A micromixer driven by two valveless piezoelectric pumps with multi-stage mixing characteristics

•Micromixer.•Valveless piezoelectric pumps.•Multi-stage mixing.•Diffuser/nozzle tube.•Tesla tubes. A novel micromixer driven by the valveless piezoelectric pump with multi-stage mixing characteristics is proposed in this paper. Two valveless piezoelectric pumps are integrated into the micromixer, and the inlet and outlet microchannels of the micropumps are composed of the diffuser/nozzle tubes and Tesla tubes. Adopting this structure as the inlet and outlet, the valveless piezoelectric pump realizes the unidirectional flow of fluid. The proposed micromixer is composed of two valveless piezoelectric micropumps enables the solution to be mixed through laminar mixing, chaotic convection mixing, and pulsating mixing in sequence, thus achieving multi-stage mixing of the solution, and the mixing effect is improved step by step.The micromixer has the advantages of controllable mixing, low cost, easy integration, and easy manufacturing. [Display omitted] A novel micromixer driven by the valveless piezoelectric pump with multi-stage mixing characteristics is proposed in this paper. Two valveless piezoelectric pumps are integrated into the micromixer, and the inlet and outlet microchannels of the micropumps are composed of the diffuser/nozzle tubes and Tesla tubes. First, the numerical simulation of the microchannel structure was carried out, and its structural parameters have been optimized to improve the working performance of the valveless piezoelectric pumps. Then, the experimental prototype was made in the laboratory, and the test platform was built. Finally, the mixing performance of the multi-stage micromixer driven by double valveless pumps was characterized by the color reaction experiment of red and blue ink. The simulation and experimental results show that: the vortex generated by the microchannel structure enhances the mixing effect of two solutions; when the working frequency of the micromixer is constant, at the region I in the microchannel, the mixing degree of two solutions increases with the increase of the output flow rate of the valveless piezoelectric pump, while the solution mixing degree at the outlet of the micromixer decreases firstly and then increases with the increase of the output flow rate of pump. When the driving voltage of the valveless piezoelectric pump is 120 Vp-p, and the working frequency is 65 Hz, the output flow rate of a single micropump is 0.20 ml/min. When the phase difference between two piezoelectric pumps is 180°, the mi