Highly sensitive strain sensors based on hollow packaged silver nanoparticle-decorated three-dimensional graphene foams for wearable electronics.

Flexible strain sensors possess a great potential for applications in wearable electronic devices for human motion detection, health monitoring, implantable medical devices and so on. However, the development of highly sensitive strain sensors remains a challenge in the field of wearable electronics. Herein, we prepared a highly sensitive strain sensor, which was composed of a three-dimensional reduced graphene oxide foam decorated with silver nanoparticles (Ag NPs) to enhance the conductivity. Then, half-cured polydimethylsiloxane was employed to get a special "hollow packaged" structure. Thanks to the synergistic conductive effect of Ag NPs and the reduced graphene oxide flakes as well as the special "hollow packaged" structure, the as-prepared flexible strain sensor not only possessed a dramatic gauge factor of 1588 (at 50% sensing strain), but also exhibited high stability in 500 cycles of 30% strain. The mechanism of the enhancement of the sensitivity with the special "hollow packaged" structure was discussed as well. Meanwhile, the detection of the bending and rotation of wrists and the bending of fingers and arms was demonstrated, showing attractiveness in human motion detection.

Three-Dimensional Graphene Structure for Healable Flexible Electronics Based on Diels-Alder Chemistry.

Wearable electronics with excellent stretchability and sensitivity have emerged as a very promising field with wide applications such as e-skin and human motion detection. Although three-dimensional (3D) graphene structures (GS) have been reported for high-performance strain sensors, challenges still remain such as the high cost of GS preparation, low stretchability, and the lack of ability to heal itself. In this paper, we reported a novel self-healing flexible electronics with 3D GS based on Diels-Alder (DA) chemistry. Furfurylamine (FA) was employed as a reducing as well as a modifying agent, forming GS by FA (FAGS)/DA bonds contained polyurethane with the "infiltrate-gel-dry" process. The as-prepared composite exhibited excellent stretchability (200%) and intrinsic conductivity with low incorporation of graphene (about 2 wt %), which could be directly employed for flexible electronics to detect human motions. Besides, the FAGS/DAPU composite exhibited lower temperature retro-DA response for the continuous graphene networks. Highly effective healing of the composites by heat and microwave has been demonstrated successfully.