Hybrid Tribo-Piezo-Electric Nanogenerator with Unprecedented Performance Based on Ferroelectric Composite Contacting Layers

This research was supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.It was recently reported that more efficient triboelectric nanogenerator (TENG)-like devices can be prepared using inversely polarized ferroelectric films made of same material as the contacting layers. In the present work, a clear correlation between the piezoelectric response of inversely polarized ferroelectric PVDF/BaTiO3 nanocomposite films and the performance of the TENG-like device based on these films is demonstrated. This observation is explained by magnified electrostatic induction that is driven by piezoelectric charges and ferroelectric properties of these films. A double capacitor model is proposed that effectively portrays the interactions between ferroelectric layers during contact-separation and subsequent charge redistributions in the external circuit. The new understanding has allowed the result of 3-fold higher open circuit voltages (2.7 kV from 5 cm2) as compared to that of a state of the art TENG. Furthermore, findings uncover the potential for vast improvement in the field of nanogenerators for mechanical energy harvesting as a significantly better piezoelectric performance of flexible nanogenerators has been reported elsewhere.ERDF 1.1.1.1./16/A/013; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

The role of intermolecular forces in contact electrification on polymer surfaces and triboelectric nanogenerators

This research was supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.The contact electrification of polymer interfaces provides an energy harvesting function to triboelectric (nano)generators (TEG). The electron transfer between contacted-separated surfaces has been considered as the main electrification mechanism for polymers in TEG. The electron transfer mechanism widely proposed in literature requires a contact between chemically different polymer materials, as well as subsequent increase of the specific contact area, which is commonly accomplished via nanostructuring. Herein, we showed that contact electrification could be controlled by intramolecular forces in the polymer bulk and adhesive forces at the contact interface, and the chemical contact between different polymers was not needed for contact electrification. The results also confirm the breaking of the covalent bond as a mechanism of the contact electrification of polymer insulators.ERDF 1.1.1.1./16/A/013; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Prospective Polymer/Nanostructured Carbon Composites for Application in Multifunctional Sensors

Recent achievements of our scientific group in design, processing and investigation of polymer-nanostructured carbon composites (PNCC) as prospective materials for non-rigid mechanical (pressure, strain) indicators, chemical vapour indicators, humidity sensors and polymeric thermistors have been presented. Complex “conductive AFM” (Fig.1), SEM, FTIR ATR, dielectric spectroscopy measurements as well as mechano-electrical, chemo-electrical, thermo-mechanical and thermo-electrical properties were studied to understand the mechanisms of the multifunctional sensing and to improve the sensing parameters

Mechanical Pressure Induced Capacitance Changes of Polyisoprene/Nanostructured Carbon Black Composite Samples

Polyisoprene/nanostructured carbon black (PNCB) composite samples with different amount of carbon black (CB) filler were prepared. Investigations of mechanical pressure induced relative capacitance changes (RCC) depending on frequency (20 Hz – 2 MHz) were conducted. It was found that PNCB samples show pronounced and rather complex RCC effect, which depends on frequency, amount of filler (1 – 10 phr of CB) and pressure (from 0 to 234 kPa). At a certain frequency and a certain filler amount RCC effect changes its sign. Pressure induced capacitance changes at least for low CB filler concentrations are caused by piezopermittivity property of the PNCB composite

Electrical Resistance Change Effect in Polyisoprene/Nanostructured Carbon Composite Induced by Laser Radiation

Polyisoprene/nanostructured carbon (PNC) composites are known for their ability to change electrical resistance rapidly under the influence of mechanical strain and vapour of volatile organic compounds. Previously testing of PNC composites containing carbon black (CB) filler were made to check for the possibility to sense optical radiation. In this study attempt to determine the difference in resistance change response depending on laser wavelength was done. PNC composite samples cyclically were irradiated with laser beams of different wavelengths. Irradiation time during one cycle was 30 s. Measure-ments with sample containing 8 phr of CB showed that relative resistance change effect is larger when irradiating the sample with 532 nm laser beam compared to 980 nm laser beam. To clarify the mechanism for such difference in relative resistance change further PNC composite tests are being made

