Nicholas Johnson has created what might be the most impressive business card in the tech world - a credit card-sized device that runs a real-time fluid simulation on a 21x21 LED matrix. The card responds to movement through an accelerometer, creating mesmerizing water-like effects that flow and splash as you tilt and shake it.
The project, called flip-card, combines hardware engineering prowess with sophisticated software. Built around the RP2350 microcontroller and programmed in Rust, it implements a FLIP (Fluid-Implicit-Particle) simulation algorithm originally developed by Matthias Müller. The device features 441 individual LEDs arranged in a perfect grid, creating a surprisingly smooth animation despite the low resolution.
Engineering Challenges and Solutions
One of the most innovative aspects of the design is its ultra-thin USB-C charging port. Rather than using a traditional connector that would make the card bulky, Johnson implemented a board-edge design inspired by Charles Lohr's work. The PCB itself slides directly into a USB-C cable, with the circuit board acting as the connector's center blade. This clever approach keeps the entire card remarkably thin while maintaining full charging functionality.
The community has been particularly impressed by the manufacturing approach. Using services like JLCPCB, the entire card including PCB fabrication and component assembly costs around $17 USD per unit for small quantities. This represents a dramatic shift in accessible electronics manufacturing, where complex designs with hundreds of components can be professionally assembled at prototype scales.
Community Reception and Practical Applications
The response from the tech community has been overwhelmingly positive, with many noting the card's effectiveness as a networking tool. Unlike traditional business cards that often end up forgotten in drawers, this electronic version becomes a desk toy that keeps the creator's contact information visible and memorable.
Most of those business cards just get tossed into a drawer or trash bin, I bet people keep this one on their desk and play around with it.
The project has sparked discussions about the future of business cards and promotional materials. While the $17 USD cost makes it impractical for mass distribution, it's perfectly suited for high-value networking situations like trade shows, job interviews, or client meetings where making a lasting impression is crucial.
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| The GitHub repository for the flip-card project, showcasing its open-source files and community engagement related to the innovative business card |
Technical Implementation and Open Source Approach
Johnson has made the entire project open source, including PCB design files, firmware code, and even a WebAssembly simulator for debugging. The fluid simulation logic is contained in a standalone Rust crate, making it reusable for other projects. The implementation demonstrates how modern microcontrollers can handle computationally intensive tasks that would have been impossible on embedded systems just a few years ago.
The project also includes thoughtful touches like power management and motion detection. The card automatically activates when moved and enters sleep mode when stationary, maximizing battery life while ensuring it's always ready to impress when needed.
This business card represents more than just a clever gadget - it's a demonstration of how accessible advanced electronics manufacturing has become and how creative engineers can leverage these tools to create truly memorable experiences.
Reference: Nicholas-L-Johnson/flip-card