Multiple device applications based on the photo-mobile polymers are proposed in the PULSE-COM project, including an energy harvesting system. This device converts light-induced movement of the photo-mobile polymer into electrical energy via the piezoelectric effect. The system consists not only of the harvester itself but must also be integrated with the rectification and energy storage devices. CBRTP has developed a system aimed at optimization of rectification unit. It consists of an arbitrary waveform generator and a rectifying circuit. Rectification of the signal is achieved by a full-bridge diode rectifier (Graetz-Polak configuration). This allows energy transfer from the piezoelectric layer to the storage unit regardless of the deformation direction, or the sign of generated voltage.
The prototype piezo-layers consist of zinc oxide nanowires deposited on metal substrates. After fabrication, the prototype is connected to an oscilloscope and external mechanical deformation is applied. The resulting voltage signal is registered by the oscilloscope and recorded. For the early prototypes, some degradation of the signal is observed during prolonged and repeated testing. Subsequently, measured voltage waveform is used as input for the arbitrary waveform generator. Afterwards, the arbitrary waveform generator emulates the piezoelectric voltage for tests of the rectification circuit. This way, the rectifying circuit can be repeatedly tested using the same signal pattern. This overcomes the technological limitations related to the piezo-layer stability. These limitations are treated independently. Thanks to the outlined approach, they do not inhibit testing of other parts of the PMP-PZL device.
Left to right: Schematic of rectifying circuit in Graetz-Polak configuration; Output voltage (VIN) from a piezoelectronic generator emphasizing positive (V+) and negative (V-) parts; Zoom on single excitation.