Foldable devices, which are now in the hands of consumers and even on display here at IFA 2022 on laptops from Lenovo and Asus, could be enjoying their rookie year. In that case, we probably have Samsung to thank, which has done most of the work to make foldable phones and flexible displays popular.
How we got this far, and how Samsung’s esteemed foldables, the Samsung Galaxy Z Flip 4 and Samsung Galaxy Z Fold 4, overcame countless design challenges is a story best told by someone on the inside: someone like Dr. Won-Joon Choi, Executive Vice President, Head of Core Product Research and Development Team and Technology Strategy Team at Mobile eXperience Business, Samsung Electronics, who sat with me at IFA 2022 in Berlin to share various design secrets and Fold development.
With foldables, Choi said, Samsung hopes, as it did with big-screen phones like the Galaxy Note a decade ago, to reshape the industry. It’s a line, along with the belief that foldables are ready to go mainstream, that Samsung likes to repeat to anyone who will listen – but I feel like with Choi the sentiment is based less on marketing hype than not hard won. experience.
Building the Z Fold and Z Flips has been “very challenging… Research and development and directing the technology strategy team at Samsung, where he builds strategic relationships with startups and global companies. It figures significantly in his work to help bring the now three-year-old Foldable business to life.
Dr. Choi gave me a rare behind-the-scenes look at the challenges and sometimes surprising solutions his team found when developing their foldable phones.
The key areas are:
- water resistance
- the hinge
- Screen size and usability
- S-Pen Compatibility
We also, however, talked extensively about the crease. You know the one that’s visible on the Samsung Galaxy Z Fold 4’s 7.6-inch foldable display and the Galaxy Z Flip 4’s 6.7-inch flexible display. But I’m getting ahead of myself. We can’t talk about the crease without first addressing 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 quickly moving on to the Galaxy Z Fold 3. Various reports claim a third-party company, Schott, is providing most of the flexible glass for the phones, with Corning doing the rest. That may be true, but Dr. Choi emphasized that this was a collaborative effort and driven largely by Samsung’s own R&D efforts.
It took years to develop the approximately 30 micrometer thick collapsible glass that sits on top of multiple layers of panel technology. “Whenever you see our innovation appearing on the market, it doesn’t appear overnight. Obviously, we started years earlier,” said Dr. Choi
Samsung didn’t bring it to the first Folds because they weren’t sure it would work. When I pressed him on exactly who is making the glass, Dr. Choi told me that in development they often have multiple tracks “even for thin glass”.
One of the ranges is Corning, which already provides the glass for the back panel of the phones. Another track is made 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, who among the three makes the glass? Dr. Choi insists that “it’s not a single source”. There is research collaboration, although “we have many of our own IPs [intellectual property] for thin glass,” he added.
Dr. Choi confirmed that the flexible glass is not from Corning, nor is the manufacturing process.
Over the years, I’ve interviewed executives at Corning and seen some of their development work for ultra-thin but flexible (non-folding) glass. Being able to bend the glass the way the Samsung Folds does is a breakthrough. I asked Dr. Choi how it was that moment when Samsung’s R&D department realized they had glass that could bend enough to support folding phones.
He smiled widely and said, “Of course we were really, really excited.”
Despite this, Samsung is still working on improving thickness and durability, adjusting each screen afterwards and analyzing materials, adhesives and thickness.
I could appreciate the challenge, but I had to ask about the crease as that’s what everyone asks me when I show the Galaxy Z Fold 4.
On the 7.6-inch screen, the crease is a uniform lump that runs the entire length of the screen. You can see it when the screen is off and always feel it when you swipe your finger across the screen. It’s not particularly noticeable when you’re using the screen.
The crease exists because of the strength of the glass material and its need to maintain what I assume is a standard bent shape. In other words, when you unfold the glass, you are unfolding something that, in its natural state, would be a bit like a glass club shell.
Understanding why it exists is one thing, but how do we get rid of it?
“It’s a fair question for collapsibles. We believe [the foldable] It’s gotten to a point where it might become mainstream, but that doesn’t necessarily mean we’re done yet,” when I Dr. Choi on how to get 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 pursuing the issue? Dr. Choi told me the research is going in two directions. One is to look at the size of the bow (that crease) when you fully fold the Z Fold 4 or Z Flip 4. Somewhat counterintuitively, you don’t want a smaller crease. A larger one would put less stress on the screen and possibly make a crease less noticeable because it would spread more smoothly over a wider section of the screen.
The other avenue of investigation is into materials. Different materials have different characteristics and may respond differently to bending. Dr. Choi said the screen would still be glass, but some attributes of the material could change to create a different, less noticeable crease shape.
Dr. Chjoi laughed and told me that’s the question everyone is asking and solving it is now “part of your homework”.
Waterproofing phones with so many mechanical moving parts also proved to be a challenge. Both Folds have two bodies connected by a hinge. The technology on these two sides is connected by a flexible printed circuit board, which must be fed on each side through holes in the chassis.
The team came up with a number of innovations to protect the delicate parts from the elements. For the holes, phones use a rubber sealant. For the most exposed hinges, anti-corrosion material is applied. Finally, Samsung has developed new waterproof components.
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 look like that. However, Dr. Choi added some R&D color, telling 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 change the structure completely.” It wouldn’t be the last time he described the development process using “recipes”.
When it came time to bring S-Pen functionality to the Galaxy Z Fold 3, they had to figure out how to fit a rigid copper-based digitizer under the flexible display. It was once again a 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 break it?'” Instead of one hard copper digitizer, they used two: one on each side of the 7.6-inch display.
Naturally, this left a small gap between the two panels. To address this, Samsung has developed an AI-based prediction algorithm that can predict where the digitizing S Pen is going on the screen and automatically fill in the small gaps.
Unfortunately, the S Pen challenges were far from over.
The thing about the Fold’s flexible display is that its natural screen shape is more of a “U”, meaning it really wants to open up along the edges. Samsung counters this with nearly a dozen magnets arranged around the edge of the display that keep it closed when folded. The problem was that these magnets interfered with the electromagnetic energy needed to make the digitizer work. Initially, “50% of the scanner failed to detect the S-Pen,” Dr. Choi
The solution? Keep magnetizing force high when closed, but then lower when Z-fold 4 is unfolded,
Listen to Dr. Choi talking is understanding that far from the folding journey being complete, it is just beginning.
Samsung has ambitions to make its foldable phones thinner and lighter. It will, as it did to fit flagship cameras to devices, optimize all the components. And folding phones might just be the beginning. Dr. Choi said Samsung is looking at many other device formats — laptops, larger screens and more — for its UTG and foldable display. Samsung insists it won’t build them unless it knows these displays add value to consumers.
IFA 2022 is Europe’s biggest technology fair, and is in Berlin to bring you all the breaking news and announcements, as well as our hands-on first impressions of the new TVs, wearables, audio devices and other gadgets on display.