26 | NewScientist | 16 April 2011

FORGET flypaper – why not catch pesky bugs chameleon-style, with the flick of a robot tongue?

Alexis Debray, an engineer at Canon in Tokyo, Japan, has created an appendage that mimics the astonishing dexterity of the chameleon’s tongue. The firm is always looking for ways to make more efficient production-line robots, he says, and a device that mimics the chameleon’s tongue may hold promise for making delicate items like cameras.

The chameleon has evolved a sticky tongue that can snap out to about twice its body length at 10 metres per second, catching bugs by surprise. Even at such speeds, though, the lizard’s lightweight tongue exerts very little force on the target. That is critical, says herpetologist Ian Stephen at the Zoological Society of London, to enable the tongue to stick to the prey rather than send it flying.

The tongue is fired out by an “accelerator” muscle that catapults off a bony support (see diagram).

When the tongue is at full stretch, a concertina-like muscle is used to rein it back in again, hopefully with dinner in its grasp.

To mimic that process, Debray

fixed a magnet representing the creature’s tongue tip to a stretchy silicone-based polymer, or elastomer, and a length of string. He fired the magnet at a target by passing a current through a coil, sending the elastomer and string “tongue” out 30 centimentres. A motor keeps tension on the apparatus, giving the magnet a

light touch on the target. It then reels in the string to retract the whole assemblage (Biomimetics and Bioinspiration, DOI: 10.1088/ 1748-3182/6/2/026002).

“This could have several applications in robotic manipulation, perhaps moving objects on a production line,” says Debray. He also likes the idea of using his invention as a bug-catcher: “It is typically an application for which high acceleration and high velocity are needed – and that’s the strong point of these tongue-like manipulators,” he says.

To improve accuracy, Debray has fitted small wings to the magnet to keep it aloft longer on its journey. “In future, movable wings will allow control of the trajectory of the tongue, which is not possible now,” he says. A computer vision system that would allow his magnet to find its target is also in development, as is a gripper to grasp objects.

Having witnessed chameleons at work, Stephen thinks the manipulator has some way to go. “I struggle to see how they will get it to focus on [a target]. How will they judge distances? It all seems very far-fetched.” Paul Marks n

“Engineers at Tor noted the flaw last year, and warned against sending BitTorrent traffic through the system”

Artificial tongue lashes out like a chameleon

By mimicking a chameleon's tongue, a robotic manipulator could be used for delicate manufacturing, or even bug-catching

Twist on a tongue

Inductive coil gun �res magnetic tongue tip while attached elastomer reduces impact force

Ballistic tongue elongates at constant velocity as accelerator muscle is ‘�red’

DRIVER

CONTROLLER

POWER SUPPLY

ACCELERATOR MUSCLE

COMPRESSED CONCERTINA-STYLE MUSCLE

COMPRESSED MUSCLE ELONGATES AND THEN RETRACTS TONGUE

BONY SUPPORTChameleon

Robotic device

MOTOR REEL STRING COIL GUN MAGNET OR GRASPER

ELASTOMER

STICKY TONGUE TIP

STICKY TONGUE TIP

Don’t share files if you want to stay anonymous online A SECURITY flaw in the popular Tor online anonymity software could put users who share files online at risk of being identified, according to details recently released by a team of researchers in France.

The open source Tor software, which is free to download, routes traffic through a series of servers, each of which encrypts the data. This is designed to make it difficult for eavesdroppers to identify anyone using the software as they send messages, browse the web or download files.

Tor is thought to be widely used by political dissidents in many

countries. In Egypt, usage spiked dramatically during the period preceding the ousting of Hosni Mubarak as president early this year. But activists may be putting themselves at risk when using Tor.

When the software is used in conjunction with the BitTorrent file-sharing system, some of the traffic may not go through the Tor network. Stevens Le Blond and colleagues at the Grenoble and Sophia Antipolis branches of French national research agency INRIA have shown that by comparing the traffic inside and outside the Tor network, it is possible to trace

online activity back to the sender.In a paper presented on 29 March at

the Workshop on Large-Scale Exploits and Emergent Threats in Boston, Le Blond and his team describe how they mounted the privacy attack. As they monitored traffic inside and outside the Tor network during a three-week period in 2010, they identified 10,000 internet protocol (IP) addresses being used to send data.

They could then have recorded the browsing histories of people operating from these addresses – although they did not do so. Government agents can often use an IP address as a means of identifying an individual user.

BitTorrent is so widely used that the de-anonymisation risk applied to almost 1 in 10 communication streams carried over Tor. “We found that a significant fraction of all Tor traffic was at risk of being traced,” says Le Blond.

Engineers at the Tor Project, the non-profit company that develops the software, noted the flaw last year – when Le Blond’s team first identified it, but before they released these details – and warned against sending BitTorrent traffic through the system.

“There are lots of vulnerabilities in Tor, and Tor has always been open about the various vulnerabilities in its system,” says Hal Roberts at Harvard University, who studies censorship and privacy technologies. “Tor is far from perfect but better than anything else widely available.” Jim Giles n

TECHNOLOGY

110416_N_TechLast.indd 26 12/4/11 10:53:11