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Yang X, Zeng P, Zhou Y, Wang Q, Zuo J, Duan H, Hu Y. High-performance, large-area flexible SERS substrates prepared by reactive ion etching for molecular detection. NANOTECHNOLOGY 2024; 35:245301. [PMID: 38478979 DOI: 10.1088/1361-6528/ad3363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 03/13/2024] [Indexed: 04/04/2024]
Abstract
In the realm of molecular detection, the surface-enhanced Raman scattering (SERS) technique has garnered increasing attention due to its rapid detection, high sensitivity, and non-destructive characteristics. However, conventional rigid SERS substrates are either costly to fabricate and challenging to prepare over a large area, or they exhibit poor uniformity and repeatability, making them unsuitable for inspecting curved object surfaces. In this work, we present a flexible SERS substrate with high sensitivity as well as good uniformity and repeatability. First, the flexible polydimethylsiloxane (PDMS) substrate is manually formulated and cured. SiO2/Ag layer on the substrate can be obtained in a single process by using ion beam sputtering. Then, reactive ion etching is used to etch the upper SiO2layer of the film, which directly leads to the desired densely packed nanostructure. Finally, a layer of precious metal is deposited on the densely packed nanostructure by thermal evaporation. In our proposed system, the densely packed nanostructure obtained by etching the SiO2layer directly determines the SERS ability of the substrate. The bottom layer of silver mirror can reflect the penetrative incident light, the spacer layer of SiO2and the top layer of silver thin film can further localize the light in the system, which can realize the excellent absorption of Raman laser light, thus enhancing SERS ability. In the tests, the prepared substrates show excellent SERS performance in detecting crystalline violet with a detection limit of 10-11M. The development of this SERS substrate is anticipated to offer a highly effective and convenient method for molecular substance detection.
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Affiliation(s)
- Xing Yang
- National Research Center for High-Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, People's Republic of China
| | - Pei Zeng
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China
| | - Yuting Zhou
- Tsinghua Shenzhen International Graduate School, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen 518055, People's Republic of China
| | - Qingyu Wang
- National Research Center for High-Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, People's Republic of China
| | - Jiankun Zuo
- National Research Center for High-Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, People's Republic of China
- Innovation Institute of the Greater Bay Area, Hunan University, Guangzhou, 511300, People's Republic of China
| | - Huigao Duan
- National Research Center for High-Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, People's Republic of China
- Innovation Institute of the Greater Bay Area, Hunan University, Guangzhou, 511300, People's Republic of China
- Advanced Manufacturing Laboratory of Micro-Nano Optical Devices, Shenzhen Research Institute, Hunan University, Shenzhen, 518000, People's Republic of China
| | - Yueqiang Hu
- National Research Center for High-Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, People's Republic of China
- Advanced Manufacturing Laboratory of Micro-Nano Optical Devices, Shenzhen Research Institute, Hunan University, Shenzhen, 518000, People's Republic of China
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2
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Zeng P, Zheng M, Chen H, Chen G, Shu Z, Chen L, Liang H, Zhou Y, Zhao Q, Duan H. Wafer-Level Highly Dense Metallic Nanopillar-Enabled High-Performance SERS Substrates for Molecular Detection. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:nano13111733. [PMID: 37299638 DOI: 10.3390/nano13111733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 05/22/2023] [Accepted: 05/23/2023] [Indexed: 06/12/2023]
Abstract
Seeking sensitive, large-scale, and low-cost substrates is highly important for practical applications of surface-enhanced Raman scattering (SERS) technology. Noble metallic plasmonic nanostructures with dense hot spots are considered an effective construction to enable sensitive, uniform, and stable SERS performance and thus have attracted wide attention in recent years. In this work, we reported a simple fabrication method to achieve wafer-scale ultradense tilted and staggered plasmonic metallic nanopillars filled with numerous nanogaps (hot spots). By adjusting the etching time of the PMMA (polymethyl methacrylate) layer, the optimal SERS substrate with the densest metallic nanopillars was obtained, which possessed a detection limit down to 10-13 M by using crystal violet as the detected molecules and exhibited excellent reproducibility and long-term stability. Furthermore, the proposed fabrication approach was further used to prepare flexible substrates; for example, a SERS flexible substrate was proven to be an ideal platform for analyzing low-concentration pesticide residues on curved fruit surfaces with significantly enhanced sensitivity. This type of SERS substrate possesses potential in real-life applications as low-cost and high-performance sensors.
