This Upcycled "Ephemeral Printer" Creates Temporary Advice — or Insults — with Laser Light

Pseudonymous maker "slartibartfist" has built a printer with self-destructing printouts — by shining a laser onto glow-in-the-dark paper.

"Got a 3D printer recently," slartibartfist explains of the project, so I thought I'd revisit an old idea: 'printing' letters with light onto glow in the dark paper. [It has] two modes: Oblique Strategies (displays a random creative idea to help you work through creative roadblocks), and Insult mode (random insult, because I have a kid and it'll make him smile)."

Traditionally, a printer is the go-to tool when you're looking for a permanent hard-copy of something — but the printer slartibartfist has built is by its very nature ephemeral. Built using primarily salvaged components, the printer uses stepper motors to run a low-power laser pointer along a sheet of glow-in-the-dark paper, charging it up such that where the laser was shining is phosphorescent when the lights go out.

While it's entirely possible to "draw" letters and arbitrary shapes by carefully controlling the motion of the laser, in the same way that a cathode-ray tube display charges the phosphor coating by magnetically steering an electron beam, slartibartfist went for an easier approach delivering higher-resolution characters: a daisy-wheel-inspired stencil.

A circular 3D-printed stencil has cut-out letters around its circumference, and a stepper motor rotates it to place the chosen letter between the laser and the paper. When the laser fires, only light in the shape of the letter hits the paper. A second motor moves the "print head" along the paper strip.

"After printing it locks you out for 30 seconds so the print can fade," slartibartfist notes, "[which] also gives the stepper drivers time to cool down so I don't need heat sinks, then it lights up its '?' and '!' buttons ready to go again."

More details are available in slartibartfist's Reddit post.