Light emitting diodes have long held the promise of more efficient
lighting for researchers. And now, with pioneering work being
done by Fred Schubert, Constellation Professor, Electrical, Computer,
and Systems Engineering, and Jong Kyu Kim, post-doctoral research
associate, that promise is coming true.
In research published spring 2005, they reveal what they believe will
prove to be a new record for the lowest refractive index material that
is used a light-emitting diode (LED). Such new materials make LEDs more
efficient and brighter. Their work has centered around two
important developments: A remote-phosphor design which suspends the
light-producing phosphor layer above the LED chip, and a conical
reflector cup which helps reflect light waves outward.
Conventional LEDs have traditionally encapsulated the phosphor layer
directly on top of the LED chip, which has inherent inefficiencies
because much of the light gets reflected directly back to the chip,
rather than outward. By suspending the phosphor layer above the
chip, there is a greater efficiency in the outward projection of the
light. Beyond that, the conical cup design directs any
downward-reflected light waves back outward, increasing the output.
An interesting discovery in this research is the finding of a new loss
mechanism; Whispering Gallery Modes. As its romantic name
suggests, Whispering Gallery Modes were discovered in the last century
by Lord Rayleigh in an experiment conducted in St. Paul’s Cathedral in
London. Rayleigh found that sound waves, such as a whisper
delivered along the smooth interior walls of the dome, continued
uninterrupted, bouncing along with very little attenuation.
Someone whispering along one side of the dome could be clearly heard
across the expanse.
Schubert contends the same effect happens within the reflector cup of
his experimental LEDs, where some of the errant light waves circle
around “endlessly” along the interior walls. “Something is needed
to interrupt these light beams, or else they “echo” around the interior
surface without becomming useful.” He’s designed a
non-deterministic reflector cup – essentially a textured surface – that
helps to bounce or diffuse these beams outward, resulting in a brighter
light.
As the world’s known fuel supply declines, higher efficiencies across a
broad spectrum of technologies will become increasingly
important. For Fred Schubert and his team of researchers,
ultra-efficient LEDs are here today, and the future looks very bright.
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Traveling on a Beam of Light
MURI Grant awarded for beamed-energy research
By Jon Wurtmann |
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“The problem with
traditional spacecraft is that the propulsive energy
source must be carried aboard the vehicle, either as liquid or
solid-fuel rocket propellants, contributing as much as 95% of the
launch weight,” says Leik Myrabo, associate professor of engineering
physics. “We’ve left all that weight behind and created a radically new
vehicle, called a lightcraft.”
As the name implies, these craft fly on a beam of light – sent from a
ground-based, pulsed infrared laser. A parabolic reflector
receives the beam and concentrates it into an annular ring engine,
heating air to a temperature five times greater than the surface of the
sun, and creating explosive thrust as the air expands. The parabolic
reflector also acts as an exhaust nozzle to direct thrust for the
spin-stabilized craft.
Myrabo’s lightcraft research has long been of interest to several space
and defense agencies, and in spring 2005 the Department of Defense
awarded him 2.25 million dollars through its Multidisciplinary Research
Program of the University Research Initiative (MURI). The
five-year MURI award will provide funding for the next stage of
lightcraft development; launching kilogram-class nano-satellites into
low-earth orbit.
Over one hundred test flights to date at White Sands Missile Base have
yielded a wealth of information, and an altitude record of 233 feet for
a non-tethered lightcraft. Myrabo has used miniature lightcraft
measuring 10 to 15 centimeters, and powered them with a 10 kilowatt
Army laser. To achieve low-earth orbit, Myrabo expects to use a
megawatt-class laser to power a craft measuring 70-140 centimeters in
diameter. At about 30 kilometers altitude and Mach 5, the engine
will transition from an airbreathing mode over to a rocket mode, as
on-board liquid hydrogen is consumed for the final push into orbit.
“This is proven technology.” Says Myrabo, “We have the materials, the
methods, and the means to create a revolution in space access.”
