Enhanced flexoelectric and piezoelectric pairing of bent polyvinylidene fluoride (PVDF) membrane with two-dimensional (2D) stannic sulfide-bismuth oxychloride (SnS2-BiOCl) heterojunction

In this study, n-type stannic sulfide (SnS2) nanosheets and p-type bismuth oxychloride (BiOCl) nanosheets prepared by hydrothermal method are utilized to construct the heterostructure SnS2-BiOCl composite through ultrasonication and grinding procedures. The piezoelectric SnS2-BiOCl heterojunction nanosheets are incorporated into the ferroelectric polyvinylidene fluoride (PVDF) membrane to fabricate the PVDF-based SnS2-BiOCl (PVDF-SnS2-BiOCl) flexoelectric strain sensor. The optimal amount of SnS2-BiOCl heterojunction in the PVDF-SnS2-BiOCl membrane is determined. A thorough analysis is conducted on the impact of bending curvature, frequency of bending, the size and thickness of the membrane, water flapping, underwater bending, resistance to fatigue from repeated bending, and resistance to corrosions from acid and alkali on the membrane's output current and voltage. The experimental and density functional theory (DFT) calculation results indicate that the PVDF-SnS2-BiOCl(2:1)-10 % membrane, functioning as a smart strain sensor, has the ability to monitor human joint movements and water fluctuations in different situations. Additionally, it can be used as a coating for polyester and linen fabrics and can be connected in series or in parallel. The experimental findings align closely with the results obtained from DFT calculations. The outcomes demonstrate that the PVDF-SnS2-BiOCl membrane strain sensor, which is highly flexible, sensitive, and attachable, is well-suited for smart wearable electronic materials.