温度敏感水凝胶包覆长周期光纤光栅传感器研究

以N-异丙基丙烯酰胺(NIPAM)为单体、N,N'-亚甲基双丙烯酰胺(MBAA)为交联剂、安息香二甲醚(DMPA)为引发剂,利用紫外光引发聚合制备了一系列温度敏感性聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶,并对其性能进行了测定.结果表明,PNIPAM水凝胶的平衡膨胀比随着交联程度的变化而改变.当交联程度适当时,水凝胶可具有最大的溶胀比.在此研究基础上,利用浸渍提拉法在长周期光纤光栅(LPFG)包层外制备了PNIPAM水凝胶薄膜包覆层.研究了得到的LPFG传感器对温度和湿度的响应性,该类型传感器表现出对温度的灵敏响应性.

LONG-PERIOD FIBER GRATING COATED WITH PNIPAM FOR THERMAL SENSING APPLICATIONS

Thermo-sensitive poly(N-isopropylacrylamide)(PNIPAM) hydrogels were prepared by UV-initiated photopolymerization and used as the cladding layer for thermal-sensing based on the long-period fiber grating(LPFG).In the reaction,N,N′-methylenebisacrylamide was used as crosslinker,benzoin dimethyl ether as initiator.The characteristics of the hydrogels were investigated with FTIR,DSC and TG.The effect of the crosslinking agent content on the swelling ratio was also investigated.The results indicated that the crosslinking agent content had a significant influence on the swelling ratio.A LPFG sensor was designed by utilizing the PNIPAM hydrogel as a sensitive cladding coating.For the preparation,a thin-film of the PNIPAM hydrogel was deposited on the LPFG using the dip-coating technique.Changes in temperature and the relative humidity(RH) cause variation of the spectral characteristics of the LPFG in both the resonant wavelength and the minimum transmission.Following the study to establish an optimized coating,the effect of the temperature and the RH variations on the performance of the sensor was investigated.The experimental results showed that the thin film parameters(thickness and refractive index) were directly related to the sensitivity of sensors,and the LPFG coated with PNIPAM hydrogel showed sensitive response to the temperature variation.Combining the advantages of film sensors and fiber optical sensors,the hydrogel-coated LPFG sensors have application prospects in different areas.