A 3D printer that works at one micrometre, built from strip lights...
Vik Olliver has been taking 3D printers apart for twenty years. Lately he has been taking them down a thousandfold. The μRepRap project builds a fabrication machine that works at one micrometre, and it does it with parts from a hardware shop.
Strip the machine back and it is a very small, very rigid CNC mill. Three NEMA17 steppers drive the axes. A sharpened probe replaces the hotend. Under the stage sits a single UV LED, cut from an eight millimetre strip light and taped beneath a window.
Deposition is the interesting part. The probe dips into a smeared layer of UV nail gel and lifts resin by capillary action. Touching the surface releases a droplet. Repeated touches build a line, then a layer, then an object. Droplets under fifteen micrometres are routine.
The current build is called PIKA, short for Printable In-place Kinematic Assembly. Its XY table prints as one piece of PLA on any ordinary FFF machine, no supports, and flexes through eight millimetres in X and Y while barely moving in Z. It holds about one micrometre of repeatable positioning across a cubic volume of roughly eight millimetres, with reliable accuracy at ten micrometres or better. A 0.5mm Benchy came off it at four micrometre layer height. Resin droplets of four micrometres have been deposited. A fibre optic probe cured lines nine micrometres wide.
The ancestry runs through the OpenFlexure Project. Their printed microscope stages proved that plastic flexures could hold sub-micron position without a granite block or an air bearing. Olliver started from that idea and pushed it toward fabrication rather than observation. An earlier frame, MAUS, managed five micrometres over a four millimetre square, though the motion was not linear. It survives in the wiki as a documented kit and on Printables as a set of STLs.
Why bother. The Intel 4004 shipped in 1971 with ten micrometre features, and the industry spent fifty years making the machinery behind that number esoteric and expensive. RepRap's original argument was that a printer should be able to reproduce its own parts. The μRepRap takes that argument down a scale: the wiki notes that a PIKA can etch its own probes.
The honest limits are in the same document. Thin layers of UV resin will not set in open air, because oxygen neutralises the activated photoinitiator before it can cure. Overhangs, folded structures, hinges and flexures at that scale are listed as work still to do. Two USB microscopes, one of them at least eight megapixels, are needed just to see what the probe is doing, plus a bench microscope between 100x and 200x to inspect the result.
Nothing here is a product. It is a platform, published under GPL-3.0, with a bill of materials, build notes and a running blog. The repository has 243 stars and was last touched on 17 October. The whole point is that someone else can build one and take it somewhere the author has not thought of.
Build notes and wiki: github.com/VikOlliver/RepRapMicron/wiki
PIKA STL files: printables.com/model/1692745
Progress log: blog.reprap.org
■ Filed from The Foundry: the Fern, Fire wing of the city.