Piezoelectrically Actuated Miniature Peristaltic Pump zy Yoseph Bar-Cohen and Zensheu Chatig Jet Propulsion Laboratory (JPL)/Caltech’ ABSTRACT There is a range of NASA experiments, instruments and applications where miniature pumps are needed. To address such needs, a piezoelectrically actuated miniature pump is being developed. This pump employs a novel volume dispIacing mechanism using flexural traveling waves that acts peristaltically and eliminates the need for valves or physically moving parts. This pump is being developed for planetary instruments and space applications. Finite element model was developed using ANSYS for the purpose of prediction of the resonance frequency of the vibrating inode for the piezo-pump driving stator. The model allows determining simultaneously the mode shapes that are associated with the various resonance frequencies. This capability is essential for designing the pump size and geometry. To predict and optimize the pump efficiency that is determined by the volume of pumping chambers the model was modified to perform harmonic analysis. Current capability allows the detennination of the effect of such design parameters as pump geometry, construction materials and operating inodes on the volume of the chambers that are formed between the peaks and valleys of the waves. Experiments were made using a breadboard of the pump and showed water-pumping rate of about 4.5 ccfmin. The pump is continually being modified to enhance the performance and efficiency. Keywords: Pumps, piezoelectric actuation, piezopump, peristaltic pump, actuators 1. INTRODUCTION NASA’s mission requirements are becoming more stringent in terms of mass, dimensions, power and cost with a growing emphasis on the reliability of planetary instruments and spacecraft subsystems. These constraints are determining the type of instniments and devices that will be used in future missions and they are impacting the requirements for pumps that can be employed. Pumps are used for a wide variety of applications including thermal management, cooling systems, mass spectrometers, vacuum-controlled devices, and compressors. NASA is increasingly beconling involved with planet surface sampling missions and zyxwvutsrqp in-situ remote analysis where there is a need to enable movement of liquids in instrumentation. The pumps are required to transport liquids, which potentially contain bacteria and other microorganisms, through filter media and the displaced volume can be as low as milliliters. Puinps [Weissler and Carlson, 1979; Lucovsky, 19891 with moving parts have critical seal problems, tend to wear relatively quick, require a reIaiively high power, exhibit a number of reliability problems, are chfficult to miniaturize and have limited temperawe performance. To address these issues, a study is currently underway at the Jet Propulsion Laboratory’s NDEAA Technologies Lab to develop a piezoelectrically actuated miniature pump (so-called piezopump) that can overcome the limitations of conventional mechanisms. Piezopwnp is being developed as a miniature low power device. zyx A novel volume displacing mechanism using flexural traveling waves, which acts peristaltically and allows the elimination of the need for valves or physically moving parts, induces the pumping effect. The pumping action is obtained by einploying the multiple chambers that are formed between peaks and valleys of the traveling wave. The foundations for the development of a piezoelectrically driven pump were laid under the NASA task, entitled “Planetary Dexterous Manipulator”, where piezoelectric motors have been developed as an alternative to conventional electric motors [Eih and Bar-Cohen, 19971. Generally, piezoelechic motors have unique characteristics that are attractive to robotic applications [Hollerbach, Hunter and Ballantyne, 1991 zyxwvutsrq ; Hagood and McFarland, 19941 including miniaturization, low power consumption, self-holding force and simple construction. With proper electronics’ logic (compensating for the effect of temperature on the piezoelectric coefficients), recent experiments at JPL have shown that these motors work effectively at temperatures of 120K and vacuum of 16-mTon- with a torque-speed performance similar to room temperature [Bar-Cohen, Bao, and Grandia, 19981. The characteristics of ultrasonic motors allows developing piezopumps that do not need valves, exhibit low backflow and have tlie potential of high reliable since no physically movtng parts are involved. In order to maximize the pump efficiency, a ’ Correspondence: JFL, (MS 82-lOS), 4800 Oak Grove Drive, Pasadena, CA 91 109-8099 Email yosi(Zjjp1.nasa.g; web: http://ndea.i pl.nasa.gov