Bionic Perception of Surface Adhesion via a Magnetized Spring-like Sensor with Axial Stretchability

Perception of surface adhesion is one essential capability of a human fingertip, which is normally realized by touching the target surface with subsequent skin vibrations. However, such functionality is difficult to realize in flexible sensors and robotic systems due to the challenges in axial stretchability with reliable electrical feedback. In this study, we developed a bionic three-dimensional flexible magnetized spring (3D-FMS) that can quantitatively recognize surface adhesion based on electromagnetic induction. Combined with the laser processing with predefined patterns, we show that a raw flexible cube can be converted to highly stretchable spring-like geometry with excellent bidirectional deformation in axial orientation. Furthermore, the mechanical elongation caused by adhesion is critical for the induced voltage signals, allowing us to establish a model that relates adhesion strength with electrical outputs in a linear behavior. Via optimization of the process parameters, the device exhibits tailored stiffness to modulate the sensing sensitivity and working range on demand. With the established interactive interface, the wearable tests and robotic integration demonstrate the potential of the 3D-FMS for adhesion perception as a human fingertip. We expect that the strategy will offer a valuable reference to explore 3D wearable devices that advances robotic systems with more bionic functions such as stickiness determination.