{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T20:56:20Z","timestamp":1792184180460,"version":"4.4.0"},"reference-count":38,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,12]],"date-time":"2026-04-12T00:00:00Z","timestamp":1775952000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"the Japan Society for the Promotion of Science","doi-asserted-by":"crossref","award":["25K01512"],"award-info":[{"award-number":["25K01512"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"crossref"}]},{"award":["25K01512"],"award-info":[{"award-number":["25K01512"]}],"id":[{"id":"https:\/\/ror.org\/00hhkn466","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>Colloidal crystals are periodic arrays of monodisperse particles that exhibit optical stopbands, which can be experimentally observed as a Bragg reflection characterized by a specific Bragg wavelength and width. Precise control of these characteristic parameters is essential for applications in structural color materials, sensors, and tunable photonic crystals. Although the Bragg reflection wavelength can be widely tuned by adjusting the lattice spacing via changes in particle size and concentration, controlling the width over a wide range\u2014such as through expansion\u2014is challenging because it is intrinsically determined by the refractive index contrast between the colloidal particles and their surrounding medium. In this study, the Bragg reflection width of non-close-packed colloidal crystals immobilized in an elastomer film was successfully expanded by adjusting the photoinitiator concentration and ultraviolet light intensity for photopolymerization. Expansion was attributed to the superposition of Bragg reflections at different wavelengths, resulting from spatial variations in the lattice spacings of the non-close-packed colloidal crystals formed during photopolymerization. Owing to the solvent-free and highly flexible nature of the elastomer-immobilized, non-close-packed colloidal crystal film, the Bragg reflection wavelength was readily tuned by mechanical compression while maintaining the expanded Bragg reflection width, thereby advancing the practical applications of structural color materials.<\/jats:p>","DOI":"10.3390\/polym18080946","type":"journal-article","created":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T13:12:26Z","timestamp":1776085946000},"page":"946","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Expansion of Bragg Reflection Width and Tuning Wavelength in Elastomer-Immobilized Non-Close-Packed Colloidal Crystal Films"],"prefix":"10.3390","volume":"18","author":[{"given":"Miyu","family":"Makino","sequence":"first","affiliation":[{"name":"Graduate School of Engineering Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Kanagawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Toshimitsu","family":"Kanai","sequence":"additional","affiliation":[{"name":"Graduate School of Engineering Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Kanagawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.colsurfa.2005.05.038","article-title":"Colloidal crystals as photonic crystals","volume":"270\u2013271","author":"Meseguer","year":"2005","journal-title":"Colloids Surf. A"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"16231","DOI":"10.1103\/PhysRevB.53.16231","article-title":"Strong effects of photonic band structures on the diffraction of colloidal crystals","volume":"53","author":"Vos","year":"1996","journal-title":"Phys. Rev. B"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1016\/j.cocis.2008.09.001","article-title":"Self-assembly of photonic crystals from polymer colloids","volume":"14","author":"Zhang","year":"2009","journal-title":"Curr. Opin. Colloid Interface Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2132","DOI":"10.1021\/cm990080+","article-title":"Single-Crystal Colloidal Multilayers of Controlled Thickness","volume":"11","author":"Jiang","year":"1999","journal-title":"Chem. Mater."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"14485","DOI":"10.1021\/acsami.8b21276","article-title":"Designing Structural-Color Patterns Composed of Colloidal Arrays","volume":"11","author":"Kim","year":"2019","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"eabj8780","DOI":"10.1126\/sciadv.abj8780","article-title":"Direct writing of customized structural-color graphics with colloidal photonic inks","volume":"7","author":"Kim","year":"2021","journal-title":"Sci. Adv."