Highly sensitive, scrub-resistant, robust breathable wearable silk yarn sensors via interfacial multiple covalent reactions for health management

The rapid development of wearable intelligent electronics, silk fabric sensors combine strain sensing functionality with comfortable wearability and high stretchability have attracted much attention of wearable electronics. However, common physical loading conductive units on silk fiber/yarn/textile sensor still faced aggregation, structural instablility and poor signal capture yet. Herein, a new preparation method of conductive silk yarn based on multiple chemical covalent bond reactions is presented. Moreover, silk/di-aldehyde cellulose nanocrystals/polypyrrole (SACP) composite yarns as flexible strain sensor was achieved by Schiff-base reaction between amino groups of silk yarn (SY) and aldehyde groups of di-aldehyde cellulose nanocrystals (DACN) and in-situ polymerization of pyrrole on the DACN hydroxyl groups. The best SACP sensor with pyrrole loading of 0.2 g (SACP0.2) showed robust mechanical strength (240 MPa), high conductivity (530 S/m), excellent sensitivity (gauge factor = 27) and outstanding dynamic durability during 12,000 cyclic stretching-releasing process. Especially, it can maintain good sensing performance after repeated rubbing and washing, and be further integrated into textile and clothing as wearable sensor by traditional sewing technology with different shapes. Moreover, SACP0.2 sensor were designed and integrated into various multifunctional health warning device for human sleep, college students' physical fitness test and trapping mosquitoes, demonstating great potential in wearable electronics.