Waterproof conductive fiber with microcracked synergistic conductive layer for high-performance tunable wearable strain sensor.

• Waterproof conductive fiber with microcracked synergistic conductive layer was designed. • High sensitivity and wide working range were achieved for the conductive fiber strain sensor. • Tunable sensing performance was achieved for the conductive fiber strain sensor. • The sensor can precisely distinguish various human movements and physiological signals. With the rapid development of wearable smart electronic devices, flexible strain sensors with high sensitivity in a wide working range are urgently demanded. Meanwhile, good self-cleaning and anti-corrosion properties are also essential for daily use. Herein, a waterproof conductive spandex fiber strain sensor with microcracked synergistic Ag nanoparticles (AgNPs)-carbon nanotubes CNTs conductive layer was designed and fabricated via the solvent swelling, non-solvent-induced phase separation (NIPS), and low surface energy treatment process. Benefiting from the stable synergistic conductive network and the ultrasensitive microcrack structure, the sensor exhibits excellent overall strain sensing performances, including high sensitivity (gauge factor is 48,310 within 335–400% strain), wide working range (0–400%), ultralow detection limit (0.1%), fast response/recovery time (80 ms/100 ms), and long-term fatigue resistance over 10,000 cycles, making it reliably and precisely distinguish both violent human movements and subtle physiological signals. More importantly, strain sensing range and sensitivity of the sensor can also be effectively tunned through changing the AgNPs loading in the synergistic conductive network, enabling it to be applicable for different application scenarios. What's more, the waterproof surface with good self-cleaning and anti-corrosion properties also endows the sensor with great potential for real-time body motion monitoring under humid and underwater environments without being interfered. This study provides a facile one-step method for the fabrication high-performance flexible strain sensor. [ABSTRACT FROM AUTHOR]