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"57893","DOI":"10.1021\/acsami.1c16500","article-title":"Colloidal Photonic Crystals of Reusable Hydrogel Microparticles for Sensor and Laser Applications","volume":"13","author":"Iwata","year":"2021","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1133","DOI":"10.1021\/acs.analchem.8b04874","article-title":"Gas-Sensing Mechanism of Silica with Photonic Bandgap Shift","volume":"91","author":"Xie","year":"2019","journal-title":"Anal. Chem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"124931","DOI":"10.1016\/j.saa.2024.124931","article-title":"Colorimetric IPN hydrogels embedded with colloidal photonic crystals: A novel approach for the detection of ethanol and Ba2+ ions in water","volume":"323","author":"Lee","year":"2024","journal-title":"Spectrochim. Acta A"},{"key":"ref_10","first-page":"7102511","article-title":"Self-Assembled Colloidal Photonic Crystal on the Fiber Optic Tip as a Sensing Probe","volume":"9","author":"Taddei","year":"2017","journal-title":"IEEE Photonics J."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"7428","DOI":"10.1002\/anie.200701992","article-title":"Highly Tunable Superparamagnetic Colloidal Photonic Crystals","volume":"46","author":"Ge","year":"2007","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3294","DOI":"10.1039\/D1MA00133G","article-title":"Elastomer-immobilized tunable colloidal photonic crystal films with high optical qualities and high maximum strain","volume":"2","author":"Tajima","year":"2021","journal-title":"Mater. Adv."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1021\/la00051a008","article-title":"A Study of Colloidal Crystal Morphology and Orientation via Polarizing Microscopy","volume":"7","author":"Monovoukas","year":"1991","journal-title":"Langmuir"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"356","DOI":"10.1016\/j.poly.2006.06.024","article-title":"Opal and inverse opal photonic crystals: Fabrication and characterization","volume":"26","author":"Waterhouse","year":"2007","journal-title":"Polyhedron"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"387","DOI":"10.1007\/s11051-016-3691-8","article-title":"Facile control of silica nanoparticles using a novel solvent varying method for the fabrication of artificial opal photonic crystals","volume":"18","author":"Gao","year":"2016","journal-title":"J. Nanopart. Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1038\/nature03946","article-title":"Ionic colloidal crystals of oppositely charged particles","volume":"437","author":"Leunissen","year":"2005","journal-title":"Nature"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"7510","DOI":"10.1021\/la700754s","article-title":"Unidirectional Crystallization of Charged Colloidal Silica Due to the Diffusion of a Base","volume":"23","author":"Murai","year":"2007","journal-title":"Langmuir"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"131743","DOI":"10.1016\/j.colsurfa.2023.131743","article-title":"NIPAm-based soft colloidal photonic crystals with high color saturation","volume":"673","author":"Wu","year":"2023","journal-title":"Colloids Surf. A"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2303","DOI":"10.1007\/s10895-016-1926-9","article-title":"Self-Assembly of Colloidal Photonic Crystals of PS@PNIPAM Nanoparticles and Temperature-Responsive Tunable Fluorescence","volume":"26","author":"Yuan","year":"2016","journal-title":"J. Fluoresc."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"100806","DOI":"10.1016\/j.colcom.2024.100806","article-title":"Colloidal photonic crystals with tunable reflection wavelengths or intensities derived from their reconfigurable structures","volume":"62","author":"Namigata","year":"2024","journal-title":"Colloid Interface Sci. Commun."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"9534","DOI":"10.1021\/ja002017n","article-title":"Photonic Crystal Chemical Sensors:\u2009 pH and Ionic Strength","volume":"122","author":"Lee","year":"2000","journal-title":"J. Am. Chem. Soc."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3113","DOI":"10.1021\/ja077979+","article-title":"Polymerized PolyHEMA Photonic Crystals: pH and Ethanol Sensor Materials","volume":"130","author":"Xu","year":"2008","journal-title":"J. Am. Chem. Soc."