Aligned cellulose nanofiber composite made with electrospinning of cellulose nanofiber - Polyvinyl alcohol and its vibration energy harvesting

This paper reports an aligned cellulose nanofiber (CNF) composite that exhibits flexibility, transparency, and improved mechanical and piezoelectric properties. The aligned CNF composite was made by electrospinning CNF-polyvinyl alcohol (PVA) blend, followed by casting CNF suspension. The CNF-PVA blend was electrospun to form a CNF-PVA fiber mat, and an optimum CNF-PVA ratio and the spinning parameters were determined by examining CNF alignment. Then, the electrospun CNF-PVA mat was coated with CNF suspension to fabricate the aligned CNF composite. The aligned CNF composite was transparent (85.3%) and had a higher orientation index (α = 0.54) than a neat CNF film. Besides, the composite showed improved mechanical properties. In consequence of CNF alignment, the piezoelectric charge constant, d₃₁ of the composite was 14.5 pC/N, which was more than double of the neat CNF film. With this piezoelectric behavior, the composite was applied to a vibration energy harvester (VEH), and it showed an output power of 5.43 nW. All about the piezoelectric and mechanical property improvement were explained in this paper. The aligned CNF composite is flexible, lightweight, environment-friendly, and low-cost.