KNN based piezo-triboelectric lead-free hybrid energy films

Abstract

In recent times, the triboelectric and piezoelectric effects have garnered significant attention towards developing advanced material composites for energy harvesting and sensory applications. In this work, potassium sodium niobate (KNN) based energy films (EF) have been developed to utilize mechanical energy while simultaneously taking advantage of triboelectric and piezoelectric mechanisms. The KNN particles were synthesized using a wet ball milling technique and then incorporated into a polyvinylidene difluoride (PVDF) matrix together with addition of multi wall carbon nanotubes (MWCNT). The film was used to develop a piezoelectric nanogenerator (PENG) fitted with copper electrodes. The piezoelectric output of the film was further tested utilizing copper electrodes, at variable tapping frequency (60 BPM to 240 BPM) and pressure (10–40 psig) were used when activating the pneumatic piston. The open circuit voltage increased with the increase of both tapping frequency and pressure. The maximum piezoelectric output voltage was observed to be 35.3 V while the maximum current was noted as 15.8 µA. The films also showed unique output signals for different types of deformations performed under hand pressure. The film was further utilized to build a piezo-triboelectric hybrid nanogenerator to check its hybrid performance. The maximum output was observed to be 54.1 V and 29.4 µA. This film was integrated with conventional electronic components (bridge rectifiers, resistors, and capacitors) and tested for its ability to harvest energy. The hybrid nanogenerator can charge a 0.1 µF capacitor to 9.4 V in 60 s. The optimum output power for the device was measured to be 0.164 W. The film was further attached with a Kapton film and showed a hybrid output of 113.2 V. This experiment endorsed the potential of the KNN based energy films for multifunctional applications like force, pressure, and motion sensing as well as lead free energy harvesting. Potassium sodium niobate (KNN) was synthesized and incorporated into PVDF along with MWCNT to produce lead-free piezoelectric and piezo-triboelectric hybrid energy films. The high piezoelectric and piezo-tribo hybrid output response showed its potential in biomechanical energy harvesting. Besides, the energy film can be utilized for biomechanical motion and pressure sensing operations. • KNN/PVDF/MWCNT based lead-free energy film was synthesized for piezoelectric and triboelectric operation. • The energy film was tested at variable pressure, load frequency, and finger motions. • The hybrid energy film showed high output of 54.1 V and 29.4 μA. • The energy film can be used for powering small electronic devices and multidimensional sensory operations.