AFM: MXene composite coaxial fiber wearable strain sensor

【Research Background】

MXenes is a large class of 2D materials with high electrical conductivity (up to 10 ⁴  S cm ^-1 ), excellent mechanical properties (Young‘s modulus of approximately 330 GPa), and excellent specific capacitance (up to 1500 F cm ^-3 ). Because of this unique combination of properties, Ti 3 C 2 MXene has been widely used in energy storage, sensing, catalysis, antennas, and neural interfaces. MXene flakes with high aspect ratio (up to 10 ⁶ ) and abundant surface functional groups are ideal materials for preparing polymer composites with new functions. Compared to commonly used fillers, an important application of MXene is in composite fibers that require both conductivity and elasticity. This combination of conductivity and stretchability is a basic requirement for sensing physical deformation such as strain. Many materials have been used as fillers to realize strain sensing composite fibers. Once this fiber is integrated into the fabric, it can be used to track human movement, sports training, rehabilitation, remote health monitoring and entertainment.

However, it has been a huge challenge to improve the electrical properties of elastic polymer fibers while maintaining their tensile properties. This is because the introduction of conductive fillers usually leads to deterioration in spinnability (ability to form fibers) or to a reduction in the tensile ability of fibers, which is not suitable for strain sensing applications. Although MXene has proved to be a promising candidate material for the development of fibers and nanofibers with significant energy storage properties, the applicability of its development of strain sensing fibers remains to be explored. Previous research on Ti 3 C 2 T x  MXene composite membranes emphasized the need to gain a deeper understanding of the behavior of MXene in composite systems in order to obtain fibers with balanced electromechanical properties suitable for strain sensing applications.

【Achievement Introduction】

Recently, Deakin University, Australia  Shayan Seyedin professor and Drexel University  Yury Gogotsi professor at the internationally renowned academic journal Advanced Functional Materials published an article entitled: MXene and Coaxial Composite Fibers with High Stretchability and Conductivity for Wearable Strain Sensing Textiles Research The paper proves that Ti 3 C 2 T x  MXene can achieve highly conductive and stretchable fibers through a scalable wet spinning process. In this paper, the effect of MXene loading on fiber spinnability and the morphology, mechanical and electrical properties of MXene / PU composite fibers are systematically studied. The doping threshold reached in this paper is ≈1.0 wt% MXene (volume fraction φ≈2.8 × 10 ⁻³), Which is much lower than the reported value of MXene-based composites (> 6 wt% MXene). This article shows that integrating MXene into PU significantly increases the Young‘s modulus (Y) of the fiber, thereby showing a high reinforcement rate (dY / dφ) of up to 20.3 GPa. This dY / dφ is higher than other PU-based composite fibers produced under similar conditions, such as GO / PU and CNT / PU. When used as a separate fiber, MXene / PU composite fibers can detect large strains (up to 152%) with a high strain factor (GF) of 12900 (at 50% strain, GF = 238), which exceeds the The literature value of the fiber strain sensor. The MXene / PU composite material is also used as the sheath, and the PU fiber is used as the core material to produce the coaxial fiber. This new fiber structure further improves the sensing performance, especially in the cyclic tensile-release deformation test. The article found that the excellent mechanical properties of MXene / PU composite fibers allow them to be woven into textiles using industrial-scale knitting machines similar to ordinary yarns. The sensing strain of knitted fabric is up to 200%, and the GF is 7.5, which is better than the existing strain sensors of knitted fabric. Using MXene / PU composite fiber, this article knitted an elbow sleeve, which can easily monitor the wearer‘s different movements by sending a signal to a personal computer. This work shows that it enhances the understanding of the behavior of MXene in composite systems, making the manufacture of fibers present a unique combination of electrical conductivity and stretchability.

       This also shows that these conductive elastic fibers based on MXenes can be integrated into strain sensing textiles for practical applications such as wearable human motion monitoring.

【Graphic introduction】

Figure 1. MXene / PU fiber spinning process and physical and SEM characterization.

Figure 2. The  effect of MXene loading on the conductivity of MXene / PU fibers produced by IPA and AcOH.

Figure 3. Mechanical properties of MXene / PU fibers spun under different conditions.

Figure 4. Characterization of electromechanical properties ofMXene / PUfibers.

Figure 5. Preparation and characterization of coaxial fiberswithMXene / PUsheath and PU core.

Figure 6. Performance characterization of MXene / PU composite fiber knitted fabric.

【Summary of this article】

     This article demonstrates the continuous production of MXene / PU composite materials and coaxial fibers that have high electrical conductivity and stretchability and can be woven into textiles using a commercial-scale knitting machine. The MXene / PU composite fiber in this article shows the lowest doping threshold (1% wt%) among other MXene-based composite materials and the highest reinforcement rate (20.3 GPa) among other PU-based composite fibers. The results show that the detection sensitivity of MXene / PU composite fiber to strain is ≈152%, and GF≈12900. In this paper, the coaxial wet spinning method is used to produce fibers with MXene / PU sheath and PU core. Compared with non-coaxial composite fibers, the stability of cyclic tensile release deformation under different strains is improved. And further proved that MXene / PU fiber has sufficient mechanical properties, can be used to mechanically weave into textiles with a specific loop pattern. The MXene / PU four-strand knitted single-piece fabric has a tension sense of up to 200%, a tensile deformation of more than 1,000 times, and has good stability. Using MXene / PU fiber, an elbow sleeve is also woven, which can be worn on the user‘s elbow and wirelessly sends signals to a personal computer to track its various movements. This work provides a detailed study of the behavior of MXene in elastic composites, which can be used in other composite systems to achieve the electrical and mechanical properties required for practical applications. The MXene-based strain-sensing fibers and textiles developed in this work provide a practical platform for a series of wearable applications that require body motion monitoring, such as exercise guidance, rehabilitation and injury prevention, patient remote health monitoring, and soft robot Technology, virtual reality and entertainment.

Literature link:

https://dx.doi.org/ 10.1002 / adfm.201910504 .

Source: MXene Frontier