“The 3Doodle pen, developed by US start-up WobbleWorks, works much like a handheld 3D printer. It contains a mains-powered heater that melts the plastic beads used in such printers. … Lift the nib in the air and a length of plastic exudes from the nib and solidifies, allowing you to create 3D objects by building up multiple wispy strands of plastic.”