**2. Piezoelectric pump with single chamber**

The piezoelectric pump with single chamber is the basic form of piezoelectric pump. The one-way fluid drive of piezoelectric pump is realized by matching with check valves. The common piezoelectric pumps with single chamber are that with single wafer, bimorph and double actuator.

#### **2.1 Piezoelectric pump with single chamber**

**Figure 1** shows the structure and working principle of the piezoelectric pump with single chamber and single wafer (PPSCSW). Single wafer piezoelectric vibrator, pump body and two check valves (inlet and outlet) constitute a closed pump chamber. The volume of the pump chamber changes with the reciprocating motion of piezoelectric diaphragm driven by AC voltage signal. The inlet valve and outlet valve are opened and closed periodically to form suction and discharge. At the suction stage, the volume of the pump chamber increases, the inlet valve opens, the outlet valve closes, and the fluid enters the pump chamber. When discharging, the volume of the pump chamber is reduced, the outlet valve is opened, the inlet valve is closed, and the fluid is discharged from the pump chamber. This circulation enables one-way flow of fluid.

**Figures 2** and **3** show the three-dimensional structure and prototype of PPSCSW. The shell and pump body are made of the polymethylmethacrylate (PMMA), which has superiorities of easy processing and transparent material. The dimension of upper, middle and bottom shells is 40 mm × 40 mm × 5.5 mm. The diameter of outlet pipe and inlet pipe is Φ7 mm. The inlet and outlet check valves made of rubber umbrella are installed in the same place, with the size of Φ10 mm × 0.5 mm. By adjusting the overall size to 40 mm × 40 mm × 16.5 mm, PPSCSW can precisely control the fluid output flow rate and pressure.

**Figure 4** is the relationships between output flowrate of PPSCSW and the driving voltage and frequency. When the driving voltage is fixed at 150 Vpp and 75 Vpp, the maximum flow rates of 5.42 ml/min and 26.55 ml/min are obtained at 20 Hz and 30 Hz, respectively. When the driving frequency is fixed at 15 Hz and 30 Hz, the flow rate increases with the increase of the driving voltage. When the driving voltage increases to 210 Vpp, the output flow rate of PPSCSW reaches 26.55 ml/min.

**Figure 1.**

*The structure and working principle of PPSCSW [12].*

*Design, Characterisation and Prospect of Piezoelectric Microfluidic Technology DOI: http://dx.doi.org/10.5772/intechopen.98559*

**Figure 2.** *The three-dimensional structure of PPSCSW [12].*

**Figure 3.** *The prototype of PPSCSW [12].*
