Abstract:

Objective The thermochromic flexible temperature sensor, visible to the naked eye, effectively addresses the issues of limited flexibility, additional power requirements, and intricate structures associated with conventional rigid temperature sensors. To advance the field of wearable temperature sensing, developing a thermochromic flexible temperature sensor with superior stretchability and multi-color integration is of significant importance. This study aims to investigate the fabrication and temperature-sensing properties of thermochromic fiber membranes produced via solution blow spinning.
Method Two types of thermochromic microcapsules were employed, with one transitioning from colorless to blue at 22 ℃ and the other transforming from colorless to pink at 35 ℃. The microcapsules were blended with a styrene-ethylene-butene-styrene (SEBS) block copolymer via a solution-based approach to prepare the spinning solution. The spinning solution was subsequently blown through a high-pressure nozzle using a solution blow spinning technique, yielding thermochromic fiber membranes. The mechanical properties, spectral and chromatic characteristics, response time, hydrophobicity, and moisture permeability of the thermochromic fiber membranes were systematically tested and analyzed. To verify their temperature-sensing performance, the thermochromic fiber membrane was applied to a standard fabric for visualized temperature detection in ambient conditions.
Results Scanning electron microscope characterization demonstrated that the blended spinning solution of SEBS and thermochromic microcapsules formed a fiber cross-mesh structure under high-pressure airflow conditions. This structural arrangement led to the degradation of fiber formation and the progressive aggregation of thermochromic microcapsules with increasing content. With the mass fraction of thermochromic microcapsules increasing from 5% to 10%, 20%, 30%, 40%, and 50%, the maximum strain of the thermochromic fiber membranes decreased sequentially from 611% to 608%, 432%, 390%, 269%, and 149%. Upon being stretched to 100% of its original length, the fiber membrane containing 30% thermochromic microcapsules withstood 26 stretching cycles prior to fracturing. Spectrum and chromaticity analyses revealed that the prepared thermochromic fiber membrane displayed a blue color at temperatures below 22 ℃, a white appearance at temperatures between 22 ℃ and 35 ℃, and a pink hue at temperatures above 35 ℃. Specifically, the fiber membrane with 30% thermochromic microcapsules underwent a color transition from white to blue within 10 s at 10 ℃, while the shift from white to pink at 60 ℃ similarly required 10 s to stabilize. The thermochromic fiber membranes exhibited excellent hydrophobicity, achieving an initial maximum water contact angle of 141.5°, which remained above 120° even after 10 min of water exposure. Following a 9-hour moisture permeability test, the water vapor permeability of the fiber membrane containing 30% thermochromic microcapsules with a thickness of 280 μm was measured at 5.08 mg/(cm²·h). Spraying thermochromic fibers onto the glass surface facilitates visualized water temperature sensing, which is crucial for ensuring safe drinking practices. By integrating the thermochromic fiber membrane with conventional fabric, intelligent wearable textiles can be developed, enabling visual sensing of environmental temperature through its temperature-color response relationship.
Conclusion The thermochromic fiber membranes enable visualized temperature sensing by exhibiting distinct color transitions across multiple temperature intervals, thereby overcoming the limitations of conventional thermochromic membranes, which are typically restricted to single-color changes and narrow temperature ranges. Experimental results demonstrate that these thermochromic fiber membranes possess excellent stretchability and hydrophobicity, underscoring their potential for applications in wearable temperature sensing. The smart wearable fabric fabricated using these thermochromic fiber membranes enables visualized temperature detection without the need for additional power input. Moreover, these membranes are facile to fabricate, lightweight, and can be seamlessly integrated with conventional fabrics, thereby significantly reducing the costs associated with practical applications.

Key words: thermochromic fiber membrane, temperature sensing, solution blow spinning, styrene-ethylene-butene-styrene block copolymer, flexible temperature sensor, thermochromic microcapsule, intelligent wearable textiles