There's a Microchip in My Toothbrush. But WHY?

Summary

The video investigates why a Philips Sonicare toothbrush head contains an NFC chip and tests what information it stores.

Reader setup

The presenter connects an ESP32-S3 to a PN532 NFC reader over I²C, then uses a simple USB-connected app to read tags. The brush head needs no battery: the reader’s 13.56 MHz field powers the chip, which communicates by subtly altering that field.

Data stored on the brush head

A new head reports no usage. The decoded data includes accumulated runtime, the last-used power setting, brush type, manufacturer information, a unique ID, and a web address. The presenter’s used head showed about five hours of use, or roughly 84% of its expected lifetime.

Pressure test

Two short powered runs—one on high and one on low—each added about two minutes to the recorded runtime. After actual brushing, however, the logged usage increased by more than the brushing time.

The presenter interprets this as evidence that the brush applies a usage multiplier based on brushing force, consistent with its pressure warning and change in vibration. This is an experiment, not a precise measurement of how the pressure calculation works.

Writing to the chip

Writing to the chip is password-protected, but the presenter uses existing reverse-engineering work and a community tool to reset the head’s usage counter to 50%. This changes the recorded data, not the brush head’s physical condition.

Repurposing the chip

An old brush head can unlock the presenter’s computer, while a new head cannot. The presenter then removes the head’s antenna and chip to show the NFC components inside.

Overall conclusion

The chip is not necessary for brushing, but it records use and appears to help estimate brush-head wear. The video is a hands-on demonstration of NFC reading, decoding, testing, and writing—not a product review or a recommendation to keep using worn brush heads.

Main speakers and sources

• Main speaker: The presenter, who builds and tests the NFC reader and toothbrush experiments.
• Referenced reverse-engineering sources: Markus Birth and Cyrill Künzi.
• Writing tool: The presenter uses a GitHub repository by atc1441 to write to the brush head.