Activity 1.1: aimed at the theoretical substantiation of the proposed solution by modeling the electrostatic field, modeling the parameters of the electrofilting process based on a factorial design as well as modeling the laser sub-assembly. Various softwares have been presented with which the electrostatic field between the spinneret and the collector can be modeled when additional annular electrodes are added. Preliminary experimental results have indicated that the presence of an increased number of electrodes may provide the ability to more precisely control the electric field gradient in the area of ​​interest and create a virtual channel that significantly improves fiber stability. The modeling of the parameters of the electrospinning process was done using a factorial design / centered, compound, rotatable program with two variables and 13 experiments. The analysis performed on the laser configurations specific to the devices used in the electroplating process allows the modeling of the laser subassembly. The laser has proven to be the most efficient heat source in melting organic and inorganic materials, especially those with a high melting temperature.

Rețeaua de discretizare și potențialul electric pentru diferite valori ale unui electrod inelar.

Activity 1.2: aimed at developing components related to electrostatic field control as well as making expressions with PEO (polyethylene oxide) solution with a concentration of 5.4% (average molecular weight 600,000 g / mol) in ethanol and control ring in order to optimize the parameters of process with influence on the diameter of the electrophilated fibers. During this activity, several solutions were studied for the control of the electric field and the properties of the electrophilated fibers. We focused on solutions based on auxiliary electrodes introduced in different regions of the path traversed by the polymer jet. The final design, proposed based on the literature, will be considered from combinations of concentrating electrodes and polymer jet directing electrodes. Also, the concentrator electrodes considered are both in the form of rings distributed along the path traversed by the polymer jet and in the form of parallel plane electrodes arranged on either side of the spinneret. Through the experiments performed combinations of process that results in significant effects on fiber morphology. The process parameters used in this study were the applied voltage, the distance between the needle and the collector and the flow rate. Images of the experiments performed by electrospinning are also presented.

Activity 1.3: aimed at developing components related to the laser subassembly. Possibilities have been sought for electrophilating more viscous solutions to be fluidized by laser heating of the nozzle end or Taylor cone. During the activity, a heating system was designed with two infrared lasers fixed on a dielectric plate with the beams in the same vertical plane as the nozzle of the electrofilament system. The focusing optics are fixed on the lasers and the shift of the focal spot on the Taylor cone is done from the settings of the Thorlab support on which they are fixed. Focus checking is done with an endoscopic camera. Several horizontally spaced horizontal rings with adjustable potentials can be attached to the dielectric support.

Banc optic pentru pozitionare diode laser; b) Dioda laser cu emisie pe lungimea de unda de 532 nm.

Activity 2.1: aimed to model the electrostatic field using realistic electrode sizes and distances. A cylindrical coordinate simulation was carried out for an assembly with a single additional circular electrode (where the Taylor cone and jet were not yet formed) and an assembly with five electrodes and spinneret, where the polarisation was chosen so that the potential along the axis of symmetry varied approximately linearly and more slowly than with a single additional electrode. The results showed a faster variation of the potential in the vicinity of the spinneret (presence of an intense electrostatic field) in the case of a single electrode compared to a slower variation in the case of five additional electrodes. In order to determine the range of variation of the independent variables of the experimental design, preliminary experiments were performed using PEO with a molecular mass of 900,000 g/mol. Three solutions of PEO in mixture with demineralized water and ethanol in different volumes (1:5, 3:2 and 5:1, A:E) with 4% concentration were made. The results include SEM images and distribution diagrams of electrospun fiber diameters. Based on the analysis and statistical processing it was found that there is a better correlation between the diameter of electrospun fibers and the amount of water in solution for smaller distances. A three-dimensional model of the laser sub-assembly was also done. The results include a effects of laser radiation study of the on liquid droplets.

Activity 2.2: aimed to change the electric field in the Taylor cone area by introducing an auxiliary electric field, resulting both in a higher ejection velocity of the electrically charged polymer and a decrease in diameter due to additional stretching. This modulation of the electric field was achieved with electrodes polarized differently from the polymer ejection needle. A classical electrospinning installation was used to which conductive rings of different diameters were attached coupled to another HV2 (0 - 25 KV) high voltage source with positive or negative polarity. The results include optical and SEM images of electrospun fibers from PEO solution on the electrospinning apparatus having attached a conductive ring.

Activity 2.3: aimed to develop the components of the sub-assembly. Therefore, two distinct directions were explored in terms of the lasers used: visible and infrared lasers. The results include a laser assembly containing 3 IR laser diodes symmetrically positioned at an angle of 1200 so that the light pressure exerted on the polymer wire is uniform.

Activity 2.4: aimed at manufacturing a first laboratory model using green lasers or IF lasers allowing a visual focusing of the beam. The aim was to provide evidence in support of the theory of laser beam conditioning of the nanofibre formation process. Two solutions of PEO (600,000 g/mol) were used in a 5:1 and 3:3 ratio of water/ethanol mixture, respectively. The results include the integrated laboratory model, SEM images and distribution diagrams of electrospun fibre diameters. It was found that electrospun fibers in the 5:1 solution are more uniform than electrospun fibers in the 3:3 solution as a function of top-to-collector distance and irradiation time.

Activity 2.5: The TECHMAT project is disseminated through the web page which is kept up to date. The results have also been disseminated in scientific papers and symposium participation as illustrated in the dissemination subsection.

Activity 3.1: aimed at integrating the developed electrospinning components into a laboratory model. The electrostatic field was influenced by introducing two innovative elements: (i) additional electrodes which act as “electrostatic lenses" and change the shape of the electric field acting on the polymer jet (ii) the laser sub-assembly, consisting of 3 laser diodes emitting at 808 nm which were positioned on 2 metal supports and coupled to an electronic system that allows the power of the laser radiation to be adjusted between 0- 330 mW. In addition, a mechanical assembly for positioning the electrospinning pump system has been integrated. This is provided with sub-assemblies for X-Y translation of the pump containing the liquid polymer. The developed technology was tested for validation using polymer solutions with different molecular weights and concentrations.

Activity 3.2: aimed to achieve intelligent control of the components integrated in the laboratory model. A voltage source with a mechanical potentiometer was transformed into an automated source with intelligent control. The control is achieved by a software component installed on a computer, and this is made in such a way as to cause the source to sweep a range of voltages, making the change at a pre-determined time. The implementation is based on a PID (Proportional-Integral-Derivative) control mode of type P. The control of the laser module composed of three laser diodes was carried out both by a PWM signal with an amplitude of 5V and an operating frequency of 60 kHz superimposed with a DC component of 2.6 V representing the opening voltage of the laser diodes. This control of the laser module was performed by means of a microsystem.

Activity 3.3: aimed at validating under laboratory conditions the final laboratory model with the two integrated subsystems, which consisted in characterizing the nanostructures in terms of morphology and chemical structure. The materials chosen to obtain the nanostructures were PEO and PANI solutions at different concentrations. The nanostructures were characterized structurally using EDX analysis, morphologically with respect to powder diameter using SEM images and statistical processing as well as in terms of chemical structure using infrared spectroscopy.

Activity 3.4: the TECHMAT project is disseminated through the web page maintained in English and Romanian at: http://www.citst.ro/projects/techmat. The project have also been disseminated through the publication of scientific papers, the organization of a workshop and a patent application as illustrated in the dissemination subsection.