Porous PDMS/CNFS composites for stretchable strain sensors

Strain sensors with flexible and stretchable characteristics have shown great potential applications in wearable devices for artificial e-skins and health monitoring/diagnosis. However, there remain some major challenges to develop sensors capable of both high sensitivity and stretchability by using a simple, cost-effective, and scalable method. In this paper, we report a new and facile method to fabricate porous polydimethylsiloxane/carbon nanofiber (p-PDMS/CNFs) composites using sugar particles coated with carbon nanofibers as the templates. Three-dimensional porous conductive PDMS nanocomposites are prepared by first infusing the templates with PDMS, curing the PDMS, and then removing sugar. The CNFs originally coated on the surfaces of sugar particles are embedded in PDMS pore walls, forming 3D conductive networks, resulting in high electrical conductivity (0.033 S/m). The resulting three-dimensional porous structure demonstrates greatly improved stretchability and compressibility compared with solid PDMS. The electrical resistance of the porous composites increases upon stretching but decreases under compression. Moreover, it is found that the resultant nanocomposites with the CNFs embedded in pore walls show excellent durability under repeated loading. The high sensitivity and reliable sensing performance endow these highly stretchable nanocomposites with a great potential as flexible sensors for wearable electronics.