TeethMark Puts a Computer Interface in Your Mouth

Your tongue might not seem like the most obvious way to control a computer, but it's actually well suited to the job. It's fast, precise, and capable of reaching individual teeth without any visual guidance. Researchers at Aarhus University have taken advantage of these abilities to develop TeethMark, a wearable interface that lets users control electronic devices by touching their teeth with their tongue.

The device resembles a transparent dental retainer that fits over the teeth. Embedded in the custom-made brace is a flexible printed circuit board containing electrodes that detect tongue movements through capacitive sensing. The system recognizes three types of gestures: tapping individual teeth, sliding the tongue across multiple teeth, and touching several teeth simultaneously.

Unlike standard touch interfaces, TeethMark also provides electrotactile feedback. Electrodes on the inner surfaces of the teeth deliver small electrical pulses that users can feel with their tongues. Additional electrodes on the outer surfaces stimulate the inside of the lips, allowing notifications to be delivered without requiring any tongue movement.

The hardware is built around an ESP32 microcontroller, which handles capacitive sensing and controls the electrical stimulation circuitry. A MOSFET driver generates the stimulation signals, while a relay switches between sensing and feedback operations to prevent interference. The four-layer flexible PCB incorporates shielding to improve sensing reliability.

To accommodate different mouths, the researchers developed a design tool that allows electrode positions to be customized using a 3D model of the user's teeth. The resulting PCB is attached to a brace printed from biocompatible dental resin, with only the gold-plated electrodes exposed.

The team evaluated TeethMark with 12 participants, who completed a short training session before testing the system. Gesture recognition accuracy reached 82.92% for tapping, 92.78% for touching multiple teeth, and 94.92% for sliding. Participants also correctly identified directional electrotactile feedback 99.17% of the time.

Beyond controlling electronics, the researchers demonstrated several potential applications. TeethMark could help language learners practice pronunciation by tracking tongue placement, provide unusual tactile sensations in virtual reality, or support tongue rehabilitation exercises. Another demonstration used tongue gestures to control a UV curing light, allowing users to keep their hands free while working.

TeethMark is still an experimental prototype, and there are some challenges to work out before it could become practical for everyday use. For example, the system needs a way to distinguish intentional gestures from ordinary tongue movements during speaking or swallowing. But the researchers have shown that the tongue and teeth can work together as a very capable interface. With further development, TeethMark could eventually make controlling electronics as simple as moving your tongue.