Banannie Wang
work

2025 Aug · YC Summer Fellow

Somniac

A headband that catches you grinding your teeth, useful in sleep.

Slides
The inside of the Somniac headband: three conductive fabric electrodes stitched into a maroon band, each with a wire running out of it
The inside of the band. Three fabric electrodes, sitting over the muscle that does the clenching.

About 1/3 of people grind their teeth at night, mostly without knowing. The result is chipped teeth, migraines, and sometimes jaw fractures. People can only guess what causes it (stress, genetics, facial structure), but there's no real explanation.

The gap

One dentist I interviewed said he often thought a patient was clenching, but he wasn't be sure. Nothing tracks it, so by the time it's visible, this means the damage is already severe.

Reading the muscle

Clenching is a masseter (around temples) contraction. Muscle contractions leak electrical activity we can read off the skin using surface EMG.

Across 8,751 samples the classifier hit 88% on a single user and 80% overall, once you account for the variation between people and between sessions. That gap is why the device calibrates to each user instead of shipping one model for everybody.

Scatter plot of surface EMG values over time, with clenching samples in red and non-clenching samples in blue forming clearly separated bands
Surface EMG, clenching in red against everything else in blue.

Making it wearable

I designed several versions of a custom circuit through two revisions, plus the firmware, BLE integration, and an iOS app to log clenching events and environment changes.

What's next

Detection, the circuit, and the app all work. What I didn't get to is comfort and intervention beyond. Maybe we could use muscle stimulation to interrupt a clench gently enough that nobody wakes up.