Jiri Chvojka

Technical University of Liberec | TUL · Department of Nonwovens and Nanofibrous Materials

Recent years have observed a significant increase in the use of degradable materials in medicine due to their minimal impact on the patient and broad range of applicability. The biodegradable polymer Polydioxanone (PDO) provides a good example of the use of such one polymer that can represent the aforementioned medical materials in the field of med...

This study presents the advantages of combining three-dimensional biodegradable scaffolds with the injection bioprinting of hydrogels. This combination takes advantage of the synergic effect of the properties of the various components, namely the very favorable mechanical and structural properties of fiber scaffolds fabricated from polycaprolactone...

Advanced solid phase extraction (SPE) fibrous sorbents including polyethylene, polypropylene poly (hydroxybutyrate), and polyamide 6 nanofibers, polycaprolactone microfibers/nanofibers, polycaprolactone microfibers/polyvinylidene difluoride nanofibers, and poly (hydroxybutyrate) microfibers/polypropylene microfibers composites, as well as commercia...

Polymeric nano- and microfibers were tested as potential sorbents for the extraction of five neonicotinoids from natural waters. Nanofibrous mats were prepared from polycaprolactone, polyvinylidene fluoride, polystyrene, polyamide 6, polyacrylonitrile, and polyimide, as well as microfibers of polyethylene, a polycaprolactone nano- and microfiber co...

Undesirable tissue adhesions remain one of the most common and dreaded postoperative complications. Biocompatible nanofibrous mats with antiadhesive surfaces represent a promising barrier method for preventing the formation of adhesions. The material developed in this work was inspired by the natural superhydrophobic lotus leaf nanostructure, which...

The study addresses changes in the surface energy of polycaprolactone nanofibre layers due to the different spinning electrodes. The value of surface energy and the associated wettability is an important aspect of polymeric biomaterials that influence the quality of interaction with biological material. The study involved the production of nanofibr...

A Matlab code for inverse characterization of fibrous materials.

The paper provides a description of the potential for the direct current- and alternating current-driven electrospinning of various linear aliphatic polyamides (PA). Sets with increasing concentrations of selected PAs were dissolved in a mixture of formic acid and dichloromethane at a weight ratio of 1:1 and spun using a bar electrode applying dire...

Structural parameters are critical for the final properties of fibrous materials. Three common parameters (i.e., porosity, thickness and average fiber diameter) of each fibrous sample are simultaneously determined based on their air penetration behavior. The Ergun-type equation and the Kozeny-type equation, with the help of the optimization method,...

Nanofibrous materials provide a large extraction capacity owing to their unique structure. Although most research conducted to date has employed nanofibers produced via the direct current (DC) electrospinning method, the resulting nanofibers have disadvantages that limit their practical use. We focused on the investigation of the electrospinning me...

Application of the poly-ɛ-caprolactone composite sorbent consisting of the micro- and nanometer fibers for the on-line extraction of non-steroidal anti-inflammatory drugs from a biological matrix has been introduced. A 100 μL human serum sample spiked with ketoprofen, naproxen, sodium diclofenac, and indomethacin was directly injected in the extrac...

The study addresses the modification of the wetting of fibrous layers of polycaprolactone via alternating current spinning. The production of the fibre layers considered in the study was initiated using a function generator. The shifting of the offset to the limits of the transmitted amplitude resulted in the production of wettable fibrous layers w...

The study addressed the production of a hydrogel nanofiber skin cover and included the fabrication of hydrogel nanofibers from a blend of polyvinyl alcohol and alginate. The resulting fibrous layer was then crosslinked with glutaraldehyde, and, after 4 h of crosslinking, although the gelling component, i.e., the alginate, crosslinked, the polyvinyl...

Microplastic fibers (MF) are released from synthetic textiles during washing and end up in the wastewater. Similarly, silver nanoparticles (AgNP), incorporated in textiles as antimicrobial agents, are released in washing machines, also reaching the wastewater treatment plants. Therefore, both MF and AgNP co-exist in the environment and enter the so...

