μDPad: A Large-Scale Multimodal PPG and IMU Dataset for Wrist-Worn Microgesture Recognition
Lars Hauptmann, Dominik Hollidt, Xintong Liu, Manuel Meier, Christian Holz (ETH Zürich SIPLab)
Summary
The authors built a wrist prototype: an Analog Devices MAX86177A PPG module with 8 photodiodes in a 2 cm circular layout on the dorsal wrist, using green + IR LEDs, plus a QMI8658 6-axis IMU, all sampled at 112 Hz. They recorded 66 participants (25 h; 9 h with hand video) performing thumb microgestures: 4 directional swipes, pinch close/open, side tap, and wrist rotation during a held pinch. The question is whether spatial PPG captures the tissue/tendon deformations under the watch.
Key facts
- License
- CC BY-NC-ND 4.0 (paper and dataset)
Reported benchmarks
Human activity recognition (IMU)
udpad · Accuracy ↑
LOSO, 60 participants, offline window classification, 6 microgestures + unknown; μDPad intermediate-fusion VGG-style 1D CNN (670k params), Acc+Gyro+PPG(green+IR); value_secondary = F1 77.0. Online HMM: 78.6% acc, 5.3% FPR (abstract states 3.7% FPR)
Updated: Oct 7, 2026