Lightcraft technology can cut launch costs by 100x to 1000x below
chemical rockets. Orbital flights are feasible with Lightcraft
engines barely above idle throttle settings, in sharp contrast with
today’s rockets that must run at the ragged edge of blowing up.
Beyond the MURI’s DoD mission, such Lightcraft could soon be launching
fleets of telecommunication microsatellites, as well as space tourists
on exciting suborbital flights - at ‘rock bottom’ prices. All
that is lacking is the energy-beaming infrastructure to ‘fuel’ this
futuristic fleet, and “infrastructure building,” he contends, is an
ideal role for government.
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Inventing a Better World
By Jon Wurtmann |
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“Just do it” is permanently ensconced in our everyday vernacular, as
both a phrase and an advertising concept. But these simple words,
administered at the right place, at the right time, by the right
person, have the power to change lives.
For Ryan O’Donnell ’04, the place was Inventor’s Studio, in the spring
of his senior year, and Burt Swersey, professor and lecturer in
mechanical, aerospace, and nuclear engineering, was the one who ushered
those fateful words of encouragement. Under Swersey’s watchful gaze,
teams of students gestate their own concepts into working prototypes,
as well as secure patents, and, in some cases, funding for further
development. It’s an education in the totality of bringing an
invention to the marketplace.
O’Donnell was part of a team of students shepherding a firefighting
training device through the stages of design, prototype, testing,
refinement, and patent application. As a result of enormous team
effort and professorial mentoring, the device not only performed to
specifications, it also ignited the entrepreneurial spirit in the team
members.
Like many of the projects in Inventor’s Studio, the firefighting
training device addresses a need in society. That’s a critical
component to the course; inventing solutions to societal problems,
making the world a better place. Offered as a senior-level course,
Inventor’s Studio helps 20 seniors each semester apply their technical
scholastic training to “Define problems that most people don’t
even know exist, to invent and patent solutions.” In the recent history
of the course, five patents have been issued, or are about to be, and
several others are pending.
“The course focuses on developing an attitude that leads to
positive change and works to build confidence in our graduates so that
they can do ‘the impossible.’", says Swersey. Those thoughts are
echoed by Tad Richman ’04, now working in a small tech start-up
“Inventor’s Studio opened my eyes and showed me new ways to think about
things. I think most importantly, it taught me not to discount
something as immediately impossible, even though it may sound
far-fetched.”
After graduating, O’Donnell joined forces with fellow teammates John
Blackburn ‘05 and Tom Rossi ’04 to form BullEx Digital Safety to market
their device. They were helped by generous funding support by the
National Collegiate Inventors and Innovators Alliance, (NCIIA), a
philanthrophic organization dedicated to “fostering invention,
innovation, and entrepreneurship in higher education as a way of
creating innovative, commercially viable, and socially beneficial
businesses and employment opportunities in the United States.”
According to Phil Weilerstein, executive director of NCIIA,
(www.nciia.org) “the Bullex team typifies the kind of focused
innovation that the Inventor’s Studio program supports. Over the past
10 years RPI has
been an active member of NCIIA’s network of university innovators. The
unique programs in design-based innovation and entrepreneurship have
enabled entrepreneurial ventures like this one to emerge from the minds
of talented young innovators. We are pleased at the continuing
evolution of the RPI programs and the entrepreneurs that they develop.”
In June 2005, BullEx opened its doors for business, just one of many
successful launches from the fertile breeding grounds of the Inventor’s
Studio. Not every project in the studio meets commercial success, but
many of the students do. In every sense, they are taught to be
intrapreneurs. Ed Browka, ’01, now an engineer with Becton,
Dickinson and Company, a large medical technologies firm, is working
today on lifesaving and life-enhancing medical products. He’s
received BD’s highest award, the Howe innovation award, for his work on
the Microinfusor drug delivery system. He reflects on his
experience, “I've been successful as an innovator in the corporate
setting using the skills I learned in Inventor's Studio.” Browka
has several patents filed and one product that he engineered already on
the market.
O’Donnell says “the Inventor’s Studio course provided us with the
support and knowledge to change thoughts and ideas into patentable
products – that make the world a better place.”
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