IMECE 2003-41493 DYNAMIC MODELING AND DESIGN OF A HIGH FREQUENCY MICRO VACUUM PUMP

ABSTRACT A dynamic model of MEMS-fabricated multistage micro vacuum pumps for use in a highly-integrated chemical monitoring system is described. A thermodynamic analysis shows that in order to meet the performance requirements of the system, the micro pump must be operated at very high frequency of approximately 50 kHz. At these frequencies, dynamic effects and resonances due to the interaction of the valves and the pump cavities can play an important limiting role in pump performance. Dynamical effects can also increase the pressure difference between pump cavities increasing the required actuation voltage. The present dynamic model uses integral forms of the momentum and mass conservation equations. Key components of the model are the viscous and inertial terms of the pump's "checkerboard" microvalves, which are evaluated using a CFD model of the valves. At low frequencies, the model results show increased mass flow rate with increased frequency in good agreement with a thermodynamic model. Maximum performance is reached at frequencies of the order of the resonant frequency of the micro pump. The model is also used to study the effect of valve timing and operating point on mass flow rate and power consumption at high frequency

Resonance Effects of Electrostatically Actuated Acoustic Jets

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77281/1/AIAA-2003-1272-471.pd

SPARC-LoRa: A Scalable, Power-efficient, Affordable, Reliable, and Cloud Service-enabled LoRa Networking System for Agriculture Applications

With the rapid development of cloud and edge computing, Internet of Things (IoT) applications have been deployed in various aspects of human life. In this paper, we design and implement a holistic LoRa-based IoT system with LoRa communication capabilities, named SPARC-LoRa, which consists of field sensor nodes and a gateway connected to the Internet. SPARC-LoRa has the following important features. First, the proposed wireless network of SPARC-LoRa is even-driven and using off-the-shelf microcontroller and LoRa communication modules with a customized PCB design to integrate all the hardware. This enables SPARC-LoRa to achieve low power consumption, long range communication, and low cost. With a new connection-based upper layer protocol design, the scalability and communication reliability of SPARC-loRa can be achieved. Second, an open source software including sensor nodes and servers is designed based on Docker container with cloud storage, computing, and LTE functionalities. In order to achieve reliable wireless communication under extreme conditions, a relay module is designed and applied to SPARC-LoRa to forward the data from sensor nodes to the gateway node. The system design and implementation is completely open source and hosted on the DigitalOcean Droplet Cloud. Hence, the proposed system enables further research and applications in both academia and industry. The proposed system has been tested in real fields under different and extreme environmental conditions in Salt Lake City, Utah and the University of Nebraska-Lincoln. The experimental results validate the features of SPARC-LoRa including low power, reliability, and cloud services provided by SPARC-LoRa.Comment: 6 pages, 8 figures, submitted for publicatio

Energy scavenging from insect flight

This paper reports the design, fabrication and testing of an energy scavenger that generates power from the wing motion of a Green June Beetle (C otinis nitida ) during its tethered flight. The generator utilizes non-resonant piezoelectric bimorphs operated in the d 31 bending mode to convert mechanical vibrations of a beetle into electrical output. The available deflection, force, and power output from oscillatory movements at different locations on a beetle are measured with a meso-scale piezoelectric beam. This way, the optimum location to scavenge energy is determined, and up to ~115 µW total power is generated from body movements. Two initial generator prototypes were fabricated, mounted on a beetle, and harvested 11.5 and 7.5 µW in device volumes of 11.0 and 5.6 mm 3 , respectively, from 85 to 100 Hz wing strokes during the beetle's tethered flight. A spiral generator was designed to maximize the power output by employing a compliant structure in a limited area. The necessary technology needed to fabricate this prototype was developed, including a process to machine high-aspect ratio devices from bulk piezoelectric substrates with minimum damage to the material using a femto-second laser. The fabricated lightweight spiral generators produced 18.5–22.5 µW on a bench-top test setup mimicking beetles' wing strokes. Placing two generators (one on each wing) can result in more than 45 µW of power per insect. A direct connection between the generator and the flight muscles of the insect is expected to increase the final power output by one order of magnitude.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90804/1/0960-1317_21_9_095016.pd

An integrated electrostatic peristaltic gas micropump with active microvalves.

A high-performance micro gas pump for high-speed micro gas chromatography (muGC) as well as several microfabrication technologies used to build the proposed micropump, are reported. A high-flow, high-pressure, low-power, and small micro gas pump is needed for sample collection and transportation in a micromachined gas chromatography. Previous micro gas pumps have suffered from low flow-rate, low pressure, large volume, and high-power dissipation. The developed micropump utilizes a number of techniques to achieve low-power electrostatic pumping in a compact module: (1) a multi-stage configuration that creates a small pressure in individual stages, and accumulates these pressures to obtain a high pressure differential across the entire pump; (2) a fluidic resonance-based operation to achieve high flow rate despite the tiny volume displacement of each pump; (3) active timing control of microvalves to regulate pump operation; and (4) several new designs including checkerboard microvalves, dual curved electrodes, and dual pumping chambers. The micropump is fabricated by using new microfabrication technologies. First, a Parylene-assisted wafer bonding technology, performed at a low-temperature of ∼230C°, constructs enclosed pumping chambers without damaging polymer structures, and provides a bond strength of 3.6MPa. Second, a wafer-level Parylene membrane transfer technique constructs pumping and valve membranes between two pumping chambers. The membranes are thin (0.8mum-thick), flexible, freestanding, and cover a shallow (∼5mum deep) and wide (∼2000mum long) recess. Third, an electrode buckling technology forms a smooth out-of-plane curved electrode using only one mask by buckling the thin films under built-in stress with a uniformity of 95% across a 100mm wafer. The fabricated 18-stage pump operates at 14 kHz and produces an air flow rate of 4.0cc/min and a pressure of 17500Pa, using a total power of ∼57mW. It has operated over a 6-month period for a total of ∼300 minutes and has a volume of 25.1x19.1x1mm3. Four- and two-stage pumps demonstrated flow rates of 3.0 and 2.1cc/min and pressures of 7000 and 2500Pa. The 4-stage pump is combined with a microcolumn and a chemiresistor to form a functioning muGC where 4 vapors are separated within 7 seconds. This is the first MEMS-GC analysis featuring an integrated micropump.Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126075/2/3224924.pd