed gold replicas preserving both edges and cavities of the DNA nanostructures. Accurate tuning of both polyhedrons’ dimensions and gold plating conditions finally enabled sub-100nm structures which show promising optical properties such as, birefringence for potential applications in photonics, metamaterials and sensing. Dedication To my family, and in particular, to my father. Acknoledgments My first and deepest thanks go to my supervisor, Dr. Pola Goldberg- Oppenheimer, who supported my journey during these three years. My growth as a fully aware scientist and also as a person, is due to this extraordinary woman who provided valuable guidance and support during the deepest moments in both my professional and personal life. Your help was fundamental for keeping me on track, for stopping me from following some of my one too many ideas, while donating time for stimulating me to pursue my paths. For all these reasons I am honestly grateful for your inspiration as a scientist and a woman. I’d like to thank my colleagues and in particular JJ Rickard for enduring my company, my crazy ideas and my slight obsession with having everything in order in the laboratories. Our different backgrounds and the consequential discussions helped me in broadening my research perspectives and attempting a lot of new experiments, and for that I sincerely thank you. Special thanks go to Georgios Gotsis, for the human support and friendship since our very first meeting. Life in the lab would have been way more solitary and tiresome without you to cheer me up. Moreover, professionally speaking, I don’t have enough words for expressing my gratitude for all your help while building new setups and arranging microscopes and cameras. I’d also like to thank all the colleagues from the Advanced Nano-Materials, Structures and Applications (ANMSA) group, Paolo, Carl, Emma, and Rachel. Our different perspectives are the real strength of the group, and I’m profoundly grateful to you all for the help given to me in our time spent together. The studies in these last three years brought me into contact with many brilliant scientists, every one of them enriching my knowledge and providing deep insights of the matter at hand. I would love to thank, in particular, Daniel Escalera Lopez, for his patience in helping me understand the electrochemical world, and Antoine Herbaut, for reminding why I tried so hard to keep my distance from pure organic chemistry and spending hours at the AFM trying to understand what happened to the samples. I want to express my gratitude to all the colleagues in the office, for all the three challenging years we’ve spent together, our discussions and the mutual help. It was a pleasure to have you all alongside me during my PhD journey. In particular, I’d like to thank James Leech for all the help with PCR, the biological insights provided and friendship over these years. Last, but not least, I want to express my infinite gratitude to my family, the one I was born within and my future one. My mother Angela, who transferred to me her limitless curiosity about the surrounding world and my beloved father Giuseppe, who let me know, when I was about 8 years old, that I was meant to pursue virtute e canoscenza (virtue and knowledge, from Poem 26, The Divine Comedy, Dante Alighieri), will have and always had my deepest love. Without the two of you and your unconditional support, strength and unity, I probably would not have reached all my goals. At last, I want to thank my husband (to-be) Claudio, who always had my back and helped me to go through the difficulties of life and work during these last three years…and also prepared a lot of dinners while I was too busy working or writing. Contents List of Figures Figure 1.1. Natural systems mirroring the golden spiral. a) Portrait of Leonardo Fibonacci (1175 – 1250), who introduced the modern Hindu-Arabic numerals in his work, Liber Abaci, and introduced the Fibonacci sequence, formed by integer number which, after the first two, are the sum of the two preceding ones. The golden spiral, in b) can be formed by the progressive juxtaposition of squares with increasing side, following the sequence. The numbers are also common in various biological systems such as c) the phyllotaxis arrangement, d) the flower head disposition, and the e) pine cone bracts. ........ 3 Figure 1.2. Water striders’s legs and butterflies’ wings nanoarchitectures. a) Water Strider are known for their ability to walk on water, which is given by the b) hydrophobic nanohair-like structures of their legs, which trap air bubbles within, and allow the Striders to float. c) Similarly, butterfly wings are comprised of thousands of d) micron scales which are in turn formed by e) nanoscaled setae, which reflect the light and letting the iridescent wings shades to arise. .............. 4 Figure 1.3. Gecko’s feet nanostructure. a) The gecko is a type of lizard which possesses the unique ability to walk vertically. More than 60% of gecko species have multiscale toes, b) which are comprised of thousands and thousands of lamellar-arranged spatulaes. c) The final extremity ends in minute setae, provoking the adhesion on surfaces because of the Van der Waals forces [20,21] that bridge the surface with each one of them. ................................................... 5 Figure 1.4. Material wettability (θsmooth) and the proportion of air trapped within a rough surface diagram ratio. Reproduced from [58] ......................... 9 Figure 1.5. The medium permittivity (ε) and magnetic permeability (μ) quadrant and related different behaviour. The first quadrant explains the common behaviour of transparent or semi-transparent materials such as glass or water. The second quadrant shows the interaction of transverse-electric light with materials with ε < 0, Fundamental in electric plasmonic materials. The third quadrant is the more interesting for optical metamaterials since the coexistence of both ε and μ < 0 determines properties such as the negative refractive index, which enables the technology behind the smart materials, “invisibility cloaks” and environment-mimicking devices. The fourth quadrant is representative of materials interacting with a transverse-magnetic polarised radiation, producing a magnetic plasma oscillation. Such phenomenon does not usually occur at optically visible wavelengths. ............................................................................ 10 Figure 1.6. Starry Night reproduction from fluorescence nanocavities DNA origami. Adapted and reproduced from [98]. ................................................... 13 Figure 2.1. Templating techniques. Top) SEM images of (a) Lotus leaf. (b) Nickel-mold replica of (a). Bottom) SEM images of: (A) Lotus leaf (fresh), (B) Colocasia leaf (fresh) and (C) Colocasia leaf (dry), (D) Lotus-leaf replica (fresh), (E) Colocasia- leaf replica (fresh) and (F) Colocasia-leaf replica (dry) surfaces. Replicated from [99]. ........................................................................................ 21 Figure 2.2. SEM images of the mosquito compound eyes at different magnification. Reproduced from [110]. .......................................................... 23 Figure 2.3. Nanosphere lithography. A range of packed nanosphere lithography-produced