A novel sub-micron, solid-state motor is introduced that uses the electric field energy of an open-gap p-n junction to accelerate a piston attached to a load (Sheehan, Putnam and Wright, Found. Phys., (in review), 2002). The open-gap voltage may be provided either via external bias or via the thermally generated electric field inherent in the depletion region of a standard p-n junction (pictured). Through variation of design parameters or applied external bias, the mechanical output power can be adjusted through several orders of magnitude, in excess of 10-8 W for device size scales ranging from 10-7 to 10-4 m per side, with corresponding high power densities in excess of 1 GW/m3.
Basic motor operation is derived using an analytic 1-D model. Detailed numerical results from a quasi-static 2-D model developed using a commercial semiconductor device simulator (Silvaco International -- Atlas) verify the primary results of the 1-D model. Laboratory tests of physical principles of device operation, using macroscopic motor parts, will be discussed.
Both linear and rotary motor designs are considered. In the linear design, the motor operates as a reciprocating electrostatic analog to the classic magnetic rail gun. Since the motor piston is propelled by forces in the junction gap, both designs require that the piston be a semiconducting dielectric. The operation of the motor depends on low values of friction between the piston and gap walls. These design criteria impose strict requirements on surface states and uniformity, and will be discussed at length.
Potential applications for this device include mechanical drives for micro- and nano-scale machines and manipulators; microfluid and thermal pumps; propulsion and inertial guidance of machines; and high-frequency oscillators. Analysis indicates frequency can be controlled by voltage, with upper-limit frequencies in excess of 50MHz. Laboratory tests and construction of this device appear feasible in the near term.
This work was supported by DOE grant ER54544 and by USD Faculty Research Grants. T. Schubert (USD, EE Dept.) and R. Piner (Northwestern Univ.) are thanked for fruitful discussions.
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