TEXTTEXTTEXTTEXTONEONEONEONEWilliamIlliamMorris(thewallpaperdesigner,ratherthanthecarmaker)suggestedthatnothingshouldhaveaplacethatisnotknowntobeusefulorbelievedtobebeautiful.OpalsOpalsOpalsOpals,though,mightbeboth.AgroupofresearchersfromtheUniversityofSouthampton,inEngland,andtheGermanPlasticsInstituteinDarmstadt,ledbyJeremyBaumberg,havediscoveredhowtocreateaplasticwiththegemstone'siridescentproperties.Theirinventioncouldbeusedtomakeasparklingsubstituteforpaint,banknotesthatarehardtocounterfeitandchemicalsensorsthatcanactasvisiblesell-bydates.Opalsgettheirmilkysheensheensheensheenandrainbowsparklefromthewaylightisscatteredbythetinycrystalsthatformthem.Thesecrystalsarestackedinwhatisknownasaface-centredcubicstructure.Thismeansthattheconstituentatomsarearrangedinalatticeofcubes,withoneextraatomsittingatthecentreofeachcube'ssixfaces.Lightenteringthislatticegetsbouncedaroundinwaysthatgeneratecolourbyreinforcingthepeaksofsomewavelengthsandcancellingoutthoseofothers.Formanyyearsresearchershavebeentryingtodevelopasyntheticsyntheticsyntheticsyntheticmaterialwiththesamelight-scatteringpropertiesasanopal,byetchingpatternsintovariousmaterials.Thatapproachhasfailed.Instead,DrBaumberghasbuilthisopalescentmaterialfromscratch.Heandhisteamgrewtinypolystyrenepolystyrenepolystyrenepolystyrenespheresuntiltheyweresome200nanometresacross,beforehardeningthemwithablastofheat.Theythencoatedthesphereswithastickypolymerpolymerpolymerpolymerbeforeheatingthemagain.Asthemixturewasbaked,thespheresmovednaturallyintoaface-centredcubicstructure.Theresultisaflexiblefilmofcrystalswithopalescentpropertiesthatcanbeusedtocoatmalleablemalleablemalleablemalleablesurfaces,producingattractiveiridescentiridescentiridescentiridescenthues.Thesizeofthespherescanbetailoredtoscatterparticularwavelengthsoflight—ausefulpropertyforsecurityapplicationsinwhichitisimportantthatmaterialscanbeidentifiedprecisely.Moreover,whenthefilmiswarped,thespace