Physics Center of Minho and Porto Universities

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Publication . Nunes-Pereira, João; Costa, Pedro; Lanceros-Mendez, Senentxu

The concept of piezoelectric energy production is based on energy-harvesting devices using generation materials such as single crystals, ceramics, polymers, and composites. These production systems can harvest wasted environmental energy and convert it essentially into electrical energy. There are different nano- and microscale power harvesters which are increasingly useful for powering mobile electronics and low-power devices, even in hardly accessible areas. Despite many efforts in the development of new materials, the most widely used materials in device applications remain the ceramics of the lead zirconate titanate family, since they still present the higher output performances in the range of milliwatts of generated power.

2018Book part

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Recent Progress on Piezoelectric, Pyroelectric, and Magnetoelectric Polymer‐Based Energy‐Harvesting Devices

Publication . Costa, Pedro; Nunes-Pereira, João; Pereira, Nelson; Castro, Nélson; Gonçalves, Sérgio; Lanceros-Mendez, Senentxu

Energy harvesting from the environment based on electroactive polymers has been increasing in recent years. Ferroelectric polymers are used as mechanical-to-electrical energy transducers in a wide range of applications, scavenging the surrounding energy to power low-power devices. These energy-harvesting systems operate by taking advantage of the piezoelectric, pyroelectric, and magnetoelectric properties of the polymers, harvesting wasted environmental energy and converting it mainly into electrical energy. There have been developed different nano- and micro-scale power harvesters with an increasing interest for powering mobile electronics and low-power devices, including applications in remote access areas. Novel electronic devices are developed based on low-power solutions, and therefore, polymer-based materials represent a suitable solution to power these devices. Among the different polymers, the most widely used in the device application is the poly(vinylidene fluoride) (PVDF) family, due to its higher output performance.

2019Journal article

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Surface wettability modification of poly(vinylidene fluoride) and copolymer films and membranes by plasma treatment

Publication . Correia, Daniela M.; Nunes-Pereira, João; Alikin, Denis; Kholkin; Carabineiro, S.A.C.; Rebouta, Luis; Rodrigues, Marco S.; Vaz, F.; Costa, C. M.; Lanceros-Mendez, Senentxu

This manuscript reports on the modification of the surface wettability of poly (vinylidene fluoride) (PVDF) and PVDF copolymer films and membranes by plasma treatments at different conditions, under oxygen and argon atmospheres. It is shown that a more pronounced decrease of the contact angle after O2 plasma treatments is obtained, with a decrease of ∼20-30° for PVDF and its copolymers films, leading also to superhydrophilic membranes. This effect is related to a defluorination process, followed by the incorporation of oxygen atoms onto the surface of membranes that occurs during the surface modification. The influence of plasma treatments on surface morphology and topography was studied by atomic force microscopy, showing a decrease in the mean surface roughness with the plasma treatments, being more noticeable for Ar treatments. Finally, it is also shown that plasma treatments under Ar and O2 did not induce modifications in the physicochemical and thermal properties of PVDF and PVDF copolymers. The chemical reaction mechanism after plasma treatment is proposed for the different copolymers.

2019Journal article

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Mesoporous poly(vinylidene fluoride-co-trifluoroethylene) membranes for lithium-ion battery separators

Publication . Costa, C. M.; Kundu, Manab; Dias, J. C.; Nunes-Pereira, João; Botelho, Gabriela; Silva, M. M.; Lanceros-Mendez, Senentxu

Mesoporous separator membranes based on poly(vinylidene fluoride-co-trifluoroethylene), PVDF-TrFE, were prepared through the removal of ZnO nanoparticles from the polymer matrix composite. Different filler concentrations were used, and the evaluation of the morphology, mechanical properties, uptake and ionic conductivity of the membranes were demonstrated that they depend on initial ZnO content in the composite. On the other hand, the vibration peaks characteristics of PVDF-TrFE and the thermal properties are independent on initial filler content. The membrane with the best ionic conductivity, 1.6 mS/cm, is the one prepared after 70 wt.% ZnO removal. The separator membranes were assembled in Li/C-LiFePO4 half-cells exhibiting good rate capability and cycling performance, the best battery performance being obtained for the PVDF-TrFE after 70 wt.% ZnO removal. The good performance of the developed separators was also demonstrated in full battery cells. Thus, a way to tailor membrane mesoporosity is presented and it is shown that the obtained membranes represent suitable separators for lithium-ion battery applications.

2019Journal article

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Evaluation of the Physicochemical Properties and Active Response of Piezoelectric Poly(vinylidene fluoride-co-trifluoroethylene) as a Function of Its Microstructure

Publication . Gonçalves, R.; Cardoso, V. F.; Pereira, Nelson; Oliveira, Juliana; Nunes-Pereira, João; Costa, C. M.; Lanceros-Mendez, Senentxu

Poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), microstructures have been produced using different solvents, including green ones, by different techniques, such as solvent casting, screen-printing, replica molding, electrospray, and electrospinning. The obtained microstructures span from simple porous and dense films to spheres, fibers, and patterned three-dimensional architectures, with no significant variation in their physicochemical and electrical properties. The simplicity, low cost, and reproducibility of the processing techniques allied to their versatility to adapt to other materials to produce controlled and tailored microstructures with specific properties demonstrate their potential in a wide range of technological applications, including biomedical, energy storage, sensors and actuators, and filtration.

2018Journal article

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