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Affiliation(s)
- Pei Zeng
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | | | - Hao Chen
- Jihua Laboratory, Foshan 528000, China
| | | | - Zhiwen Shu
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
- Greater Bay Area Innovation Institute, Hunan University, Guangzhou 511300, China
| | - Lei Chen
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
- Greater Bay Area Innovation Institute, Hunan University, Guangzhou 511300, China
| | - Huikang Liang
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
- Greater Bay Area Innovation Institute, Hunan University, Guangzhou 511300, China
| | - Yuting Zhou
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Beijing 100084, China
| | - Qian Zhao
- State Key Laboratory of Tribology in Advanced Equipment, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Huigao Duan
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
- Greater Bay Area Innovation Institute, Hunan University, Guangzhou 511300, China
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3
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Yang Y, Duan S, Zhao H. Advances in constructing silver nanowire-based conductive pathways for flexible and stretchable electronics. NANOSCALE 2022; 14:11484-11511. [PMID: 35912705 DOI: 10.1039/d2nr02475f] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
With their soaring technological demand, flexible and stretchable electronics have attracted many researchers' attention for a variety of applications. The challenge which was identified a decade ago and still remains, however, is that the conventional electrodes based on indium tin oxide (ITO) are not suitable for ultra-flexible electronic devices. The main reason is that ITO is brittle and expensive, limiting device performance and application. Thus, it is crucial to develop new materials and processes to construct flexible and stretchable electrodes with superior quality for next-generation soft devices. Herein, various types of conductive nanomaterials as candidates for flexible and stretchable electrodes are briefly reviewed. Among them, silver nanowire (AgNW) is selected as the focus of this review, on account of its excellent conductivity, superior flexibility, high technological maturity, and significant presence in the research community. To fabricate a reliable AgNW-based conductive network for electrodes, different processing technologies are introduced, and the corresponding characteristics are compared and discussed. Furthermore, this review summarizes strategies and the latest progress in enhancing the conductive pathway. Finally, we showcase some exemplary applications and provide some perspectives about the remaining technical challenges for future research.
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Affiliation(s)
- Yuanhang Yang
- Virginia Commonwealth University, Department of Mechanical and Nuclear Engineering, BioTech One, 800 East Leigh Street, Richmond, VA 23219, USA.
| | - Shun Duan
- Virginia Commonwealth University, Department of Mechanical and Nuclear Engineering, BioTech One, 800 East Leigh Street, Richmond, VA 23219, USA.
- State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Biomedical Materials of Natural Macromolecules (Beijing University of Chemical Technology), Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing 100029, China
| | - Hong Zhao
- Virginia Commonwealth University, Department of Mechanical and Nuclear Engineering, BioTech One, 800 East Leigh Street, Richmond, VA 23219, USA.
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4
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Broadband Perfect Absorber in the Visible Range Based on Metasurface Composite Structures. MATERIALS 2022; 15:ma15072612. [PMID: 35407943 PMCID: PMC9000352 DOI: 10.3390/ma15072612] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 03/27/2022] [Accepted: 03/31/2022] [Indexed: 11/16/2022]
Abstract
The broadband perfect absorption of visible light is of great significance for solar cells and photodetectors. The realization of a two-dimensional broadband perfect absorber in the visible range poses a formidable challenge with regard to improving the integration of optical systems. In this paper, we numerically demonstrate a broadband perfect absorber in the visible range from 400 nm to 700 nm based on metasurface composite structures. Simulation results show that the average absorptance is ~95.7% due to the combination of the intrinsic absorption of the lossy metallic material (Au) and the coupling resonances of the multi-sized resonators. The proposed perfect absorber may find potential applications in photovoltaics and photodetection.
