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

Polymer Chemistry Nanoscience Organic Polymeric Materials Chemistry Materials Science Materials Chemistry
perovskite luminescence humidity sensor strain sensor multifunction flexible environment-friendly

Academic Background

With the rapid development of the Internet of Things and wearable electronics, the demand for smart sensors in fields such as physiological monitoring, smart clothing, and human-computer interaction has been increasing. In particular, flexible multifunctional sensors have attracted significant attention due to their potential applications in skin humidity detection and physiological activity monitoring. However, existing visual multifunctional humidity-strain sensors still face numerous challenges after integration, such as suboptimal sensing performance, poor durability, noticeable temperature interference, and difficulties in large-scale production. To address these issues, researchers have begun exploring new materials and structural designs to enhance sensor performance and stability.

Perovskite materials have been widely applied in smart wearable electronics in recent years due to their excellent optical properties, low cost, and ease of fabrication. However, the stability of perovskite materials under humidity and mechanical strain remains a technical bottleneck. To tackle this, this study proposes a flexible, visual, multifunctional humidity-strain sensor based on ultra-stable perovskite luminescent fibers, aiming to overcome the limitations of existing sensors through innovative material and structural designs.

Source of the Paper

This paper was jointly completed by a research team from Wuhan Textile University and Wuhan University of Technology. The main authors include Xiaofang Li, Qi Liu, Yunpeng Liu, and others. The paper was published in Advanced Fiber Materials in 2025, with the DOI 10.1007/s42765-025-00518-9.

Research Process

1. Material Preparation and Structural Design

The research team employed an environmentally friendly wet-spinning and dip-coating method to prepare a flexible, visual, multifunctional humidity-strain sensor with a coaxial structure. The core of the sensor consists of perovskite/thermoplastic polyurethane (TPU), while the outer layer is composed of carbon nanotubes/sodium polyacrylate (PAAS). The specific steps are as follows:

  • Wet Spinning Process: The perovskite precursor solution is mixed with TPU and rapidly formed into fibers through wet spinning. During this process, solvent molecules are quickly extracted by the water coagulation bath, resulting in the rapid formation of TPU fibers and the homogeneous crystallization of perovskite nanocrystals.
  • Dip-Coating Process: The perovskite/TPU fibers obtained from wet spinning are immersed in a carbon nanotube/PAAS solution to form a uniform conductive outer layer. Through thermal annealing, residual solvents are removed, ultimately yielding sensor fibers with a coaxial structure.

2. Physical Property Characterization

The researchers conducted detailed physical property characterizations of the prepared sensor fibers, including surface morphology, elemental distribution, and mechanical properties. Using techniques such as scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), they confirmed that the carbon nanotube/PAAS layer uniformly covered the fiber surface, and perovskite nanocrystals were evenly distributed in the TPU matrix. Additionally, mechanical property tests showed that the sensor fibers exhibit high elasticity (strain up to 800%), fully meeting the requirements of wearable electronics.

3. Luminescence Performance Testing

By adjusting the composition of perovskite, the research team successfully achieved green, red, and blue luminescence of the sensor fibers under ultraviolet (UV) light irradiation. Photoluminescence (PL) spectroscopy and CIE chromaticity coordinate tests demonstrated that the sensor fibers exhibit high brightness, a wide color gamut, and excellent color tunability. Furthermore, even under 200% tensile deformation, the fibers maintained uniform and bright luminescence, showcasing their great potential in flexible display applications.

4. Humidity Sensing Performance Testing

The sensor fibers exhibited excellent performance in humidity sensing, with a resistance change of up to 130% at a relative humidity (RH) of 95%. The response and recovery times were 3.2 seconds and 4.0 seconds, respectively, with a hysteresis of only 3.5%. Additionally, the sensor fibers maintained stable humidity responses in high-temperature environments, demonstrating excellent resistance to temperature interference. Through dynamic humidity cycling tests and friction tests, the researchers further validated the durability and stability of the sensor fibers.

5. Strain Sensing Performance Testing

In strain sensing, the sensor fibers exhibited gauge factors (GF) of 2.9 and 27.0 in the strain ranges of 0-95% and 95-200%, respectively. The response and recovery times were 0.2 seconds and 0.3 seconds, fully meeting the requirements for real-time monitoring of rapid human movements. Moreover, the sensor fibers maintained stable strain responses in high-temperature environments, showcasing their excellent resistance to temperature interference.

6. Multifunctional Application Demonstration

The research team demonstrated the multifunctional applications of the sensor fibers in information encryption, physiological activity monitoring, and hazard warning. By weaving sensor fibers of different colors into fabrics, the researchers achieved information hiding and encryption. Additionally, the sensor fibers can be used to monitor human skin humidity, breathing frequency, and joint movements, highlighting their broad application prospects in wearable electronics.

Research Conclusions

This study successfully developed a flexible, visual, multifunctional humidity-strain sensor based on ultra-stable perovskite luminescent fibers. Through innovative material and structural designs, the sensor fibers exhibited outstanding performance in humidity sensing, strain sensing, and information encryption, characterized by high sensitivity, fast response, low hysteresis, and excellent durability. Furthermore, the sensor fibers’ preparation method is environmentally friendly, low-cost, and suitable for large-scale production, offering new possibilities for their applications in smart clothing, electronic skin, and physiological monitoring.

Research Highlights

  1. Innovative Material Design: By combining perovskite nanocrystals with TPU, high stability and high brightness luminescence were achieved.
  2. Coaxial Structural Design: The outer carbon nanotube/PAAS layer is responsible for humidity sensing, while the core perovskite/TPU layer handles strain sensing, enabling multifunctional integration.
  3. Excellent Sensing Performance: The sensor fibers exhibited high sensitivity, fast response, and low hysteresis in both humidity and strain sensing.
  4. Broad Application Prospects: The sensor fibers demonstrated significant potential in information encryption, physiological monitoring, and hazard warning.

Other Valuable Information

The research team also showcased the application of the sensor fibers in coal mine safety warnings and nighttime sportswear. By integrating the sensor fibers into safety helmets and work clothes, the researchers achieved real-time humidity monitoring and hazard warnings. Additionally, the sensor fibers can be used to monitor skin humidity and joint movements during exercise, providing new tools for sports health management.

This study not only offers new insights into the development of flexible multifunctional sensors but also opens up new directions for the application of perovskite materials in wearable electronics.