X-Message-Number: 15721
From: "Mark Plus" <>
Date: Thu, 22 Feb 2001 10:44:58 -0800



February 22, 2001
The Incredible Shrinking Robot, Self-Contained and Untethered

THE latest vehicle Dr. Doug Adkins helped build does not turn on a dime so 
much as it can climb one. Dr. Adkins is part of a Sandia National 
Laboratories team that has created what the researchers believe is the 
world's smallest untethered robot.

While they are unable to document that claim, the robot is unquestionably 
tiny: less that one-quarter of a cubic inch in size and under one ounce in 

That may eventually allow sensor-laden versions of the robot to crawl 
through pipes or electrical ducts to diagnose problems or creep around 
buildings to detect toxic gases. Like ants, several minirobots could swarm 
to disarm land mines or bombs. Dr. Adkins anticipates that the robots will 
be mass- produced within five to six years.

The minirobot work was something of a departure for Dr. Adkins, who usually 
develops hand-held chemical sensors. "Those are about the size of a 
calculator," he said. "This was a little more complicated."

About six months ago, Dr. Adkins was asked to work on the robot by Dr. Ed 
Heller, another researcher at Sandia, in Albuquerque. In 1996, Dr. Heller 
helped build a self- contained robot known as the Mini Autonomous Robot 
Vehicle, or MARV, that was one cubic inch. That was about as small as robots 
could be built using conventional parts and fabricating technology.

One of the breakthroughs in making something even smaller had more to do 
with careful shopping than engineering. The robot needed a microprocessor, 
which is not in itself heavy or bulky. But microprocessors have a protective 
shell and tiny wires that account for about 80 percent of the 
microprocessor's volume, Dr. Adkins said.

The laboratory planned to have the robot itself serve as the 
microprocessor's shell. After some searching, researchers learned that 
Microchip Technology Inc., a manufacturer of programmable microprocessors, 
would sell the laboratory just the guts of the microprocessor without the 
shell and wires.

To build the robot body, the researchers turned to a relatively new 
technique called stereolithography. It starts with a type of epoxy resin 
that cures only when zapped with a specific color of laser light. Once Dr. 
Adkins had a computer-generated design for the robot bodies, lasers in 
Sandia's stereolithography laboratory began building it up with layers of 
epoxy, each one six-thousandths of an inch thick. About a dozen bodies were 
made, but they are not much to look at. "They're the color of natural epoxy, 
like the stuff you get at Home Depot," Dr. Adkins said.

The luck that researchers had when they went hunting for processors vanished 
when it came time to power the robot. Somewhat arbitrarily, they decided 
that the robot must operate for 15 to 20 minutes.

As any cell phone user can attest, small size and longevity seem to be 
mutually exclusive when it comes to batteries. The most compact batteries 
capable of that performance were three button cells, the type usually used 
in watches. Sitting on the robot's back, the cells are by far the robot's 
largest and heaviest feature.

One of the biggest shortcomings of the earlier minirobot was its wheels. 
They had to be relatively large to lift the body off the ground, but a large 
wheel is more difficult to start rolling, particularly for tiny motors. 
"They had problems getting it to crawl across any surface that wasn't flat," 
Dr. Adkins said.

Two solutions were found. The researchers had discovered that a Swiss 
company, RMB Miniature Bearings, made very small motors that came with 
transmissions. The motors, for autofocus camera lenses, were so small that 
the company's Web site shows one being dwarfed by a ladybug.

The RMB transmission helped overcome the traction problem by making more 
efficient use of the motor's output. But the problem was not fully solved 
until Dr. Adkins decided to abandon wheels in favor of treads. After testing 
several materials for treads that are two millimeters wide, Dr. Adkins found 
his answer in one of his daughter's party balloons, which he used for 

"Those things rolled around on the balloons for a long time," he said of the 
minirobots. Unfortunately the balloon latex was prone to lose its 
elasticity, causing the treads to fall off. A material laboratory at Sandia 
eventually produced a silicone-latex tread that was more durable.

In an era when some scientists are working on robots that can automatically 
rebuild themselves to perform different tasks, the Sandia minirobots are not 
brilliant performers. They are limited by a processor memory of eight 

For now, that means the minirobot can follow a simple programmed route over 
and around coins at a sedate 20 inches a minute. One of its performances can 
be viewed at www.sandia.gov/media/NewsRel/NR2001/images/MicroRobotDemo2.MPG. 
(Much to Dr. Adkins' dismay, a nervous Dr. Heller repeatedly prods the robot 
with a pair of tweezers in that video.) Recently a heat sensor was added, so 
now the robot's array includes backing up when confronted by a heat gun.

Chemical sensors, a microphone and even a camera may be added, but Dr. 
Adkins is cautious. "There are some very small cameras," he said. "The 
problem is the amount of data you'd then have to move out of that things. 
You'd kind of swamp the processor."

What the minirobot lacks in talent, it may make up for with price, to say 
nothing of compactness. Dr. Adkins estimated that parts for the tiny robot 
cost about $500. But he said that any mass production would significantly 
reduce that amount. He said he expected that a production version would sell 
for "a couple hundred dollars."

Unfortunately, at that price, the minirobot is unlikely to include a 
fail-safe technology for preventing users from misplacing it.

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