These are the secrets of the Samsung Galaxy Fold and the future of that fold

Foldable devices, now in the hands of consumers and even seen here at IFA 2022 in laptops from Lenovo and Asus, can enjoy their breakthrough year. If so, we probably owe it to Samsung, which has done the lion’s share of the work to make foldable phones and flexible screens mainstream.

How we got this far and how Samsung’s estimable foldable devices, the Samsung Galaxy Z Flip 4 and Samsung Galaxy Z Fold 4, overcame countless design challenges is a story best told by an insider: someone like Dr. Won-Joon Choi, Executive Vice President, Head of Flagship Product R&D Team & Technology Strategy Team at Mobile eXperience Business, Samsung Electronics, who sat down with me at IFA 2022 in Berlin to release a bunch of Fold design and development secrets to give.

With foldable devices, Dr. Choi me, Samsung hopes to reshape the industry, as it did a decade ago with large-screen phones like the Galaxy Note. It’s a line, along with the belief that foldables are ready to go mainstream, that Samsung is happy to repeat to anyone willing to listen — but I feel with Choi the sentiment is based less on marketing language than hard-won experience.

dr. Samsung’s Won-Joon Choi at IFA 2022 (Image credit: Future)

Building the Z Fold and Z Flips was “very challenging…there are a lot of limitations and challenges that foldable have from our perspective,” said Dr. Cho, who has been with Samsung since 2016 and actually has two responsibilities as the leader of the flagship R&D and running Samsung’s Technology Strategy Team, where he builds strategic relationships with startups and global companies. It’s something that plays an important role in his work to bring the now three-year-old Foldable business to fruition.

dr. Choi gave me a rare behind-the-scenes look at the challenges and sometimes surprising solutions his team encountered while developing his foldable phones.

The main areas are:

  • Sustainability
  • Water resistance:
  • the hinge
  • Screen size and usability
  • Compatibility with S-Pen

However, we also talked extensively about the fold. You know the one that’s visible on both the 7.6-inch foldable screen of the Samsung Galaxy Z Fold 4 and the 6.7-inch flexible screen of the Galaxy Z Flip 4. But I’m leading the way. We can’t talk about the fold without first tackling the remarkable ultra-thin glass-covered displays.

Samsung’s ultra-thing glass, or UTG, appeared after two generations of Folds, starting with the Samsung Galaxy Z Flip 3 and then moving quickly to the Galaxy Z Fold 3. Several reports claim that a third party, Schott, has the flexible glass for the phones, while Corning does the rest. That may be so, but Dr. Choi emphasized that this was a collaborative effort and driven in large part by Samsung’s own R&D efforts.

It took years to develop the approximately 30-micrometer thick bendable glass that sits atop multiple layers of panel technology. “Every time you see our innovation hit the market, it’s not overnight. Obviously, we’re starting years earlier,” said Dr. choi.

Samsung Galaxy Z Flip 4 review Bora Purple open acute angled 16:9

Credit: Future/Alex Walker-Todd

Samsung didn’t bring it to early Folds though, as they weren’t sure if it would work. When I insisted on who exactly makes the glass, Dr. Choi me that in development they often have multiple tracks “even for thin glass”.

One track is Corning, who supplies all the glass of the back panel of the phones. Another track is done by a display partner (Samsung Display). The rest is “our own activity or research that makes UTG a reality,” said Dr. choi.

I asked again, which of the three makes the glass? dr. Choi insists it is “no source”. There is research collaboration, although “we have a lot of our own IPs” [intellectual property] for thin glass,” he added.

dr. Choi has confirmed that the flexible glass is not Corning’s, nor is the process of making it.

Over the years, I’ve interviewed Corning execs and seen some of his development work for ultra-thin, yet flexible (not bendable) glass. Being able to bend glass like Samsung Folds does is a breakthrough. I asked Dr. Choi what that moment was like when Samsung’s R&D realized they had glass that could bend enough to support foldable phones.

He smiled broadly and said, “Of course we were very, very excited.”

Samsung Galaxy Z Flip 4 in purple

(Image credit: Samsung)

Despite this, Samsung is still working on improving thinness and durability, customizing each screen later, and looking at materials, adhesives, and thickness.

I appreciated the challenge, but I had to ask about the fold because that’s what everyone asks me when I show them the Galaxy Z Fold 4.

