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Applying Biometrics to The Problems Closest to Us

APEX is a fingerprint point-of-sale system that makes checkout more efficient by cutting the time required to grab your phone or card. Mostly though, APEX is a technological exploration of fingerprint technology and how it can be applied to the problems closest to our daily lives.
My Role
Interaction Designer, Hardware Engineer
My Team
Mia Tomblin — Interface Designer
Bonnie Sun — Industrial Designer
Angelique Dale — Industrial Designer
Project Duration
5 weeks (April - May 2018)
In my sophomore year of my undergraduate program, I took an Interactive Product Design class as part of my Industrial Design program. For the last 5 weeks of class I worked with a group of 3 other designers to create a checkout system which endeavored to make checkout quicker and easier through biometrics.
Starting with an Observation

We noticed that everyone carries wallets. Most people have multiple compartments to carry credit cards, debit cards, reward cards, and IDs, but keeping up with cards can be difficult for people. People can lose or damage their cards. Trying to find a specific card can hold up lines and lead to longer wait times for everyone. Even with phone payments people must take out their phone - an unideal situation if you don't keep your phone on your person or have it buried in a bag.

Most importantly, both wallets and phones are things one must have on their person in order to make a transaction. What if we could skip this requirement altogether and instead endeavor to make a checkout process that is agnostic to the objects we carry?

Design Goal

How can we design something that is agnostic to the objects we carry?
Fingerprint As Identity Validation

We saw promise in using fingerprint as a form of payment validation in order to create an object agnostic form of checkout. Fingerprint validation struck a nice balance in that it provided more efficiency compared to a traditional payment card but still required intentionality from the customer as opposed to more invasive forms of biometric verification such as facial recognition.

First Iteration

The initial design for our fingerprint checkout system was designed with 2 users in mind: the customer and the cashier. The screen incorporates a ball and socket swivel mechanism to allow the cashier to turn the screen towards the customer.

First Iteration Prototype

We lasercut the cardboard frame and adding score lines to create the bending shape in the concept drawing.

Moving to Self-Checkout

Ultimately, we chose to update this design to a self-checkout system (eliminating the need for the swivel mechanism) for a couple major reasons.

1. Expedite the checkout process.

2. Increased Sense of Personal Safety

Upon talking to peers about our concept, I came to realize that people had reservations about using biometrics in a traditional checkout line, namely that traditional checkout lines require a customer to be in much closer proximity to other people in line. This is in stark difference to a self-checkout where those in closest proximity are other customers at other self-checkout stations as opposed to people in line for the same checkout station. The perception of increased privacy in a self-checkout setting made people much more comfortable with using biometric validation.

Second Iteration

The second iteration of our system has a much simpler design with a wall mount to accommodate self-checkout. The wall mount is intended to make it easier to place the system at an ergonomic level for scanning while standing.

In order to accommodate those who felt uncomfortable with using biometric validation we also incorporated a card reader located on the side of the design in case people choose to opt out of the fingerprint verification. We agreed as a group that it was important for us to give people the choice to opt out and to not make it an inconvenient decision to do so.

Iteration 2 Prototype

We bent the metal frame that houses the screen and lasercut an acrylic casing to hold the electronic components. The horizontal striations were created using scouring pads.

Final Design

We ended up using the form factor of the second iteration for our final design due to it's simplicity and it's easy set-up. With our form factor finalized, we prototyped the shell of the final design by waterjetting metal then bending it into shape. We created a casing that houses a tablet and slides into the metal frame out of lasercut acrylic. The metal has a cutout to house the fingerprint sensor and the acrylic housing also has room for hardware components. All that was left after creating the shell was to implement the hardware and interface component.

Circuit Diagram

A diagram of the Arduino set-up we initially planned for the final design: depending on whether or not the fingerprint sensor accepts a print, an LED located at the top of the system will light green for approved, red for denied, and blue when on standby. In addition to this set-up, I programmed an interface to guide the customer along their transaction journey.

Setting up the Sensor

I first set up the fingerprint sensor prior to putting the hardware into the final casing. This was my first time ever using a fingerprint sensor so it took a bit of time for me to learn how to wire it so it was reading data properly.

APEX Interface

The APEX interface flow is relatively straightforward and meant to use minimal screens for a quicker checkout experience. Once the customer completes checking out items they are prompted to scan their fingerprint. Once doing so, they will either be approved or denied - if approved they can choose which account they would like to use and complete their payment.

Connecting Interface to Hardware

Once I completed the hardware interaction and my teammate Mia completed the interface design, I connected the interface to the fingerprint sensor via Processing.

The Code

To implement the interface, I used Processing so that when a user taps on a certain area of the interface they are led to the next step of the checkout process. I also connected our Arduino Uno to Processing so that the customer is shown the appropriate screen.

The Completed Prototype

To implement the interface, I used Processing so that when a user taps on a certain area of the interface they are led to the next step of the checkout process. I also connected our Arduino Uno to Processing so that the customer is shown the appropriate screen.


I learned a lot about connecting 2D interfaces to 3D implementations through this project. Additionally I learned a lot about how sensor choices can affect important design factors such as ergonomics (in this case the choice to do a fingerprint sensor meant that we needed to adjust our design so that it could comfortably accommodate someone lifting their arm towards the sensor area). I had a lot of fun playing around with the fingerprint sensor and learning Processing through this project.

More importantly though, this project made me think more deeply about privacy and safety. One thing that I contemplated could have been improved as we reached the end of the project was making sure we prioritized users feeling safe and secure using our system. For example, could our system have had a privacy screen or a hood of some sort? Additionally, I came to wonder what measures, beyond the design my team had worked on, would need to be taken in order for a system like this to truly be secure and to keep people's information secure.