▎ 摘　　要

NOVELTY - Film strain sensor having wide test range and high sensitivity, comprises a strain film in middle layer and protective films on both sides; where the strain film in the middle layer is a film composed of nano-silver particles/multi-layer graphene composite nano-sheet filler and polyurethane elastic resin; the nano-silver particle/multi-layer graphene composite nano-sheet is a flat sheet without wrinkles, and the nano-silver particle grows on the surface of the multi-layer graphene sheet in situ, and the nano-silver particles/multi-layer graphene composite nano-sheets are parallel to each other and parallel to the bottom surface in the film. USE - Used as film strain sensor. ADVANTAGE - The film strain sensor: has wide strain range. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing film strain sensor, comprising (i) adding 80 ml N,N-dimethylformamide and 20 ml deionized water into a glass bottle, and mixing well to obtain a mixed solvent, adding 200 mg expanded graphite into mixed solvent and ultra-sonicating for 4 hours using ultrasonic machine to obtain uniform multi-layer graphene dispersion liquid, adding the multi-layer graphene dispersion liquid into a polytetrafluoroethylene tank, adding 600 mg silver nitrate, and 1 ml aqueous ammonia into the multi-layer graphene dispersion liquid, stirring with a magnetic stirrer at room temperature for 10 minutes to obtain dispersion liquid, adding 250 mg ascorbic acid, 2 g anhydrous sodium acetate, and 30 mg polyvinylpyrrolidone into the dispersion liquid, stirring with the magnetic stirrer at room temperature for 10 minutes, and transferring the dispersion to 50 ℃ water bath, stirring in the water bath at 300 revolutions per minute for 1 hour, centrifugally cleaning the product for 3 times with deionized water, and 3 times with alcohol, and placing in an oven at 70 ℃ for 24 hours to drying to obtain dry nano-silver particles/multi-layer graphene composite nano-sheet, (ii) adding 20-40% dry nano-silver particles/multi-layer graphene composite nano-sheet and aqueous polyurethane elastic paint into container, (iii) dropwise adding deionized water while stirring until the mixture has a suitable viscosity, (iv) continuing to stir for 1 hour, and allowing to stand at room temperature for half an hour to obtain strain film slurry, (v) using 0.2 mm thick transparent polyurethane film as base, coating the slurry on the polyurethane film by a coating machine to obtain film, and maintaining the thickness of the film to 10-200 μm, applying stress in parallel direction with the base, and generating strain by the film, which is main functional layer of sensor i.e. strain film, and resulting in a change in resistance, (vi) drying and curing the strain film in the oven at 70 ℃, and (viii) scraping and drying layer of polyurethane film on the surface of the strain film to obtain upper protective film with thickness of 0.2 mm.