**2.2 Piezoelectric pump with single chamber and a bimorph actuator**

As the name implies, the bimorph actuator is composed of two PZT disks with mechanical serial and parallel structure. **Figure 5** shows the structure of a piezoelectric pump with single chamber and a bimorph actuator (PPSCBA). The working principle of PPSCB is similar to that of PPSCSW in **Figure 1**. However, compared with single wafer piezoelectric pump, double piezoelectric actuators usually have symmetrical structures. In theory, PPSCBA can monitor the output performance by using a PZT disk as a monitor, which will make it more widely application.

In order to study the PPSCBA, the three-dimensional structure and prototype of PPSCBA have been designed, as shown in **Figures 6** and **7**. A bimorph is used as the actuator and sensor. The check valve is an umbrella valve made of rubber.

**Figure 4.** *The relationship between flowrate and driving frequency and voltage [12].*

**Figure 5.** *The structure of PPSCBA [13].*

**Figure 6.** *The three-dimensional structure of PPSCBA [13].*

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

**Figure 7.** *The prototype of PPSCBA [13].*

#### **Figure 8.**

*The relationship between flowrate and driving frequency and voltage [13].*

The material of pump body is PMMA. The overall dimension of PPSCBA is 40 mm × 40 mm × 17 mm. When one PZT disc is used as the driver and the other as the monitor, the monitor of output flow rate is achieved.

As shown in **Figure 8**, when one piezoelectric wafer of the bimorph piezoelectric vibrator is used as the driver and the other as the sensor, the relationship between the output flow rate and the sensing voltage of PPSCBA and the driving frequency and voltage is analyzed. When the driving voltage is fixed at 150 Vpp, the peak values of sensing voltage and output flow, 6.88 Vpp and 3.12 ml/min, are obtained at 21 Hz. Therefore, the optimal frequency of PPSCBA is able to realize self-sensing. When the driving frequency is fixed at 21 Hz, the flow rate and sensing voltage increase with the increase of driving voltage, and the increasing trend is similar. When the driving voltage increases to 300 Vpp, the output flow rate and sensing voltage reach the maximum, which are 28.71 ml/min and 28.0 Vpp respectively. Therefore, PPSCBA can realize the self-sensing of output flow rate.

#### **2.3 Piezoelectric pump with single chamber and double piezoelectric actuator**

In order to improve the drive ability of pump chamber, the piezoelectric pump with single chamber and double piezoelectric actuator (PPSCDPA) is proposed. **Figure 9** shows the structure of PPSCDPA. PPSCDPA consists of an inlet, two

#### *Piezoelectric Actuators - Principles, Design, Experiments and Applications*

**Figure 9.** *The structure of PPSCDPA [14].*

#### **Figure 10.** *The 3-D structure of PPSCDPA [14].*

**Figure 11.** *The prototype of PPSCDPA [14].*

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

piezoelectric diaphragm, two check valves, a pump chamber, a pump body and an outlet. The vibration of the two piezoelectric diaphragms is the same, that is, their driving voltage signals are the same. In the process of suction, two piezoelectric diaphragms bend out of the chamber at the same time; while discharging, the two piezoelectric diaphragms bend to the chamber at the same time. Combined with the unidirectional characteristic of the check valve, the PPSCDPA can realize the one-way transportation of fluid from the inlet to the outlet under the AC voltage signal drive.

The three-dimensional structure and prototype of PPSCDPA with the overall dimension of 65 mm × 40 mm × 12 mm are shown in **Figures 10** and **11**, respectively. The check valves are umbrella valve made of rubber. The material of pump body is PMMA. The performance test platform of PPSCDPA is established, and the output performance of piezoelectric pump is tested. The experimental results show that the maximum flow rate of 45.98 ml/min is achieved when the driving parameters are 15 Hz and 200 Vpp.
