a paper published this week in the Proceedings of
the National Academy of Sciences, University of Michigan
researchers explain how and why using a femtosecond
pulsed laser enables extraordinarily precise nanomachining.
The capabilities of the ultra-fast or ultra-short
pulsed laser have significant implications for basic
scientific research, and for practical applications
in the nanotechnology industry.
the researchers working at the Center for Ultrafast
Optical Science wanted to use the ultra-fast laser
as a powerful tool to study structures within living
cells, said Alan Hunt, assistant professor, Department
of Biomedical Engineering.
turned out we could push much farther than expected
and the applications became broad, from microelectronics
applications to MEMS (microelectromechanical systems)
to microfluidics," Hunt said. One of the most
perplexing problems in nanotechnology is finding an
efficient and precise way to build and machine the
tiny devices. For example, a human hair is about 100,000
unique physics of an ultra-short pulsed laser used
at a very high intensity make it possible to selectively
ablate or cut away features as small as 20 nanometers,
Hunt said. This is possible because of the unique
physics of how extremely short pulses of light interact
with matter; specifically using femtosecond pulses,
a blast of light just a quadrillionth of a second
there is no easy way to machine a wide variety of
materials on the nanometer scale, Hunt said, and the
technique with capabilities closest to the ultrafast
laser is electron beam lithography. Even this approach
does not allow machining below the surface or within
the technique used to make computer chips, is used
to do such machining on a larger scale but is difficult
to get to the nanometer scale, requires specific materials
and can generally only be used on one plane. For example,
that means that channels on a chip cannot cross without
mixing, placing a severe constraint on the microfluidics
and "lab on a chip" designs.
the unique physics of the femtosecond pulse allows
machining in 3-D, Hunt said.
we have three channels on a plane, we can link the
outer two without cutting into the center one, we
can go down over and up, we can cut a U-shape,"
Hunt said. "Not being constrained to one plane,
the level of complexity that can be achieved is much
research team included Hunt; Gerard Mourou, professor
of electrical engineering and computer science; Ajit
Joglekar, who recently completed his doctorate in
biomedical engineering; Hsiao-hua Liu, a post doc
at the Center for Ultrafast Optical Science; and Edgar
Meyhofer, associate professor of biomedical engineering
and mechanical engineering.