Pseudonymous maker "Ray1235225" has built an Arduino-driven RGB LED cube that's powered entirely wirelessly, from a Samsung smartphone or standalone charging pad.
"It’s simply a 4x4x4 RGB LED cube (aka 'Charlie cube') running on an Arduino Nano," Ray explains of the project, "and is fully powered by a Qi wireless charging receiver. It doesn't use any batteries since the cube uses less than 5W of power, and the Samsung [Galaxy] S21 Ultra phone can conveniently reverse charge up to 5W."
Initially, Ray was planning to build his own Qi-compatible receiver — but hit upon a handy shortcut. "I was researching a bit about designing a custom wireless charging receiver," Ray explains, "but I found that the ones they sell online for adding wireless charging to phones without it was more convenient and reliable. I ripped open a wireless charging receiver, de-soldered the micro-USB cable and soldered terminals directly to the PCB."
"I will probably change the coil design in the future for more functional accessories that use wireless charging. I've made copper coils in past projects and I think making channels (CNC or laser engraved) for the wire to follow will be ideal, and use some math to determine the specifications of the coil to provide the required power."
More details are available in Ray's Reddit thread on the project.