Rinaldo Filho Gregorio

Bio: Rinaldo Filho Gregorio is an academic researcher from University of Minho. The author has contributed to research in topics: Dielectric & Polyvinylidene fluoride. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Non-Porous Polyvinylidene Fluoride (Pvdf) Films in the Beta Phase and Processing Method Thereof

Abstract: The invention reports a new film of the beta phase of polyvinylidene fluoride (PVDF) and its processing for the elimination of porosity, using a compression force along the thickness direction of the sample at a high temperature. The join action of the compression force and the temperature eliminates the porosity of the PVDF beta phase, improving its mechanical (Young's modulus, yielding and breaking stress, yielding and breaking strain), electrical (dielectric constant, electric rupture) and electromechanical properties (electromechanical coupling, piezoelectric coefficients) and, therefore, the use of the material in technological applications. Non-porous material, 95 to 100% in beta phase and with crystallinity degrees higher than 50%, is obtained.

Touchscreen based on acoustic pulse recognition with piezoelectric polymer sensors

Abstract: This article describes the concept, design, fabrication and experimental results of a touchscreen based on acoustic pulse recognition. It uses piezoelectric transducers fabricated from the piezoelectric polymer poly(vinylidene fluoride), PVDF, in its beta phase. The transducers are located at the edges of the panel in order to receive the acoustic pulses generated by the touches. Each transducer is connected to a readout electronic circuit composed by a differential charge amplifier and a comparator, whose output signal is attached to a microcontroller. The microcontroller uses an algorithm to determine the location of the touch, based on the time differences of the transducer signals. The touchscreen itself is made of ordinary glass, providing good durability and optical transparency. The experimental results obtained with the first prototype demonstrate the effectiveness of the method.

Piezoelectric element including fluororesin film

Abstract: There is provided a piezoelectric element, including: a porous fluororesin film made of a first fluororesin; and a nonporous fluororesin layer stacked on at least one surface of the porous fluororesin film and made of a second fluororesin, wherein the first fluororesin is different in type from the second fluororesin, and when 50 pores are selected in descending order from a pore having the longest thickness-direction length, of pores present in a cut surface of the porous fluororesin film in a thickness direction, an average value A 50 of thickness-direction lengths of the 50 pores is 3 μm or smaller.

Heating of samples by acoustic microagitation for improving reaction of biological fluids

Abstract: This article describes an acoustic microagitator for being used in biological fluids analysis. It is known that a piezoelectric transducer, with its vibration, can be used for mixing fluids. However, in this case, the piezoelectric transducer is also used to heat the samples, improving the reaction of fluids that benefit from that effect. The piezoelectric transducer is fabricated from a poly(vinylidene fluoride) polymer, in the beta phase (β-PVDF). This concept is demonstrated theoretically and by measuring the temperature profile in a regular 1 cm optical lightpath glass cuvette, using capillary thermocouples. This system can further be included in a lab-on-a-chip device, acting as a microreactor, for clinical diagnosis.

The permeation and moisture transmission properties of a thermosensitive membrane barrier for chemical protective clothing

Abstract: The liquid chemical permeation properties and water vapour transmission properties of temperature sensitive poly(vinylidene fluoride) (PVDF) grafted N-isopropylacrylamide (NIPAAM) (NIPAAM-g-PVDF) copolymer membranes as a smart barrier layer in chemical protective clothing are studied in this research. Both modified thermally induced method and modified plasma induced method are employed to oxidise PVDF polymer for its copolymerisation with NIPAAM monomers. In the thermal induced method, NIPAAM-g-PVDF polymer materials are synthesised via the copolymerisation of ozone activated PVDF polymer with NIPAAM monomers below a lower critical solution temperature of NIPAAM (30°C). An effective supercritical carbon dioxide drying method is used as an alternative drying method to remove the solvent from the ozone activated PVDF polymer in conventionally copolymerisation is successfully applied and a new direct copolymerisation route by adding NIPAAM polymer into ozone activated PVDF in solutions without the drying process of the activated PVDF polymers. The NIPAAM-g-PVDF made by the new copolymerisation process is much simpler than the conventional method and the processing time needed is much shorter. In the oxygen plasma induced copolymerisation method, the porous PVDF membranes produced from the phase inversion method are treated oxygen plasma before they were copolymerised with NIPAAM monomer in N,N-dimethylformamide (DMF) solvent aqueous solution below the lower critical solution temperature of NIPAAM (30°C). The structural characteristics of heat-pressed NIPAAM-g-PVDF nanoporous membranes produced from the above two methods are investigated. The influence of the microstructure of the nanoporous copolymer membranes on both their water vapour transfer properties and dynamic permeation rate has been studied. The mechanisms of liquid/vapour permeation through the thermal sensitive copolymer nanoporous membranes are analysed and investigated. In this study, it is found that the breakthrough time and permeation rate of nanoporous NIPAAM-g-PVDF membranes are influenced by the proportion of NIPAAM components, the membrane thickness, the crystallinity and the porous structure of the NIPAAM-g-PVDF membranes. It is also found that the water vapour permeability of the heat-pressed NIPAAM-g-PVDF membranes at both 20°C and 40°C are influenced by the membrane thickness, the total pore volume and the porosity of the membranes. The water vapour permeability coefficient of the NIPAAM-g-PVDF nanoporous membranes is determined by both the proportion of thermal sensitive NIPAAM components and associated porous structure of the copolymer membranes.

Texture piezoelectric polymer film of high transverse effect and preparation method of film

Abstract: The invention discloses a texture piezoelectric polymer film of high transverse effect and a preparation method of the film. The nonisothermal crystallisation process of the film prepared by the solution method is controlled to realize preferable orientation of molecular dipole moment of the film is realized, and the piezoelectric polymer film of the texture structure in which the molecular dipoles are arranged preferably along the plane of the film is prepared. The piezoelectric polymer film is characterized in that the horizontal piezoelectric effect of the film is higher than that of a film of the same components but without texturizing, can be applied to preparation of a sensor of high transverse piezoelectric effect, and has good application prospects in the fields of a flexible nano generation system and a novel energy collection system.