In order to improve the output capacity of a piezoelectric pump when transferring gas, this paper presents a compact resonant piezoelectric diaphragm pump (hereinafter referred to as the piezoelectric diaphragm pump), which is driven by a rectangular piezoelectric vibrator. The compact structure can effectively release the vibrating constraints of the vibrator, and enlarge its center output displacement, so as to increase the volume change rate of the pump chamber. Based on the structure and the working principle of this piezoelectric diaphragm pump, a dynamic model for the diaphragm system is established in this paper, and an analysis on factors affecting the resonant frequency of the system is then conducted. We tested on the prototype under the driving voltage of 260 Vpp. The results show that the diaphragm system reaches resonance under the driving frequency of 265 Hz, which is very close to the fundamental frequency of check valve. Compared with the rectangular piezoelectric vibrator’s amplitude, the diaphragm’s amplitude is double amplified. At this time, the piezoelectric diaphragm pump achieves the maximum gas flow rate as 186.8 mL/min and the maximum output pressure as 56.7 kPa.

To improve the stability and reliability of the piezoelectric micro-pump, the cause of air block phenomenon is analyzed on the structure of wheel check valve. During the movement of the bubble in the micro-channel, pressure drop occurs, the main factor which influences the bubble going through is opening height of the wheel check valve. Five groups of wheel check valves with different structures are used to test the wheel check valve opening height and air block probability. The experiment results show that reducing the wheel check valve thickness or diameter ratio can both increase the wheel check valve opening height, and decrease the air block probability. Through experiment, the optimum combination of the wheel check valve structure is obtained within the samples: as the thickness is 0.02 mm, the diameter ratio is 1.2, the wheel check valve opening height gets 252 µm, and within the given bubble volume, the air block probability is less than 2%.

In the field of controlled drug delivery system, there are still many problems on those reported micro-valves, such as the small opening height, unsatisfactory particle tolerance and high cost. To solve the above problems, a novel normally-closed piezoelectric micro-valve is presented in this paper. The micro-valve was driven by circular unimorph piezoelectric vibrator and natural rubber membrane with high elasticity was used as the valve stopper. The small axial displacement of piezoelectric vibrator can be converted into a large stroke of valve stopper based on hydraulic amplification mechanism. The experiment indicates that maximum hydraulic amplification ratio is up to 14, and the cut-off pressure of the micro-valve is 39kPa in the case of no working voltage. The presented micro valve has a large flow control range (ranging from 0 to 8.75mL/min).

Tunnel construction in China is increasing year by year. With the passage of time, China will usher in the peak period of tunnel engineering repair, and it is vital to study in advance the influential nature of tunnel lining crack disease as well as management measures. By summarising a large amount of relevant literature, this paper analyses the main locations where cracks are generated in tunnel linings. Through the method of finite element numerical analysis, 24 cases of cracks of different widths and depths were modelled and calculated for each location of lining vaults, shoulders and side walls, respectively, to analyse the influence of different cases on the internal forces and deformation of the lining. The study shows that the stress concentration around the crack tip decreases with the increase of the crack width, while the stress concentration around the crack tip increases with the increase of the crack depth. The stresses in the other main parts of the lining increase after the crack is created, which has a deteriorating effect on the load-bearing capacity and stability of the lining structure. With the increase in crack width and depth, the sinking deformation of the vault and the heaving deformation of the back arch increase, especially when the cracks are large, but lining cracking has less effect on the lateral deformation of the lining. Compared to cracks in the top and shoulder of the arch, cracks in the side walls have a more pronounced effect on the distribution of internal forces around the cracks.

In this paper, we studied the effect of surface wettability on the bubble tolerance of a piezoelectric membrane pump, by applying the super-hydrophilic or super-hydrophobic surface to the key elements on the pump. Wettability for the flow passage surface has a direct influence on the air bubbles flowing in the fluid. Based on the existing research results, we first analyzed the relationship between the flow passage surface of the piezoelectric pump and the bubbles in the fluid. Then we made three prototypes where pump chamber walls and valve plate surfaces were given different wettability treatments. After the output performance test, results demonstrate that giving super-hydrophilic treatment on the surface of key elements can improve the bubble tolerance of piezoelectric pump; in contrast, giving super-hydrophobic treatment will reduce the bubble tolerance.

Fluidic driving device plays an important role in the delivery and distribution of minute amount of the liquid in the micro-fluidic system. Due to the unique advantages of simple structure, short response time, and low power consumption, piezoelectric actuation was employed to implement the microfluidic transportation. A piezoelectrically driven microfluidic device, piezoelectric pump, was developed and widely applied in many fields in last three decades. As a kind of displacement pump, piezoelectric pumps is able to realize accurate transportation of the liquid because of per stroke of output fluid is equal to the volumetric change of pumping chamber. And the output flow rate and pressure is easily to be controlled through adjusting the driving voltage or frequency. In this chapter, the design, structure, working principle and the characterisation of piezoelectric pumps with single chamber and multiple chambers are introduced.