Silver nanowire-based stretchable strain sensors with hierarchical wrinkled structures

As an engineering frontier, highly stretchable sensors are widely applied in many fields, such as human motion detection, personal healthcare monitoring, and human-machine interactions. In this study, novel silver nanowire (AgNW)-based stretchable sensors with hierarchical wrinkled structures were fabricated through a two-step process, namely water-induced swelling and AgNW deposition. As highly soluble additives, sodium chloride particles were incorporated into the elastomer matrix. Upon soaking in dopamine aqueous solution, significant swelling was introduced onto the elastomer substrate. The dopamine deposition is accompanied with the swelling process, which endows the sample surface with ultra-hydrophilicity. Additionally, the dopamine-modified swollen samples “capture” the nanowires when subsequently immersed in AgNW/ethanol suspension, because the dopamine acts as a highly adhesive layer. Finally, the sensors with wrinkled conductive network have been constructed upon removal of residual water. Both films and 3D printed sensors were fabricated and their electrical properties were systematically characterized. The fabricated sensors exhibit high sensitivity when subjected to external deformation from 10% to 100% strains, good electrical repeatability during 8000 stretching/releasing cycles, and reliable electrical responses in different frequencies of stretching/releasing. Human motion detection has been demonstrated using the 3D printed sensors, revealing the potential application in wearable electronics for healthcare monitoring and rehabilitation.