Design and fabrication of flexible strain sensor based on ZnO-decorated PVDF via atomic layer deposition

Highlights: • Selective deposition of ZnO onto PVDF was realized via a simple plasma-assistant ALD. • ZnO/PVDF based sensor shows a high sensitivity towards the low-strain ranging from 0.1% to 0.6%. • ZnO-patterned sensor can be used to detect the motion of body and sense the position of loading. Introducing patterned sensors onto polymer substrates has been regarded as a promising way to manufacture multifunctional and integrated flexible sensors, because of their huge potential applications in wearable devices. However, the scalable production of these electronic devices is still limited by the complex process required to achieve high quality. Here, we utilized poly(vinylidene fluoride) (PVDF) as the polymer substrate for its good toughness and environmental stability to fabricate flexible strain sensors with designed patterns. Thanks to the effective plasma pretreatment on PVDF with low activity, the piezoresistive ZnO nanolayer was directly deposited onto the surface of PVDF membrane via atomic layer deposition (ALD). Subsequently, the ZnO/PVDF based strain sensor exhibits a high performance to monitor the strain below 6%, and especially towards the very low strain ranging from 0.1% to 0.6%, which was difficult to be precisely detected by other methods. Interestingly, utilizing the low chemical activity of PVDF, the patterned deposition of ZnO could be facilely achieved via a relatively simple selective plasma pretreatment, which leaded to different wearable sensors be designed, and an array-style sensor be fabricated as in-situ sensors to detect the position under loading. Therefore, this work offers a new strategy to design and fabricate novel integrated wearable electronics.