The use of needles in surgical practice goes beyond the general suturing of tissue and stitching. With the ever-increasing role of robotic surgery, it is essential not to underestimate the importance of haptic interaction in the training of needle insertion techniques. Needle interaction with soft tissues is influenced by several factors including...

On-line solid phase extraction coupled with liquid chromatography enables high sample throughput, preconcentration of analytes, efficient clean-up, and separation in a single step. Our comparison study focused on the selection of an optimal SPE sorbent for on-line extraction of ochratoxins A and B allowing fast and sensitive control of mycotoxin co...

The electrospinning process that produces fine nanofibrous materials have a major disadvantage in the area of productivity. However, alternating current (AC) electrospinning might help to solve the problem via the modification of high voltage signal. The aforementioned productivity aspect can be observed via a camera system that focuses on the jet...

The experiment involved the study of differences between the surface energy of various fibrous layers. The experimental approach was based on changes in several parameters such as the concentration of the polymeric solution, differences in the molecular weight, the use of different solvents and the method applied for the preparation of the samples....

Effect of physicochemical properties including dissociation constant (pKa) and partition coefficient (log P) of the compounds on their extraction efficiency in sample preparation using fibrous polymer sorbents has been demonstrated. Poly-ε-caprolactone as meltblown/electrospun composite fibers, and polypropylene, polyethylene, poly(3-hydroxybutyrat...

This research involved the production of polycaprolactone fiber layers via the alternating current electrospinning method. To construct the micro/nanofiber scaffold, mixtures of two molecular weight solutions, Mn 45 000 and Mn 80 000, were spun in differing proportions in a solvent system containing acetic acid, formic acid, and acetone in a ratio...

Microplastic fibers (MF) are released from synthetic textiles during washing and end up in the wastewater. Similarly, silver nanoparticles (AgNP), incorporated in textiles as antimicrobial agents, are released in washing machines, also reaching the wastewater treatment plants. Therefore, both MF and AgNP co-exist in the environment, and enter the s...

Anastomotic leakage is a dreadful complication in colorectal surgery. It has a negative impact on postoperative mortality, long term life quality and oncological results. Nanofibrous polycaprolactone materials have shown pro-healing properties in various applications before. Our team developed several versions of these for healing support of colore...

The experiment addressed the alternating current (AC) electrospinning of polyamide 6 (PA 6) solutions composed of organic acids, which are commonly employed in direct current (DC) electrospinning systems. Initial testing revealed that it is not possible to AC spin ordinary PA 6 solutions so as to provide a product that can be used in subsequent mat...

Glaucoma disease therapy frequently involves the application of a glaucoma implant. This approach is effective in terms of reducing the intraocular pressure via the filtering of intraocular fluid from the anterior chamber into the drainage pathways. The basic properties of such implants comprise of long-term stability and the filtering of fluids wi...

Hydrogels are suitable for osteochondral defect regeneration as they mimic the viscoelastic environment of cartilage. However, their biomechanical properties are not sufficient to withstand high mechanical forces. Therefore, we have prepared electrospun poly-ε-caprolactone-chitosan (PCL-chit) and poly(ethylene oxide)-chitosan (PEO-chit) nanofibers,...

Effective process, including a cartridge packing polypropylene fiber sorbent modified by following on-line polydopamine coating, for on-line solid phase extraction in 2D UHPLC system has been developed. Hydrophobic surface of mechanically stable polypropylene fibers was hydrophilized using an automated and reproducible in situ coating process to en...

Poly-ε-caprolactone nanofibrous polymer has been used as an alternative to restricted access media for extraction of proteins-containing biological samples and direct transfer in the chromatographic system. Three commercial cartridges differing in length and i.d. have been manually packed with the composite material prepared from poly-ε-caprolacton...

This study deals with a new combination of alternating current (ac) electrospinning and bubble electrospinning. Research devoted to the combination of these two methods for the preparation of nanofibrous and microfibrous mats has been carried out. The design, construction, and description of bubble electrospinning are described in this article. The...

A magnetic stirring device allowing semi-dispersive solid phase extraction of eight bisphenols (A, AF, AP, C, BP, G, M, and Z) from river waters using polymer nano- and microfibers followed by HPLC with spectrophotometric detection has been developed and applied. About 50 mg of fibers were placed in a round, cage-like housing consisting of two iden...

