Energy Harvesting Using High-Strength and Flexible 3D-Printed Cellulose/Hexagonal Boron Nitride Nanosheet Composites

Abstract

As a natural polymer, cellulose is abundant, low-cost, robust, and biodegradable and can be chemically modified. This work explores the enhancement of mechanical, thermal, and flexoelectric properties of three-dimensional (3D)-printed carboxymethyl cellulose (CMC) due to the addition of mechanically exfoliated hexagonal boron nitride (hBN). hBN was observed to act as a rheology modifier, and CMC reinforced with 2% hBN exhibited the maximum apparent viscosity of 12.24 Pa·s at a shear rate of 100 s –1 . The 0.5% hBN/CMC film exhibited the highest mechanical and thermal stability. A flexoelectric energy harvester was fabricated out of 3D-printed hBN/CMC composites to test the effectiveness of strain-induced charge production. By varying the load resistance and applied pressure, we were able to measure the voltage and current flowing through the device. We found that a load resistance of 180 kΩ connected across a 2% hBN/CMC device resulted in the highest power delivery of 5.5 nW. When mechanical strain is applied, a charge state fluctuation and spontaneous polarization in the hBN/CMC matrix are seen. This phenomenon can be explained based on the flexoelectric energy-harvesting mechanism, supported by density functional theory (DFT) calculations.