MSMA

MicroSensors and MicroActuators

Georgia Tech MEMS group

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Development of Conductive - fuel - based Chemical Microactuators

Priya Gadiraju, Brian English, Mark G. Allen

This work focuses on the design, fabrication, and characterization of chemical microactuators used for the steering of moving aerodynamic bodies. Chemical microactuators are mm or micron scale devices that convert the chemical energy stored in a fuel into mechanical force, which can either act as a thrust on the body or can eject gas that interacts with the flow surrounding the body, thereby effecting steering. Conventional microfabrication, lamination and laser machining techniques were used in fabricating the actuator device. The performance of the device is tested in terms of burn rate and gas generation capabilities, and performance of the devices is correlated to geometry, fuel chemistry, and energy input by means of electrical, thermal, and chemical models. The combustion work focuses on both conventional chemical actuators and conductive-fuel chemical actuators.

Conventional chemical microactuators operate by using electrical energy to heat an igniter (e.g., by passing current through a metallic wire), allowing heat to be transferred from the wire to the fuel, and initiating a reaction within the fuel. The combustion gases that are generated upon ignition are ejected through a nozzle, thereby producing thrust and/or interaction with the flow. These devices have been demonstrated to exhibit N scale forces with millisecond rise times. These devices have been packaged into arrays, integrated with control and power electronics, and integrated into a small-scale projectile for demonstration. The flight system has been verified, and the divert authority will be confirmed.

In addition, we propose to simplify the actuator design by utilizing microelectromechanical systems (MEMS)-based chemical microactuator which integrates the fuel and the ignition element. This is done by making the fuel conductive by adding conductive powder to conventional fuel and using MEMS technology to produce electrical sources and sinks in a variety of geometries to pass current through the fuel. With this concept, the nonuniform heating of fuel is minimized thereby achieving better performance with less energetic, safer fuels. A wide range of conductive fuels that could be used for projectile steering on these scales are developed. These fuels were then tested in the fabricated 2D and 3D microactuator devices for their performance.

PIV image of the released jet from the microcombustor Tilted view of fabricated actuator with close view of pillars

Combustor firing Assembly Soldered assembly

Sponsor: DARPA (http://192.5.18.102/ucar/programs/mafc.htm)

Other Projects:

Electrodeposited helical coils using excimer laser micromachining à

Last modified on March 9, 2006