A highly sensitive and drift-free iontronic sensor enabled by a polarity-balanced polyelectrolyte for surgical force sensing.

Iontronic pressure sensors featuring high sensitivity are promising across different emerging fields. In applications requiring high-fidelity sensing such as surgeries, reliable pressure monitoring necessitates sensitivity and stability at the same time to ensure safety. However, existing iontronic sensors often face a trade-off between them-soft ionic materials with high conductivity often present pronounced viscoelasticity, resulting in a low sensitivity-to-drift-rate (S/D) ratio. Here, we report a polyelectrolyte-based iontronic pressure sensor that achieves a nearly one order-of-magnitude improvement in S/D ratio over state-of-the-art designs using a polarity-balance strategy in the polyelectrolyte to simultaneously regulate ionic conductivity and viscoelasticity. The resulting sensor exhibits ultrahigh sensitivity (119.5 per kilopascal) and exceptional stability (drift rate < 1%) under prolonged pressures up to 450 kilopascals, enabling nearly drift-free pressure detection for high-precision surgical operations in both surgeon-operated and robotic-assisted procedures. This work provides an extensible material design strategy to enhance sensitivity while suppressing signal drift in soft pressure sensors, with broad relevance to robotics, medical devices, and wearables.