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Yu, S., Dong, S., Jiao, X., Li, C., and Chen, D. (2019). Ultrathin Photonic Polymer Gel Films Templated by Non-Close-Packed Monolayer Colloidal Crystals to Enhance Colorimetric Sensing. Polymers, 11.","DOI":"10.3390\/polym11030534"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"829","DOI":"10.1038\/39834","article-title":"Polymerized colloidal crystal hydrogel films as intelligent chemical sensing materials","volume":"389","author":"Holtz","year":"1997","journal-title":"Nature"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3322","DOI":"10.1021\/ja021037h","article-title":"Photonic crystal carbohydrate sensors: Low ionic strength sugar sensing","volume":"125","author":"Asher","year":"2003","journal-title":"J. Am. Chem. Soc."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1990","DOI":"10.1021\/am302804b","article-title":"Centrifugation-Induced Water-Tunable Photonic Colloidal Crystals with Narrow Diffraction Bandwidth and Highly Sensitive Detection of SCN\u2212","volume":"5","author":"Ma","year":"2013","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"5673","DOI":"10.1021\/cm062582a","article-title":"Reversible Deformation of Opal Elastomers","volume":"19","author":"Viel","year":"2007","journal-title":"Chem. Mater."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"11350","DOI":"10.1021\/acsnano.7b05885","article-title":"Chameleon-Inspired Mechanochromic Photonic Films Composed of Non-Close-Packed Colloidal Arrays","volume":"11","author":"Lee","year":"2017","journal-title":"ACS Nano"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1365","DOI":"10.1021\/la0521037","article-title":"Photonic Rubber Sheets with Tunable Color by Elastic Deformation","volume":"22","author":"Fudouzi","year":"2006","journal-title":"Langmuir"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"586","DOI":"10.1016\/j.colsurfa.2016.07.030","article-title":"Independent control of optical stop-band wavelength and width of colloidal photonic crystals","volume":"506","author":"Kanai","year":"2016","journal-title":"Colloids Surf. A"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"389","DOI":"10.1002\/1521-4095(200103)13:6<389::AID-ADMA389>3.0.CO;2-L","article-title":"The Fabrication and Bandgap Engineering of Photonic Multilayers","volume":"13","author":"Jiang","year":"2001","journal-title":"Adv. Mater."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1021\/la052071n","article-title":"Doped Colloidal Photonic Crystal Structure with Refractive Index Chirping to the [111] Crystallographic Axis","volume":"22","author":"Park","year":"2006","journal-title":"Langmuir"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"3503","DOI":"10.1021\/la0621160","article-title":"Tuning the Effective Width of the Optical Stop Band in Colloidal Photonic Crystals","volume":"23","author":"Kanai","year":"2007","journal-title":"Langmuir"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Amano, A., and Kanai, T. (2023). Tuning of Optical Stopband Wavelength and Effective Bandwidth of Gel-Immobilized Colloidal Photonic Crystal Films. Gels, 9.","DOI":"10.3390\/gels9010056"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"370","DOI":"10.2109\/jcersj2.118.370","article-title":"Fabrication of large-area silica colloidal crystals immobilized in hydrogel film","volume":"118","author":"Kanai","year":"2010","journal-title":"J. Ceram. Soc. Jpn."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1226","DOI":"10.1143\/JJAP.40.L1226","article-title":"Quick Fabrication of Gigantic Single-Crystalline Colloidal Crystals for Photonic Crystal Applications","volume":"40","author":"Sawada","year":"2001","journal-title":"Jpn. J. Appl. Phys."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1157","DOI":"10.1038\/s41428-021-00512-z","article-title":"Tuning and fixing of uniform Bragg reflection color of gel-immobilized colloidal photonic crystal films","volume":"53","author":"Iwasawa","year":"2021","journal-title":"Polym. J."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2203","DOI":"10.3390\/ai5040108","article-title":"Predicting the Multiphotonic Absorption in Graphene by Machine Learning","volume":"5","year":"2024","journal-title":"AI"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/8\/946\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T04:55:34Z","timestamp":1777006534000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/8\/946"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,12]]},"references-count":38,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["polym18080946"],"URL":"https:\/\/doi.org\/10.3390\/polym18080946","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,12]]}}}