Road signs and abrasives that evolved from an overhead projector

24th Jan 2022

An advance in technology more than 60 years ago changed the way we make things, and it’s not done making an impact on new technology.

That scientific breakthrough heralds back to the technology that went into clunky overhead projectors. Maybe you remember them if your teacher used one at school. Or maybe you used transparencies with a projector back in the day to give an important presentation. There was actually a lot of science in that unwieldy piece of equipment.

A teacher uses a 3M overhead projector in a high school classroom in 1960. Source: 3M

It started in the late 1950s when a young physicist named Roger Appeldorn was working at 3M. His boss challenged him to create a better transparency - the slide used to project images on the screen. And after he produced that, his next task was making a projector that was small and not too costly - something customers were asking for but couldn’t get the existing in the market.

In 1962, Appledorn’s team presented their creation: a projector with a Fresnel lens made with a structured-surface plastic. The Fresnel lens was developed in the 1800s for focusing the beam of a lighthouse lamp. The original lens was large and heavy and made of glass. Later versions made use of plastic, but the quality was not quite up to par.

The new 3M technology improved the lens quality by creating structured surfaces that could be replicated in a very precise fine pattern, invisible to the naked eye, with thousands of structures per square inch. The technology was later termed “microreplication”. This development allowed inventors to use plastic with grooves and other patterns - that had the benefits of cut glass without the weight or the cost.

Since then, microreplication has been used for more than 50 unique applications - ones that you probably interact with in your everyday life. After the huge success of the projector, 3M engineers found additional uses for the 3M Fresnel lens - in traffic lights to signal a left turn, for the lens in LED watches, and for microfilm readers.

Revolution on the Highway

You can also thank microreplication technology for helping revolutionise the visibility of highway signs with a new version of retroreflective sheeting. Scientist Tim Hoopman needed to figure out how to take reflective prismatic structures with cube corners, and make them fit onto a continuous sheet that could be rolled up. They had to be consistently efficient in returning light from vehicle headlights, while also being tiny enough to fit on a thin sheet. And it had to withstand everything from the hot sun to icy sleet.

It was a lengthy process, but the microreplicated material made its way to roadways across the country by the late 1980s. The uses for the technology continue to evolve - into daytime fluorescent traffic signs and work-zone cones.

At the same time, 3M scientists also found that microreplication could be applied to reflective film - something that would eventually be used in laptops and cell phones. The technology creates micro-prismatic structures that are produced on a thin film, with an evenly smooth and reflective surface on one side, and tiny prismatic grooves on the other side. This film extends the life of your batteries by enhancing the brightness of screens without having to leverage additional energy. Instead of reflecting the light that would otherwise go in random directions - like toward the ceiling or floor - it enhances light directed to you, the viewer.

A Gritty Breakthrough

Breakthroughs in technology often come with mixing and matching two technologies to get the best of both worlds. The combination of an abrasive ceramic grain and the flexibility of the microreplication technology led to a huge advance for abrasives used in sanding belts and grinding wheels.

3M Precision-Shaped Grains continuously fracture to form sharp points that slice more cleanly and last longer than conventional ceramic grains. If you are using abrasives with this technology, you don’t have to use as much elbow grease to get the same result.

"It's a much more user-friendly abrasive. You can either go faster or use less pressure."

Wayne Maurer, a 3M technical manager, works with a team that applies microreplication technology to abrasives. He led the original five-member team that was tasked with developing a better abrasive after a competitor came out with a new mineral technology. “The abrasives division was very focused on developing the next generation of abrasives technology,” he says. “That team was the one that eventually developed 3M Precision-Shaped Grain technology that we use today.

3M Precision-Shaped Grains (right) are precisely shaped compared to conventional grains (left). Source: 3M

He explains that a typical piece of sandpaper uses mineral particles that have all different shapes and sizes - some of which are dull or round. “Microreplication allows us to make mineral particles that are all the same size and shape with very sharp edges to them,” he says. “This leads to a number of advantages.” In addition to being sharper, which helps them cut better, these particles are of the same height - so they are all active in the grinding process.

The result? Customers can get the job done faster.

Wayne links the difference between standard sandpaper and engineered abrasives to cutting meat with a butter knife versus a steak knife: you have to press much harder to make it work. The same thing applies for abrasives. “You don’t have to push as hard to finish something at the same rate,” he says. “So, it’s a much more user-friendly abrasive. You can either go faster or use less pressure.

What’s Next?

Wayne also believes we are much closer to the beginning of the journey than the end.

Technology has enabled us to make engineered abrasives that we’ve never made before,” he says. “By studying how these perform, we get new insights. The next generation of precision-engineered abrasives will come out of these studies, largely thanks to what microreplication has provided.

Another use for the technology? Tiny needles for drug delivery in a solid and hollow option. The tiny needles deliver drugs by applying them to the skin via a patch, or microneedle array vs a more traditional syringe. Early in 2017, 3M partnered with a pharmaceutical company to study the use of a new cancer vaccine.

And when will that more patient-friendly shot be available? Scientists are working on it.

Article originally published by 3M New Zealand.