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Toropov N, Osborne E, Joshi LT, Davidson J, Morgan C, Page J, Pepperell J, Vollmer F. SARS-CoV-2 Tests: Bridging the Gap between Laboratory Sensors and Clinical Applications. ACS Sens 2021; 6:2815-2837. [PMID: 34392681 PMCID: PMC8386036 DOI: 10.1021/acssensors.1c00612] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/28/2021] [Indexed: 12/15/2022]
Abstract
This review covers emerging biosensors for SARS-CoV-2 detection together with a review of the biochemical and clinical assays that are in use in hospitals and clinical laboratories. We discuss the gap in bridging the current practice of testing laboratories with nucleic acid amplification methods, and the robustness of assays the laboratories seek, and what emerging SARS-CoV-2 sensors have currently addressed in the literature. Together with the established nucleic acid and biochemical tests, we review emerging technology and antibody tests to determine the effectiveness of vaccines on individuals.
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Affiliation(s)
- Nikita Toropov
- Living
Systems Institute, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Eleanor Osborne
- Living
Systems Institute, University of Exeter, Exeter EX4 4QD, United Kingdom
| | | | - James Davidson
- Somerset
Lung Centre, Musgrove Park Hospital, Parkfield Drive, Taunton TA1 5DA, United Kingdom
| | - Caitlin Morgan
- Somerset
Lung Centre, Musgrove Park Hospital, Parkfield Drive, Taunton TA1 5DA, United Kingdom
| | - Joseph Page
- Somerset
Lung Centre, Musgrove Park Hospital, Parkfield Drive, Taunton TA1 5DA, United Kingdom
| | - Justin Pepperell
- Somerset
Lung Centre, Musgrove Park Hospital, Parkfield Drive, Taunton TA1 5DA, United Kingdom
| | - Frank Vollmer
- Living
Systems Institute, University of Exeter, Exeter EX4 4QD, United Kingdom
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Abstract
Researchers in the field of whispering-gallery-mode (WGM) microresonators have proposed biointegrated low-threshold WGM lasers, to enable large-scale parallel single-cell tracking and barcoding. Although the reported devices have so far been primarily investigated in model applications, most recent results represent important steps towards the development of in vivo tags and sensors that utilize the unique and narrow spectral features of miniature WGM lasers.
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Affiliation(s)
- Nikita Toropov
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK.
| | - Frank Vollmer
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK.
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Toropov N, Zaki S, Vartanyan T, Sumetsky M. Microresonator devices lithographically introduced at the optical fiber surface. Opt Lett 2021; 46:1784-1787. [PMID: 33793543 DOI: 10.1364/ol.421104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/10/2021] [Indexed: 06/12/2023]
Abstract
We present a simple lithographic method for fabrication of microresonator devices at the optical fiber surface. First, we undress the predetermined surface areas of a fiber segment from the polymer coating with a focused CO2 laser beam. Next, using the remaining coating as a mask, we etch the fiber in a hydrofluoric acid solution. Finally, we completely undress the fiber segment from coating to create a chain of silica bottle microresonators with nanoscale radius variation [surface nanoscale axial photonics (SNAP) microresonators]. We demonstrate the developed method by fabrication of a chain of five 1 mm long and 30 nm high microresonators at the surface of a 125 µm diameter optical fiber and a single 0.5 mm long and 291 nm high microresonator at the surface of a 38 µm diameter fiber. As another application, we fabricate a rectangular 5 mm long SNAP microresonator at the surface of a 38 µm diameter fiber and investigate its performance as a miniature delay line. The propagation of a 100 ps pulse with 1 ns delay, 0.035c velocity, and negligible dispersion is demonstrated. In contrast to previously developed approaches in SNAP technology, the developed method allows the introduction of much larger fiber radius variation ranging from nanoscale to microscale.
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Toropov N, Cabello G, Serrano MP, Gutha RR, Rafti M, Vollmer F. Review of biosensing with whispering-gallery mode lasers. Light Sci Appl 2021; 10:42. [PMID: 33637696 PMCID: PMC7910454 DOI: 10.1038/s41377-021-00471-3] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 01/04/2021] [Accepted: 01/09/2021] [Indexed: 05/04/2023]
Abstract
Lasers are the pillars of modern optics and sensing. Microlasers based on whispering-gallery modes (WGMs) are miniature in size and have excellent lasing characteristics suitable for biosensing. WGM lasers have been used for label-free detection of single virus particles, detection of molecular electrostatic changes at biointerfaces, and barcode-type live-cell tagging and tracking. The most recent advances in biosensing with WGM microlasers are described in this review. We cover the basic concepts of WGM resonators, the integration of gain media into various active WGM sensors and devices, and the cutting-edge advances in photonic devices for micro- and nanoprobing of biological samples that can be integrated with WGM lasers.
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Affiliation(s)
- Nikita Toropov
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK.
| | - Gema Cabello
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK
| | - Mariana P Serrano
- Departamento de Química, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, La Plata, 1900, Argentina
| | - Rithvik R Gutha
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK
| | - Matías Rafti
- Departamento de Química, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, La Plata, 1900, Argentina
| | - Frank Vollmer
- Department of Physics and Astronomy, Living Systems Institute, University of Exeter, Exeter, EX4 4QD, UK.
