Department of Construction Engineering, National Yunlin University of Science and Technology, Douliou 64002, Taiwan.
Sensors (Basel). 2011;11(9):8550-68. doi: 10.3390/s110908550. Epub 2011 Sep 2.
Optical fiber sensors based on waveguide technology are promising and attractive in chemical, biotechnological, agronomy, and civil engineering applications. A microfluidic system equipped with a long-period fiber grating (LPFG) capable of measuring chloride ion concentrations of several sample materials is presented. The LPFG-based microfluidic platform was shown to be effective in sensing very small quantities of samples and its transmitted light signal could easily be used as a measurand. The investigated sample materials included reverse osmosis (RO) water, tap water, dilute aqueous sample of sea sand soaked in RO water, aqueous sample of sea sand soaked in RO water, dilute seawater, and seawater. By employing additionally a chloride ion-selective electrode sensor for the calibration of chloride-ion concentration, a useful correlation (R2 = 0.975) was found between the separately-measured chloride concentration and the light intensity transmitted through the LPFG at a wavelength of 1,550 nm. Experimental results show that the sensitivity of the LPFG sensor by light intensity interrogation was determined to be 5.0 × 10(-6) mW/mg/L for chloride ion concentrations below 2,400 mg/L. The results obtained from the analysis of data variations in time-series measurements for all sample materials show that standard deviations of output power were relatively small and found in the range of 7.413 × 10(-5)-2.769 × 10(-3) mW. In addition, a fairly small coefficients of variations were also obtained, which were in the range of 0.03%-1.29% and decreased with the decrease of chloride ion concentrations of sample materials. Moreover, the analysis of stability performance of the LPFG sensor indicated that the random walk coefficient decreased with the increase of the chloride ion concentration, illustrating that measurement stability using the microfluidic platform was capable of measuring transmitted optical power with accuracy in the range of -0.8569 mW/ [Formula: see text] to -0.5169 mW/ [Formula: see text]. Furthermore, the bias stability was determined to be in the range of less than 6.134 × 10(-8) mW/h with 600 s time cluster to less than 1.412 × 10(-6) mW/h with 600 s time cluster. Thus, the proposed LPFG-based microfluidic platform has the potential for civil, chemical, biological, and biochemical sensing with aqueous solutions. The compact (3.5 × 4.2 cm), low-cost, real-time, small-volume (∼70 μL), low-noise, and high-sensitive chloride ion sensing system reported here could hopefully benefit the development and applications in the field of chemical, biotechnical, soil and geotechnical, and civil engineering.
基于波导技术的光纤传感器在化学、生物技术、农学和土木工程应用中具有很大的潜力和吸引力。本文提出了一种配备长周期光纤光栅（LPFG）的微流控系统，能够测量几种样品材料的氯离子浓度。实验结果表明，当氯离子浓度低于 2400mg/L 时，基于 LPFG 的传感器的光强度检测灵敏度确定为 5.0×10(-6)mW/mg/L。通过对所有样品材料的时间序列测量数据变化进行分析，得出的结果表明，输出功率的标准偏差相对较小，范围在 7.413×10(-5)-2.769×10(-3)mW 之间。此外，还得到了相当小的变异系数，范围在 0.03%-1.29%之间，并且随着样品材料中氯离子浓度的降低而减小。此外，对 LPFG 传感器稳定性性能的分析表明，随机游走系数随着氯离子浓度的增加而减小，这表明微流控平台能够以 -0.8569 mW/[Formula: see text]到 -0.5169 mW/[Formula: see text]的精度测量传输光功率。此外，在 600 s 时间簇中，偏置稳定性范围小于 6.134×10(-8)mW/h，在 600 s 时间簇中，偏置稳定性范围小于 1.412×10(-6)mW/h。因此，所提出的基于 LPFG 的微流控平台具有用于水溶液的民用、化学、生物和生化传感的潜力。本文报道的紧凑（3.5×4.2cm）、低成本、实时、小体积（∼70μL）、低噪声和高灵敏度的氯离子传感系统有望有益于化学、生物技术、土壤和岩土以及土木工程领域的发展和应用。
