Piezoelectric Sensors Based on Cellulose Nanocrystals

Cellulose nanocrystals (CNCs) are renewable nanomaterials obtained by strong acid hydrolysis of biomass. CNC surface charge and properties can be manipulated and controlled during the hydrolysis process, whereby a tunable measure of surface charge and active moieties can be engineered. The electric dipole moment of CNCs has been measured using transient electric birefringence, with a reported 4400 ± 400 D magnitude permanent dipole along the CNC long axis. Many natural materials, including wood, show piezoelectric properties by virtue of the non-centrosymmetric orientation of their molecular components. However, we will show how CNCs – unlike other natural materials – have unique, tunable, and long-lasting piezoelectric response, alone or in combination with other polymeric materials.
It was discovered that the piezoelectric response of CNC films strongly depended on the surface properties of CNCs and the ionic strength of the CNC dispersion. An increase in |d33| from 0.4 to 5.5 pC N-1 was observed by converting CNCs from Na-form to H-form, and this value was further improved to 82.6 pC N-1 by controlling the ionic strength of the CNC suspensions before evaporation-induced self-assembly (EISA). This d33 value was higher than that typically observed for PVDF, the most widely used piezoelectric polymer material, as well as PZT-polymer composites, and some piezoelectric ceramics, e.g., BiFeO3.
The presentation will detail the mechanisms responsible for these unique responses governed by controllably manipulating CNC surface characteristics, and how this knowledge can be applied to develop sustainable, cost-effective organic electronic materials for a variety of end-use engineering and biomedical applications.

Wadood Y. Hamad has expertise in materials science and nanotechnology and is currently Research Manager of the Transformation and Interfaces Group within the Bioproducts Innovation Centre of Excellence at FPInnovations. Also Adjunct Professor at the Department of Chemistry, University of British Columbia since 2012, Dr Hamad has sought to provide a vision for advancing high-level R&D. His focus is on eco-sustainable design and the application of an inter-disciplinary scientific approach spanning the fields of materials science, physics, chemistry, and biology to develop useful bio-inspired materials and structures for engineering and medical applications. A pioneer in the research and development of renewable, nontoxic nanomaterials, particularly his ground-breaking research on the structure-property-process interrelations of cellulose nanocrystal (CNC) processing. Dr Hamad was granted the Distinguished Nanoscientist Award and FiberLean Industries Prize by the Nanotechnology Division of the Technical Association of the Pulp and Paper Industry, TAPPI (USA) in June 2018. Wadood was elected fellow of the Royal Society of Chemistry (UK) and the Institute of Materials, Mining and Metallurgy (UK) in 2017. He is the recipient of other honours and awards, notably the Tech21 visiting professorship at Université Grenoble Alpes, France in 2018.
His work has led to over 27 families of patented applications and over 130 peer-reviewed book chapters, scientific papers, and authoritative reviews, as well as several monographs.