From: Michael M. Butler (firstname.lastname@example.org)
Date: Mon Jan 14 2002 - 23:49:28 MST
Just in time to adapt for monitoring the Indian subcontinent watershed contamination effects when the
India-Pakistan conflict goes nuclear! Yay!
-------- Original Message --------
Date: Mon, 14 Jan 2002 22:27:26 -0800
From: Dan Lynch <email@example.com>
Swarms Of Tiny Robots To Monitor Water Pollution
The University of Southern California School of Engineering has
received a $1.5 million research grant from the National Science
Foundation to create swarms of microscopic robots to monitor
potentially dangerous microorganisms in the ocean.
"With increasing urban runoff, sewage spills and blooms of harmful
algae off heavily populated coastal areas, it is very important to be
able to sense, and then identify, particular ocean microorganisms
quickly," said Ari Requicha, a USC professor of computer science and
the project's principal investigator. "The quicker we learn that a
pathogen is present in the water, the sooner we can warn people and
begin action to correct the situation."
The project spans the fields of nanotechnology, robotics, computer
science and marine biology, but is centered on the development of the
ultra-small robotic sensors and software systems to control them.
Requicha directs the USC School of Engineering's Laboratory for
Molecular Robotics where his team has been experimenting with
nanometer-scale structures for nearly seven years.
(One nanometer is one/one-billionth of a meter. A nanometer is to a
meter what a small grape is to the entire Earth.)
In the 1980s, scientists discovered that the sharp silicon tip of the
newly invented scanning probe microscope not only produced images
revealing individual atoms and molecules, but it sometimes moved them.
The computer-controlled microscope scans microscopic samples, sensing
their minute atomic forces and precisely mapping the surface at a
molecular or even atomic level.
Working with colloidal gold and silver balls as small as two
nanometers, and string-like organic molecules called dithiols that
tether the balls to each other, Requicha's group has programmed their
atomic force microscope -- a particular kind of scanning
probe-microscope -- to slide the "nanoscale" particles into precise
positions on tiny slabs of mica or silicon.
They can chemically link the particles to form crude assemblies, and
they can make "nanowires" by depositing metals on strings of
carefully positioned balls.
"We do this at room temperature and at normal air pressure, and we
can also work in water and other liquids, which is crucial for
biological applications," said Requicha.
The group has made a nanoscale single-electron transistor and an
optical waveguide, which is a structure used to guide light. They are
working on an actuator, or switch, and are starting to fabricate more
complex 3D "nanostructures" by building up successive layers of
nanoscale assemblies. Each layer is surrounded by a "sacrificial"
material that holds it in place and that is removed when all the
layers are complete to leave a tiny nanoelectromechanical device.
Substances being investigated for use as the sacrificial material
include charged polymers, zinc phosphonate films and organic
compounds containing silicon known as silanes.
Requicha said it will be possible to build nanoscale devices with
electrical and mechanical components so that the devices could propel
themselves, send electronic signals and even compute. While
individual nanoscale devices would have far less computing power and
capability than full-sized devices, the plan is to have vast numbers
of them operating in concert.
It often takes Requicha's team weeks to assemble even a simple
nanoscale object, but the procedure can be automated once the
computer programming is perfected. Other labs are working on atomic
force microscopes with more than one tip. Requicha said a single
atomic force microscope could theoretically have an array containing
thousands or even millions of tips, all controlled by the same
computer program to manufacture large numbers of nanoscale devices.
David Caron, professor of biological sciences and a co-investigator
on the project, said ocean robots needn't be terribly complicated or
powerful to be useful. A single robot might sense only whether the
water is fresh or saline and communicate by a faint radio signal only
with other robots closest to it, which would then relay the
information to other robots in the network linked to the Internet by
still more robots.
In the next year, Caron hopes to attach an antibody to a microscope
tip. He recently created an antibody that binds to Aureococcus
anophagefferens, the toxic algae known as Brown Tide. With the same
procedure widely used to test for HIV and other diseases, he can
reliably test for the algae.
"That test takes a day in the lab, which is an improvement over
current testing, but it's still not fast enough," said Caron. The
microscope should detect the algae the instant a microorganism binds
to the antibody on its tip.
Requicha estimates that it will be a decade before the researchers
can build and deploy nanoscale robots in the ocean capable of the
kind of instant and specific test like Caron's for Brown Tide. Along
the way, he hopes the project will spin off technology in marine
biology and other areas.
"Suppose we put 15-nanometer particles on a grid with 100-nanometer
spacing, which we can routinely do in our lab today. If we interpret
the presence of a particle as a binary one and its absence as a zero,
we have a scheme to store data," he said. "The bit density is 10
gigabytes per square centimeter, which means we have data storage
that is 100 times better than today's compact disks. And it could be
even greater with smaller particles and spacing."
The USC researchers will first build small robots that will move,
sense and communicate while tethered in a tank of water in a
laboratory. They will gradually progress to building and controlling
increasingly larger numbers of increasingly smaller freely moving
robots. The end goal of the project will be to create robots that are
as small as the microorganisms that they seek to monitor.
"Today, we commonly do experiments with five or ten robots," said
Gaurav Sukhatme, USC assistant professor of computer science and a
co-investigator on the project. "But we'll need algorithms to
coordinate a million or more robots. That is a daunting problem, and
we must start laying out the foundations for large numbers of robots
long before they are a reality."
Requicha said that nanotechnology today is at the same stage of
development as the Internet was in the late 1960's.
"The idea that we'll have swarms of nanorobots in the ocean is no
more far-fetched than the idea of connecting millions of computers
was then," he said. "I don't think these robots will be confined to
the ocean. We will eventually make robots to hunt down pathogens or
repair cells in the human body."
The grant is from the National Science Foundation's Information
Technology Research program. Maja Mataric, associate professor of
computer science and director of the USC School of Engineering's
Robotics Research Laboratories, and Deborah Estrin, a computer
networking specialist from UCLA, are also co-investigators on the
project. - By Bob Calverly
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