Nowadays, the detection of protein molecules’ structure, living cells’ size and organic nanospheres’ shape is an important topic in biomedical and chemical studies. Flow cytometry is a rapid way to quantitatively analyze tens of thousands of particles and cells, and to sort the specific group of them in a fast-flowing fluid simultaneously. At present, there are several methods to detect particle/cell, such as using fluorescence labelling cells, capturing particles by laser trapping, parallel electrodes or surface acoustic waves. However, some fluorescent dyes used in biochemical analysis are detrimental or harmful. The detection method of using laser trapping usually accompanies with photochemical reaction. And, the preparation process of chips integrated with magnetic field, electric field or surface acoustic wave generation devices is complicated and these methods are only suitable for certain kinds of particles/cells. Therefore, it is especially important to fabricate a device that can meet all these requirements.

We present a non-contact, label-free, and real-time monitoring flow cytometer to realize continuous particles recognition based on an FP cavity embedded in a microchannel, which is fabricated in a Polydimethylsiloxane (PDMS) microfluidic chip. The Fabry-Pérot cavity is composed of a pair of aligned fiber Bragg gratings (FBGs). Compared with conventional fiber based FP cavity, the fiber Bragg grating based FP cavity (FBG-FP) is more attractive for the particle detection due to its higher reflectivity, sensitivity and Q factor. In our experiment, the solution containing different polystyrene micro-spheres is injected into the microchannel and the resonant wavelength shift is observed. Such a device might contribute to complex separation and mixture of particles/cells recognition in medical, chemical and clinical researches.

The research was published in Bei Jiang, Hailang Dai, Yun Zou, and Xianfeng Chen, "Continuous detection of micro-particles by fiber Bragg grating Fabry-Pérot flow cytometer," Opt. Express  26, 12579-12584 (2018).