Mehāniskās deformācijas izraisītas maiņstrāvas vadāmības izmaiņas poliizoprēna / nanostrukturēta oglekļa kompozītos

Daudzas zinātnieku grupas izstrādā un testē polimēru/elektrovadošu nanodaļiņu kompozītus pielietojumam dažādos sensoros. Mūsu darbs tika veikts, lai varētu labāk optimizēt poliizoprēna/nanostrukturētu oglekļa kvēpu (PNOK) kompozītus pielietojumam sensoros, veicot vadāmības relatīvo izmaiņu (VRI) mērījumus maiņstrāvas režīmā atkarībā no kompozītu mehāniskās deformācijas. PNOK paraugi ar dažādu nanostrukturētu oglekļa kvēpu pildvielas daudzumu tika testēti frekvenču diapazonā no 20 Hz līdz 2 MHz. Mērījumi parādīja, ka VRI maksimums PNOK paraugiem ar zemu oglekļa pildvielas daudzumu (4-5 masas daļas nanostrukturētu oglekļa kvēpu uz 100 masas daļām poliizoprēna) atrodas tikai pie pašām zemākajām mērītajām frekvencēm, bet PNOK paraugi ar augstu pildvielas koncentrāciju (8-10 masas daļas pildvielas) uzrādīja plašu, nemainīga lieluma VRI plato līdz vismaz 10 kHz

Mechanical Pressure Induced Capacitance Changes of Polyisoprene/Nanostructured Carbon Black Composite Samples

Electroconductive polyisoprene/nanostructured carbon black (PNCB) composites show pronounced resistance change effect when subjected to mechanical deformation. This effect has been used to develop flexible mechanical pressure and organic solvent vapor sensors. To advance the composites for sensor applications there is a need for additional studies concerning nanoparticle movement while applying mechanical pressure. Investigation of mechanical pressure induced relative capacitance changes (RCC) depending on frequency (20 Hz – 2 MHz) was conducted. It was found that PNCB samples show pronounced and rather complex RCC effect, which depends on frequency, amount of filler (1 – 10 phr of CB) and pressure (from 0 to 234 kPa)

Influence of Laser Radiation on Electrical Resistivity of Polyisoprene/Nanostructured Carbon Composites

It is known that polymer/carbon nanotube composites are being tested for their potential use in optoelectronic devices. It is also known that polyisoprene/nanostructured carbon (PNC) composites have a pronounced resistance change under the influence of mechanical strain and vapour of volatile organic compounds. The goal of this study was to test PNC composites for their potential use as optoelectronic materials. Measurements of relative resistance change of poly- isoprene/nanostructured carbon black composites irradiated by semiconductor laser beam were conducted. One illustration of composites photoresistivity measurements at different intensities of laser radiation is given in Fig.1. Two competing mechanisms of composites resistivity change, induced by laser radiation, have been proposed: 1) photoconductivity of carbon nanostructures and 2) exponential reduction of tunnelling currents between carbon nanostructures in composite caused by to thermo-optically induced matrix expansion. Further photoresistivity and optical studies of PNC composites are in progress

Bolometric Photoresponse of Polymer/Nanostructured Carbon Composite

Attempts to utilize polymer/carbon nanoparticle composites for use in optoelectronics are being made (e.g., single-walled carbon nanotubes are being used as polymer fillers). Polyisoprene/nanostructured carbon (PNC) composites show large resistance change effect as mechanical strain is applied4. Therefore, it was expected that PNC composites also could show bolometric photoresponse. In this study, bolometric photoresponse measurements of PNC composites containing carbon black (CB) filler irradiated by a laser beam of different wavelengths were conducted