Fabrication of TPE/CNTs film at air/water interface for flexible and superhydrophobic wearable sensors

Flexible sensing materials have become scientific hotspot in smart sensors. For outdoor uses, wearable electronic sensors must meet the challenges from water, sweat, or other liquids. Herein, a simple strategy was described to fabricate nanocomposite film of thermoplastic elastomer and carbon nanotubes (TPE/CNTs) at air/water interface for wearable electronics with liquid repelling property. Firstly, mixture suspension of TPE and CNTs was pumped into water and kept still to form a TPE/CNTs sheet at the water surface. Then the sheet was stabilized by spraying with N-hexane and transferred out of the air/water interface to obtain a free-standing TPE/CNTs film. The resultant film is conductive with a resistance of 15KΩ and superhydrophobic with a CA of 160°. When applied as a sensor, it shows excellent performance with superior sensitivity (The gauge factor is about 1), fast response time (100–150 ms), stable response over 1000 stretching-relaxing cycles, and wide sensing ranges (stretching: over 76%). Importantly, it can be used in wet conditions, making it capable to be wearable electronic devices for fast response, long-term and reliable human behavior monitoring.