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Photonic crystal sensors use photonic crystals: nanostructures composed of periodic arrangements of dielectric materials that interact with light depending on their particular structure, reflecting lights of specific wavelengths at specific angles. Any change in the periodicity or refractive index of the structure can give rise to a change in the reflected color, or the color perceived by the observer or a spectrometer.[1] That simple principle makes them useful colorimetric intuitive sensors for different applications including, but not limited to, environmental analysis, temperature sensing, magnetic sensing, biosensing, diagnostics, food quality control, security, and mechanical sensing.[citation needed] Many animals in nature such as fish or beetles employ responsive photonic crystals for camouflage, signaling or to bait their prey.[2] The variety of materials utilizable in such structures ranging from inorganic, organic as well as plasmonic metal nanoparticles makes these structures highly customizable and versatile. In the case of inorganic materials, variation of the refractive index is the most commonly exploited effect in sensing, while periodicity change is more commonly exhibited in polymer-based sensors. Besides their small size, current developments in manufacturing technologies have made them easy and cheap to fabricate on a larger scale, making them mass-producible and practical.

Types and structures

Biosensors and integrated lab-on-a-chip

As properly designed photonic crystals exhibit high sensitivity, selectivity, stability, and their electricity-free operation if needed, they have become highly researched portable biological sensors. Developments in analysis, device miniaturization, fluidic design and integration have catapulted the development of integrated photonic crystal sensors in what is known as lab-on-a-chip devices of high sensitivity, low limit of detection, faster response time and low cost.[3] A large range of analytes of biological interest such as proteins, DNA,[4] cancer cells,[5] glucose[6] and antibodies can be detected with this kind of sensors, providing fast, cheap and accurate diagnostic and health-monitoring tools that can detect concentrations as low as 15 nM.[citation needed] Certain chemical or biological target molecules can be integrated within the structure to provide specificity.[7]

Chemical sensors

As chemical analytes have their own specific refractive indices, they can fill porous photonic structures, altering their effective index and consequently their color in a finger-print like manner. On the other hand, they can alter the volume of polymer-based structures, resulting in a change in the periodicity leading to a similar end effect. In ion-containing hydrogels, their selective swelling results in their specificity. Applications in gaseous and aqueous environment have been studied to detect concentrations of chemical species, solvents, vapors,[8] ions,[9] pH[10] and humidity. The specificity and sensitivity can be controlled by the appropriate choice of materials and their interaction with the analytes, that can achieve even label-free sensors.[11] The concentration of chemical species in vapor or liquid phases as well as in more complex mixtures can be determined with high confidence.[12][13]

Mechanical sensors

Different mechanical signals such as pressure, strain, torsion and bending can be detected with photonic crystal sensors. Commonly, they are based on the deformation-induced change in the lattice constants in flexible materials such as elastomeric composites or colloidal crystals, causing a mechano-chromic effect as they stretch or contract.[14]

3D photonic crystals

Synthetic opals are three dimensional photonic crystals usually made of self-assembled nanospheres of diameters on the order of hundreds of nanometers, where the high refractive index material is that of the spheres and the low-index material is air or another filler. On the other hand, inverse opals are structures where the interstitial space between the spheres is filled with another material and the spheres are consequently removed, providing a larger free volume for faster diffusion of chemical species.[15]

Photonic crystal fibers

Photonic crystal fibers are a special types of optical fibers that has contain air holes distributed in specific patterns around a solid or hollow core. Due to their high sensitivity, inherent flexibility, and small diameters, they can be used in a variety of situations requiring high robustness and portability. Compared to traditional optical fibers, they are highly birefringent with tailorable dispersion, limited loss and endless single-mode propagation for a long range of wavelengths and have a very fast sensing response.[16]

2D gratings and slabs

One-dimensional slabs with two dimensional order cause by selective removal of material, creating a pattern of holes or grooves in an otherwise homogeneous material is a popular photonic crystal structure used in sensing.[17]

