Home' Technology Review : August 2005 Contents 86
From the Lab
FROM THE LAB
itself---in rat cell cultures and living mice.
In one experiment, they stimulated heart
muscle cells from 12-week-old rats with
growth factors in the presence or absence
of a p38 inhibitor. They looked for signs of
key molecular events associated with the
various stages of cell division.
: While the researchers dem-
onstrated cell division in a lab dish, they
did not demonstrate it in live animals.
They are now injecting the inhibitor and
growth factors into rats with damaged
hearts and looking for signs of regrowth.
The researchers will also have to ensure
that they can control the cell growth and
avoid causing cancer.
Source: Engel, F. B., et al. 2005. P38 MAP kinase
inhibition enables proliferation of adult mammalian
cardiomyocytes. Genes and Development 19:1175--87.
Lens allows optical microscopy
down to 60 nanometers
: A team from the University of
Califor nia, Berkeley, has devised a silver
"superlens" that could increase the reso-
lution of light microscopy by about a factor
of six. The lens doesn t di ract light like
conventional glass lenses. Instead, it uses
evanescent waves, which are produced
when light hits a lens at such an angle that
it bounces o instead of passing through.
Evanescent waves emerge on the other
side of the lens and add optical infor ma-
tion to normal "propagating" light waves,
but they decay very quickly over short dis-
tances. By capturing and amplifying these
weak waves, the researchers obtained im-
ages with 60-nanometer resolution.
: High-resolution imaging
methods such as electron microscopy can t
image living tissue. Light microscopy can.
Its resolution, however, is limited by the
wavelength of the light used. And 400
nanometers is the shortest wavelength
that doesn t damage tissue. Evanescent
waves allow researchers to get around this
limitation. The technique could eventually
allow researchers to watch, in real time,
biological processes such as protein inter-
actions in samples of living tissue---events
that can now be studied only indirectly.
Previous research has used evanescent
waves to construct images in piecemeal
fashion. The Berkeley team, led by Xiang
Zhang, has shown that it s possible to take
a clear and complete picture in one shot.
: The researchers made a lens
out of a 35-nanometer-thick lm of silver.
They chose a light source whose frequency
matched the resonant frequency of the
lens s surface electrons. The light shone
through the word "NANO," inscribed in
letters with a 40-nanometer line width on
a piece of chromium through ion beam li-
thography. When the light hit the lens, the
silver electrons resonated with the evanes-
cent waves, boosting their energy. The
superlens directed the waves onto light-
sensitive material to capture the image.
: The superlens didn t spread out
the evanescent waves enough that the hu-
man eye could see the image directly; it had
to be observed with an atomic force micro-
scope. Future research will curve the lens
so that it can further spread the waves and
pass them into, say, a ber-optic cable. Su-
perlenses might then be integrated into
Source: Fang, N., et al. 2005. Sub-di raction-limited
optical imaging with a silver superlens. Science
Ink-jet manufacturing for faster
: Using conventional ink-jet print-
ing equipment, Henning Sirringhaus of
the University of Cambridge in England
and colleagues built organic-polymer cir-
cuits with switching speeds more than 100
times greater than those of existing poly-
mer circuits. They printed circuit features
that they estimated to be smaller than 100
nanometers, less than one--one-hundredth
the size of the smallest features previously
produced through ink-jet printing.
: Thin, exible, and cheap
plastic electronics could have many appli-
cations, from solar cells to radio frequency
identi cation labels in product packaging.
Ink-jet printing is an attractive manufac-
turing option because it deposits materi-
als quickly and cheaply over large areas.
But so far, it has yielded features no
smaller than 20 micrometers, while the
features of typical integrated circuits mea-
sure tens of nanometers. The Cambridge
team seems to have broken the resolution
barrier, making ink-jet printing viable.
: The researchers produced their
ultrasmall features using a homebuilt ink-
jet printer. They deposited a conducting
polymer "ink" as droplets on glass. They
then chemically modi ed the droplets
surfaces so they would repel additional
droplets. A second set of droplets was ap-
plied; these owed o of the rst set, land-
ing a tiny distance away. That distance
represents the smallest feature size this
technique can achieve. The researchers
laid out transistors: the closely spaced
droplets formed electrodes, and an or-
ganic semiconductor lled the gap be-
tween them. The researchers estimated
the width of this gap based on the perfor-
mance of the transistors.
: The researchers are now using
better-performing organic semiconduct-
ing materials. They are also producing
circuits that involve hundreds of intercon-
Source: Sele, C. W., et al. 2005. Lithography-free, self-
aligned inkjet printing with sub-hundred-nanometer
resolution. Advanced Materials 17:997--1001.
COURTESY OF NICHOLAS XUANLAI FANG
Nanoimaging using a superlens. Top: ion beam
image of letters etched in chromium. Middle:
superlens image of letters on light-sensitive
material. Bottom: optical image without
superlens. Scale bar: two micrometers.
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