Flexible Fingerprint Sensors and Sensors Expo: Dr. Rouzet Agaiby

Interview conducted by Zoe PeterkinJun 20 2018

In this interview, Dr. Rouzet Agaiby speaks to AZoSensors about flexible fingerprint sensors and Sensors Expo & Conference 2018.

How do fingerprint sensors work?

There are various types of fingerprint sensors out there. The most common ones used in mobile phones are the capacitive type, which means that they sense the different capacitance of the surfaces of the finger between the ridges and the valley of your fingerprint, and thereby reconstruct that image and authenticate the user.

The fingerprint sensor is almost like a camera that captures an image of your fingerprint and then matches it against some pre-saved profile. If it sufficiently matches the pre-saved profile then the user is granted access; if it doesn't then it blocks the user from using the device.

Capacitive sensors have been mostly used in mobile phones, but there are other types of fingerprint sensors. There are the optical fingerprint sensors which, as the name suggests, use light instead of capacitance. An optical sensor captures the fingerprint image in the presence of light, like a camera, and matches it against some pre-saved image.

Then you have new versions of fingerprint sensors called ultrasonic, which send a wave to the finger and measure the reflected wave that gets sent back. By subtracting the waves that you sent and the waves that you get back, you can reconstruct an image of the fingerprint and again match it.

Finally, there's the thermal, which is based on the minor differences in temperature between the ridges and valleys of the fingerprint. It can construct what a fingerprint actually looks like and again match the person.

Each of these types have different types of sensitivity, and some are more sensitive to different types of environments. For example, the capacitor is very sensitive to dry fingers - it also won't work if your finger is wet - whereas ultrasonic can work underwater, optical will not work in the dark and so on.

Each one of them has their limitations and so different solutions will be optimal for different applications.

Image credit: Iaremenko Sergii/Shutterstock

How will fingerprint sensors help to increase technology and device security?

If we think about how mobile devices started, the cell phone was just a device that you used to call other people, and that's it. These days that’s often only a small part of a phone’s usage, and it has become critical for smart phones to have secure access so that when they're in the wrong hands, that person doesn’t have access to the data or the information.

As things like mobile payment and ticketing became more common uses of a mobile phone (you can now use your phone to access the London Underground, for example - you don't need an Oyster Card) you need to secure them even more.

Pin codes will not be enough, and are easy to observe. We need to make sure that whatever fingerprint sensors are used are very secure in terms of the actual technology, and also the associated software and algorithms that encrypt that data.

Why do you think that security is even more important with the introduction of IoT?

IoT, basically, is all about connected devices. You don't want one device to be very secure and another less so, because the security of the overall system will only be as strong as the weakest link. And so, by making all the devices very secure, have encryption, have the fingerprint sensing integrated in them, then you can guarantee that you're authenticating the right user. You know who's connected to that network, at what time, and the kind of activity that they are carrying out. So because of that, you try to make your system secure by authenticating the right user, as much as possible.

How do you think FlexEnable's flexible fingerprint sensors will face and improve on that kind of security challenge?

There are several advantages within our technology that makes our flexible fingerprint sensors quite unique in that you can make them over a large area cost effectively. If you notice, the kind of sensors that you see in mobile devices are as small as a button. The reason that they're as small as a button is mostly cost, but also, it’s because you don't want to take up too much space on your device. You have batteries, you have cameras, you have so many other components in mobile phones and all these components are competing for space at the expense of the screen.

If you can make your device very thin and easily integrated without taking that real estate that all the other components are competing for, then you can make your device fingerprint enabled as a large area, without compromising all the other components.

By making a large area, thin, flexible fingerprint sensor you can make it as large as the display size and, because it's thin, you can integrate it behind the display and then have your whole display area sensitive to your fingerprint. Then you can use multi-finger authentication to get access to applications instead of a single finger authentication - you can imagine that it's more difficult to get a copy of all the ten fingerprints.

For example, for very secure applications, you can have a user use a combination of fingers like the index finger, then the left hand thumb followed by the right pinky for example, as the combination that will unlock a certain application. So a hacker will not know which finger combination you are using to authenticate the device and even if they have your fingerprints they will have to try many combinations before they get to it.

Overall, it's just trying to make things more difficult for the wrong user to hack into the system. The idea really is to make large area, thin, robust fingerprint sensors that can be easily integrated into devices, so then you're not competing for price and space on the final device.

How are 2D materials playing a part in this?

We use 2D materials (materials that are similar in dimensions to graphene) that have high electrical performance, and by using such materials we can increase the performance of flexible devices and can create higher resolution displays and sensors.

You can use this to print amplifier or driver circuitry that is currently made using brittle and expensive silicon. By printing such circuitry on plastic using these 2D materials, you can make your device fully flexible and very easy to integrate. And again, you can either fold it inside the mobile device, for example, or fold it around corners without worrying about anything brittle breaking.

What can attendees expect on the whole from your session at the conference?

Definitely an overview on the current fingerprint sensor technologies, the pros and cons of each, and then the integration challenges, because technologies can be very good as a standalone component, but at the end of the day you have to make them operate in an end user application. And it's these integration challenges that I'll be talking about, and how our technology can help ease some of those challenges.

Is there anything in particular that you're looking forward to at the conference?

I’m looking forward to seeing what other technologies are out there. You read a lot about different technologies in articles, but it'll be nice to actually see them and have a good close up look at them.

About Dr. Rouzet Agaiby

As the Senior Business Development Engineer at FlexEnable, Dr. Rouzet Agaiby has over ten years' experience in a number of areas, including: semiconductor manufacturing, flexible electronics and solar cells. She has a PhD in semiconductor technology from the University of Newcastle and also an MBA from Manchester Alliance Business School.