Abstract:

Objective With the development of artificial intelligence, wearable technology has become a research hotspot, driving the rapid development of all types of sensors. Sensors used in wearable devices should not only have sensitive and stable sensing performance, but should also have excellent flexibility, air permeability, and integration with textiles. Polymer based flexible pressure sensors have significant advantages in flexibility and integration with textiles, and have been developed rapidly. However, most of these sensors are thin films or gel shaped, which seriously affects their breathability and wearing comfort.
Method Aiming at the problems of poor air permeability, poor moisture permeability and low wearing comfort of film-based and gel-based flexible sensors, a preparation strategy of all-textile-based flexible electronic fabrics based on piezoresistive effect was proposed. A structural model was constructed based on the electrode layer of 1+1 rib conductive fabric and the middle conductive layer of MXene modified cotton fabric (as shown in Fig. 1-3). The flexible electronic fabric with sandwich structure was formed by sewing and compounding various functional layers, and its wearing comfort and sensing performance were studied. Furthermore, its potential for industrial production in the future was expounded.
Results The sensitivity of the flexible electronic fabric in the low pressure range (0-3 kPa) is about 0.409 5 kPa^-1 (as shown in Fig. 4), which is caused by the working mechanism of the piezoresistive flexible sensor. A 2 g weight can make resistance change rate of the flexible electronic fabric exceed 3% (as shown in Fig. 6), which is mainly due to the excellent mechanical properties of the 1+1 ribbed conductive fabric. This enables the flexible electronic fabric to achieve large deformation under small external forces, resulting in rapid changes in resistance values to achieve excellent responsiveness. In addition, the MXene modification of cotton fabrics also gives the flexible electronic fabric a lower minimum pressure detection limit and better low-pressure monitoring performance. The response time of the flexible electronic fabric is less than 50 ms as Fig. 5 shows, sufficient for human motion signal monitoring. The stable resistance changes were maintained after 8 000 pressure cycles, indicating that the flexible electronic fabric maintains good resilience and conductive material wear resis-tance(Fig. 8). In addition, thanks to the full textile configuration of the flexible electronic fabric, it has better air permeability of 270.49 mm/s and moisture permeability of 3 420 g/(m²·24 h), representing better comfort. The flexible electronic fabric can realize the dynamic monitoring of the object, and it is convenient to predict the size and weight of the object qualitatively according to the image size and color depth as illustrated in Fig. 11. The flexible electronic fabric has excellent recognition ability for human body dynamic signals (as shown in Fig.12).
Conclusion This paper introduces a flexible electronic fabric with piezoresistive effect, which is composed of 1+1 ribbed conductive fabric and MXene modified cotton fabric. It has high sensitivity, fast response and excellent cycle durability. It is able to sense, record and distinguish the pressure of human movement, and achieve dynamic monitoring. On the basis of meeting the sensing requirements, the composition of the whole fabric can meet the needs of thermal-moist comfort and contact comfort of the human body. It has the potential to achieve large-scale industrial production due to its easy preparation process and stable performance, and has broad application prospects in the fields of sports training, medical care and military protection. In the future, the accuracy, sustainability, interactivity and data analysis and feedback of intelligent textiles need be further studied to meet the needs of the end-users with improved behavior.

Key words: all-textile-based, flexible piezoresistive sensor, electronic fabric, sensing performance, MXene