Novel double-layered materials with different properties of each side were prepared via needleless electrospinning and compared in terms of morphology, wettability, adhesion and proliferation of mouse fibroblasts. The materials consist of hydrophilic poly(vinyl alcohol) fibers with low (PVA_L) or high (PVA_H) degree of hydrolysis, and hydrophobic p...

Polycaprolactone composite nanofibers coated with a polydopamine layer are introduced as a new type of absorption material for on-line solid phase extraction (SPE) in chromatographic system. A hybrid technology combining the electrospinning and melt blowing was used for the preparation of 3D-structured microfiber/nanofibrous polycaprolactone compos...

Gelatin is a biocompatible polymer that is widely used in tissue engineering. Nowadays, nanofibrous scaffolds are produced mainly by the direct voltage spinning method which, however, does not currently have the same production capacity as the newly developed alternating current (AC) spinning technology. Using AC spinning, nanofibrous layers made f...

Nanotechnologies allow the production of yarns containing nanofibres for use in composites, membranes and biomedical materials. Composite yarns with a conventional thread core for mechanical strength and a nanofibrous envelope for functionality, e.g. biological, catalytic, have many advantages. Until now, the production of such yarns has been techn...

Nylon 6 nanofibers were tested for their ability to serve as a sorbent for solid phase extraction (SPE). The regular nanostructure providing a great sorption area and amidic functionality should lead to the assumption that nylon 6 nanofibers could be used as a novel sorbent with great potential for sample pre-treatment. However, due to the substant...

The influence of electrospun nanofibres made from polyamide 6 (PA6) on the gas bubble size distribution by volume in fibre/thermoset-matrix systems cured without a vacuum was comprehensively studied via various methods. An analysis of the microstructural, thermal and dielectric properties proved that the unique structure of PA6 electrospun nanofibr...

Three different approaches has been used to obtain nano/micro fibers and their diversity and extraction properties were examined. The effect of their structure on stability in an ultra-high-performance liquid chromatography (UHPLC) system during on-line SPE procedure was monitored. Five types of various nano/micro fiber polymers were used as sorben...

Fibrous scaffolds are desired in tissue engineering applications for their ability to mimic extracellular matrix. In this study we compared fibrous scaffolds prepared from polycaprolactone using three different fabrication methods, electrospinning, electro-blowing and melt-blown combined with electrospinning. Scaffolds differed in morphology, fiber...

A novel application of nanofiber polymers in the wide area of a sample preparation techniques known as solid phase extraction has been studied. We demonstrated application of nanofibers as sorbents for use in a system including on-line extraction coupled with column-switching high performance liquid chromatography. Four types of nanofibers includin...

Additive manufacturing, also called 3D printing, is an effective method for preparing scaffolds with defined structure and porosity. The disadvantage of the technique is the excessive smoothness of the printed fibers, which does not support cell adhesion. In the present study, a 3D printed scaffold was combined with electrospun classic or structure...

Polyamide 6 nanofiber polymers were used as modern sorbents for on-line solid phase extraction (SPE) coupled with liquid chromatography. The on-line SPE system was tested for the determination of bisphenol A in river water samples. Polyamide nanofibers were prepared using needleless electrospinning, inserted into a mini-column cartridge (5 × 4.6 mm...

Abstrakt: Kompozitní polymerní nanomateriály obsahující nano a mikro částice sloučenin těžkých kovů mohou efektivně zeslabovat gamma a rtg záření. Úspěšně byla odzkoušena příprava a inkorporace nanočástic oxidů a wolframanů těžkých kovů do polymerních nano a mikrovláken pomocí bezjehlového elektrostatického zvlákňování. Měření zeslabení ionizujícíh...

Herein, we describe a simple spinneret setup for needleless coaxial electrospinning that exceeds the limited production capacity of current approaches. The proposed weir spinneret enables coaxial electrospinning from free liquid surface. This approach leads to the formation of coaxial nanofibers with higher and uniform shell/core ratio, which resul...

