This paper reports the integration of a biconvex micro optofluidic lens into a flow cytometer. The complex optofluidic and microfluidic channel networks are integrated on a single chip. Flow cytometers are widely applied to environmental monitoring, industrial testing and biochemical studies. Integrating a fow cytometer into microfluidic networks helps to miniaturize the system and make it portable for field use. The integration of optical components, such as lenses, further improves the compactness and thus has been intensively studied recently. However, the current designs suffer from severe light scattering due to the roughness of the solid-based lens interface. In this paper, we propose a micro optofluidic system using an optofuidic liquid lens to focus the light beam. Benefting from the smooth liquid-liquid lens interface and the refractive index matching liquid as cladding streams, a light beam can be well focused without scattering. The variations of the signal peak values are reduced owing to the small beam width at the beam waist. Compared to the macroscale systems and microscale systems with solid lenses, the device presents a more efficient and accurate performance on both counting and sizing of particles. The paper reports an analytical parametric study of the lens, followed by the experimental performance of the cytometer. The cytometer was able to detect and discriminate particles with different sizes.

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