Pneumatic Rigid-Soft Coupled Finger with Self-Powered Triboelectric Tactile Sensing toward Potential Application in Lunar Exploration

Robotic manipulation in future lunar-surface operations and planetary sample-return missions requires end effectors capable of accommodating irregular objects while maintaining reliable tactile feedback under uncertain contact conditions. Motivated by these challenges, we present a terrestrial proof-of-concept of a pneumatic rigid-soft coupled robotic finger integrating structural regulation and self-powered triboelectric tactile sensing. The finger combines rigid skeletons, fiber-constrained pneumatic chambers, and a finger-pad sensing unit to enable compliant deformation, posture regulation, and tactile perception. A flexible single-electrode triboelectric sensor based on a PDMS-MXene composite generates electrical signals through contact electrification and electrostatic induction without external electrical excitation, while pneumatic actuation, signal acquisition, and computational processing require external power. At an input pressure of 140 kPa, the proximal interphalangeal, distal interphalangeal, and metacarpophalangeal regions achieved bending angles of approximately 84°, 76°, and 65°, respectively. The sensor exhibited stable outputs at contact frequencies of 1-10 Hz and a sensitivity of 0.11 V/kPa over 10-120 kPa. Incorporating 6 wt% MXene increased the output voltage by 50.8% compared with pure PDMS. Combined with a convolutional neural network-long short-term memory model, the system achieved classification accuracies of 97.6% for 10 representative laboratory materials and 99.5% for four surface-roughness levels under controlled terrestrial conditions. Grasping experiments further demonstrated compliant manipulation and tactile perception. These results establish the feasibility of the proposed sensing approach under laboratory conditions, while its applicability to planetary geological materials and space environments remains to be validated.