On the 7.6-inch display, the crease is a uniform pit that runs the length of the screen. You can see it when the screen is off and you always feel it when you run your finger over the screen. It is not particularly noticeable when you use the screen.

The fold exists because of the strength of the glass material and the need to maintain what I believe to be a standard curved shape. In other words, if you unfold the glass, you bend something that in its natural state would look a bit like a glass taco shell.

dr. Won-Joon Choi from Samsung

dr. Won-Joon Choi from Samsung (Image credit: Samsung)

Understanding why it is there is one thing, but how do we get rid of it?

“It is a fair question for foldable. We believe” [the foldable] has reached a point where it can go mainstream, but that doesn’t necessarily mean we’re done yet,” when I talk to Dr. Choi on getting rid of the crease. “Reducing the crease is definitely on the list. It’s one of the technical challenges we want to overcome.”

How actively is Samsung dealing with the problem? dr. Choi told me that research goes in two directions. One is looking at the size of the arc (that fold) when you fully fold the Z Fold 4 or Z Flip 4. Somewhat counter-intuitively, you don’t want a smaller fold. A larger one would put less strain on the screen and potentially make for a less noticeable crease, as it would spread more smoothly over a wider area of ​​the screen.

Samsung Galaxy Z Fold 4

Credit: Peter Hoffmann

The other avenue of research is in materials. Different materials have different properties and may react differently to folding. dr. Choi said the screen would still be glass, but some material characteristics could change to create a different, less noticeable fold shape.

dr. Chjoi laughed and told me that this is the question everyone is asking and that solving it is now “part of his homework”.

Waterproofing phones with so many mechanical moving parts also proved challenging. Both Folds have two bodies connected by a hinge. The technology on those two sides is connected by a piece of flexible circuit board, which must be fed through holes in the chassis on each side.

The team came up with a number of innovations to protect the delicate parts from the elements. For the holes, the phones use a rubber sealant. For the more exposed hinges, they apply anti-corrosion material. Finally, Samsung developed new, waterproof components.

Samsung Galaxy Z Fold 4

(Image credit: Samsung)

With the latest Z Fold, Samsung wanted to make the cover screen bigger and I had already heard stories about how they redesigned the hinge to make it that way. dr. However, Choi added a bit of R&D color and told me his team went through “10-20 recipes to reduce size and weight for six to nine months. It kept failing and then decided to completely change the structure.” It wouldn’t be the last time he described the development process as using “recipes”.

When it came time to bring S-Pen functionality to the Galaxy Z Fold 3, they had to figure out how to get a rigid copper-based digitizer under the flexible display. It was another trial and error process for Dr. choi. This time there were almost 100 recipes.

Finally, “someone came to my office and said, ‘Hey, Won-Choo, why don’t we just break it down?'” Instead of one rigid copper digitizer, they used two: one on each side of the 7, 6-inch screen.

This naturally left a small gap between the two panels. To address that, Samsung has developed an AI-based prediction algorithm that can predict where the digitizing S Pen will go on the screen and automatically fill in the small gaps.

Unfortunately, the S Pen’s challenges were far from over.

The thing about the Fold’s flexible screen is that the natural shape of the screen is more of a “U”, meaning it really wants to pop open around the edges. Samsung counters that with nearly a dozen magnets placed around the edge of the display that keep it closed when folded. The problem was that those magnets interfered with the electromagnetic energy needed to run the digitizer. Initially, “50% of the digitizer failed to detect the S-Pen,” Dr. Choi me.

The solution? Keep the magnetizing force high when closed, but then turn it all the way down when the Z-fold 4 is unfolded,

Listening to Dr. Choi is understanding that the folding journey is far from complete, but has only just begun.

Samsung has ambitions to make its foldable phones thinner and lighter. It will, as it did to fit flagship-level cameras into the devices, optimize every single component. And foldable phones may just be the beginning. dr. Choi said Samsung is looking at many other device form factors — laptops, larger screens, and more — for its UTG and foldable display. Samsung insists it won’t build them unless it knows such displays add value to consumers.

IFA 2022 is Europe’s biggest tech show, and GadgetMasti is in Berlin to bring you all the latest news and announcements, plus our hands-on first impressions of the new TVs, wearables, audio devices and other gadgets on display.