Enhanced Piezoelectricity in Sustainable-By-Design Chitosan Nanocomposite Soft Thin Films for Green Sensors

Piezoelectricity,
the generation of an electric charge in response
to mechanical stress, is a key property in both natural and synthetic
materials. This study significantly boosts the piezoelectric response
of chitosan, a biodegradable biopolymer, by integrating chitin/surface-deacetylated
chitin nanocrystals into natural chitosan-based thin films. The resulting
materials, produced in our laboratories, achieve d33 values of up to 18.7 ± 1.1 pm V–1, a marked improvement over 8.9 ± 0.6 pm V–1 observed in pure chitosan films, thanks to the increased crystallinity
provided by the nanocrystals. We utilize piezoresponse force microscopy
(PFM) to accurately measure the d33 coefficient,
employing an engineered extraction method that eliminates the electrostatic
contribution, which can overestimate the piezoelectric response. This
work introduces a soft, elastomer-like piezoelectric thin film entirely
derived from upcycled biowaste. The chitosan-based films combine high
elasticity (up to 40% strain) with a low Young’s modulus (∼100
MPa), closely mimicking soft biological tissues. Unlike previously
reported piezoelectric materials, which typically rely on synthetic
or inorganic components, our films are fully biobased and mechanically
compliant, making them ideal for applications in prosthetics, wearable
devices, soft robotics, and sustainable energy harvesting.