Leung Angela, Rijal Kishan, Shankar P Mohana, Mutharasan Raj
Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA.
Biosens Bioelectron. 2006 Jun 15;21(12):2202-9. doi: 10.1016/j.bios.2005.11.022. Epub 2006 Jan 6.
Geometry of tapered fiber sensors critically affects the response of an evanescent field sensor to cell suspensions. Single-mode fibers (nominally at 1300 nm) were tapered to symmetric or asymmetric tapers with diameters in the range of 3-20 microm, and overall lengths of 1-7 mm. Their transmission characteristics in air, water and in the presence of Escherichia coli (JM101 strain) at concentrations of 100, 1000, 7000 and 7 million cells/mL were measured in the 400-800 nm range and gave rich spectral data that lead to the following conclusions. (1) No change in transmission was observed due to E. coli with tapers that showed no relative change in transmission in water compared to air. (2) Tapers that exhibited a significant difference in transmission in water compared to air gave weak response to the presence of the E. coli. Of these, tapers with low waist diameters (6 microm) showed sensitivity to E. coli at 7000 cells/mL and higher concentration. (3) Tapers that showed modest difference in water transmission compared to air, and those that had small waist diameters gave excellent response to E. coli at 100-7000 cells/mL. In addition, mathematical modeling showed that: (1) at low wavelength (470 nm) and small waist diameter (6 microm), transmission with water in the waist region is higher than in air. (2) Small changes in waist diameter (approximately 0.05 microm) can cause larger changes in transmission at 470 nm than at 550 nm at waist diameter of 6 microm. (3) For the same overall geometry, a 5.5 microm diameter taper showed larger refractive index sensitivity compared to a 6.25 microm taper at 470 nm.
锥形光纤传感器的几何形状对倏逝场传感器对细胞悬液的响应有着至关重要的影响。单模光纤（标称波长为1300 nm）被拉制成对称或不对称的锥形，直径范围为3 - 20微米，总长度为1 - 7毫米。在400 - 800纳米范围内测量了它们在空气、水中以及存在浓度为100、1000、7000和700万个细胞/毫升的大肠杆菌（JM101菌株）时的传输特性，得到了丰富的光谱数据，从而得出以下结论。（1）对于在水中与在空气中传输无相对变化的锥形，未观察到大肠杆菌导致的传输变化。（2）在水中与在空气中传输有显著差异的锥形对大肠杆菌的存在反应较弱。其中，腰径较小（6微米）的锥形在7000个细胞/毫升及更高浓度时对大肠杆菌表现出敏感性。（3）在水中与在空气中传输有适度差异的锥形以及腰径较小的锥形在100 - 7000个细胞/毫升时对大肠杆菌有良好的响应。此外，数学建模表明：（1）在低波长（470纳米）和小腰径（6微米）时，腰区有水时的传输高于有空气时。（2）在腰径为6微米时，腰径的微小变化（约0.05微米）在470纳米处比在550纳米处能引起更大的传输变化。（3）对于相同的整体几何形状，在470纳米时，直径为5.5微米的锥形比直径为6.25微米的锥形表现出更大的折射率灵敏度。
