Microfluidic Flow Rate Detection With a Large Dynamic Range by Optical Manipulation

Sensitive flow rate detection with a large dynamic range is highly desirable for the lab-on-a-chip applications. We demonstrate an optofluidic flow rate detection method based on the optical manipulation of a single microparticle by a cleaved single-mode fiber (SMF). The microbalance between the optical force and the flow force on the single polystyrene microparticle was used as a new strategy for the detection. Due to the inverse sensitivity, the limit of detection is pushed down to 20 nL/min by detecting the manipulation length as a function of the flow rate. The measurement range of about three orders of magnitude is achieved. The experimental results indicate that the method produces a good repeatability for the flow rate measurement. The cleaved SMF for the optofluidic manipulation also enables low cost, repeatable, and mass production of the sensing device.