https://www.sciencedaily.com/releases/2023/05/230501164001.htm

The system repurposes technology from new bone-conduction microphones, known as Voice Pickup Units (VPUs), which detect only those acoustic waves that travel along the surface of objects. It works in noisy environments, along odd geometries such as toys and arms, and on soft fabrics such as clothing and furniture.

Called SAWSense, for the surface acoustic waves it relies on, the system recognizes different inputs, such as taps, scratches and swipes, with 97% accuracy. In one demonstration, the team used a normal table to replace a laptop's trackpad.