Flexible, Visual, and Multifunctional Humidity-Strain Sensors Based on Ultra-Stable Perovskite Luminescent Filaments

Abstract

Flexible multifunctional sensors have attracted much attention in applications such as physiological monitoring, smart clothing, and electronic skin. However, the visual and multifunctional humidity-strain sensors following integration face the challenges of suboptimal sensing performance, inferior durability, mutual interference, and difficulties on large-scale production. Herein, a flexible, visual, and multifunctional humidity-strain sensor based on ultra-stable perovskite luminescent filament (carbon nanotubes/sodium polyacrylate (PAAS)/perovskite/thermoplastic polyurethane (CPPT)) with coaxial structure is first introduced by the environmental-friendly wet-spinning and dip-coating method. The CPPT filaments display homogeneous and bright luminescence under 200% deformations, tunable emission spectrum, wide color gamut, and high stability due to the polymer-encapsulation effect and uniform distribution of perovskite nanocrystals. The carbon nanotubes/PAAS as the outer layer undertakes radial thickness expansion upon moisture exposure. The elastic perovskite/thermoplastic polyurethane as the core bears large deformation during stretching. The CPPT filaments achieve a resistance change of 130% in the relative humidity of 95%, fast response/recovery (3.2/4.0 s), small hysteresis (3.5%), high durability, and weak interference from temperature. Besides, it obtains a Gauge factor of 27.0 at a strain of 95–200%, fast response/recovery (0.2/0.3 s), and negligible interference from temperature. The flexible CPPT filaments not only show great potential in humidity sensing, strain sensing, and information encryption but also open up new opportunities for facile integration into more complex scenarios, such as human physiological activity monitoring with an early hazard warning.

Graphical Abstract