Fabry-Pérot mirrors

Fabry-Pérot mirrors are planar photonic crystal where the periodicity is maintained only in the z-dimension.[18] sputtered porous inorganic sensors, spin-coated polymer sensors and self-assembled block-copolymers are a few of the commonly used planar 1D structures.[19][20]

References

  1. ^ Paola Lova; Giovanni Manfredi; Davide Comoretto (2018). "Advances in Functional Solution Processed Planar 1D Photonic Crystals". Advanced Optical Materials. 6 (24): 1800730. doi:10.1002/adom.201800730. hdl:11567/928329. S2CID 105380075.
  2. ^ Wang, Hui; Zhang, Ke-Qin (2013-03-28). "Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors". Sensors. 13 (4): 4192–4213. doi:10.3390/s130404192. PMC 3673079. PMID 23539027.
  3. ^ Emiliyanov, Grigoriy; Høiby, Poul; Pedersen, Lars; Bang, Ole (2013-03-08). "Selective Serial Multi-Antibody Biosensing with TOPAS Microstructured Polymer Optical Fibers". Sensors. 13 (3): 3242–3251. doi:10.3390/s130303242. PMC 3658743. PMID 23529122.
  4. ^ Frascella, Francesca; Ricciardi, Serena; Rivolo, Paola; Moi, Valeria; Giorgis, Fabrizio; Descrovi, Emiliano; Michelotti, Francesco; Munzert, Peter; Danz, Norbert; Napione, Lucia; Alvaro, Maria (2013-02-05). "A Fluorescent One-Dimensional Photonic Crystal for Label-Free Biosensing Based on Bloch Surface Waves". Sensors. 13 (2): 2011–2022. doi:10.3390/s130202011. PMC 3649429. PMID 23385414.
  5. ^ Zhang, Ya-nan; Zhao, Yong; Zhou, Tianmin; Wu, Qilu (2018). "Applications and developments of on-chip biochemical sensors based on optofluidic photonic crystal cavities". Lab on a Chip. 18 (1): 57–74. doi:10.1039/c7lc00641a. PMID 29125166.
  6. ^ Nakayama, Daisuke; Takeoka, Yukikazu; Watanabe, Masayoshi; Kataoka, Kazunori (2003-09-15). "Simple and Precise Preparation of a Porous Gel for a Colorimetric Glucose Sensor by a Templating Technique". Angewandte Chemie. 115 (35): 4329–4332. doi:10.1002/ange.200351746.
  7. ^ Cunningham, Brian T.; Zhang, Meng; Zhuo, Yue; Kwon, Lydia; Race, Caitlin (May 2016). "Recent Advances in Biosensing With Photonic Crystal Surfaces: A Review". IEEE Sensors Journal. 16 (10): 3349–3366. Bibcode:2016ISenJ..16.3349C. doi:10.1109/JSEN.2015.2429738. PMC 5021450. PMID 27642265.
  8. ^ Lova, Paola; Manfredi, Giovanni; Bastianini, Chiara; Mennucci, Carlo; Buatier de Mongeot, Francesco; Servida, Alberto; Comoretto, Davide (2019-05-08). "Flory–Huggins Photonic Sensors for the Optical Assessment of Molecular Diffusion Coefficients in Polymers". ACS Applied Materials & Interfaces. 11 (18): 16872–16880. doi:10.1021/acsami.9b03946. hdl:11567/944562. PMID 30990014. S2CID 116863542.
  9. ^ Dodero, Andrea; Lova, Paola; Vicini, Silvia; Castellano, Maila; Comoretto, Davide (2020-06-04). "Sodium Alginate Cross-Linkable Planar 1D Photonic Crystals as a Promising Tool for Pb2+ Detection in Water". Chemosensors. 8 (2): 37. doi:10.3390/chemosensors8020037.
