A Textile Proximity/Pressure Dual-Mode Sensor Based on Magneto-Straining and Piezoresistive Effects
In human-machine interaction, the unpredictable nature of human movements demands precise real-time control of machines to ensure human safety. As a pair of strongly related tactile perceptions, proximity and pressure information are equally crucial in monitoring human body motion and avoiding unnecessary collisions. In this process, proximity sensing can help the machine adjust its moving direction in advance, while pressure sensing enables the machine to implement timely actions at the proper pressure level. Thus, the synergy of proximity and pressure perception is vital for the smart control of robots in human-machine interactions and the development of intelligent prosthetic devices.
Flexible tactile sensors capable of detecting both proximity and pressure have been widely studied, but integrating high-performance proximity and pressure sensing functions into a single sensor using a simple fabrication process remains a challenge.
The researchers developed a dual-mode textile sensor capable of detecting both proximity and pressure by exploiting the magneto-straining and piezoresistive effects. This novel dual-mode textile sensor is fabricated through a simple process that involves coating functional materials in a concentric pattern onto a spandex substrate. The concentric pattern consists of a magnetic layer (Fe3O4/PDMS) in the center and a conductive layer around made of MXene/PEDOT: PSS composite.
The concentric design enables the sensor to perceive proximity and pressure information effectively. In proximity sensing mode, when a magnet or magnetized object approaches the dual-mode textile sensor, the magnetic layer in the central area generates an induced magnetic force that stretches the surrounding conductive region out of the plane. Consequently, the resistance of the dual-mode textile sensor increases dramatically due to the separation of the conductive network.
Conversely, when the magnet or magnetized object contacts and begins to press the dual-mode sensor, its resistance decreases from the maximum value due to the recovery of the stretched conductive network. The turning point in the resistance change, serving as an indicator, represents the switch to working mode. This unique mechanism allows the dual-mode sensor to distinguish between proximity and pressure working modes, providing an accurate perception of approaching distance and applied pressure.
Benefiting from the embedded MXene nanosheets in the conductive layer, the fabricated dual-mode sensor exhibits high sensitivity for both proximity (13.76 mm−1) and pressure sensing (0.7 kPa−1). Additionally, a fast response time (60 ms) and the ability to withstand over 5000 cycles of approaching-separation tests are achieved, proving the sensor’s reliability and durability for long-term usage.
The applications of the dual-mode sensor are diverse and impactful. It can be utilized for real-time monitoring of human-robot interactions, such as handshakes and gait analysis in prosthetic patients. The sensor ensures safe and intelligent collaboration between humans and machines by monitoring approaching distance and contact pressure during interactions.
The textile proximity/pressure dual-mode sensor offers a versatile and reliable solution for integrating contact and contactless sensing, promisingly unlocking safe and smooth human-machine interactions. The simple sensor fabrication process developed in this work allows for batch production, making it adaptable for various practical scenarios.