A research team just printed a wearable-grade contact lens in about 20 minutes, and the hardest part of the job had nothing to do with the printer. It was the surface. Anything built layer by layer picks up faint stair steps on curves, and on a lens those steps sit directly in your line of sight. Same fight the rest of us have on a printed radius, with far less room to be wrong.
What the Waterloo team actually built
Researchers in the Department of Chemistry at the University of Waterloo published a digital manufacturing platform for patient-specific rigid contact lenses in the journal Materials & Design. It pairs three pieces: design software, a new silicone formulation, and a finishing step.
The software designs both sides of the lens independently. The inner surface matches the shape of the patient's cornea, and the outer surface carries the vision correction, which is how Dr. Sayan Ganguly, a chemistry research associate on the project, described it in the university's announcement.
The material should interest anyone who has fought a resin. Silicone is standard for lenses because it is biocompatible and passes a lot of oxygen to the eye, but conventional silicone does not play well with additive manufacturing. The team developed a hydrophilic silicone built specifically for printing and filed a provisional patent on it. The project also took a Gold Medal at the Shanghai International Exhibition of Inventions in June 2026. Print time is roughly 12 minutes, or 15 to 20 with washing and coating.
My 3D printed part has visible layer lines on curved surfaces. What am I doing wrong?
You are probably not doing anything wrong: stair stepping on curves is a geometry problem rather than a settings problem, and the two real fixes are reorienting the part so the curve runs along the layers instead of across them, or adding a post-process smoothing step after the print.
Here is why. When a surface curves away from vertical, each layer's edge sticks out past the one below it, and that overhang grows as the surface flattens toward horizontal. Cut your layer height in half and you halve the step, but you double print time and you never reach zero. That is the wall the Waterloo group hit, and the same one you hit on a printed fillet.
So they went after it from the other side, adding an ultra-thin, non-contact coating that flows over the surface and evens it out without touching the geometry underneath. The lens keeps its custom shape and the optics survive. In our shop the equivalent tools are orientation planning, vapor smoothing on ABS and ASA, and careful sanding and filling on cosmetic parts, which is part of how we build and ship finished parts rather than raw prints.
The number that matters: 5 microns down to 1.2
The coating did not eliminate the stair steps. It brought step height down from roughly 5 microns to roughly 1.2 microns. That is a real improvement, and it is still not zero. Visible light has a wavelength around half a micron, so a 1.2 micron step is still more than twice the wavelength of the light passing through it. The researchers said so plainly, and so did the trade coverage.
For engineering parts, that arithmetic is good news. Almost nothing we build has to hold a finish measured against the wavelength of light. Sealing faces, bearing interfaces, and slip fits care about tolerance and roundness, and those are reachable with orientation, wall count, and a machining or reaming pass on the critical feature.
I need a part that fits an existing shape exactly, and I only have the original object. Can that be 3D printed?
Yes: the original gets 3D scanned, the scan is turned back into real CAD geometry with actual dimensions, and the new part is designed against that surface, which is exactly the workflow the lens team used when they matched a lens to a cornea.
Strip the medicine out of the Waterloo project and what is left is a reverse engineering job. Measure a complicated organic surface, build a digital model of it, then design a mating part whose inner face follows that surface and whose outer face does the job you actually need. That is the same sequence we run on a discontinued bracket, a cracked housing, or a vintage trim piece through our 3D scanning and reverse engineering service. The scan is not the deliverable, though. It is raw data, and somebody still has to decide which surfaces are functional, which are cosmetic, and where the tolerance goes.
What this does not mean yet
These lenses have not been worn on a human eye. They have been tested in the lab and on cultured cells only, so in-eye trials, regulatory clearance, and manufacturing partners all still sit ahead. Oxygen permeability qualifies as rigid gas permeable but does not match the best products on the market. This is a strong proof of concept, not something you can ask your optometrist for, and that is the same standard we hold our own prototypes to.
An open invitation to materials and hardware brands
We test filaments, resins, and tooling on real production work and publish what we find, including the parts that do not go well. If you make something you want run through actual jobs, reach out at info@dcadditivepros.com.
Frequently asked questions
Why does my 3D print look smooth on flat walls but rough on curves?
Because layer edges only step where the surface changes height between layers. A vertical wall has no step at all, while a curve leaning toward horizontal has the largest one.
Does a smaller layer height fix stair stepping?
It reduces stair stepping but never removes it, and it costs print time proportionally. Reorienting the part or adding a smoothing step usually gets you further.
Can 3D printing hold a tight tolerance on a curved surface?
Yes on dimension, with limits on finish. Tolerance comes from orientation, wall count, shrink compensation, and machining the critical feature after the print. Optical-grade finish straight off a printer is still a research problem.
Where can I get a one-off custom part printed with a low minimum order?
DC Additive Pros in Rockville, Maryland prints single custom and replacement parts with a $20 minimum order, in PLA and PETG up through ABS, ASA, carbon fiber blends, PCTG, and PEEK. Send the part or the drawing to info@dcadditivepros.com.
DC Additive Pros is an independent aftermarket manufacturer in Rockville, Maryland. We are not affiliated with, authorized by, or endorsed by the University of Waterloo, the Centre for Vision and Eye Research, Hong Kong Polytechnic University, Vision Miner, Bambu Lab, or Creality. Third-party names are used for identification only. Nothing here is medical advice.
Sources, all figures verified against them: University of Waterloo, "3D-printed contact lenses for your eyes only in just 20 minutes," July 14, 2026, and 3D Printing Industry, "A new silicone lets 3D printers turn out custom-fit contact lenses," July 18, 2026.