This paper details the design and fabrication ofmillimeter-scale solid propellant rockets for one-timedeployment of wireless sensor platforms, known as Smart Dust.Each microrocket assembly is an integrated system, incorporatinga combustion chamber, composite propellant grain, nozzle,igniter, and thermoelectric power converter. Solid propellant isadvantageous for a millimeter-scale single-use device because ofits simple implementation, unlike liquid propellants, whichrequire a more elaborate system of pumps and valves. Thereforethe total system volume and complexity are minimized.One type of combustion chamber was fabricated in silicon;however, thermal losses to the silicon sidewalls during combustionthrough a 1.5mm2cross section of fuel were too high toreliably maintain a burn. Successful combustion was demonstratedin cylindrical alumina ceramic combustion chambers with thermalconductivities five times lower than silicon and cross sectionsof 1-8mm2. Thrusts of 10-15mN were measured forceramic rockets weighing under lg, with specific impulses up to15s.Silicon nozzles integrated with polysilicon microheaters andthermopiles for thermal power conversion were microfabricated ina single process. Fuel ignition by polysilicon microheaterssuspended on a low-stress nitride (LSN) membrane wasdemonstrated. Microheaters require less than 0.5W of power toignite a propellant composed primarily of hydroxyl-terminatedpolybutadiene (HTPB) with ammonium perchlorate (AP) oxidizer.They are suspended for thermal isolation through bulkpost-processing by a backside deep reactive ion etch (DRIE). Theetched hole beneath the igniter area also serves as a nozzlethrough which high-velocity combustion gases exit the rocket.Thermopiles, which generate voltages proportional to hot andcold junction temperature differentials, have been fabricated inthe same process as igniters, and span backside DRIE thermalisolation cavities. Ten-junction thermopiles produced a maximumpower of20µW. With potential temperature differences ofhundreds of degrees and a total of 120thermocouple junctionsfabricated on the silicon nozzle chip, hundreds of milliwatts ofpower could feasibly be produced during the microrocket's flight andused to augment the Smart Dust power supply
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