Invisible Fingerprint Sensors Will Help Save Smartphone Design

Clever new tech will make smartphones sleek---and secure---again.
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Paul Taylor

A few years ago, smartphones began sprouting odd, circular growths. Sometimes these growths would appear on the front, other times on the back, but they pretty uniformly conquered high-end handsets with all the speed and subtlety of a virus. These are fingerprint sensors, and as much as they've increased smartphone security, they've been a pain on smartphone design. Good thing they're about to go invisible.

This week, LG Innotek revealed its new "under glass fingerprint sensor." Rather than a dedicated surface-level ring, it bakes the components into the display itself. Fingerprint Cards, the Swedish company behind the rapid-response scanners in Google's latest Nexus devices, recently showed off similar tech as well. We have the technology. Which means that soon, you'll be able to simply rest your thumb on a smartphone's display to unlock it. Presto.

That's welcome news for smartphone users, who won't have to grope for a gawky mini-discus every time they want to access their handsets. It's even more exciting for smartphone makers, who have had to grapple with how to incorporate a terrific feature that, until now, has required a dime-sized hardware blemish to work.

A Scanner Roundly

Let's be clear about one thing upfront: Fingerprint scanners are terrific. They're fast, convenient, and let you, if you so choose, opt out of having to type in some kludgy alphanumerical password every time you want to access your smartphone. Which, according to a recent Deloitte survey, can add up to nearly 50 times per day.

We're smartphone addicts, and fingerprint sensors are our always-connected IV drip. They've also improved, and quickly. The Nexus 5X and 6P reliably unlock in a blink, while the iPhone 6S and 6S Plus Touch ID system took heat last fall for being too fast. How often in life is a piece of technology's prime inconvenience that it's too good at its job?

No surprise, then, that fingerprint sensors have for many people become an ingrained part of the smartphone experience. According to research group IHS, fingerprint sensor sales jumped from 316 million units in 2014 to 499 million in 2015, with 1.5 billion (that's with a b) expected as soon as 2020.

That's not to imply that they're a perfect security; as always, that convenience comes with some cost. Not only can scanners be spoofed with modest effort, a California judge recently ruled that the FBI could compel "the girlfriend of an alleged Armenian gang member" to unlock her iPhone with her finger, so that the data inside could be screened for potential evidence. To break a password to similar effect, they would have had to read her mind.

An invisible fingerprint scanner won't do much to fix those issues. But you know what it can fix? Smartphone designs that have had to compromise for way too long.

Invisible Touch

There are worse things in the world than an extraneous circle on your smartphone. Given the choice, though, they're better without it.

"The first experience of picking up a phone should be delight," says Nick Cronan, co-founder and creative director of Branch. "You should be excited or impressed or delighted by the way it feels in your hand, or the surfacing, or the edge's details, or how intuitive it is... First impressions are huge."

Cronan speaks from a position of unique authority here; his company worked with Nextbit on Robin, one of the most eye-catching new smartphones of recent memory. As part of that process, he's also intimately familiar with the challenges of trying to make a fingerprint sensor disappear.

"Ultimately that's what we do as designers. We're trying to focus the consumer back on the experience rather than being distracted by the details," Cronan says. "Any opportunity to put the full experience to the forefront, and have everything simply support that, make that experience delightful? That's a win, I think."

In the case of Robin, that meant taking an unusual approach. Rather than placing a fingerprint scanner on the front, like the iPhone, or back, like the Nexii or some LG phones, Robin combines its reader with the power button on the phone's side. (Sony tried this as well in the Xperia Z5, but dropped it as a feature before the phone hit the US market).

It's clever, but it's also a half-measure, and not half as appealing as having it hidden altogether.

"[Designers] just like to have options," says Cronan. Limitations are oftentimes things we have to design around, especially on a phone. They're so small, and have so many requirements, and are so technically challenging. Getting rid of things is always great."

There are practical benefits to a glass-encased fingerprint sensor as well. A more cohesive enclosure makes for easier waterproofing, and burying the sensor more effectively protects it from performance-altering nicks. LG also promises a false-acceptance rate of a low .002 percent, which is low!

Then there are the buts, which we should run through as well. LG doesn't, for instance, specify the false rejection rate, which is how often biometric security doesn't recognize you as, well, yourself, and which can be a frustrating user experience. It's also unlikely that you'll see them in an iPhone any time soon; because of its 2012 acquisition of Authentec, Apple relies on in-house tech for Touch ID.

There's also the small matter of these still being mere components, rather than actually in products. Maybe they're slow! Maybe they don't work as advertised! And they'll almost certainly be confusing, at least at first.

"From the standpoint of usability it might be worse," says Jonas Damon, Executive Creative Director at frog, a global design and strategy firm. "Are capacitive buttons better than tactile buttons? They are more durable, more waterproof and cheaper, but they require the addition of an icon so people know where to touch."

All valid concerns, and potentially another trade-off between intuitive use and looks. Fortunately, Cronan says, people tend to be fast studies. "If it's a new gesture it has to be learned," he says. "But that can be learned pretty quickly."

Unlocked Potential

If this new technology does work as promised, we'll also learn pretty quickly how to use it in other capacities.

"Theoretically if you're able to have a digital key of your fingerprint, you could make any display or console your access point, if it's personalized." says Cronan.

That may sound a little disquieting, or even dystopian, to security researchers, given the various vulnerabilities inherent in fingerprint usage, and Cronan acknowledges that there's a big difference between a sensor embedded in a desktop and one at an ATM.

But think of how fingerprint scanners already manifest in smartphones, which carry some of the the most sensitive information you have. They're convenient, and encouraged, but also optional, and malleable. You can assign multiple fingers, or none at all. You can opt for a password or secret pattern instead of it, or in addition. Ideally, it's one part of a security suite, that works together to lock down your digital life. Why couldn't it also do that with, say, your car?

For now, though, we can expect to see invisible fingerprint sensors on smartphones popping up in the second half of this year. Or not see them, really. That's kind of the point.