Is it art – or science? The robotic Rubens that redefines portraiture

Nick Clark sits for Paul, the computer with a head for figures

Meet Paul, the toast of this year's London Art Fair. He has one arm, he scribbles out portraits in 20 minutes and uses a biro. Oh, and he's a robot.

The machine – think rudimentary Wall-E with a sketch pad – was designed by Patrick Tresset, who is part artist and part scientist, to mimic his style of drawing. Yet, human artists beware; next the Frenchman plans to build a robot that can develop its own distinct style.

Paul, who has wowed viewers from Istanbul to the US, was a highlight of the 24th London Art Fair, which closed last night. His portraits, which were among the cheapest works at the fair at £30 each, were hugely popular. "They were selling non-stop," Mr Tresset said. "The reaction has been incredible."

The machine is described as a "cybernetic face-sketcher" and an "obsessive drawing entity" which works off light and shade. Mr Tresset said: "It does not know what a face is."

The robot's "eye" – a camera that swivels up and down – scans a subject's face, while its mechanical "arm," clutching a biro, does a sketch. The work takes up to 25 minutes and each one ends with a flourish as Paul adds a signature.

At the moment the robot does not learn or develop, but its intentionally "clumsy robotics" mean it has its own distinctive quirks. It was built for less than £300 and supported with a second-hand laptop.

Patrick Tresset aims to develop the machine. "A few years ago I would have said it wouldn't be possible, but now I believe a robot will be able to develop its own style. It all depends on whether I can secure funding," he said.

He wants to feed a range of drawings, paintings and images, " then the robot can develop his own style. I think it is possible with more research and work. We will have robots in the home in the near future; it's not too much of a stretch to think some may have artistic skill."

The project grew from a university PhD. He was a painter and draughtsman for 15 years, but "lost my passion for drawing". He wanted to see if he could develop a robot that could simulate it. "I had always loved computers as a kid. Now I'm trying to remove myself from the process. The way the robot draws is similar to my style."

He believes he remains the artist at the heart of Paul's work. "The robot in some ways is a replacement for myself. For the moment I'm still the author of the drawing and the author of the robot."

The Robot Rubens will next appear in February at the Kinetic Art Fair in London, which celebrates the centenary of World War II codebreaker Alan Turing's birth.

Meanwhile Jonathan Burton, in his seventh year as director of the London Art Fair, said visitor numbers this year had held up on 2011's levels and gallery owners were relatively positive.

The London Art Fair specialises in modern British and contemporary art. It comprises more than 100 galleries with work sold from £30 to £70,000.