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Langley KR, Li EQ, Vakarelski IU, Thoroddsen ST. The air entrapment under a drop impacting on a nano-rough surface. SOFT MATTER 2018; 14:7586-7596. [PMID: 30069555 DOI: 10.1039/c8sm01070f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We study the impact of drops onto a flat surface with a nano-particle-based superhydrophobic coating, focusing on the earliest contact using 200 ns time-resolution. A central air-disc is entrapped when the drop impacts the surface, and when the roughness is appropriately accounted for, the height and radial extent of the air-disc follow the scaling laws established for impacts onto smooth surfaces. The roughness also modifies the first contact of the drop around the central air-disc, producing a thick band of micro-bubbles. The initial bubbles within this band coalesce and grow in size. We also infer the presence of an air-film residing inside the microstructure, at radial distances outside the central air-disc. This is manifest by the sudden appearance of microbubbles within a few microseconds after impact. The central air-disc remains pinned on the roughness, unless it is chemically altered to make it superhydrophilic.
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Affiliation(s)
- Kenneth R Langley
- Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.
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Shen D, Zou G, Liu L, Wu A, Duley WW, Zhou YN. Investigation of impact and spreading of molten nanosized gold droplets on solid surfaces. APPLIED OPTICS 2018; 57:2080-2086. [PMID: 29603997 DOI: 10.1364/ao.57.002080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 02/09/2018] [Indexed: 06/08/2023]
Abstract
Understanding the impact dynamics and spreading of molten nanosized droplets on a solid surface is a crucial step towards the design and control of nano-fabrication in many novel applications of nanotechnology. In this context, molecular dynamic (MD) simulations have been conducted to compute temperature and dynamic contact angles of nano-droplets during impact. The evolution of the morphology of a molten metallic nano-droplet impacting on a substrate has been studied using a combination of experimental and simulation techniques. Femtosecond lasers have been used to transfer nanosized gold droplets. Droplet morphology calculated in MD simulations is found to be in good agreement with that seen in scanning electron microscopy (SEM) images. It is found that the spreading of nanoscale molten gold droplets upon impact is enhanced by increasing the droplet impact energy. As observed in experimental data, MD simulation results show that a high droplet-substrate heat transfer rate together with increased wettability of the substrate facilitates spreading and results in a thinner metal deposit after solidification.
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Shen D, Zou G, Liu L, Zhao W, Wu A, Duley WW, Zhou YN. Scalable High-Performance Ultraminiature Graphene Micro-Supercapacitors by a Hybrid Technique Combining Direct Writing and Controllable Microdroplet Transfer. ACS APPLIED MATERIALS & INTERFACES 2018; 10:5404-5412. [PMID: 29357228 DOI: 10.1021/acsami.7b14410] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Miniaturization of energy storage devices can significantly decrease the overall size of electronic systems. However, this miniaturization is limited by the reduction of electrode dimensions and the reproducible transfer of small electrolyte drops. This paper reports first a simple scalable direct writing method for the production of ultraminiature microsupercapacitor (MSC) electrodes, based on femtosecond laser reduced graphene oxide (fsrGO) interlaced pads. These pads, separated by 2 μm spacing, are 100 μm long and 8 μm wide. A second stage involves the accurate transfer of an electrolyte microdroplet on top of each individual electrode, which can avoid any interference of the electrolyte with other electronic components. Abundant in-plane mesopores in fsrGO induced by a fs laser together with ultrashort interelectrode spacing enables MSCs to exhibit a high specific capacitance (6.3 mF cm-2 and 105 F cm-3) and ∼100% retention after 1000 cycles. An all graphene resistor-capacitor (RC) filter is also constructed by combining the MSC and a fsrGO resistor, which is confirmed to exhibit highly enhanced performance characteristics. This new hybrid technique combining fs laser direct writing and precise microdroplet transfer easily enables scalable production of ultraminiature MSCs, which is believed to be significant for practical application of micro-supercapacitor microelectronic systems.
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Affiliation(s)
- Daozhi Shen
- Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, P. R. China
| | - Guisheng Zou
- Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, P. R. China
| | - Lei Liu
- Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, P. R. China
| | - Wenzheng Zhao
- Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, P. R. China
| | - Aiping Wu
- Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, P. R. China
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Kuchmizhak A, Vitrik O, Kulchin Y, Storozhenko D, Mayor A, Mirochnik A, Makarov S, Milichko V, Kudryashov S, Zhakhovsky V, Inogamov N. Laser printing of resonant plasmonic nanovoids. NANOSCALE 2016; 8:12352-61. [PMID: 27273005 DOI: 10.1039/c6nr01317a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Hollow reduced-symmetry resonant plasmonic nanostructures possess pronounced tunable optical resonances in the UV-vis-IR range, being a promising platform for advanced nanophotonic devices. However, the present fabrication approaches require several consecutive technological steps to produce such nanostructures, making their large-scale fabrication rather time-consuming and expensive. Here, we report on direct single-step fabrication of large-scale arrays of hollow parabolic- and cone-shaped nanovoids in silver and gold thin films, using single-pulse femtosecond nanoablation at high repetition rates. The lateral and vertical size of such nanovoids was found to be laser energy-tunable. Resonant light scattering from individual nanovoids was observed in the visible spectral range, using dark-field confocal microspectroscopy, with the size-dependent resonant peak positions. These colored geometric resonances in far-field scattering were related to excitation and interference of transverse surface plasmon modes in nanovoid shells. Plasmon-mediated electromagnetic field enhancement near the nanovoids was evaluated via finite-difference time-domain calculations for their model shapes simulated by three-dimensional molecular dynamics, and experimentally verified by means of photoluminescence microscopy and Raman spectroscopy.
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Affiliation(s)
- A Kuchmizhak
- School of Natural Sciences, Far Eastern Federal University, 8 Sukhanova str., Vladivostok 690041, Russia. and Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Science, Vladivostok 690041, Russia
| | - O Vitrik
- School of Natural Sciences, Far Eastern Federal University, 8 Sukhanova str., Vladivostok 690041, Russia. and Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Science, Vladivostok 690041, Russia
| | - Yu Kulchin
- Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Science, Vladivostok 690041, Russia
| | - D Storozhenko
- Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Science, Vladivostok 690041, Russia
| | - A Mayor
- Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Science, Vladivostok 690041, Russia
| | - A Mirochnik
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Science, Vladivostok, 690022, Russia
| | - S Makarov
- ITMO University, St Petersburg 197101, Russia
| | - V Milichko
- ITMO University, St Petersburg 197101, Russia
| | - S Kudryashov
- ITMO University, St Petersburg 197101, Russia and Lebedev Physical Institute, Russian Academy of Science, Moscow 119991, Russia
| | - V Zhakhovsky
- Dukhov Research Institute of Automatics (SC Rosatom), 127055 Moscow, Russian Federation
| | - N Inogamov
- Dukhov Research Institute of Automatics (SC Rosatom), 127055 Moscow, Russian Federation and Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Russian Federation
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