Scientists in the US have created a roller ball pen that can be used to draw functioning circuit boards.
The research team at the University of Illinois used conductive silver ink to sketch electrical circuits on paper, wood and other flexible surfaces.
Although similar pens have been available for a number of years, their ink tends not to be bendable when dry.
Most of the work in this area is focused on developing inkjet printers capable of creating circuits.
"We use 3D printing in our work, which is an increasingly popular way of manufacturing material, but it's also quite expensive," said Dr Jennifer Lewis, Professor of Materials Science and Engineering at the University of Illinois.
"We've always said that we want to find low tech approaches to high tech devices."
Dr Lewis explained that the formulation of the ink in the pen was slightly different to that used in inkjet printers.
"The ink that we made has the same type of flow behaviour as normal ink in a pen, except that we've added functionality to the ink. Our pen can write on paper and different other surfaces, not just the conventional circuit boards, so it's much more flexible."
The University of Illinois research team has also been able to add components to a hand drawn circuit, including LED lights and a battery.
However, such basic uses may be the limit of the pen's abilities according to Dr Graham Martin, Director of Inkjet Research Centre at University of Cambridge: "It's nice for the hobbyists, but I would say if you wished to create a circuit board which is at all complex you wouldn't want to draw it by hand."