Manchee C P K, Zamora V, Silverstone J W, Veinot J G C, Meldrum A
Department of Physics, University of Alberta, Edmonton, AB, Canada.
Opt Express. 2011 Oct 24;19(22):21540-51. doi: 10.1364/OE.19.021540.
Capillaries present a promising structure for microfluidic refractive index sensors. We demonstrate a capillary-type fluorescent core microcavity sensor based on whispering gallery mode (WGM) resonances. The device consists of a microcapillary having a layer of fluorescent silicon quantum dots (QDs) coated on the channel surface. The high effective index of the QD layer confines the electric field near the capillary channel and causes the development of WGM resonances in the fluorescence spectrum. Solutions consisting of sucrose dissolved in water were pumped through the capillary while the fluorescence WGMs were measured with a spectrometer. The device showed a refractometric sensitivity of 9.8 nm/RIU (up to 13.8 nm/RIU for higher solution refractive index) and a maximum detection limit of ~7.2 x 10(-3) RIU. Modeling the field inside the capillary structure, which is analogous to a layered hollow ring resonator, shows that sensitivities as high as 100 nm/RIU and detection limits as low as ~10(-5) RIU may be achievable by optimizing the QD film thickness.
毛细血管为微流控折射率传感器提供了一种很有前景的结构。我们展示了一种基于回音壁模式（WGM）共振的毛细管型荧光核心微腔传感器。该器件由一个微毛细管组成，其通道表面涂覆有一层荧光硅量子点（QD）。量子点层的高有效折射率将电场限制在毛细管通道附近，并导致荧光光谱中出现WGM共振。将蔗糖溶解于水的溶液泵入毛细管，同时用光谱仪测量荧光WGM。该器件的折射灵敏度为9.8 nm/RIU（对于更高的溶液折射率，最高可达13.8 nm/RIU），最大检测限约为7.2×10⁻³ RIU。对类似于分层空心环谐振器的毛细管结构内部的场进行建模表明，通过优化量子点薄膜厚度，灵敏度可高达100 nm/RIU，检测限可低至约10⁻⁵ RIU。
