A comprehensive review on the state-of-the-art of piezoelectric energy harvesting

Flexible PVDF based piezoelectric nanogenerators

Piezoelectric materials are widely referred to as "smart" materials because they can transduce mechanical pressure acting on them to electrical signals and vice versa. They are extensively utilized in harvesting mechanical energy from vibrations, human motion, mechanical loads, etc., and converting them into electrical energy for low power devices. Piezoelectric transduction offers high scalability, simple device designs, and high-power densities compared to electro-magnetic/static and triboelectric transducers. This review aims to give a holistic overview of recent developments in piezoelectric nanostructured materials, polymers, polymer nanocomposites, and piezoelectric films for implementation in energy harvesting. The progress in fabrication techniques, morphology, piezoelectric properties, energy harvesting performance, and underpinning fundamental mechanisms for each class of materials, including polymer nanocomposites using conducting, non-conducting, and hybrid fillers are discussed. The emergent application horizon of piezoelectric energy harvesters particularly for wireless devices and self-powered sensors is highlighted, and the current challenges and future prospects are critically discussed.

Piezoelectric Materials for Energy Harvesting and Sensing Applications: Roadmap for Future Smart Materials

Making use of nanoenergy from human – Nanogenerator and self-powered sensor enabled sustainable wireless IoT sensory systems

Performance enhancements in poly(vinylidene fluoride)-based piezoelectric nanogenerators for efficient energy harvesting

Highly durable piezoelectric energy harvester based on a PVDF flexible nanocomposite filled with oriented BaTi2O5 nanorods with high power density

With the rapid development of wearable devices, a highly sensitive flexible piezoelectric sensor shows tremendous potential for future demands. Here, we report a novel lead-free flexible piezoelectric sensor fabricated by a composite with chain-distributed (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 (BCZT) particles in a polydimethylsiloxane (PDMS) matrix. The BCZT particles were prepared by a conventional solid oxide process and then dispersed in PDMS oriented by the application of a dielectrophoretic alignment field. The fabricated aligned flexible composite with 8 vol% BCZT addition had a high open circuit voltage of 28.8 V (peak-to-peak), which was nearly twice as high as that of the randomly dispersed composite. This new mechanically reinforced flexible piezoelectric composite was demonstrated to resolve the problems of the weak stress transfer to piezoelectric elements and the poor dispersion of fillers in the polymer matrix. The 8 vol% BCZT/PDMS composite was incorporated into a flexible piezoelectric touch sensor, which possesses excellent sensitivity in a wide pressure range and an extraordinary cycling stability. These results indicate that the fabricated flexible piezoelectric sensor has great potential in the wireless sensor network and wearable electronic fields.

The alignment of BCZT particles in PDMS boosts the sensitivity and cycling reliability of a flexible piezoelectric touch sensor

High-performance lead-free piezoelectric materials have become a hot topic in the field of advanced functional materials. In 2009, the (1 − x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 (BZT–BCT) system with surprisingly high piezoelectric properties was first proposed by Liu and Ren; as a milestone discovery in the field of ferroelectrics, it has aroused extensive attention. In this review, initially, we highlight the remarkable electrical properties of the BZT–BCT system, and then summarize the advances in the BZT–BCT material based on five aspects including the origin of its high properties, preparation and poling, grain size control, chemical modification and texture design. We focus on a systematic discussion of its phase boundaries, domain structure, and defect chemistry in relation to improved dielectric and piezoelectric properties. In addition, the device performance of BZT–BCT materials is also evaluated. Due to their excellent comprehensive properties, BZT–BCT materials have been widely studied in various applications such as energy harvesters, flexible sensors and energy storage capacitors. Finally, based on the state-of-the-art knowledge, we present an outlook on the challenges and application prospects of BZT–BCT materials. This review will help promote the practical applications of BZT–BCT materials, and accelerate the development of lead-free ferroelectric materials in specific fields.

High-performance lead-free ferroelectric BZT–BCT and its application in energy fields

Giant current performance in lead-free piezoelectrics stem from local structural heterogeneity

Flexible piezocomposites have emerged as promising materials for highly durable wearable devices. Here, we propose a new design strategy, namely particle alignment engineering, to develop high performance flexible piezocomposites by dielectrophoresis (DEP). An ultrahigh piezoelectric voltage coefficient (g33) of 600 × 10-3 V m N-1 is achieved by a composite of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 (BCZT) particles aligned in a polydimethylsiloxane (PDMS) matrix. To the best of our knowledge, this g33 value is by far the highest ever achieved in piezocomposites. The significantly improved poling electric voltage applied to the BCZT particles and hugely enhanced stress-transfer capability of the aligned composite synergistically contribute to the record-high piezoelectric response in flexible piezocomposites. The fabricated flexible piezoelectric touch sensor and wearable keyboard possess an excellent sensitivity and cycling stability, which demonstrate a promising strategy for exploring high performance piezocomposites for flexible device application.

Xin Gao

Papers

Highly durable piezoelectric energy harvester based on a PVDF flexible nanocomposite filled with oriented BaTi2O5 nanorods with high power density

The alignment of BCZT particles in PDMS boosts the sensitivity and cycling reliability of a flexible piezoelectric touch sensor

High-performance lead-free ferroelectric BZT–BCT and its application in energy fields

Giant current performance in lead-free piezoelectrics stem from local structural heterogeneity

High performance piezocomposites for flexible device application