Thermospun Conductive Composites with a Wide Strain Range, Excellent Fatigue Resistance, and High Linearity for Fibrous Strain Sensors

Abstract

The development of a fibrous conductive elastomer with the ability to withstand large deformations and exhibit linear stretching sensitivity is significant and challenging for wearable strain sensors. Herein, a continuous thermospinning strategy is presented to fabricate a fibrous strain sensor (MCPF sensor) that offers a wide sensing range, excellent fatigue resistance, high linearity, and good mechanical properties. The MCPF consists of CNTs modified by a silane coupling agent (KH570-CNT) and polydimethylsiloxane (PDMS) as the conductive substances and elastic substrates, respectively. The interface between KH570-CNT and PDMS is enhanced, resulting in superior mechanical properties of the MCPF sensor. The MCPF exhibits a wide strain range (0− 100%), good stretch repeatability for 1000 cycles of 50% strain, and excellent conductivity. Additionally, the MCPF can be knitted onto a stretchable fabric, enabling excellent flexibility. The fibrous sensor assembled with the MCPF demonstrates high linearity, minimal response time (<120 ms), high cyclic stability (>70,000 s), and stable responses under various strain ranges and cyclic frequencies. In practical applications, the MCPF sensor can simulate the monitoring of large and facet joint movements, indicating its wearability, wide detection range, extremely high sensitivity, and timely responsiveness. Through modification with a silane coupling agent, the aggregation between CNTs is effectively reduced, and CNTs can be uniformly dispersed in the PDMS substrate. This control over aggregation improves the dispersion of CNTs in PDMS, resulting in the excellent mechanical, electrical, and sensing properties observed in the prepared MCPF. Therefore, the fibrous conductive elastomer fabricated using the continuous thermospinning strategy holds promise for producing high-performance wearable strain sensors.

Enhancement of the Electric-Force Response of Carbon Black/Silicone Rubber Composites by Silane Coupling Agents

“…The C=C, C-O, and C=O of the modified composite are shifted to 283.7 eV, 284.3 eV, and 284.8 eV. Similar to the results of other studies [ 25 ], the peaks of C=C, C-O, and C=O were only slightly shifted after modification with silane coupling agents, suggesting that the chemical modification of KH550 by silicon can still be detected on CB.…”

“…Figure 5 a demonstrates the resistance–strain response curve of the CB-KH550/VMQ composite, which exhibits excellent repeatability and stability with increasing strain. As shown in Figure 5 b, the CB-KH550/VMQ composite obtains a response time of 66 ms at a small strain of 1% and a tensile rate of 200 mm/min, which is faster compared to other composites [ 25 , 32 , 33 , 34 , 35 ], and the shorter response time means that the composites can respond to the external stimuli quickly. Meanwhile, the stabilized resistance response of strain sensors under different tensile rates is also very important in practical engineering applications.…”

“…Silane coupling agents have low surface energy and can be evenly distributed on the treated surface, thus improving compatibility and dispersion between dissimilar materials. Han et al [ 25 ] used a silane coupling agent (KH570) to modify CNT to fabricate CNT/PDMS composites via a continuous thermal spinning strategy. Through the KH570 modification of CNT modification, the aggregation between CNTs was effectively reduced so that the CNTs could be uniformly dispersed in the PDMS matrix.…”