Papers by Author: José Gerardo Rocha

Abstract: Project aims to develop a system that allows to provide to the People with Special Needs (PSN) a relief to the level of the sensitive perception of discomfort, assuring greater independence, welfare, quality of life, prevention of illnesses/wounds, through the development of textile and polymers applications (cushions, mattresses and mattresses overlays) with functions of monitoring and control of pressure in the body's areas in contact with the support surfaces. In this group of PSN will be enclosed the people with serious motor limitations conditioning their mobility/deambulation, such as bed rest people, patients under effect of sedatives or anaesthesia during long surgeries (intra and post operative), patients and users in general of wheelchairs. These people have, for the most part of the cases, a commitment of sensitivity in the body's areas in contact with the support surfaces, or its motor capacity does not allow them to move regularly of position autonomously, as it would do a healthy person unconsciously. Then, insufficient sanguineous irrigation occurs as result of pressure exceeding too long the tissue capillary pressure depriving tissues of oxygen and essential nutrients, owing to ischemia and hypoxia, which then causes the pressure ulcers (PU) development.

Abstract: This paper describes a fully-integrated lab-on-a-chip device for testing and monitoring biochemical parameters in biological fluids. The major innovation of this microdevice is the application of an acoustic microagitation technique with automatic electronic control based on a β-PVDF piezoelectric polymer placed underneath the microfluidic structures. Experimental results regarding the influence of the thickness of the polymer on the reaction rate of biological fluids are presented. Moreover, the study of the transmittance curve of β-PVDF with transparent conductive electrodes is also presented. Transparent electrodes are a constraint once the polymer is incorporate underneath the reaction chamber due to the analytical measurement by spectrophotometry.

Abstract: The kinetics of the isothermal crystallization of the γ-phase Poly(vinylidene fluoride) has been investigated. Samples were prepared from the melt at different crystallisation temperatures and the variation of the microstructure of the samples was monitored with time by optical microscopy. Raman and Infrared transmission spectroscopies also show the appearance of the γ-phase for higher crystallisation temperatures. Two types of γ-phase spherulites have been identified. These spherulites represents different ways to obtain the γ-phase and show different thermal stability. The correlation between microstructure and kinetic parameters allows the tailoring of the microstructure by choosing the crystallisation conditions of the samples.

Abstract: One of the main problems for the use of ferroelectric materials for sensor applications, especially for tactile sensors, is the separation of the pyro- and piezoelectric responseproduced by temperature and pressure changes, respectively. We present two different approaches to achieve this goal. The first approach is based on the study of the signal in the frequency domain and uses a signal processing to separate the approach is based on a double layer configuration of electroactive polymers. In this case, the piezoelectric response is equal in each layer, whereas, the pyroelectric response dominates in the layer exposed to the temperature variations. The pyro- and piezoelectric responses are separated by estimating the diference between the signals of two layers and the signal from one of the layers, correspondingly.