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.

Unlike 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.

The team evaluated EpiPad in experiments involving 20 participants. 2 millimeters on users who were not included in the training data.

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