A Game Changer

Have you ever sat out of a card game because the rules were so complicated that you didn’t want to put in the effort needed to learn them? Or do you find card games uninteresting because they lack the interactivity of digital games? If so, a very unique — and somewhat odd — robot created by a team at the University of Chicago and the National Taiwan University might be right up your alley.

Their invention, called CARDinality, is an interactive, card-shaped robot that can spice up a card game by adding locomotion and haptic feedback to any playing card. Once this ultra-thin robot is attached to a card it can be programmed to slide it across a table, perhaps to move it to a discard pile, or it can cause a card to vibrate, indicating the next action a player is supposed to take. These are just a few of CARDinality’s possibilities, but the actions can be customized for each use case.

A semi-flexible printed circuit board (PCB), measuring just 0.3 mm in thickness, was designed to serve as the backbone of CARDinality. The dimensions of the PCB are slightly smaller than a standard playing card. A Seeed Studio XIAO NRF52840 Sense microcontroller development board was integrated into the design to provide processing power, wireless connectivity, an inertial measurement unit, and a LiPo charging circuit. A set of four eccentric rotating mass vibration motors provide for locomotion and haptic feedback. A 180 mAh LiPo battery, only 1 mm in thickness, powers the robot.

The CARDinality software is used to establish a Bluetooth connection with another nearby device, such as a laptop computer, to control the robot’s behavior. This software also contains a set of motor configurations that are required to produce omni-directional motion. Additionally, a gesture classification feature is available that interprets data received from the onboard inertial measurement unit. Testing with a MacBook Air 2021 M1 laptop demonstrated that at least ten robots could be controlled simultaneously without encountering performance issues.

Determining the set of motor configurations that could produce motion was no easy task, so the team took a computer-vision based approach to finding them. This gave them a total of 76 motor output patterns that can slide the robot across the surface of a table in any direction, or cause it to rotate in either direction.

While the PCB and battery are quite thin at 1.3 mm, the size of the motors cause one end of the robot to extend to 4.7 mm in thickness. This, in turn, causes the cards to sit at an angle on top of CARDinality, which is not ideal if you want the hardware to disappear into the background. There is some room for a redesign of the circuit, so it may be possible to resolve that issue in the future.

Whether or not anybody actually wants a swarm of robots accompanying their card game remains to be seen. But in any case, CARDinality is an interesting idea that is worth checking out.