ブックタイトル高分子　POLYMERS　62巻12月号

概要

高分子　POLYMERS　62巻12月号

Front-Line Polymer Science高分子科学最近の進歩Apart from the common stimulus（see I）,hydrogels responsive to biological molecules havebeen widely exploited. Because they can generate aresponse to specific biological molecules, includingglucose, proteins and DNA, hydrogels responsive tobiological molecules have found important applicationsin the field of biosensors. Based on the expansionand contraction qualities of substance-discriminatinghydrogels, a series of sensors that can recognizedifferent materials have been successfully developed.3．Photonic crystal hydrogelsThe sensing properties of hydrogels are mostlybased on their swelling, shrinking responses, orchanges in their mechanical properties（reversiblerepeated bending）. This means that a volume swellratio measurement is required to determine testmolecule concentration. Because hydrogels are not ableto perform this measurement themselves, detectionmethods are limited and have low sensitivity. Theseshortcomings have greatly restricted the applicationsof smart hydrogels in sensors.In recent years, with their unique size and interfaceeffects, nanomaterials have found potential applicationsin the sensing field. PhCs are a relatively new kindof nanomaterial with periodic arrangement of two ormore dielectric materials. Because of their orderedmicrostructure, the basic characteristics of the PhCsinclude their PBG. This results in light with certainwavelengths located within the PBG being prohibitedfrom propagating through the PhCs. 22）,23）Anyresponse that causes a change in the material latticeconstant or average refractive index will cause a shiftof PBG position. 24）,25）Thus, PhCs can be combinedwith the previously mentioned smart hydrogels toproduce PhC hydrogels that can respond to externalstimuli. Changes in the hydrogel volume or refractiveindex can be detected as a corresponding shift inthe peak position of their Bragg diffraction. Thus,a self-expressing sensor is obtained（Fig.1）. In thefollowing section, we will overview the strategies usedto fabricate responsive PhC hydrogels and currentresearch regarding these responsive hydrogels inbiosensors.3.1 Strategies for fabricating responsive PhChydrogelsMany nanostructures have been achieved by usingdifferent strategies including top-down or bottom-upapproaches. Fig.2 shows three typical types of PhCswith one-dimensional（1D）, two-dimensional（2D）＊は、e！高分子のSupporting Informationにハイパーリンクされています。Fig.1Fig.2Schematic illustration of PhC hydrogel sensors. Thechange of（a）refractive index and（c）lattice parametercaused（b）the shift of the reflection spectrum. 24）,25）Schematic illustration of common types of PhCs andtheir turning mechanisms. 26）and three-dimensional（3D）spatial configurations.The dielectric constant of 1D PhC has a periodicallyordered structure along one direction in space, usuallyin the form of a layered structure. The 2D and 3DPhCs have the periodically ordered structures alongtheir corresponding 2 and 3 dimensions in space.Most of the 1D PhCs have linear grating structuresor multilayer structures. The 1D two and three gratingsare fabricated by lithography or etching and are usedas templates for replicating PhC hydrogels directly. Themultilayer structured PhCs are commonly achievedusing layer-by-layer（LBL）deposition techniques. 27）-29）To endow such a 1D PhC with responsive properties, thelayers should be designed with porous structures forthe replication of the hydrogels or should be directlycomposed of stimulus-responsive polymer materials.Layered PhC hydrogels can also be obtained by theself-assembly of block copolymers. 30）,31）The layeredstructure formed through the self-assembly of theblock copolymer has a convenient tunable ability. If itssize is controlled within the visible wavelength range,the PhC will be endowed with structural colors. 32）,33）The 2D PhCs usually include 2D gratings andmonolayer colloidal crystal arrays（CCAs）. Like744 c2013 The Society of Polymer Science, Japan高分子62巻12月号（2013年）