Self-Repairing and Energy-Harvesting Triboelectric Sensor for Tracking Limb Motion and Identifying Breathing Patterns

The increasing prevalence of health problems stemmingfrom sedentarylifestyles and evolving workplace cultures has placed a substantialburden on healthcare systems. Consequently, remote health wearablemonitoring systems have emerged as essential tools to track individuals'health and well-being. Self-powered triboelectric nanogenerators (TENGs)have exhibited significant potential for use as emerging detectiondevices capable of recognizing body movements and monitoring breathingpatterns. However, several challenges remain to be addressed in orderto fulfill the requirements for self-healing ability, air permeability,energy harvesting, and suitable sensing materials. These materialsmust possess high flexibility, be lightweight, and have excellenttriboelectric charging effects in both electropositive and electronegativelayers. In this work, we investigated self-healable electrospun polybutadiene-basedurethane (PBU) as a positive triboelectric layer and titanium carbide(Ti3C2T x ) MXeneas a negative triboelectric layer for the fabrication of an energy-harvestingTENG device. PBU consists of maleimide and furfuryl components aswell as hydrogen bonds that trigger the Diels-Alder reaction,contributing to its self-healing properties. Moreover, this urethaneincorporates a multitude of carbonyl and amine groups, which createdipole moments in both the stiff and the flexible segments of thepolymer. This characteristic positively influences the triboelectricqualities of PBU by facilitating electron transfer between contactingmaterials, ultimately resulting in high output performance. We employedthis device for sensing applications to monitor human motion and breathingpattern recognition. The soft and fibrous-structured TENG generatesa high and stable open-circuit voltage of up to 30 V and a short-circuitcurrent of 4 mu A at an operation frequency of 4.0 Hz, demonstratingremarkable cyclic stability. A significant feature of our TENG isits self-healing ability, which allows for the restoration of itsfunctionality and performance after sustaining damage. This characteristichas been achieved through the utilization of the self-healable PBUfibers, which can be repaired via a simple vapor solvent method. Thisinnovative approach enables the TENG device to maintain optimal performanceand continue functioning effectively even after multiple uses. Afterintegration with a rectifier, the TENG can charge various capacitorsand power 120 LEDs. Moreover, we employed the TENG as a self-poweredactive motion sensor, attaching it to the human body to monitor variousbody movements for energy-harvesting and sensing purposes. Additionally,the device demonstrates the capability to recognize breathing patternsin real time, offering valuable insights into an individual'srespiratory health.