Glass capillary assembled microfluidic three-dimensional hydrodynamic focusing device for fluorescent particle detection

A simple fabrication and reusable microfluidic three-dimensional hydrodynamic focus device is proposed in this study, which can be used for fluorescent particle counting and fluorescence intensity detection. The three-dimensional hydrodynamic focus microfluidic device offers numerous advantages over devices with a two-dimensional focus function. However, the fabrication process of most such devices is relatively complicated. In this study, a three-dimensional hydrodynamic focus device is fabricated by assembling commercially available square, round, and tapered glass capillaries. The inner diameter of the square capillary matches the outer diameter of the circular capillary to ensure that the centers of different capillaries are on the same axis. Thus, the device can provide a symmetric three-dimensional hydrodynamic focus flow. The proposed device can control the diameter of the focused flow by changing the flow rate of the sheath and sample flow. Standard fluorescent beads and fluorescent cells are passed through this device to accurately count the number of fluorescent particles and detect the intensity of fluorescence.