Sarah Tew/CNET

When I finally got my hands on the Royole Flexpai, the world's first flexible smartphone, I couldn't stop obsessing about the rubber spine as I opened and closed it. I worried that I was going to break it, but the two halves snapped into place via magnets just fine. Watching the Android operating system flex and bend on the display kept me riveted.

But then I tried using the phone.

I tapped the screen, and nothing happened. When it finally did, another widget popped over the main menu. I folded out the display, and waited for the screen to reorient itself. And waited. Tap, tap, tap. Nothing, nothing, nothing. It was definitely not ready for prime time.

Now playing: Watch this: Samsung's foldable phone is coming soon

To be fair, the phone I tried out wasn't a commercial-ready unit yet, and the Royole engineer who showed me the phone said updates were coming daily.

But that first awkward experience underscores some of the growing pains that flexible smartphones are likely to endure as they make their debut this year. The idea of a device that you unfold to enlarge, or roll up to put in your pocket, is the stuff of sci-fi movies, the kind of thing I grew up fantasizing about. Only, it's real now, and it opens the door to new types of designs beyond the boring slab of plastic or metal.

"Remember when we went from the keyboard to the screen," Verizon CEO Hans Vestberg said in an interview on Monday at CES 2019. "It was so huge. Innovation came with it."

Vestberg declined to comment on whether Verizon would sell a foldable phone.

I first saw Royole's FlexPai this week at CES, where LG also showed off a 65-inch OLED television that rolls up into a box. And then there was the beautiful "LG waterfall" formed from dozens of curved displays at the entrance to its booth.

Flexible displays have long been hyped up, but Samsung put some substance behind the hype last November when it showed off a prototype foldable Galaxy smartphone. In October, Huawei, the No. 2 smartphone maker in the world, confirmed that it was working on a similar device. At CES, a number of handset makers spoke to me about their experiences.

Now playing: Watch this: Galaxy S10, 5G and foldable phones make news at CES 2019

But a new design could also mean new interface, and that could prove awkward and buggy. Some handset vendors talked about the challenge of making a bendable phone able to handle daily use, while others noted that the software and interface required by new design could be complicated. Google has said it would support foldable phones in its next version of Android, but that's nearly a year away.

While I'm genuinely excited about flexible phones, I'm also skeptical. If foldable devices represent a revolution in design, what we see in 2019 will be the catalyst.

Just don't expect a big spark.

Samsung Galaxy X or Galaxy F?

If anyone can create a polished product, it's Samsung.

The company has teased a foldable phone for years, and it's finally ready to deliver in the first half.

"2019 is the perfect blend of consumer interest in this technology and technology advancements," said Suzanne de Silva, director of product marketing and strategy for Samsung Electronics, in an interview with CNET.

The rumored Galaxy X or Galaxy F is expected to make an appearance at Samsung's Unpacked event in February, even if the focus will be on the flagship Galaxy S10 smartphone. Unlike the Flexpai, whose screens fold on the outside, Samsung's flexible screen will be on the inside, and the device will close up like a clamshell. (There's also a smaller, more standard screen on the outside.)

De Silva called it a feat of engineering, noting that the phone has an articulated spine that allows it to open and close smoothly like a book. When the FlexPai is folded, there's still an annoying gap in the middle, as in the Microsoft Surface Book laptop.

Samsung

But just as important as the hardware is the software, and having an experience that best makes use of all that screen real estate. Samsung, however, has had a mixed history with its software and user experience. Part of me is worried about the challenges of a completely new design scheme.

De Silva said Samsung is focusing on the software, including the ability to run three apps simultaneously and to do one-handed navigation even with the bigger display.

Others are more cautious.

"While it seems obvious that people would love a small phone that has a big display, until we see these phones, it won't be clear whether consumers are willing to accept the trade-offs that new form factors inevitably bring," said Avi Greengart, an analyst at Global Data.

Revolution or gimmick?

Whether it succeeds or fails, Samsung's entry into the foldable phone world will make an impact. The Galaxy Note franchise made obscenely big displays a thing. The foldable Galaxy phone could similarly drag the rest of the industry into this area.

Beyond Samsung and Huawei, handset makers at the show talked about the challenges of using flexible displays. China's TCL, the company that makes BlackBerry and Alcatel smartphones, said it would create a flexible device by 2020, which could be a phone. It has the help of its own display maker, China Star Optoelectronics Technology, which makes displays for its phones and televisions.

"Having this in house gives us an advantage," said Stefan Streit, general manager of global marketing for TCL.

LG, which also has a sister company that works on displays, has already toyed with this area.

"You saw our rollable TVs," said LG Chief Technology Officer I.P. Park. "You can assume we can do much more there."

Skeptics everywhere

But Park didn't commit to any timing on a foldable phone. He also cast some doubt on such a device's ability to withstand wear and tear.

"I don't think anybody has a 100 percent solution at this point," Park said.

Royole said that its phone was tested for 200,000 bends, and is already on back order.

An executive from another handset maker that didn't want to identified noted that bending a phone with the display on the outside (FlexPai method) is much easier than on the inside (Samsung method). That person's company was still working on the durability issue of the inside-folding option.

"There's lots of work to be done before it becomes consumer-friendly," the executive said.

Sarah Tew/CNET

Patrick Moorhead, an analyst at Moor Insights, expects five to 10 companies to announce a foldable device, and he said he was impressed by what he saw at CES. "I'm expecting much higher-quality devices in February" at the Mobile World Congress trade show, he said.

MediaTek Chief Financial Officer David Ku, likewise, was skeptical about the prospects for foldable phones in China because of the potential cost. "I would say it's a few years to go," he said.

With all the focus on 5G this year, flexible phones may end up as a side act until that new networking technology matures.

"2019 is about 5G and full display designs," said Wayne Lam, an analyst at IHS. "I would say the market won't get really interesting until 2020."

CNET's Shara Tibken and Lynn La contributed to this story.

Published Jan. 11 at 5:42pm PT. Update: Jan. 12 at 5:57pm PT to correct the statement that TCL will release a foldable phone in 2020. It will release a foldable device, which could be a phone.

CES 2019: See all of CNET's coverage of the year's biggest tech show.

Galaxy S10 launch date confirmed: Tune in Feb. 20 for Samsung's Unpacked event.