FY2010 - Oak Ridge National Laboratory

Director’s R&D Fund—
Advanced Energy Systems
patent application be submitted to the United States Patent and Trademark Office within the next
3 months.
The DOE Office of Energy Efficiency and Renewable Energy offers significant funding opportunities in
the Industrial Technologies Program for new energy efficiency approaches, and during the next year of
the project we plan to pursue funding from these sources. Commercial partners such as L3 (Dallas) that
have considerable experience in ferroelectric materials have expressed interest in teaming with ORNL for
future projects based on this technology. In addition, several programs at DARPA have energyscavenging
components, and by teaming with defense contractors such as Lockheed Martin, we will
pursue these opportunities in FY 2011.
Results and Accomplishments
Our efforts during FY 2010 focused on (1) designing and modeling the operation of a resonating bimorph
pyroelectric capacitor structure, (2) fabricating test cantilever and pyroelectric capacitor structures, and
(3) setting up the temperature-controlled test station for characterization and temperature cycling of the
fully integrated pyroelectric capacitive devices. We made significant progress in accomplishing all these
tasks as summarized below.
We modeled the operation of a thermally controlled and electrically assisted bimorph capacitive structure
to understand the device performance requirements and to assist in the design and fabrication of the
pyroelectric energy conversion structures to be fabricated in the second year of the project. These
modeling studies show that tip deflections of several tens of microns, with temperature differentials of
200°C, are possible with multilayer pyroelectric capacitive cantilever structures that are 1–3 mm in length
and of optimized thickness. Based on these simulations, we designed our first set of bimorph and
pyroelectric capacitor test structures. We fabricated pyroelectric capacitors from two types of pyroelectric
material to explore the issues involved in the fabrication and operation of these temperature-cycled
capacitive structures, and their integration into resonating cantilevers to form pyroelectric current
generating devices. The first is a polyvinylidene fluoride–trifluoroethylene copolymer (PVDF-TrFE or
copolymer)–based capacitor. We have also explored aluminum nitride (AlN) as a pyroelectric material in
the capacitive microcantilever structures. A series of simple cantilevered bimorph structures have been
fabricated to understand the thermal resonating properties of millimeter-sized structures. Bilayer and
trilayer thermally responsive structures have been fabricated from low thermal expansion SiO 2 , higher
thermal expansion aluminum, and much higher thermal expansion SU-8 in a first attempt to understand
the thermal and mechanical responsivity of these structures. A test setup has been assembled to
temperature cycle the bimorph test cantilever structures and to characterize the pyroelectric and electrical
current generating properties of the AlN capacitive structures. This test setup consists of a Labviewcontrolled
temperature controller and TE cooler module, a firewire video camera used to obtain images of
the moving cantilever structures, and an accurate three-dimensional translation stage that will enable us to
accurately position the cantilever structures between the hot and cold source and sink.
Information Shared
Hunter, Scott R., and Panos G. Datskos. 2010. MEMS Based Pyroelectric Energy Scavenger. U. S. Patent
Application 12/874,407, filed September 2.
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