Introduction of the revolutionary drop-on-demand (DoD) inkjet printing technique for microelectronics allows the use of flexible substrate, organic and inorganic materials, and low-cost volume fabrication. However, inks of different functional materials for varieties of applications are still under development. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), a potential candidate for mechanical and acoustic sensors, actuators, energy harvesting and nonvolatile memory applications, is a copolymer that exhibits piezo-, pyro-and ferro-electric properties. During this work, inkjetprinted films using high molecular weight PVDF-TrFE were developed and characterized to investigate their morphology and crystallinity. Modified waveform and very low jetting frequency have been used to accommodate relaxation time of the polymeric ink during jetting. Crystallographic studies confirm the presence of a β-phase, which exhibits spontaneous polarization per unit cell.
The properties of mineral suspensions do not evolve linearly with particle mass fraction. For some critical concentrations these properties are abruptly modified due to a change of relative interparticle interaction force prevalence. Using kaolin and glass beads as model materials, physicochemical stability and rheological measurement have been carried out in order to propose a global and discriminant parameter enabling the nature of particle interactions to be identified. Different types of suspensions were studied namely: diluted suspensions, concentrated suspensions and solid suspensions. Physico-chemical stability, studied by optical dispersion analysis (Turbiscan MA 2000) enables the clarification rate to be measured and to propose a new global parameter, the "phase separation index". In addition, rheological analysis was realized by the means of viscous flow measurement. Behaviour of solid suspensions is satisfactorily described by Oswald de Waele power law in the whole range of concentration studied which tends to demonstrate that the interactions remains the same in this range.
Unitary carbon nanoparticles with a well-defined shape and a range of diameters between 50 nm and 300 nm have been synthetized from the pyrolysis of resorcinol formaldehyde copolymer. This divided solid has a molecular organization similar to carbon black with a more regular shape and a higher diameter. Thus, carbon nanospheres appear to be adapted to the development of accurate sensors. Inkjet-printable dispersion was prepared with this material and a mixture of N-methyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone. This ink is the proof of concept that it is possible to form continuous layers on polyimide flexible substrate with resistive properties which exhibit temperature sensitivity.
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