Mechanical arm copies motion of real limbs and can repeat actions

Mechanical limb:A mechanical arm developed by three fifth-year students from St Michael's College, Dublin, holds promise as a replacement for patients who have lost limbs.

It approximates the movement of a real limb and can be programmed to repeat specific movements.

The limb uses "muscle wires", thin but tough metal wires made of a nickel-titanium alloy, explains James Clifford (16), who developed the prototype arm with Daniel Ferrick and Eoin McGowan, both 17.

"It is completely different than most metals in that it contracts as it heats up," James says. It shrinks by as much as 8 per cent, a factor that makes it ideal in a mechanical arm.

Daniel says that while a muscle is made up of thousands of strands, the arm needs just eight. They entered a robotic arm in last year's BT Young Scientist exhibition and wanted to develop it further for the 2007 event.

They found that hot air and steam were the best ways of heating the muscle wire, but "trying to control the direction of the air was very difficult" and caused a "massive amount of difficulty", Daniel says.

They decided to use a small electric current to heat the wire but this in turn required an elaborate electronic control system that could move the arm but also determine its position in space. "It is all controlled by a laptop computer," Eoin says.

They started work on the arm in October and worked right through the Christmas holidays to get the arm working for the exhibition. The result is an impressive combination of electronic control systems and a working arm that mimics human movement.

Darina Storey and Michelle O'Dea of St Wolstan's community college, Co Kildare, also used a laptop in their project, but for a completely different reason.

It supports digital voice analysis which can be used to spot a liar.

"We can hear it in your voice" is the title of this project from the two 16-year-olds who are in transition year. "It is about lie detecting and seeing if a change occurs in your voice if you tell a lie," Michelle says.

The research is based on the use of free internet voice analysis software called Wavesurfer, Darina says. It can measure the pitch or frequency of the voice and the gap or "wavelength" between words, factors which help identify a dissembler.

Darina says they got 10 volunteers to prepare short texts for reading into the computer, one truthful and one full of lies, Darina said. Michelle says that although their sample size was small, they found that nine out of the 10 could be detected when lying.

"When lying we are looking at really high frequency and short wavelengths. It is quite reliable."

There is a level of doubt in most forms of lie detection, but they are still of value to the police. Voice analysis isn't used here at the moment, but the two believe it should.

"We got really good results," Darina says.