Vladimir Velebny

Transversal electrostatic strength of patterned collector affecting alignment of electrospun nanofibers

Conventional electrospinning produces randomly ordered nanofibers, however many potential applications require precisely defined morphology and anisotropic properties of nanofibrous materials. In this work, a collector consisting of two segments has been used to prepare uniaxially ordered nanofibers. Optimized collector design comes from both analytical calculations of electrostatic strength in the vicinity of the electrodes and from experimental verification by polyvinyl alcohol nanofibers fabrication. The transversal electric strength is a key factor in achieving very well aligned nanofibers. The results presented here help provide a better understanding of the electrically induced alignment mechanism.

An Electrostatic Spinning Technology with Improved Functionality for the Manufacture of Nanomaterials from Solutions

The last decade has seen an extensive development of the field of nanomaterials which are currently being used in their first commercial applications. This rapid development is necessarily connected with certain technological demands. This paper describes a technology for the manufacture of nanomaterials from solutions by electrostatic spinning or spraying. Although this method has been well known since the last century, there are still only a few high-quality devices that can be used for the research of new nanomaterials. The main reason for this is that the process of nanomaterials manufacturing is influenced by numerous processing parameters which need to be properly regulated, and furthermore all device components must be resistant to interference from high voltage. The technological requirements are thus stringent. Moreover, such a device must be multifunctional, compact and affordable. This paper describes the technical aspects of a unique laboratory device, i.e., device modules and central control, measured processing parameters, and their effect on the produced materials. The developed laboratory device meets the most demanding criteria for a nanotechnological laboratory device and helps facilitate and speed up the research and development of new nanomaterials produced in high electrostatic field.

Raman Spectroscopy Based Method for the Evaluation of Compositional Consistency of Nanofibrous Layers

Electrospinning is currently a very popular method used across a number of industries. Electrospinning enables the production of nanofibrous layers of various structures and compositions. The production of a multi-component nanofibrous layer may result in an uneven distribution of the individual components throughout the layer. Confocal Raman spectroscopy combined with statistical methods allows these layers to be analysed by determining their chemical composition and thus provides feedback for the spinning process. This paper presents a method which combines Raman spectroscopy analysis and its subsequent evaluation with singular value decomposition (SVD). Automated measurement of Raman spectra makes it possible to gather extensive spectral data from a particular area selected on a sample; the spectra are measured from a specific volume and not from individual fibres. Samples require no preparation for the analysis and the non-destructive nature of Raman spectroscopy ensures their reusability. When spectra of the individual component materials are included for reference, the subsequent SVD analysis of the spectral data makes it possible to determine the chemical composition of the measured areas, thus providing the content percentages of the individual components, which can be displayed either in the form of a scattered plot or a Raman map.

Non‐invasive diagnostic system and its opto‐mechanical probe for combining confocal Raman spectroscopy and optical coherence tomography

Non-invasive optical diagnostic methods allow important information about studied systems to be obtained in a non-destructive way. Complete diagnosis requires information about the chemical composition as well as the morphological structure of a sample. We report on the development of an opto-mechanical probe that combines Raman spectroscopy (RS) and optical coherence tomography (OCT), two methods that provide all the crucial information needed for a non-invasive diagnosis. The aim of this paper is to introduce the technical design, construction and optimization of a dual opto-mechanical probe combining two in-house developed devices for confocal RS and OCT. The unique benefit of the probe is a gradual acquisition of OCT and RS data, which allows to use the acquired OCT images to pinpoint locations of interest for RS measurements. The parameters and the correct functioning of the probe were verified by RS scanning of various samples (silicon wafer and ex vivo tissue) based on their OCT images - lateral as well as depth scanning was performed. Both the OCT and RS systems were developed, optimized and tested with the ultimate aim of verifying the functionality of the probe. Picture: Schematic illustration and visualization of the developed RS-OCT probe.