SEM images of nickel-coated TMV arrays patterned using
photolithography onto a silicon wafer (Image: University of
Maryland, College Park)
The first virus to be discovered was the Tobacco mosaic
virus (TMV) back in 1898. It is a rigid, rod-shaped virus
that, under an electron microscope, looks like uncooked
spaghetti. This widespread virus devastates tobacco, tomatoes,
peppers and other plants but in the lab, engineers at the
University of Maryland's A. James Clark School of Engineering
and College of Agriculture and Natural Resources, have managed
to harness and exploit the self-replicating and self-renewing
characteristics of TMV to build tiny components for more
efficient lithium-ion batteries.
To create the highly efficient batteries the researchers
first modified the TMV rods to bind perpendicularly to the
metallic surface of a battery electrode and arrange the rods in
intricate and orderly patterns on the electrode. Because TMV can
be programmed to bind directly to metal, the resulting
components are lighter, stronger and less expensive than
conventional parts. They then coated the rods with a conductive
thin film that acts as a current collector and finally the
battery's active material that participates in the
electrochemical reactions.
10-fold increase in energy capacity
This results in an electrode with a greatly increased surface
area that increases its capacity to store energy and enables
fast charge/discharge times. The new batteries boast up to a
10-fold increase in energy capacity over a standard lithium-ion
battery. The researchers say that the use of the TMV virus in
fabricating batteries can be scaled up to meet industrial
application needs. And because the TMV becomes inert during the
manufacturing process, the batteries do not spread the virus.
"The resulting batteries are a leap forward in many ways and
will be ideal for use not only in small electronic devices but
in novel applications that have been limited so far by the size
of the required battery," said Ghodssi, director of the
Institute for Systems Research and Herbert Rabin Professor of
Electrical and Computer Engineering at the Clark School.
"The technology that we have developed can be used to produce
energy storage devices for integrated microsystems such as
wireless sensors networks. These systems have to be really small
in size - millimeter or sub-millimeter - so that they can be
deployed in large numbers in remote environments for
applications like homeland security, agriculture, environmental
monitoring and more; to power these devices, equally small
batteries are required, without compromising in performance,"
added Ghodssi.
Virus suited for other jobs
While the focus of the
University of
Maryland researchers has been on energy storage, they say
that the structural versatility of the TMV template used to
create the highly efficient lithium-ion batteries means it could
also be used in a variety of other applications.
"One of our lab's ongoing projects is aiming at the
development of explosive detection sensors using versions of the
TMV that bind TNT selectively, increasing the sensitivity of the
sensor. In parallel, we are collaborating with our colleagues at
Drexel and MIT to construct surfaces that resemble the structure
of plant leaves. These biomimetic structures can be used for
basic scientific studies as well as the development of novel
water-repellent surfaces and micro/nano scale heat pipes," said
Ghodssi.
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