NEWS: NYTimes: Bacteria-Sized Machine Made to Work by Scientists

[janet paterson <janet313@xxxxxxxxxxx>]

Scientists Make a Bacteria-Size Machine Work

November 25, 2000 - In the continuing march toward miniaturization, scientists 
have now not just built microbe-size contraptions. They have also found a way 
to make them move.

Writing in Friday's issue of the journal Science, scientists at Cornell 
University report that they hooked up a tiny motor to a metal propeller and 
spun the propeller around at up to eight revolutions a second.

"This is the first true nano machine," said Dr. Carlo D. Montemagno, professor 
of biological engineering at Cornell and senior author of the Science paper.

"Nano" is a Greek prefix meaning "one-billionth," and nanotechnology refers to 
devices that are a few nanometers ? a few billionths of a meter ? in size. A 
single silicon atom, by comparison, is about one- quarter of a nanometer wide.

Since the motor draws its energy from the same organic molecules that power 
living cells, Dr. Montemagno suggests that scientists may one day be able to 
build robots much smaller than bacteria that will be able to repair cellular 
damage, manufacture medicines and attack cancer cells.

"This opens the door to make machines that live inside the cell," Dr. 
Montemagno said. "It allows us to merge engineered devices into living systems."

A second paper in today's Science captures another type of minuscule motion: a 
clump of tin, pushed by chemical forces, scurries around like an amoeba on a 
surface of copper, leaving behind a thin trail of bronze alloy.

"The tin island looks like it's alive as it's grazing along the copper 
surface," said Dr. Norman C. Bartelt, a staff scientist at Sandia National 
Laboratories in Albuquerque and one of the researchers.

"It moves to clean regions of the surface, eating the substrate and spitting 
out the copper atoms it eats in the form of bronze. It's amazing an inanimate 
system on such a small scale emulates something that's living."

In an accompanying commentary, Dr. Flemming Besenbacher of the University of 
Arhus in Denmark and Dr. Jens K. Norskov of the Technical University of Denmark 
say the motion of the tin island can be considered as a new type of nanomotor.

They calculate that the system is roughly as efficient as an automobile engine 
at converting chemical energy to mechanical horsepower.

The motivation for the Sandia research was not nanomachines. "We're interested 
in the reliability of nuclear weapons," Dr. Bartelt said. The scientists were 
investigating electrical junctions between solder ? a mix of tin and lead ? and 
copper wires.

In the experiments, hundreds of thousands of tin atoms were dropped, one by 
one, onto a copper surface. At room temperatures, copper atoms continually 
jiggle around, bouncing the tin atoms along the surface until they coalesced 
into larger clumps.

At the same time, the tin atoms slowly swap places with some of the copper 
atoms, forming a two- dimensional layer of bronze, an alloy of copper and tin.

Because tin atoms are larger than copper atoms, they cause a bulge when they 
enter the surface. This hill causes the tin clump to slide off to a pristine 
copper section. After a few minutes, all of the tin atoms are absorbed into the 
copper.

How the motion might be harnessed for a useful device is not at all clear. Dr. 
Bartelt calls the notion of using the roaming tin islands as motors 
"far-fetched." However, he suggests that the tin clumps could be used as 
battering rams to push other tiny objects around or be assembled into larger 
structures.

Dr. Besenbacher said the perspective piece was not meant as a prediction, but 
to inspire researchers to brainstorm about the newly discovered phenomenon.

"I can think of at least some ideas of how to do it," he said. "Whether it 
works or not, I don't know. It certainly should stimulate people to think along 
these lines in the future."

The Cornell work melds two lines of nanotechnology research that have been 
pursued for the past few years. Just as electrical engineers have been cramming 
smaller and smaller transistors onto computer chips, nanotechnology scientists 
have crafted tinier and tinier sculptures, including levers, beams, suspended 
wires and a model of a guitar with strings 100 silicon atoms wide. But without 
a way to make them move, the structures were sometimes little more than tiny 
art pieces.

Meanwhile, other researchers have been building tiny motors inspired by 
machinery inside living cells. The so-called biomolecular motors run on 
adenosine triphosphate, or ATP for short, the same energy-rich molecule that 
powers chemical reactions within cells.

Dr. Montemagno's group grafted nickel propellers onto the central shafts of 400 
biomolecular motors. Of those, 395 remained motionless, when immersed in a 
solution full of ATP. But 5 spun.

The propellers are relatively long ? 750 nanometers, or about one-30,000th of 
an inch ? which allowed the researchers to videotape them spinning. In one 
section of the video, a dust particle can be seen being sucked into the 
spinning propeller before being kicked out again.

"Today a propeller, tomorrow you can start putting other things on it," said 
Dr. Ralph C. Merkle, a principal fellow at the nanotechnology company Zyvex in 
Dallas. "It's moving in a direction where the end point might actually be 
useful."

Potential applications might include "smart dust," sunlight- powered sensors to 
detect dangerous chemicals. If activated, a tiny motor might open a valve to 
release a visible warning dye.

Dr. Montemagno also envisions robots that interact with the machinery inside 
living cells, somewhat like a virus, to produce healing drugs.

"We're going to have the device self-assemble inside the human cell," he said. 
"That's what we're working on now."

To battle cancer, cells might be genetically modified by the nanorobots to 
produce tumor-killing chemicals. But such chemicals are usually deadly to 
healthy cells, too, so other nanorobots might swim through the cells, 
collecting the toxic chemicals and then dump them directly onto the cancer 
cells. For long trips to Mars and other planets, astronauts might also carry an 
array of drug-producing nanorobots that can be injected into the body as needed.

"This is 15-year or 20-year thinking that I'm talking about," Dr. Montemagno 
said. "Life is really an orchestration of a bunch of nanomachines running 
around."


By KENNETH CHANG
Copyright 2000 The New York Times Company



janet paterson, an akinetic rigid subtype parkie
53 now /44 dx cd / 43 onset cd /41 dx pd / 37 onset pd
TEL: 613 256 8340 SMAIL: POBox 171 Almonte Ontario K0A 1A0 Canada
EMAIL: janet313@xxxxxxxxxxx URL: