Piezoelectric pump faces unprecedented challenges when higher expectation and requirements need to be met in their applications mainly to medical treatment,hygiene and public health,and preventive healthcare.Specifically,the piezoelectric pump with valve has the disadvantages of complex structure,high duty cycle of valves,and valve movement lagged behind piezoelectric ceramics oscillation.In an attempt to inhibit its shortcomings,some researchers presented novel concepts for structural design of piezoelectric pump with valve,which could become a new research focus.Among them,the investigation into various soft valves,represented by soft structure valves made of rigid materials and soft material valves made of flexible materials,has been fruitful in recent years.The integrated design of both material and structure can tackle the problems encountered in the study of piezoelectric pump with valve,thus simplifying the pump structure,reducing the duty-cycle of valves,and improving the lagging of valve motion.In addition,new inventions of pump structure have sprung up,such as the pumps containing a single-chamber with double-drive,single-chamber with single-drive in series and single-chamber with single-drive in parallel,as well as the mixed-chamber in series and parallel.After surveying the recent progresses made by dominant academia in the development of piezoelectric pump encompassing valve,with a particular emphasis on structure design of both valve and pump body,we also summarize and identify the future research directions.
Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling.However,this cooling system requires a separate pump to drive the fluid transfer,which is uneasy to minimize and reduces their reliability and applicability of the whole system.In order to avoid these problems,valveless piezoelectric pump with fractal-like Y-shape branching tubes is proposed.Fractal-like Y-shape branching tube used in microchannel heat sinks is exploited as no-moving-part valve of the valveless piezoelectric pump.In order to obtain flow characteristics of the pump,the relationship between tube structure and flow rate of the pump is studied.Specifically,the flow resistances of fractal-like Y-shape branching tubes and flow rate of the pump are analyzed by using fractal theory.Then,finite element software is employed to simulate the flow field of the tube,and the relationships between pressure drop and flow rate along merging and dividing flows are obtained.Finally,valveless piezoelectric pumps with fractal-like Y-shape branching tubes with different fractal dimensions of diameter distribution are fabricated,and flow rate experiment is conducted.The experimental results show that the flow rate of the pump increases with the rise of fractal dimension of the tube diameter.When fractal dimension is 3,the maximum flow rate of the valveless pump is 29.16 mL/min under 100 V peak to peak(13 Hz)power supply,which reveals the relationship between flow rate and fractal dimensions of tube diameter distribution.This paper investigates the flow characteristics of valveless piezoelectric pump with fractal-like Y-shape branching tubes,which provides certain references for valveless piezoelectric pump with fractal-like Y-shape branching tubes in application on electronic chip cooling.
半球缺群相比于单一的半球缺具有更好的正、反向流体阻力不等特性,为分析其流阻变化对泵送性能的影响,对泵腔内半球缺群的行数、列数及行列间距的变化进行了研究。推导出半球缺群的正、反向阻力系数作用规律,流阻试验及泵流量试验验证了该规律分析计算流阻及泵流量的可行性;在有限行、列间距范围内,计算及试验流阻差及泵流量均随半球缺群行数、列数的增加而增加;在驱动电压及频率为120 V、6 Hz时,半球缺群3×4、4×3、4×4行列分别获得45.5 m L/min、46.2 m L/min、47.75 m L/min泵流量;理论与试验流量的最大偏差为23.23%。研究表明,半球缺群的流阻作用规律可以用来分析及预测泵流量;增加行数及列数并适当控制行、列间距均能提高泵流量,且增加行数比增加列数能获得更好的输出效果。
Existing researches on no-moving part valves in valve-less piezoelectric pumps mainly concentrate on pipeline valves and chamber bottom valves,which leads to the complex structure and manufacturing process of pump channel and chamber bottom.Furthermore,position fixed valves with respect to the inlet and outlet also makes the adjustability and controllability of flow rate worse.In order to overcome these shortcomings,this paper puts forward a novel implantable structure of valve-less piezoelectric pump with hemisphere-segments in the pump chamber.Based on the theory of flow around bluff-body,the flow resistance on the spherical and round surface of hemisphere-segment is different when fluid flows through,and the macroscopic flow resistance differences thus formed are also different.A novel valve-less piezoelectric pump with hemisphere-segment bluff-body(HSBB)is presented and designed.HSBB is the no-moving part valve.By the method of volume and momentum comparison,the stress on the bluff-body in the pump chamber is analyzed.The essential reason of unidirectional fluid pumping is expounded,and the flow rate formula is obtained.To verify the theory,a prototype is produced.By using the prototype,experimental research on the relationship between flow rate,pressure difference,voltage,and frequency has been carried out,which proves the correctness of the above theory.This prototype has six hemisphere-segments in the chamber filled with water,and the effective diameter of the piezoelectric bimorph is 30mm.The experiment result shows that the flow rate can reach 0.50 mL/s at the frequency of 6 Hz and the voltage of 110 V.Besides,the pressure difference can reach 26.2 mm H2O at the frequency of 6 Hz and the voltage of 160 V.This research proposes a valve-less piezoelectric pump with hemisphere-segment bluff-body,and its validity and feasibility is verified through theoretical analysis and experiment.
JI JingZHANG JianhuiXIA QixiaoWANG ShouyinHUANG JunZHAO Chunsheng
