**4. Conclusion**

Piezoelectric microfluidic technology is currently undergoing a period of prosperous development, partly motivated by the demands for pumping devices in the fields of drug delivery, biological fluid handling, micro total analysis systems, electrophoresis detection, liquid cooling of microelectronics and polymerase chain reaction (PCR). To meet various application requirements, quite a few novel principles and configurations have been presented over the last two decades, including liquid micropump, air micropump, single-chamber micropump, multi-chamber micropump, single-actuator micropump, multi-actuator micropump. This work mainly presented the structure and operating principle of single-chamber and multi-chamber piezoelectric micropumps and demonstrated an application in the field of chip water-cooling system. Some influencing factors on the performance of the piezoelectric micropumps were tested by the experimental frequency and voltage responses. Experimental results showed that there was an optimal driving frequency to maximize the flowrate of the piezoelectric micropump. Basically, the output flowrate was enhanced with the increasing driving voltage. It was helpful to increase the flowrate and backpressure of micropumps through combining the pumping chamber in parallel and serial, respectively. In this work, a maximum flowrate of about 280 ml/min could be achieved by combining five chamber in serial as well as the maximum output pressure approximately approached 11 kPa. Therefore, this work can be used as a reference and guideline for the design and application of piezoelectric microfluidic technology.