  10. ^ Lee, Kangtaek; Asher, Sanford A. (October 2000). "Photonic Crystal Chemical Sensors: pH and Ionic Strength". Journal of the American Chemical Society. 122 (39): 9534–9537. doi:10.1021/ja002017n.
  11. ^ Megahd, Heba; Oldani, Claudio; Radice, Stefano; Lanfranchi, Andrea; Patrini, Maddalena; Lova, Paola; Comoretto, Davide (2021). "Aquivion–Poly(N-vinylcarbazole) Holistic Flory–Huggins Photonic Vapor Sensors". Advanced Optical Materials. 9 (5): 2002006. doi:10.1002/adom.202002006. S2CID 234179225.
  12. ^ Lova, Paola; Manfredi, Giovanni; Boarino, Luca; Comite, Antonio; Laus, Michele; Patrini, Maddalena; Marabelli, Franco; Soci, Cesare; Comoretto, Davide (2015-04-15). "Polymer Distributed Bragg Reflectors for Vapor Sensing". ACS Photonics. 2 (4): 537–543. doi:10.1021/ph500461w. hdl:11696/32604.
  13. ^ Burgess, Ian B.; Mishchenko, Lidiya; Hatton, Benjamin D.; Kolle, Mathias; Lončar, Marko; Aizenberg, Joanna (2011-08-17). "Encoding Complex Wettability Patterns in Chemically Functionalized 3D Photonic Crystals". Journal of the American Chemical Society. 133 (32): 12430–12432. doi:10.1021/ja2053013. PMID 21766862.
  14. ^ Zhang, Rui; Wang, Qing; Zheng, Xu (2018-03-29). "Flexible mechanochromic photonic crystals: routes to visual sensors and their mechanical properties". Journal of Materials Chemistry C. 6 (13): 3182–3199. doi:10.1039/C8TC00202A.
  15. ^ Shin, Jinsub; Braun, Paul V.; Lee, Wonmok (September 2010). "Fast response photonic crystal pH sensor based on templated photo-polymerized hydrogel inverse opal". Sensors and Actuators B: Chemical. 150 (1): 183–190. doi:10.1016/j.snb.2010.07.018.
  16. ^ De, Moutusi; Gangopadhyay, Tarun Kumar; Singh, Vinod Kumar (2019-01-23). "Prospects of Photonic Crystal Fiber as Physical Sensor: An Overview". Sensors. 19 (3): 464. doi:10.3390/s19030464. PMC 6387015. PMID 30678109.
  17. ^ Tomljenovic-Hanic, Snjezana; de Sterke, C. (2013-03-08). "Reconfigurable, Defect-Free, Ultrahigh-Q Photonic Crystal Microcavities for Sensing". Sensors. 13 (3): 3262–3269. doi:10.3390/s130303262. PMC 3658745. PMID 23529124. S2CID 1785564.
  18. ^ Lova, Paola; Manfredi, Giovanni; Comoretto, Davide (2018). "Advances in Functional Solution Processed Planar 1D Photonic Crystals". Advanced Optical Materials. 6 (24): 1800730. doi:10.1002/adom.201800730. hdl:11567/928329.
  19. ^ Lova, Paola; Megahd, Heba; Comoretto, Davide (2020-02-14). "Thin Polymer Films: Simple Optical Determination of Molecular Diffusion Coefficients". ACS Applied Polymer Materials. 2 (2): 563–568. doi:10.1021/acsapm.9b00964. hdl:11567/988752. S2CID 213899672.
  20. ^ Reddy, Karthik; Guo, Yunbo; Liu, Jing; Lee, Wonsuk; Khaing Oo, Maung Kyaw; Fan, Xudong (November 2011). "On-chip Fabry–Pérot interferometric sensors for micro-gas chromatography detection". Sensors and Actuators B: Chemical. 159 (1): 60–65. doi:10.1016/j.snb.2011.06.041.