On the basis of liquid‐phase reduction mechanism, a novel synthesis method to prepare silver nanoparticles (AgNPs) is proposed, which uses piezoelectric‐actuated three‐phase flow pulsating mixing microfluidic chip. In order to study and explore the influence of different factors on the synthesis of AgNPs, a series of related synthesis experiments were carried out. The corresponding experimental conditions include the concentration of sodium hydroxide and reducing agent solution, polyvinylpyrrolidone (PVP) dosage, inlet flow rate, and synthesis temperature. The synthesized AgNPs were characterized by the UV‐Vis absorption spectrophotometer and transmission electron microscopy. The effects of different experimental conditions on the controllable synthesis of AgNPs were analyzed, and the optimum synthesis conditions of AgNPs were obtained. Experimental results show that the spherical AgNPs with an average particle diameter of about 29 nm, high yield, fine morphology, and good monodispersity were synthesized using the microfluidic chip under the conditions of the working frequency (200 Hz), the initial concentration of silver nitrate (1 mM), the synthesis temperature (80°C), the concentration ratio of sodium hydroxide to silver nitrate (2 : 1), the concentration ratio of glucose to silver nitrate (4 : 1), the inlet flow rate (3.5 ml/min), and the quality ratio of PVP to silver (more than 1 : 1). The related research shows that it is an efficient synthesis method to develop the controllable synthesis experiments of AgNPs under multifactors using the three‐phase pulsating mixing microfluidic chip.

Based on the multi-chamber series structure, a piezoelectric micropump with high output performance is proposed in this paper. The proposed micropump is composed of the circular unimorph piezoelectric vibrator, the cantilever check valve, and the pump body. First, the working process of the piezoelectric micropump was analyzed in detail. Then, the effect of the key dimension parameters on the output performance of the micropump was explored. The key dimension parameters mainly refer to the height of the pump chamber and valve opening (the deformation size of the valve). Finally, experimental prototypes with different parameters were fabricated for the evaluation of the output performance of the micropump. The experimental results show that when the pump chamber height is 0.1 mm and the valve opening is 0.4 mm, the piezoelectric micropump has a good comprehensive output performance. In particular, at 170 V and 120 Hz, the maximum flow rate of the dual-chamber series pump is 65.5 mL/min, and at 100 Hz, the maximum output pressure reaches 59.1 kPa. Moreover, at a certain voltage of 170 V, when the drive frequency is 450 Hz and 550 Hz, the output flow rate and pressure of the four-chamber series pump reach a maximum of 110 mL/min and exceed 140 kPa, respectively. In addition, the volumes of the proposed single-chamber, dual-chamber series, and four-chamber series micropumps are 22 mm × 22 mm × 5 mm, 32.6 mm × 22 mm × 5 mm, and 53.8 mm × 22 mm × 5 mm, respectively. The proposed piezoelectric micropump has the advantages of simple structure, low cost, miniaturization, and high output performance, thus gaining potential practicality for biomedical applications, cooling systems, fuel supply, chemical applications, etc.

Active micromixers have been widely used in chemistry, biomedicine and many micro analyses as it offers low reagent consumption, controllable mixing process, safe, and reliable. Based on piezoelectric (PZT) drive technology and numerical simulation results, a self-circulation micromixer with high frequency vibration has been designed and fabricated. The micromixer is composed of PZT micropump, vibration substrate, mixing pool with double U-shaped inlet and outlet, upper cover plate and lower substrate. The performance of the micromixer’s self-circulation and high frequency vibration is evaluated by experimental tests. Experimental results show that: When the drive voltage and frequency of the self-circulation reflux micropump are set to 100 V and 100 Hz, respectively, a significant vortex flow is generated in the mixing pool, and the vortex flow speed is as high as 320 r min ⁻¹ . When the driving frequency of the vibration substrate is set to its first resonance frequency, the displacement of its center point is the largest up to 28.1 µ m. Furthermore, the vortex flow speed of the fluid in the mixing pool and the vibration intensity of the vibration substrate can be adjusted separately by regulating the driving voltage of the PZT micropump and vibration substrate.

The synthetic jet piezoelectric air pump is a potential miniature device for electronic cooling. In order to improve the performance of the device, a small-sized synthetic jet piezoelectric air pump is proposed in this work, which is mainly characterized by petal-shaped inlet channels. First, the structure and working principle of the piezoelectric vibrator and the proposed pump are analyzed. Then, three synthetic jet piezoelectric air pumps with different inlet channels are compared. These inlets are the direct channels, the diffuser/nozzle channels, and the petal-shaped channels, respectively. Furthermore, the performance of the synthetic jet piezoelectric air pump with the petal-shaped inlet channels is optimized by orthogonal tests. Finally, the simulation was used to investigate the heat dissipation capability of the synthetic jet piezoelectric pump. The experimental results show that among the three inlet channels, the petal-shaped channel can greatly improve the performance of the pump. The unoptimized pump with petal-shaped channels has a maximum flow rate of 1.8929 L/min at 100 V, 3.9 kHz. Additionally, the optimized pump with petal-shaped channels reaches a maximum flow rate of 3.0088 L/min at 100 V, 3.7 kHz, which is 58.95% higher than the unoptimized one. The proposed synthetic jet piezoelectric air pump greatly improves the output performance and has the advantages of simple structure, low cost, and easy integration. The convective heat transfer coefficient of the synthetic jet piezoelectric pump is 28.8 $\mathrm{W}/\left({\mathrm{m}}^2·°\mathrm{C}\right)$, which can prove that the device has a better heat dissipation capability.