Researchers at North Carolina State University have developed a wearable technology that turns the forearm into a trackpad, allowing smartwatch users to scroll, zoom and click without touching the device’s tiny screen.Called EpiPad, the system uses a compact millimeter-wave (mmWave) radar sensor to track finger movements and measure how firmly users press their skin. This enables multi-finger gestures and pressure-sensitive controls similar to those found on laptop trackpads.The researchers say the approach could give smartwatches a larger input surface without increasing their screen size. It could also provide a way to control screenless wearables, including smart glasses.EpiPad’s sensor array measures approximately 5 by 4 millimeters. It is mounted on a wristband and detects the subtle changes in the skin caused when fingertips press against the forearm.Radar tracks finger pressureUnlike conventional touchscreens, EpiPad does not require users to touch a display. Instead, its radar system detects movements and pressure through changes in the signals reflected from the skin.The researchers developed a signal-processing method based on millimeter-wave phase dynamics to estimate applied force. Lightweight machine-learning models then help recognise gestures and interpret the user’s input.Users must first complete a short calibration routine that adapts the system to their individual movements. The process takes 3 minutes and 54 seconds, according to the research paper.The current prototype resembles a wristband with an exposed circuit board. However, the researchers say its components could eventually be integrated into conventional smartwatch designs.Tested across 20 usersThe team evaluated EpiPad in experiments involving 20 participants. The system achieved 92.8 percent gesture-recognition accuracy and 90.2 percent force-detection accuracy, with a ranging precision of 10.2 millimeters on users who were not included in the training data.In a separate real-time evaluation, participants performed smartwatch input tasks using three methods: a conventional touchscreen, a tilt-based cursor, and EpiPad. The researchers reported that EpiPad outperformed the other two approaches in both error rate and efficiency.The results suggest that using the forearm as an input surface could make small wearable devices easier to control. However, the findings are based on a proof-of-concept prototype and a relatively small user study, rather than a commercially available product.The researchers estimate that the functional components, including the radar sensor array, could cost less than $10. That figure is an estimate from the research team, not the price of a finished device.The technology could eventually extend beyond smartwatches. The researchers suggest that screenless wearables, such as smart glasses, could use the skin as an interactive surface, allowing users to issue commands without relying on a display or physical buttons.The research was detailed in a paper titled “EpiPad: Enabling Multi-Finger and Force-Sensitive Skin Interface for Smartwatches,” published in the Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies. The work was presented at the UbiComp/ISWC 2026 conference in Shanghai.