Needleless electrospinning of PA6 fibers: The effect of solution concentration and electrospinning voltage on fiber diameter

Needleless electrospinning is the process of forming thin material fibers from the open surface of its solution or melt in a strong electrostatic field. Electrospun non-woven materials are used in various applications that require specific fiber diameters and pore size distributions. Fiber diameter depends on the properties of the polymer solution and manufacturing conditions. A needleless electrospinning process using the Nanospider setup was investigated using the commonly used polyamide 6 (PA6) solution in a mixture of acetic and formic acids. Polymer solutions with different polymer concentrations were characterized by viscosity, surface tension and electrical conductivity. An increase in polymer content in the solution resulted in the exponential increase of the solution viscosity, polynomial increase of electrical conductivity and had almost no effect on surface tension. The effect of the polymer concentration in the solution, as well as electrospinning voltage on fiber diameter and diameter distribution, was investigated using scanning electron microscopy images. The average fiber diameter linearly increases with the increased polymer concentration and also demonstrates an increase with increased electrospinning voltage, although less pronounced. Therefore, a change in the PA6 solution concentration should be used for the robust adjustment of fiber diameter, while changes in electrospinning voltage are more appropriate for fine tuning the fiber diameter during the process of needleless electrospinning. © 2020 Journal of Mechanical Engineering.Slovenian Research AgencySlovenian Research Agency - Slovenia [L2-7550, P2-0264]; Fresenius Kabi Deutschland Gmb

Non-Stationary Problems of Theory of Elastic Thin Shells of Revolution

Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Brezigelno elektropredenje vlaken PA6: vpliv koncentracije raztopine in električne napetosti na premer vlaken

Needleless electrospinning is the process of forming thin material fibers from the open surface of its solution or melt in a strong electrostatic field. Electrospun non-woven materials are used in various applications that require specific fiber diameters and pore size distributions. Fiber diameter depends on the properties of the polymer solution and manufacturing conditions. A needleless electrospinning process using the Nanospider setup was investigated using the commonly used polyamide 6 (PA6) solution in a mixture of acetic and formic acids. Polymer solutions with different polymer concentrations were characterized by viscosity, surface tension and electrical conductivity. An increase in polymer content in the solution resulted in the exponential increase of the solution viscosity, polynomial increase of electrical conductivity and had almost no effect on surface tension. The effect of the polymer concentration in the solution, as well as electrospinning voltage on fiber diameter and diameter distribution, was investigated using scanning electron microscopy images. The average fiber diameter linearly increases with the increased polymer concentration and also demonstrates an increase with increased electrospinning voltage, although less pronounced. Therefore, a change in the PA6 solution concentration should be used for the robust adjustment of fiber diameter, while changes in electrospinning voltage are more appropriate for fine tuning the fiber diameter during the process of needleless electrospinning

Three-dimensional surface wave in half-space and edge waves in plates with mixed boundary conditions on the front edge

In the first part of this paper, the propagation of sinusoidal three-dimensional surface waves is investigated for an isotropic elastic half-space with mixed boundary conditions. It is assumed that the boundary is fixed in one of the tangential directions and traction free in the other directions. The exact dispersion relation is derived which shows the existence and uniqueness of the three-dimensional surface wave. The speed of this wave depends on the angle of propagation and lies between the shear wave speed and Rayleigh wave speed. The graphs of this dependence are presented for various values of Poisson ratio. In the second part of this paper, the three-dimensional edge waves in plates with mixed boundary conditions on the edge are investigated. The faces of the plate are assumed to be traction free. Both symmetric and antisymmetric solutions of three-dimensional dynamic equations of elasticity are considered. It is assumed that the edge is fixed in one of the tangential directions and traction free in the normal and the other tangential direction. Asymptotic analysis is performed, which shows that there is an infinite spectrum of higher order edge waves in such plates. The results of numerical calculations based on the modal expansion method are presented to confirm asymptotic analysis. In addition, by the numerical investigation the fundamental edge wave was found in the symmetric case (the edge is fixed in the tangential direction transversally to the faces). The phase velocity of this wave tends to some limit value depending on the Poisson ratio as the wave number increases. In the antisymmetric case the first higher order wave has the same limit value. The dispersion curves are presented for various values of Poisson ratio

Investigation of deflection of the CNT/G composite by molecular dynamics simulation

Graphene and nanomaterials based on graphene have been using in the field of biomedicine as a material for biosensorics. The main components in biosensors are sensors, which must be flexible, scalable, sensitive and reliable. The deformation of the material changes its electrical resistance, therefore the study of the mechanical properties of composites, consisting of nanotubes and graphene, is the urgent task. Currently, active development of methods for the synthesis of composites consisting of graphene and parallel to it oriented nanotubes have been carrying. However, papers on the investigation of the optical and electronic properties of this composition was carried out not enough, and papers on the investigation of the mechanical properties of composites have not been found. The aim of this work is a theoretical investigation of the depending the bending force on the transverse displacement of atom in center of the composite material consisting of graphene and parallel to it (8,0) zigzag nanotubes. The choice of a nanotube (8,0) for research in this work is due to the minimum diameter of the nanotubes that make up the composite of this type. The stability of the composite was estimated by calculating the value of enthalpy and is characterized by a negative value of enthalpy. It was established that enthalpies do not change depending on the distance between the axes, along which the nanotubes belonging to the composites are oriented. Composite material was retained on both edges by support in the absence of a substrate. The search for the equilibrium state of the structure was determined by the molecular mechanics method using the Brenner energy potential within the framework of the molecular dynamics method. Mathematical modeling of the action of the needle of the atomic force microscope was carried out using the single-layer armchair carbon nanotube. The interaction between the armchair nanotube and the composite is carried out by means of the van der Waals forces

Construction of Customized Palatal Orthodontic Devices on Skeletal Anchorage Using Biomechanical Modeling

Orthodontic implants have been developed for the implementation of skeletal anchorage and are effectively used in the design of individual orthodontic devices. However, despite a significant amount of clinical research, the biomechanical aspects of the use of skeletal anchorage have not been adequately studied. The aim of this work was to numerically investigate the stress–strain state of the developed palatal orthodontic device supported by mini-implants. Four possible options for the placement of mini-implants in the bone were analyzed. The effect of a chewing load of 100 N on the bite plane was investigated. The study was carried out using biomechanical modeling based on the finite element method. The installation of the palatal orthodontic device fixed on mini-implants with an individual bite plane positioned on was simulated. The dependence of equivalent stresses and deformation changes on the number and location of the supporting mini-implants of the palatal orthodontic device was investigated. Two materials (titanium alloy and stainless steel) of the palatal orthodontic device were also investigated. The choice of a successful treatment option was based on the developed biomechanical criteria for assessing the surgical treatment success. Application of the criteria made it possible to estimate the stability and strength of fixation of each of the considered mini-implants installation options. As a result, options for the mini-implants optimal placement were identified (the first and the fourth which provide distributed front and side support of the device), as well as the preferred material (titanium alloy) for the manufacture of the palatal orthodontic device

Preoperative planning software in vertebrology: issues and outlook

It is established that relevance of the use of computer systems of the preoperative planning in activities of scientific and medical staff was confirmed 62.3% of the respondents. According to the survey 34.4% of respondents do not use any computer planning systems, and 21.3% of respondents could not name any specific system they are using. Problem of the lack of systematic training of specialized professionals working with specialized software products was revealed – 62.3% of respondents obtain the information about the specialized software products only in the frames of various kinds of conferences and workshops