# A High-Performance Piezoelectric Micropump with Multi-Chamber in Series
## 1 Introduction  
With the increasing development of MEMS technology, microfluidic technology has also been continuously improving. Micropumps are called the heart of microfluidics. They enable micro and precise fluid delivery and, thus, have vital application prospects in various fields, such as biomedicine [1; 2; 3], cooling systems [4; 5; 6], fuel supply [7; 8; 9], and chemical fields [10; 11; 12].  
Most micropumps can be categorized into two groups: mechanical micropumps (with moving parts) and non-mechanical micropumps (without moving parts) [13]. Micro diaphragm pumps and peristaltic micropumps are the main representatives of the mechanical micropumps. The common principle employs a pump chamber that is closed with a flexible diaphragm on at least one side. Oscillatory movement of the diaphragm generates a two-phase pump cycle with periodic volume changes. The valves act as \"fluidic rectifiers\" that direct the bidirectional fluid movement generated inside the pump chamber into a desired unidirectional flow [14].  
Piezoelectric driving is the drive mechanism used for different micro pumps, including peristaltic pumps, and it uses the piezoelectric vibrator (piezo-vibrator) as the powersource. The inverse piezoelectric effect of piezoelectric ceramics [15] promotes the periodic deformation of the piezo-vibrator (which manifests as piezo-vibrator vibration on the macroscopic scale) and then changes the volume of the pump chamber to realize fluid pumping. In recent years, the piezoelectric micropump has received increasingly more attention and has become one of the hot spots and focuses of research at home and abroad.  
High output performance has always been an important goal of piezoelectric micropump development, which can be achieved through a variety of approaches, such as increasing the number of pump chambers and exploring a variety of pump chamber connection forms (series, parallel, and parallel-series). [PERSON] [16] designed a five-chamber series PZT pump with dimensions of 170 mm \(\times\) 50 mm \(\times\) 20 mm. The experimental results show that the output pressures of three-chamber, four-chamber, and five-chamber piezoelectric pumps are 39%, 83%, and 128% higher than that of single chamber pump, and the maximum flow rates are 25.9%, 49.2%, and 67.8% higher than that of single chamber pumps. The maximum output flow rate can reach 469.2 mL/min, and the maximum output pressure can reach 16.1 kPa. [PERSON] [17] proposed a parallel-series configuration for bimorph piezoelectric actuator micropumps. The results show that under the excitation of 60 V, the maximum flow rate of the parallel piezoelectric micropump is 422 mL/min and the maximum pressure is 0.12 kPa, while the maximum flow rate of the series form is 98 mL/min and the maximum pressure is 0.34 kPa. [PERSON] [18] reported a low-voltage piezoelectric pump for small hydraulic systems. The pump uses laser-cut spring steel to create a passive globe valve in the shape of four leaves, which has a total volume of 45 cm\({}^{3}\). The test results show that the maximum output flow and pressure reach 186 mL/min and 125 kPa, respectively.  
It is evident that these micropumps are basically unable to meet the requirements for high output flow rate, high output pressure, and small size all at the same time. In order to solve the above problems to the maximum extent, based on the series structure, a high-output piezoelectric micropump using the circular unimorph piezo-vibrator and the cantilever check valve is presented in this work. It aims to achieve breakthrough high-output performance of miniaturized piezoelectric pumps with adjustable output flow and output pressure, thus gaining strong practicality in biomedicine, cooling systems, fuel supply, chemical applications, etc.