Electrospinner: Wrapped spiral fiber strain sensor: Establishing a coaxial mutual inductance effect sensing mechanism to achieve interactive perception in extreme environments!

Background

Fiber strain sensors have good compatibility with fabrics and are an indispensable component for sensing human and environmental information in future smart fabric systems. However, traditional fiber strain sensors have poor stability in wearable scenarios such as complex deformation and high and low temperatures, which limits their practical applications.

Recently, Chen Peining's team at Fudan University published a research result entitled "Robust Fiber Strain Sensor by Designing Coaxial Coiling Structure with Mutual Inductance Effect" in Advanced Fiber Materials. This work constructed a fiber strain sensor based on mutual inductance effect by winding a conductive fiber with a coaxial spiral structure on a polyurethane elastic polymer fiber substrate. Thanks to the unique sensing mechanism and structural design, the device has excellent stability and reliability, can withstand 100,000 100% strain cycles, and can still maintain stable signal response under extreme conditions such as high and low temperatures (-30 °C to 160 °C), extrusion (500 N/cm) and torsional deformation. The smart fabric system constructed with fiber strain sensors shows good application potential in fields such as human-computer interaction and personal health management.

The main point of this paper

Based on the mutual inductance effect, this work designs a coaxial spiral structure on the polyurethane fiber, in which the inner spiral coil serves as the electrical signal input end and the outer spiral coil serves as the electrical signal output end (Figure 1a). When the fiber strain sensor device is stretched, the pitch of the inner coil increases, resulting in a decrease in the change in magnetic flux in the outer coil, thereby reducing the output voltage. The pitch of the coil can be precisely controlled by changing the preparation conditions (Figure 1b-d), realizing the large-scale continuous preparation of the sensor device (Figure 1e-g).

When stretched, the decrease in the rate of change of the device's magnetic flux leads to a decrease in the output voltage. By establishing a corresponding relationship between the output voltage and the strain, the strain sensing function can be realized (Figure 2a). The fiber strain sensor device has excellent sensing performance, showing good linear response and a hysteresis coefficient as low as 1.3% in the strain range of 0~100% (Figure 2b-c). The sensor device has good dynamic stability, and the response characteristics at 1 Hz frequency are almost the same as those at 0.25 Hz frequency (Figure 2d), and it can stably cycle for more than 100,000 times under 100% large strain (Figure 2e), which exceeds the cycle performance of most resistive and capacitive sensor devices (Figure 2f).

Thanks to the highly reliable coaxial spiral structure, the sensor device still shows good stability in complex environments such as extreme temperatures from -30 °C to 160 °C, extrusion of 500 N/cm, and torsional deformation (Figure 3a-d). Compared with typical resistive and commercial capacitive strain sensor devices, the fiber strain sensor device does not rely on the resistance change of the conductive material, and the morphological change of the substrate has almost no effect on the coaxial spiral structure. Therefore, the fiber strain sensor device can stably output signals under torsional deformation and high temperature environment (Figure 3e). The finite element method was used to compare the stress distribution of the coaxial spiral structure and the double-layer structure. The stress of the double-layer structure is much lower than that of the coaxial spiral structure, which verifies the inherent stability of the fiber strain sensor device (Figure 3f-g).

Through mature industrial weaving technology, large-area (40 cm× 25 cm) sensing fabrics (Figure 4a-c) are further prepared, which are expected to be used in extreme scenarios such as outer space (Figure 4d). For example, in high and low temperature environments and vacuum environments, the sensor device can still ensure stable signal output (Figure 4e-f), and can still stably transmit signals under the crush of a car weighing 1720 kg. The fiber sensor devices are woven and integrated to obtain an intelligent fabric display system, which captures the strain changes of the finger joints and integrates the output voltage signals from the sensor array to identify the deformation of the hand. As shown in Figure 4j-k, different gesture information will cause the sensor array to generate specific voltage signals. By accurately identifying the voltage changes at the sensing points, different functional instructions can be triggered, such as displaying oxygen levels or sending a distress signal "SOS".

In summary, strain sensing fiber is an ideal wearable material. The anisotropic conductive network fiber prepared by the freeze-dried coaxial spinning strategy shows high sensitivity and linearity in a wide strain range, providing a useful reference for the preparation of high-performance wearable strain sensing fiber materials.

Electrospinning Nanofibers Article Source:

https://link.springer.com/article/10.1007/s42765-024-00445-1