The glass between you and a fraudster is thinner than a hair

We unlock our smartphones more than 100 times a day, and increasingly, instead of swiping right or in a pattern, we swipe a finger on a button, and wait for our personal key – our fingerprint – to unlock the door.

But for fingerprint sensors to gain wider use and offer more utility, they’ll need to perform better and more reliably so the experience is seamless.

Smartphone fingerprint sensors are among the breadth of applications made possible with ultra-thin glass. In this post, I’ll explain how ultra-thin glass elevates the performance of fingerprint sensors and grows their potential in mobile devices.

How do fingerprint sensors work? Electricity.

Fingerprint sensors work similarly to digital cameras. When you hit the shutter button on a digital camera, light enters the lens and is converted into electrical signals. The image created from those signals is stored as a picture.

Instead of capturing light, fingerprint sensors map the dielectric signals of the ridges, valleys, and grooves of your fingerprint when pressed to a screen. By reading every dielectric signal, the sensor creates an image of a fingerprint, and stores it. That’s the baseline all other fingerprints are judged against.

And like a camera, the linchpin of a sensor’s reliability and responsiveness is its components.

Thin as can be, and stronger than most

Our mobile devices are more than just phones – they’re wallets and check depositories, and our fingerprints are now our PIN number. Because mobile payment adoption is growing, the security and reliability of fingerprint sensors is essential for device makers, application developers, and consumers. Which means components must be increasingly sophisticated.

Ultra-thin glass is one such component, an amazing material thinner than a human hair and tough as nails that’s turning our phones’ fingerprint sensors, smaller than a dime, into the keyhole to our entire social, professional, and financial lives.

The thinner the glass, the more sensitive it can be. Measuring down to just 50 µm, SCHOTT’s ultra-thin glass enables fingerprint sensors to work reliably and at the highest performance levels every time you lay your finger on one.

For this precise application, ultra-thin glass must have a high dielectric constant, meaning electric signals pass through it more effectively on their way to the sensor. Other materials, like plastics and other variations of glass, have lower constants, so the sensors tend to be less responsive. The result of a high dielectric constant means a fingerprint is more reliably scanned and compared to the image on file within the sensor’s memory.

Another advantage is the flatness of ultra-thin glass. Sure, every smartphone cover seems flat, but even a slight defect on the surface can interrupt the sensor’s ability to accurately read a print. Ultra-thin glass of the highest quality is rolled, making it extremely flat and consistent in its surface, which again means the sensor will work more reliably and be more responsive throughout its lifetime.

One more thing. Our smartphones deal with many stresses – they’re dropped, scratched, and punished in our pockets and purses, making chemical strengthening a must. SCHOTT has been able to chemically strengthen its ultra-thin glass to be four times stronger than traditional thin glasses, which ensures that the glass fronting of a fingerprint sensor won’t break and render the underlying sensor useless. SCHOTT also engineered it with the high dielectric constant and flatness that complement its use in fingerprint sensors.

In the future of digital payments and access, fingerprints are key

Though fingerprint sensors are primarily used to unlock a smartphone, in recent years these sensors have acted as another way to access bank accounts and log into applications. Their reliability and responsiveness, therefore, is crucial to smartphone users who have grown accustomed to entering their bank accounts with just a thumbprint.

No single property gives ultra-thin glass its superiority in fingerprint sensor applications. But this material is more than just a sensor covering – it creates new options for designers and engineers of wearables, cars, and hundreds of other technologies. As a material, it’s superb because of the sum of its parts – it’s strong, it’s thin, and it’s engineered to excel in any application. As an idea in the mind of a designer, it’s unlimited in its potential.

January 12, 2016


Dave Vanderpool
Advanced Optics
SCHOTT North America, Inc.