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Radioisotope-Powered Self-Reciprocating Cantilever for Micro Power Generation

Author
Li, Hui
Abstract
Micro electromechanical systems (MEMS) provide many devices in
sub-millimeter size for sensing and actuation. However, the lack
of size-compatible power supplies prohibits entire systems to be
within the same scale. The same problem of battery scaling exists
for micro electronic devices. Reported in this dissertation is a
novel way of micro power generation with radioisotopes. Due to the
high energy densities and long half-lives of selected
radioisotopes, high energy density power sources with extremely
long operation time are possible.
Conversion of direct charge collection to mechanical actuation is
the main achievement. A cantilever with a conductive collector
collects the emitted electrons from a Ni-63 beta source. Due to
charge conservation, positive charges are left in the radioactive
source. The resulting electrostatic force moves the cantilever
toward the source. When the cantilever contacts the source,
charges are neutralized and the spring force pulls the cantilever
back to its initial position. This cycle repeats itself as long as
the radioactive source is active. Therefore a self-reciprocating
cantilever is realized. An electromechanical model is developed to
characterize the cantilever and verified with experimental
results. The factors that limit the energy conversion efficiency
are discussed. Further, radio frequency (RF) pulse generation at
the end of the reciprocation cycle is achieved using a dielectric
cantilever with metal electrodes, due to the excitation of
dielectric waveguide mode. This RF pulse could be used for
self-powered remote sensing and wireless communication. To
generate electricity, a piezoelectric unimorph replaces the
cantilever. At the end of the reciprocation, the sudden release of
the unimorph excites its mechanical vibration, thereby generating
electricity through the piezoelectric element.
The radioisotope-powered self-reciprocating cantilever provides a
single platform for mechanical actuation, RF pulse generation and
electrical power generation. Integration of all these functions
holds great potential to enable self-powered autonomous systems.
Description
Prof. Amit Lal
Prof. Rajit Manohar
Prof. Michael Spencer
Sponsorship
DOE NEER Grant
DARPA MTO
Date Issued
2005-07-21Subject
micro power; radioisotope; cantilever
Type
dissertation or thesis