Highly Sensitive Aquatic Iontronic-Based Tri-Axis Force Sensor Array for Underwater Robotic Gripping

Robotic gripping and manipulation are common tasks in underwater exploration and archeological applications. The robotic contact force sensing in aquatic environments faces several technical challenges, such as high hydraulic pressure will greatly affect the sensor’s sensitivity and sensing accuracy. Herein, we developed a novel aquatic iontronic-based tri-axis force sensor array (ITFSA) for contact force sensing during underwater robotic gripping applications. Utilizing water as a natural ion carrier, the proposed ITFSA has a packaging-free structure design to create a balanced hydraulic environment for underwater force detection. A large-area-ratio electrode pair is designed to improve the force detection sensitivity and linearity. Also, a relative detection method (RDM) was proposed to achieve unified performance in different aquatic environments. Characterization tests showed that the ITFSA exhibits a high normal force detection sensitivity of 0.058 N−1 with a detection range of 0–12 N, shear force detection sensitivities are measured as 0.079 and 0.085 N−1 with a detection range of 0–2 N in two orthogonal directions, respectively. Moreover, our developed ITFSA has generally consistent performances in various aquatic environments. After that, underwater robotic gripping experiments were performed and showed that the ITFSA can accurately detect three-axis forces and reflect characteristics of various underwater objects, showing its promising applications in underwater robotic manipulation.