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Shu Z, Chen Y, Feng Z, Liang H, Li W, Liu Y, Duan H. Asymmetric Nanofractures Determined the Nonreciprocal Peeling for Self-Aligned Heterostructure Nanogaps and Devices. ACS APPLIED MATERIALS & INTERFACES 2022; 14:1718-1726. [PMID: 34978176 DOI: 10.1021/acsami.1c19776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Planar heterostructures composed of two or more adjacent structures with different materials are a kind of building blocks for various applications in surface plasmon resonance sensors, rectifiers, photovoltaic devices, and ambipolar devices, but their reliable fabrication with controllable shape, size, and positioning accuracy remains challenging. In this work, we propose a concept for fabricating planar heterostructures via directional stripping and controlled nanofractures of metallic films, with which self-aligned, multimaterial, multiscale heterostructures with arbitrary geometries and sub-20 nm gaps can be obtained. By using a split ring as the template, the asymmetric nanofracture of the deposited film at the split position results in nonreciprocal peeling of the film in the split ring. Compared to the conventional processes, the final heterostructures are defined only by their outlines, thus providing the ability to fabricate complex heterostructures with higher resolutions. We demonstrate that this method can be used to fabricate heterodimers, multimaterial oligomers, and multiscale asymmetrical electrodes. An Ag-MoS2-Au photodiode with a strong rectification effect is fabricated based on the nanogap heterostructures prepared by this method. This technology provides a unique and reliable approach to define nanogap heterostructures, which are supposed to have potential applications in nanoelectronics, nanoplasmonics, nano-optoelectronics, and electrochemistry.
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Affiliation(s)
- Zhiwen Shu
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
| | - Yiqin Chen
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
| | - Zhanyong Feng
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
| | - Huikang Liang
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
| | - Wanying Li
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Yuan Liu
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Huigao Duan
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, China
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6
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Luo S, Hoff BH, Maier SA, de Mello JC. Scalable Fabrication of Metallic Nanogaps at the Sub-10 nm Level. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2102756. [PMID: 34719889 PMCID: PMC8693066 DOI: 10.1002/advs.202102756] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/09/2021] [Indexed: 06/01/2023]
Abstract
Metallic nanogaps with metal-metal separations of less than 10 nm have many applications in nanoscale photonics and electronics. However, their fabrication remains a considerable challenge, especially for applications that require patterning of nanoscale features over macroscopic length-scales. Here, some of the most promising techniques for nanogap fabrication are evaluated, covering established technologies such as photolithography, electron-beam lithography (EBL), and focused ion beam (FIB) milling, plus a number of newer methods that use novel electrochemical and mechanical means to effect the patterning. The physical principles behind each method are reviewed and their strengths and limitations for nanogap patterning in terms of resolution, fidelity, speed, ease of implementation, versatility, and scalability to large substrate sizes are discussed.
