Using a single laser pulse, a group of researchers at Delft University of Technology in The Netherlands has devised a method that allows silicon, in the polycrystalline form used in circuitry, to be produced directly on a paper substrate from liquid silicon ink. The process can be expanded to create biomedical sensors and stretchable electronics.

The capacity for printing silicon ink onto substrates has existed for some time, but has required a 350° C thermal annealing step—far too hot for many flexible surfaces. The researchers' new method bypasses the thermal annealing and transforms the liquid silicon directly into polysilicon.

In an oxygen-free environment, the researchers skimmed liquid polysilane by a blade. To coat the liquid polysilane directly on paper, the team then annealed the layer with an excimer-laser.

The laser blast lasted a few tens of nanoseconds, leaving the paper intact. In testing its conductive performance, the Delft researchers found that thin-film transistors using the laser-printed layer exhibited mobility as high as those of conventional poly-silicon conductors.