fig1
Figure 1. Structural design and working principle of the paper-based device with PHL. (A) Application scenario and optical photo (author team members shown; photographed by the authors); (B) Detailed structure, including a haptic feedback unit and a loudspeaker unit; (C) Block diagram showing the working principle of the device; (D) Key advancements and application scenarios. PHL: Passive haptic learning; PLA: polylactic acid.
