Tilted magnetic micropillars enabled dual-mode sensor for tactile/touchless perceptions

The smart flexible devices that can implement both tactile and touchless sensing in real-time have attracted abundant interest due to the high demand for human-machine interaction (HMI), internet of things (IoT) and virtual reality (VR) system. However, obtaining the sensor that can precisely monitor signals via contact/non-contact modes without overlapping while in a facile and cost-effective methodology is still a challenge. Herein, we introduce a flexible dual-mode capacitive sensor for pressure (contact) and magnetic field (non-contact) detection based on magnetic tilted micropillar array (MTMPA) via a facile and tunable methodology. The MTMPA sandwiched in AgNW/PDMS electrodes can response to the external pressure and magnetic field with bidirectional deflection, allowing the sensor to precisely distinguish different stimuli in real-time without overlapping. With the optimal structure, the sensor exhibits high performance of magnetic response with sensitivity of −0.69 T-1, detection limit of 25 mT and excellent recoverability. The sensor also exhibits high pressure sensitivity of 0.301 kPa−1 (0–2 kPa) with the ultra-low detection limit of 1.2 Pa with excellent repeatability and mechanical robustness. As a proof of concept, practical wearable tactile applications (e.g. pulse-sensing, voice recognition, finger touching, pressure mapping and dynamic tracking) and touchless demonstrations such as magnetic field identification and trajectory tracking have been presented. The sensitive response of the sensor to external magnetic fields also enables us to customize the non-contact Braille recognition system through arranging specific magnet patterns, where the characters such as ‘a’, ‘b’, ‘c’, and ‘d’ have been well distinguished without direct contact. The results experimentally prove the profound significance of the methodology for potential uses towards health monitoring, body motion feedback, and human-machine interface, etc.