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Affiliation(s)
- Sihai Luo
- Department of ChemistryNorwegian University of Science and Technology (NTNU)TrondheimNO‐7491Norway
| | - Bård H. Hoff
- Department of ChemistryNorwegian University of Science and Technology (NTNU)TrondheimNO‐7491Norway
| | - Stefan A. Maier
- Nano‐Institute MunichFaculty of PhysicsLudwig‐Maximilians‐Universität MünchenMünchen80539Germany
- Blackett LaboratoryDepartment of PhysicsImperial College LondonLondonSW7 2AZUK
| | - John C. de Mello
- Department of ChemistryNorwegian University of Science and Technology (NTNU)TrondheimNO‐7491Norway
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7
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Shi H, Zhu X, Zhang S, Wen G, Zheng M, Duan H. Plasmonic metal nanostructures with extremely small features: new effects, fabrication and applications. NANOSCALE ADVANCES 2021; 3:4349-4369. [PMID: 36133477 PMCID: PMC9417648 DOI: 10.1039/d1na00237f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/14/2021] [Indexed: 06/14/2023]
Abstract
Surface plasmons in metals promise many fascinating properties and applications in optics, sensing, photonics and nonlinear fields. Plasmonic nanostructures with extremely small features especially demonstrate amazing new effects as the feature sizes scale down to the sub-nanometer scale, such as quantum size effects, quantum tunneling, spill-out of electrons and nonlocal states etc. The unusual physical, optical and photo-electronic properties observed in metallic structures with extreme feature sizes enable their unique applications in electromagnetic field focusing, spectra enhancing, imaging, quantum photonics, etc. In this review, we focus on the new effects, fabrication and applications of plasmonic metal nanostructures with extremely small features. For simplicity and consistency, we will focus our topic on the plasmonic metal nanostructures with feature sizes of sub-nanometers. Subsequently, we discussed four main and typical plasmonic metal nanostructures with extremely small features, including: (1) ultra-sharp plasmonic metal nanotips; (2) ultra-thin plasmonic metal films; (3) ultra-small plasmonic metal particles and (4) ultra-small plasmonic metal nanogaps. Additionally, the corresponding fascinating new effects (quantum nonlinear, non-locality, quantum size effect and quantum tunneling), applications (spectral enhancement, high-order harmonic wave generation, sensing and terahertz wave detection) and reliable fabrication methods will also be discussed. We end the discussion with a brief summary and outlook of the main challenges and possible breakthroughs in the field. We hope our discussion can inspire the broader design, fabrication and application of plasmonic metal nanostructures with extremely small feature sizes in the future.
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Affiliation(s)
- Huimin Shi
- Center for Research on Leading Technology of Special Equipment, School of Mechanical and Electrical Engineering, Guangzhou University Guangzhou 510006 China
| | - Xupeng Zhu
- School of Physics Science and Technology, Lingnan Normal University Zhanjiang 524048 China
| | - Shi Zhang
- College of Mechanical and Vehicle Engineering, Hunan University Changsha 410082 China
| | - Guilin Wen
- Center for Research on Leading Technology of Special Equipment, School of Mechanical and Electrical Engineering, Guangzhou University Guangzhou 510006 China
| | | | - Huigao Duan
- College of Mechanical and Vehicle Engineering, Hunan University Changsha 410082 China
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8
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Zeng P, Shu Z, Zhang S, Liang H, Zhou Y, Ba D, Feng Z, Zheng M, Wu J, Chen Y, Duan H. Fabrication of single-nanometer metallic gaps via spontaneous nanoscale dewetting. NANOTECHNOLOGY 2021; 32:205302. [PMID: 33571970 DOI: 10.1088/1361-6528/abe576] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ultrasmall metallic nanogaps are of great significance for wide applications in various nanodevices. However, it is challenging to fabricate ultrasmall metallic nanogaps by using common lithographic methods due to the limited resolution. In this work, we establish an effective approach for successful formation of ultrasmall metallic nanogaps based on the spontaneous nanoscale dewetting effect during metal deposition. By varying the initial opening size of the exposed resist template, the influence of dewetting behavior could be adjusted and tiny metallic nanogaps can be obtained. We demonstrate that this method is effective to fabricate diverse sub-10 nm gaps in silver nanostructures. Based on this fabrication concept, even sub-5 nm metallic gaps were obtained. SERS measurements were performed to show the molecular detection capability of the fabricated Ag nanogaps. This approach is a promising candidate for sub-10 nm metallic gaps fabrication, thus possessing potential applications in nanoelectronics, nanoplasmonics, and nano-optoelectronics.
