A Multimodal, Multicontact, and Scalable Soft Robot Skin Enabled by Layered Structures

The human tactile sensing system, comprising various mechanoreceptors, is essential for perceiving and interacting with the environment and objects. It enables the detection of multimodal stimuli and their localization. Inspired from this system, we propose a robotic skin designed to enhance sensing modalities and localization capabilities. The robotic skin utilizes a layered design incorporating two sensing mechanisms: a Hall-effect sensor and a force-sensing resistor (FSR). The Hall-effect sensor detects global movement by recognizing stimuli in both the normal and shear directions; on the contrary, the FSR provides position information with higher spatial resolution. The Hall-effect sensor and the FSR mimic the functions of Ruffini endings and Merkel cells, respectively, in the human tactile system. Structurally, the stiffness differences between layers are designed to ensure proper functional operation. As a result, the skin can detect both normal and shear stimuli while providing localization capabilities with restricted crosstalk. The skin is attached to the tip of a robotic arm, demonstrating the ability to control 6 degrees of freedom through various types of touch. Furthermore, it enables the robot to protect itself from external obstacles and facilitates intuitive control through human-robot interaction. By interpreting and responding to external touch, the robotic skin enables intuitive interaction, making it highly suitable for dynamic and unpredictable environments, as well as collaborative settings.