Understanding Photolithography In The Watch Industry

TLDR: Photolithography is a microfabrication process adapted from semiconductor manufacturing. It allows for the creation of micron and nano-scale components with extreme precision. In watchmaking, photolithography is being used more and more frequently due to its ability to produce extremely precise movement parts at scale.

Want to know more? Read on...

At first glance, the world of horology looks like it hasn’t evolved in the last few hundred years.

‍We still tell the time with hands spinning in a circle, and those hands are still powered by springs and gears.
As the rest of the world has moved on, us watch nerds have stuck with our flawed, yet endearing wristwatches of metal, gold, and oil.
Something interesting has begun to happen, however. The brands we know and love have been injecting innovation into their processes and products without us noticing. Movements are being taken over by exotic materials, and as a result, our watches are getting more reliable, accurate and durable than ever. It’s strange though, regardless of what we do, they will never be as practical as something built with microchips instead of old Swiss men.

But that’s not really the point, is it. We don't love these things because they are practical. We love them because they are beautiful and make us feel good.
In saying that, why do brands spend millions of dollars trying to improve upon a technology that was made redundant decades ago? Shouldn’t they be focussing on what really sells watches, emotion? It’s like building a model T-ford out of carbon fibre. Yes, it would perform slightly better, but it will never be a BMW M3. Nevertheless, this innovation is happening at an ever-increasing rate and our watches are getting incrementally better by the day.

But what’s driving this push for accuracy and performance? It’s not silicone, 3D modelling or younger Swiss men. (although that last one might help).

No, it’s UV light.

What Is Photolithography, And How Does It Work?

Photolithography is a microfabrication process adapted from semiconductor manufacturing. It allows for the creation of micron and nano-scale components with extreme precision. In watchmaking, photolithography is being used more and more frequently due to its ability to produce extremely precise movement parts at scale. It's a technology that has driven our insatiable craving for electronics, data, and computing power for the last two decades, and it’s only just started to make its way into analogue industries like watch making. We’re about to get technical here folks, so If you’re a regular reader, buckle up, this is a heavy one.

How Does Photolithography Work?

This is a little complicated, but it’s helpful to know.

1. Substrate Preparation — A base material, usually mono-crystalline silicon, is cleaned and prepared. In watches, this could be a future hairspring, escapement, or gear. This is called the wafer.
2. Photoresist Application — A light-sensitive polymer called photoresist is applied as a thin layer on the substrate via spin-coating. (Put on as a liquid, then spun really fast to spread it out).
3. Soft Baking — The wafer is gently heated to remove solvent and help the resist adhere properly.
4. Mask Alignment and UV Exposure — A photomask (like a stencil with micro scale patterns) is aligned over the substrate. The wafer is then exposed to ultraviolet (UV) light, which changes the chemical structure of the photoresist in exposed areas.
5. Developing — The wafer is developed in a solution that removes either the exposed or unexposed photoresist, depending on the type (positive or negative). This is just like film photo processing (anyone born after the year 2000 can ask their parents what that is).
6. Etching or Deposition — If etching, unwanted material on the exposed parts is removed (e.g., using plasma or chemicals). If deposition, new material (e.g., silicon dioxide) is added to the exposed regions.
7. Stripping — The remaining photoresist is removed, leaving the desired microstructure behind.

This process can be repeated multiple times with different masks to build up complex, layered components.

I would be very surprised if anyone was still reading, so if you are, you get a free watch!

Only kidding…

Photolithography In The Watch Industry

Movement parts are really, really small in case you haven’t noticed. And how accurate those parts can be made depends heavily on the machines you are using to produce them. First we had people, like you and I, that would sit on a bench in Switzerland, probably overlooking some cows, using manual tools to file, cut and polish raw metal until it turned into gears, springs, and bridges. This method, although romantic, doesn’t produce the most accurate parts. There’s human error, limitations in our eyesight and shaky hands from eating too much fondue. That last one is true, I swear.

Modern-day production has generally relied upon CNC machines to produce parts in bulk. These ‘Computer Numerical Cutting’ machines use a teeny tiny drill bit that is controlled by a digital model and cuts each part out. This is much more accurate and repeatable than any human could achieve.

Just a quick note here to say that the use of this modern tech, although prolific, isn’t used everywhere. There are still brands out there that do things the old-fashioned way, with eyes, hands and fondue. Tradition in the watch industry is still alive and well.

The main problem with modern CNC at the micro scale required is the geometric constraints in which the tools can cut. Deep internal angles, under cuts and three-dimensional layering are all difficult to achieve with a machine that cuts using a rotating tool tip. This causes things like the teeth on a wheel to have rounded angles instead of sharp ones, potentially affecting efficiency and making movement nerds mad for some reason.

This is where photolithography comes in. Using the process outlined above, watch brands have the freedom to create components that were all but impossible with traditional techniques. Let’s explore some examples.

Which Watch Brands Are Using Photolithography?

Rolex

Let’s take a look at Rolex’s new Dynapulse escapement, released in the Land Dweller in 2025. I won’t get into the technical details about how this ‘sequential distribution escapement’ works, I’ll let this fantastic Monochrome article handle that. If we look at the image above, specifically the geometry of the wheel teeth. They look almost alien, and would be impossible to produce on a CNC machine. They are made from Syloxi (silicone) and Although Rolex doesn’t advertise their production techniques, these would most likely have been produced in with Photolithography.

Ulysse Nardin

In 2001, Ulysse Nardin released the Freak, and with it, the first use of silicone in a watch movement. It was revolutionary stuff, and was marketed as a way to increase efficiency via weight reduction, temperature stability and geometric optimisations. UN calls their process to produce these parts ‘Deep Reactive Iron Etching (DRIE)’ which is fundamentally the same process as Photolithography.

Zenith

As usual, Zenith reached for new heights with their use of Silicone and Photolithography in their Defy Lab released in 2017. This watch has a single component, the ‘Zenith Oscillator’ that replaces multiple within the balance and escapement modules. The entire piece, which fills out most of the dial, vibrates at a precise frequency and Is very impressive to watch. The Zenith Oscillator flat out wouldn’t have been possible without photolithography. The precision and accuracy required to produce it at scale is mind-blowing.

Has your brain melted yet? Mine has.

As I was researching this article, it came to me that perhaps, there is an emotional appeal to raw innovation like photolithography. Maybe watch brands are right to lean into the future and make these products easier for us to live with. Even though you’re probably not allowed to eat fondue while you do it, photolithography is here to stay. I just hope saying “My watch has a balance wheel that was made using UV light projected onto a silicone wafer” doesn’t become commonplace. Watch collecting is nerdy enough as it is.

Cya in the next one.

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