This article deals with the continual incorporation of particles by the ultrasonic dispersion in situ into a nanofibrous matrix produced by the electrospinning process. The new technology is based on the use of the needleless electrospinning method in combination with the ultrasound-enhanced dispersion of sub-micro or micro particles, which are dep...

This study describes the production, testing and characterization of biodegradable scaffolds for bone tissue, which consist of the exact ratio of meltblown microfibers and nanofibers produced through the electrostatic field. All fibrous materials were produced from polycaprolactone. Three kinds of materials were prepared in the experiment with the...

Nonwoven nanofibers as a new material for possible improving properties of electrical insulation are considered in this paper. Polyamide nanofibers are used for modification of commonly used three-component mica-based high voltage electrical insulating material (epoxy resin, glass cloth and mica). Influence of different volume ratio and density of...

Keywords: mesenchymal stem cells, cell penetration, fibrous scaffold, Forcespinning®, electrospinning

Paper deals with evaluation of chosen properties of newly developed modification of insulation material, composite based on glass-mica-epoxy material. The main reason for this analysis was to optimize the specific design of material. For improving some of mechanical and electrical properties the currently used material was modified by incorporation...

Nanofibrous materials are essential components for a range of applications, particularly in the fields of medicine and material engineering. These include protective materials, sensors, cosmetics, hygiene, filtration and energy storage. The most widely used and researched technology in these fields is electrospinning. This method of producing fiber...

The contribution describes preparation of the so-called "green composites" in which polycaprolactone serves as matrix and the reinforcement consists of nano-and micro-dust of selected exotic woods, i.e., teak, garapa and massaranduba. The composites were processed into nanofibers (by electrostatic spinning technology Nanospider) and their thermal s...

This article aims with the continual incorporation of particles by ultrasonic dispergation in situ into nanofibrous matrix produced by electrospinning process. The technology is based on usage of needleless electrospinning method in combination with ultrasound enhanced sputtering of sub-micro or micro particles in between nanofibers depositing onto...

Introduction to combination of 3D printing and electrospinning technology with more open nanofibrous structure based on special patterning. Focusing on knee cartilage tissue engineering.

Analysis of textile materials often includes measurement of structural anisotropy or directional orientation of textile object systems. To that purpose, the real-world objects are replaced by their images, which are analyzed, and the results of this analysis are used for decisions about the product(s). Study of the image data allows one to understa...

This work introduces an electrospinning method for laboratory-scale production of nanofibrous materials from polyvinylalcohol (PVA) nanofibres. A procedure for the subsequent production of twisted yarns from the aligned nanofibrous strand is introduced as well. Both needle and needleless electrospinning variants were employed. Mechanical properties...

Cell infiltration is a critical parameter for the successful development of 3D matrices for tissue engineering. Application of electrospun nanofibers in tissue engineering has recently attracted much attention. Notwithstanding several of their advantages, small pore size and small thickness of the electrospun layer limit their application for devel...

The paper describes preparation of nano fiber composites made of polyvinyl butyrate (PVB) and wood dusts. The used wood dusts of nano-and micro-dimensions were obtained by grinding of exotic woods, garapa and teak. Electrostatic spinning technology Nanospider was used to prepare nanoparticles from some mixtures (Polymer PVB (10 wt%) + ethanol; Poly...

Alternating current electrospinning method for preparation of nanofibrous materials On the basis of the article: L. Vysloužilova, P. Pokorny, P. Mikes, M. Bilek, R. Deliu, E. Amler, M. Buzgo, K. G. Kornev, D. Lukas: Characteristic hydrodynamic time of electrospinning (to be published) we can successfully use the alternating current for electrospinn...

Objectives: We prepared 3D poly (ε-caprolactone) (PCL) nanofibre scaffolds and tested their use for seeding, proliferation, differentiation and migration of mesenchymal stem cell (MSCs). Materials and methods: 3D nanofibres were prepared using a special collector for common electrospinning; simultaneously, a 2D PCL nanofibre layer was prepared u...

The history of electrospinning is briefly introduced at the beginning of the article. The fundaments of the process are then analysed physically to be translated into a successful technology. Self-organisation of fluid in electrospinning is perceived as a consequence of various instabilities, based on electrohydrodynamics and, thus, highlighted as...