[tt] wired: newscientist: robotic gripper can grab cells, move them around, tell how much force it is applying

[Alejandro Dubrovsky]

(
http://technology.newscientist.com/channel/tech/dn13725-tiny-robotic-hand-has-the-gentlest-touch.html?feedId=online-news_rss20
)

Tiny robotic hand has the gentlest touch

 * 13:56 17 April 2008
 * NewScientist.com news service
 * Mason Inman
 

A tiny pair of robotic tweezers with the most sensitive grip yet can
pick up and move individual cells without damaging them, guided by their
own sense of touch. They could be used to probe the properties of living
tissue, or create microscale and nanoscale devices.

The robotic gripper can exert as little as 20 nanoNewtons of force and
are the first to be able to feel the strength of their grip on objects
so delicately, says Yu Sun of the University of Toronto in Canada, who
led their development.

"We're applying very well-known concepts from robotics down to the
micrometre scale," Sun says. Previous pincers are fumbling by
comparison, unable to sense such feedback. "You would break the objects
being manipulated, or break the microgrippers."

The grippers are the first to not only feel their grip strength, but
also when they touch a surface. This allows them to sense when they've
run into things, helping them get close to cells and other objects
without damaging collisions.
Get a grip

Those abilities mean that when connected to a microscope and the right
software the grippers can work reliably without human control. At their
most sensitive, they exert only enough force to support 2 millionths of
a gram against the pull of gravity.

The tweezers' arms are about 3 millimetres long, with fine tips able to
grasp cells just 10 micrometres across. In trials using pig heart cells,
the pincer could pick up and move the cells without damaging them.
Holding them with only 100 nanoNewtons of force, the gripper squashed
the cells out of shape by only 15%.

The grippers are controlled by software that can identify individual
cells and move the tweezers into position in just a few seconds. That's
much faster than a person could do, Sun says.
Touchy feely

The grippers have a kind of sense of touch that lets them know how
strongly they are holding a cell. They can grasp a cell with a pre-set
force in less than a second. They are the first to not only feel their
grip strength, but also when they bump up against a surface. This
crucial allows them to move autonomously and sense when they've run into
things, helping them get close to cells and other objects without
breaking the grippers."

In tests the tweezers picked up and arranged cells into a line to show
off their skills. They could be used to assess mechanical properties of
biological materials and tissues, or to create microscale and nanoscale
devices."

But they could have many other uses too, Sun says. "They can grasp
silicon parts, and they can put things together," he adds. "So it's
really a flexible and dexterous hand."

The grippers are cheap too because they are etched from a silicon wafer,
using the well-established processes used by the computer industry. When
prepared in a batch of about 100, the grippers cost around US$50, Sun
says, and if mass produced, might cost about US$10.
Factory workers

The tweezers' ability to feel its own grip strength and movement makes
them useful for automated micromanipulation, says Jason Gorman of the
National Institute of Standards and Technology in Gaithersburg, US. "It
appears that the force sensing is having a significant effect on the
manipulation dexterity," he adds. Their manipulation of the cells is
"impressive".

But Gorman agrees that they could be more usefully applied to assembling
microdevices – especially complex high-end sensors that can't be made
through the usual fabrication techniques.

Journal reference: Journal of Micromechanics and Microengineering (DOI:
10.1088/0960-1317/18/5/055013)