Penguin DIY Built Invisible Earphones That Vanish Inside a Custom Ear Cast

Penguin DIY started with a pair of ordinary true wireless earbuds and finished with two objects that barely read as audio gear. One half is a clear resin plug cast from a mold of his own ear, meant to sit fully inside the canal. The other half is the tip of a pen. Both still pair to a phone over Bluetooth, and both still take a charge from a case he opened and rewired so the original contacts could reach the new shapes.

Factory buds already hide the majority of their hardware, so making them disappear wasn’t a huge leap. The housings might be disposed of by simply throwing them away. He meticulously removed the Bluetooth board, lithium polymer cell, tiny speaker driver, and charge components from the shells, removing any extraneous connectors and pieces that only made sense when everything was put together in a plastic shell. The test pads on the board showed him where to attach the battery, charging, and audio connections. Then, under a microscope, extremely fine enameled copper wire was threaded onto those pads; conventional sized leads would not have fit in the tighter space. The resistors, capacitors, status LEDs, and touch controls remained on the board. Then he had to pack the speaker, cell, and board into a tiny cylinder, making sure no joint shorted against another.

A regular 3D printer could certainly produce a replacement shell in an afternoon, but he was having none of it. Instead, he selected a molded earpiece. Molding compound was applied first, followed by silicone to capture the shape, and then clear resin to construct the final shape from the negative. The speaker goes in front, followed by the board and cell pack, with the resin sealing on top to keep moisture and repeated use from pulling the joints apart. There’s a small magnet placed into the outside face to give a tool something to grab onto, because after that thing is fully pushed into the ear canal, there’s extremely little room to grab onto.

By his second bud, he had changed his approach. Same stripped out board, same careful soldering, because only the housing now serves as the pen’s business end. When you hold it up to your mouth, it transforms into a tiny wireless mic, with the earpiece handling listening chores. Phone audio is still transmitted to both. One of the bespoke parts simply vanishes inside the ear, while the other appears suspiciously like stationary. The radio is still the one that came with the original buds.

Instead of installing a new dock, charging continues to take place from the original case. He did move the contacts to accommodate both of the custom pieces so that they could charge, as this is the only practical method to manage those little cells once the original housings are gone. The sound quality is basically the same as it was with the previous drivers; there is no new amp or codec here, just an increase in size. A finished earpiece is almost unnoticeable from the side and takes up much less space than the initial bud.

There is one last thing to consider. With a lithium polymer cell buried deep in an ear canal, there isn’t much of a path out if something goes wrong, and the resin makes it difficult to remove. Penguin DIY shows the duo in action; if you do decide to imitate this build, you are placing a battery in a spot that fingers cannot readily reach.
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