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Yu Q, Zaki S, Yang Y, Toropov N, Shu X, Sumetsky M. Rectangular SNAP microresonator fabricated with a femtosecond laser. Opt Lett 2019; 44:5606-5609. [PMID: 31730118 DOI: 10.1364/ol.44.005606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
Surface nanoscale axial photonics (SNAP) microresonators, which are fabricated by nanoscale effective radius variation (ERV) of the optical fiber with subangstrom precision, can be potentially used as miniature classical and quantum signal processors, frequency comb generators, and ultraprecise microfluidic and environmental optical sensors. Many of these applications require the introduction of nanoscale ERV with a large contrast α, which is defined as the maximum shift of the fiber cutoff wavelength introduced per unit length of the fiber axis. The previously developed fabrication methods of SNAP structures, which used focused CO2 and femtosecond laser beams, achieved α∼0.02 nm/μm. Here we develop a new, to the best of our knowledge, fabrication method of SNAP microresonators with a femtosecond laser, which allows us to demonstrate a 50-fold improvement of previous results and achieve α∼1 nm/μm. Furthermore, our fabrication method enables the introduction of ERV that is several times larger than the maximum ERV demonstrated previously. As an example, we fabricate a rectangular SNAP resonator and investigate its group delay characteristics. Our experimental results are in good agreement with theoretical simulations. Overall, the developed approach allows us to reduce the axial scale of SNAP structures by an order of magnitude.
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Crespo-Ballesteros M, Yang Y, Toropov N, Sumetsky M. Four-port SNAP microresonator device. Opt Lett 2019; 44:3498-3501. [PMID: 31305557 DOI: 10.1364/ol.44.003498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 06/14/2019] [Indexed: 06/10/2023]
Abstract
It is well known from quantum mechanics that the transmission amplitude of a symmetric double-barrier structure can approach unity at the resonance condition. A similar phenomenon is observed in optics for light which propagates between two waveguides weakly coupled through a microresonator. Examples of microresonators used for this purpose include ring, photonic crystal, toroidal, and bottle microresonators. However, ring and photonic crystal photonic circuits, once fabricated, cannot be finely tuned to arrive at the mentioned resonant condition. In turn, it is challenging to predictably adjust coupling to toroidal and bottle microresonators by translating the input-output microfibers, since the modes of these resonators are difficult to separate spatially. Here we experimentally demonstrate a four-port micro-device based on a SNAP microresonator introduced at the surface of an optical fiber. The eigenmodes and corresponding eigenwavelengths of this resonator are clearly identified for both polarization states by the spectrograms measured along the length of the fiber. This allows us to choose the resonant wavelength and simultaneously determine the positions of the input-output microfiber tapers to arrive at the required resonance condition.
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Bochek D, Toropov N, Vatnik I, Churkin D, Sumetsky M. SNAP microresonators introduced by strong bending of optical fibers. Opt Lett 2019; 44:3218-3221. [PMID: 31259925 DOI: 10.1364/ol.44.003218] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 05/06/2019] [Indexed: 06/09/2023]
Abstract
We introduce a new method of the fabrication of surface nanoscale axial photonic (SNAP) microresonators through strong bending of an optical fiber. We experimentally demonstrate that geometric deformation and refractive index variation induced by bending is sufficient for the formation of a SNAP bottle resonator with nanoscale effective radius variation (ERV) along the fiber axis. In our experiment, we bend the optical fiber into a loop and investigate the properties of the fabricated tunable bottle resonator as a function of the loop dimensions. We find that the introduced ERV is approximately proportional to the local curvature of the loop, while the ERV maximum is proportional to the maximum of the loop curvature squared. The advantages of the demonstrated method are its simplicity, robustness, and ability to mechanically tune introduced resonant structures. This is of crucial importance for the creation of robust and tunable SNAP devices for applications in optical classical and quantum signal processing and ultraprecise sensing.
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Lepeshov S, Gorodetsky A, Krasnok A, Toropov N, Vartanyan TA, Belov P, Alú A, Rafailov EU. Boosting Terahertz Photoconductive Antenna Performance with Optimised Plasmonic Nanostructures. Sci Rep 2018; 8:6624. [PMID: 29700414 PMCID: PMC5919981 DOI: 10.1038/s41598-018-25013-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 04/11/2018] [Indexed: 12/14/2022] Open
Abstract
Advanced nanophotonics penetrates into other areas of science and technology, ranging from applied physics to biology, which results in many fascinating cross-disciplinary applications. It has been recently demonstrated that suitably engineered light-matter interactions at the nanoscale can overcome the limitations of today's terahertz (THz) photoconductive antennas, making them one step closer to many practical implications. Here, we push forward this concept by comprehensive numerical optimization and experimental investigation of a log-periodic THz photoconductive antenna coupled to a silver nanoantenna array. We shed light on the operation principles of the resulting hybrid THz antenna, providing an approach to boost its performance. By tailoring the size of silver nanoantennas and their arrangement, we obtain an enhancement of optical-to-THz conversion efficiency 2-fold larger compared with previously reported results for similar structures, and the strongest enhancement is around 1 THz, a frequency range barely achievable by other compact THz sources. We also propose a cost-effective fabrication procedure to realize such hybrid THz antennas with optimized plasmonic nanostructures via thermal dewetting process, which does not require any post processing and makes the proposed solution very attractive for applications.
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Affiliation(s)
| | - Andrei Gorodetsky
- ITMO University, St.Petersburg, 197101, Russia.
- Aston Institute of Photonic Technologies, Aston University, Birmingham, B4 7ET, UK.
- Department of Chemistry, Imperial College London, London, SW7 2AZ, UK.
| | - Alexander Krasnok
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas, 78712, USA.
| | | | | | - Pavel Belov
- ITMO University, St.Petersburg, 197101, Russia
| | - Andrea Alú
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Edik U Rafailov
- Aston Institute of Photonic Technologies, Aston University, Birmingham, B4 7ET, UK
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