A piezoelectric impinging jet valve is used as a study object to investigate the effect of the ball needle in the existing impinging jet and nozzle structure of the valve on the performance of the jet. First, FLUENT software is used under different ball needle and nozzle structural parameters to simulate the pressure distribution that the ball needle and nozzle in the pressure cavity form when the ball needle hits the nozzle, by arranging the structure model of the ball needle and impact valve nozzle. The piezoelectric impact injection valve and the experiment test system are then designed. Test results show that the ball needle and nozzle structural parameters are closely related to the injection performance of the impact valve. Under certain conditions, a greater needle radius corresponds to a smaller nozzle aperture and taper. Moreover, high-viscosity liquid jetting is easily achieved. By using a ball needle with a radius of 1.5 mm, a taper angle of 60°, and a nozzle diameter of 0.1 mm, we can realize the industrial viscosity of 58 000 cps in glue spray, and the injection plastic fluid volume is 0.62 μ l.

To compensate for the insufficiency and instability of solder paste dispensing and printing that are used in the SMT (Surface Mount Technology) production process, a noncontact solder paste jetting system driven by a piezoelectric stack based on the principle of the nozzle-needle-system is introduced in this paper, in which a miniscule gap exists between the nozzle and needle during the jetting process. Here, the critical jet ejection velocity is discussed through theoretical analysis. The relations between ejection velocity and needle structure, needle velocity, and nozzle diameter were obtained by FLUENT software. Then, the prototype of the solder paste jetting system was fabricated, and the performance was verified by experiments. The effects of the gap between nozzle and needle, the driving voltage, and the nozzle diameter on the jetting performance and droplet diameter were obtained. Solder paste droplets 0.85 mm in diameter were produced when the gap between the nozzle and needle was adjusted to 10 μm, the driving voltage to 80 V, the nozzle diameter to 0.1 mm, and the variation of the droplet diameter was within ±3%.

Micro-droplet jetting manufacture is a new 3D printing technology developed in recent years. Presently, this new technology mainly aims at ejecting a low-viscosity medium. Therefore, a device for ejecting high-viscosity molten liquid is designed by analyzing the injection principle of high-viscosity molten liquid. Initially, the cooling mechanism is designed to overcome the defect that the piezoelectric stacks cannot operate in high-temperature conditions. Thereafter, the mathematical model of the liquid velocity in the nozzle is derived, and the factors influencing injection are verified by Fluent. Subsequently, a prototype of the jet printer is fabricated, and the needle velocity is tested by the laser micrometer; the relationship between voltage difference and the needle velocity is also obtained. The experimental results matched the theoretical model well, showing that the voltage difference, needle radius, nozzle diameter, and taper angle are closely related to the injection performance of the 3D jet printer. By using a needle with a radius of 0.4 mm, a nozzle with a diameter of 50 μm, a taper angle of 90°, a supply pressure of 0.05 Mpa, and a voltage difference of 98 V, a molten liquid with a viscosity of 8000 cps can be ejected with a minimum average diameter of 275 μm, and the variation of the droplet diameter is within ±3.8%.

An unconventional inchworm actuator for precision positioning based on piezoelectric (PZT) actuation and electrorheological fluids (ERFs) control technology is presented. The actuator consists of actuation unit (PZT stack pump), fluid control unit (ERFs valve), and execution unit (hydraulic actuator). In view of smaller deformation of PZT stack, a new structure is designed for actuation unit, which integrates the advantages of two modes (namely, diaphragm type and piston type) of the volume changing of pump chamber. In order to improve the static shear yield strength of ERFs, a composite ERFs valve is designed, which adopts the series-parallel plate compound structure. The prototype of the inchworm actuator has been designed and manufactured in the lab. Systematic test results indicate that the displacement resolution of the unconventional inchworm actuator reaches 0.038 μm, and the maximum driving force and velocity are 42 N, 14.8 mm/s, respectively. The optimal working frequency for the maximum driving velocity is 120 Hz. The complete research and development processes further confirm the feasibility of developing a new type of inchworm actuator with high performance based on PZT actuation and ERFs control technology, which provides a reference for the future development of a new type of actuator.

In order to improve levitation capability and stability of ultrasonic standing wave, a novel levitation device was presented, which adopted concave spherical surface on the emitter and the reflector. Using ANSYS software, the acoustic field generated by the concave spherical emitting surface was analyzed and the formation of ultrasonic standing wave was simulated. Based on the simulation result, the distribution and maximum acoustic pressure under different radius of concave spherical surface on the emitter and the reflector were ascertained. Through the MATLAB simulation, the optimal structural parameter and levitation position were predicted. Based on the optimization result, the prototype of standing wave levitation device was designed and manufactured. In the laboratory, the radiation force was tested and levitation experiments were also carried out and the actual levitation position was in accordance with the simulation results. When the distance between the emitter and the reflector equaled to about 34.9 mm, three steel balls of 3 mm diameter could be levitated at the same time in three disparate nodes position, the levitation capability and stability were demonstrated to be enhanced largely.