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Affiliation(s)
- Pei Zeng
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Zhiwen Shu
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Shi Zhang
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Huikang Liang
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Yuting Zhou
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Dedong Ba
- Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000, People's Republic of China
| | - Zhanzu Feng
- Science and Technology on Material Performance Evaluating in Space Environment Laboratory, Lanzhou Institute of Physics, Lanzhou 730000, People's Republic of China
| | - Mengjie Zheng
- Jihua Laboratory, Foshan 528000, People's Republic of China
| | - Jianhui Wu
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Yiqin Chen
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
| | - Huigao Duan
- College of Mechanical and Vehicle Engineering, National Engineering Research Centre for High Efficiency Grinding, Hunan University, Changsha 410082, People's Republic of China
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Tan YJ, Susanto GJ, Anwar Ali HP, Tee BCK. Progress and Roadmap for Intelligent Self-Healing Materials in Autonomous Robotics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2002800. [PMID: 33346389 DOI: 10.1002/adma.202002800] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 08/05/2020] [Indexed: 06/12/2023]
Abstract
Robots are increasingly assisting humans in performing various tasks. Like special agents with elite skills, they can venture to distant locations and adverse environments, such as the deep sea and outer space. Micro/nanobots can also act as intrabody agents for healthcare applications. Self-healing materials that can autonomously perform repair functions are useful to address the unpredictability of the environment and the increasing drive toward the autonomous operation. Having self-healable robotic materials can potentially reduce costs, electronic wastes, and improve a robot endowed with such materials longevity. This review aims to serve as a roadmap driven by past advances and inspire future cross-disciplinary research in robotic materials and electronics. By first charting the history of self-healing materials, new avenues are provided to classify the various self-healing materials proposed over several decades. The materials and strategies for self-healing in robotics and stretchable electronics are also reviewed and discussed. It is believed that this article encourages further innovation in this exciting and emerging branch in robotics interfacing with material science and electronics.
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Affiliation(s)
- Yu Jun Tan
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
- Institute of Innovation in Health Technology (iHealthtech), National University of Singapore, Singapore, 117599, Singapore
| | - Glenys Jocelin Susanto
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Hashina Parveen Anwar Ali
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Benjamin C K Tee
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
- Institute of Innovation in Health Technology (iHealthtech), National University of Singapore, Singapore, 117599, Singapore
- Electrical and Computer Engineering, National University of Singapore, Singapore, 117583, Singapore
- N.1 Institute of Health, National University of Singapore, Singapore
- Institute of Materials Research and Engineering, Agency for Science Technology and Research, Singapore, 138634, Singapore
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10
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Zhu X, Zhang S, Shi H, Zheng M, Wang Y, Xue S, Quan J, Zhang J, Duan H. Huge field enhancement and high transmittance enabled by terahertz bow-tie aperture arrays: a simulation study. OPTICS EXPRESS 2020; 28:5851-5859. [PMID: 32121799 DOI: 10.1364/oe.386076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 02/03/2020] [Indexed: 06/10/2023]
Abstract
Sub-wavelength aperture arrays featuring small gaps have an extraordinary significance in enhancing the interactions of terahertz (THz) waves with matters. But it is difficult to obtain large light-substance interaction enhancement and high optical response signal detection capabilities at the same time. Here, we propose a simple terahertz bow-tie aperture arrays structure with a large electric field enhancement factor and high transmittance at the same time. The field enhancement factor can reach a high value of 1.9×104 and the transmission coefficient of around 0.8 (the corresponding normalized-to-area transmittance is about 14.3) at 0.04 µm feature gap simultaneously. The systematic simulation results show that the designed structure can enhance the intensity of electromagnetic hotspot by continuously reducing the feature gap size without affecting the intensity of the transmittance. We also visually displayed the significant advantages of extremely strong electromagnetic hot spots in local terahertz refractive index detection, which provides a potential platform and simple strategy for enhanced THz spectral detection.
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