Design and performance of flexible polymeric piezoelectric energy harvesters for battery-less tyre sensors

A piezoelectric energy harvester for battery-less tyre sensors has been developed. It consists of two key elements: (a) a piezoelectric material-polyvinylidene difluoride (PVDF) film and (b) an electrode-a conductive elastomer filled with carbon black and single-wall carbon nanotubes (SWCNTs). It was designed as a flexible patch in a sandwich-like configuration, which can be mounted onto the inner liner of a tyre. The patch was fabricated by inserting a PVDF film in between two conductive elastomer sheets. The development started with improving the conductivity of the elastomer by adding 6 wt% of SWCNT masterbatch. The adhesion between the interfaces was improved through surface modification of the PVDF film by introducing oxygen functional groups via a plasma treatment and further modification with a thiocyanate silane. The successful surface modification of the PVDF film was affirmed by x-ray photoelectron spectroscopy. T-peel and fatigue tests showed durable and stable adhesion between PVDF and conductive elastomer, confirming that the silane can effectively bridge the two components. A glueing method is proposed to adhere the patch to the tyre inner liner compound. The harvester is estimated to sufficiently power a reference tyre sensor, producing 28 mu W cm(-2).