A soft sub-degree-resolution omnidirectional hemispherical haptic fingertip for spatiotemporal extended reality applications

Human fingertip possesses exceptional haptic acuity, attributed to dense mechanoreceptors and spatial distribution for precise recognition. Currently, multimodal artificial haptic interfaces have been developed to perceive pressure and shear signals for advanced extended reality applications, while real-time three-dimensional (3D) force detection remains challenging. Here, we propose a soft hemispherical intelligent haptic fingertip system that uses a rigid orthogonal framework to effectively decouple 3D force. The system can detect contact force with both high sensitivity and high resolution. A benchmark shear force sensitivity of 52.35 N⁻¹, with a resolution of 0.01 N is achieved by the fingertip system. Furthermore, the fingertip system has suppressed the decoupling error in the orthogonal direction especially under 3D force. Additionally, we employ machine learning algorithms to obtain an enhanced resolution in the identification of tangential angles under the interference of normal force. When integrated with wireless circuitry, the haptic fingertip system achieves low-latency visual intelligent interactions, showcasing its potential for extended reality applications.