Andrea Ehrmann

Hochschule Bielefeld University of Applied Sciences and Arts · Fachbereich Ingenieurwissenschaften und Mathematik

The terms “nano” and “nanomaterials” have come to be buzz words describing tremendous advances in research and development during the last decades [...]

Nanofiber mats with a high surface-to-volume ratio can be prepared by electrospin-ning. The Porosity is sometimes reported to be tunable by blending different materials, e.g., water-soluble poly(ethylene oxide) (PEO) with not water-soluble poly(acrylonitrile) (PAN). Here, nanofiber mats were electrospun from different PAN:PEO ratios, using a wire-b...

Citation: Malczyk, M.; Blachowicz, T.; Ehrmann, A. Coupled System of Dual-Axis Clinostat and Helmholtz Cage for Simulated Microgravity Experiments. Appl. Sci. 2024, 14, 9517. Abstract: The experimental investigation of plant growth under space conditions is a necessary prerequisite of long-term space missions. Besides experiments in space, many stu...

--- Sustainable and Green Materials --- Free download link: https://www.tandfonline.com/eprint/4JVZ7RVQAM7PX256CEGF/full?target=10.1080/29965292.2024.2404716 --- Needleless electrospinning enables producing large-area nanofiber mats. As a previous study showed, however, the homogeneity of such large nanofibrous membranes regarding thickness and mas...

Nanofibers can be produced by various techniques, such as a broad range of electrospinning techniques to produce nanofiber mats from different polymers or polymer blends, often filled with metallic or semiconducting nanoparticles or by different nanotechnological bottom-up or top-down methods. They are important parts of a wide variety of energy ap...

While hydrogen is regularly discussed as a possible option for storing regenerative energies, its low minimum ignition energy and broad range of explosive concentrations pose safety challenges regarding hydrogen storage, and there are also challenges related to hydrogen production and transport and at the point of use. A risk assessment of the whol...

The experimental investigation of plant growth under space conditions is a necessary prerequisite of long-term space missions. Besides experiments in space, many studies are performed under simulated microgravity, using a clinostat. However, the Earth magnetic field is usually not taken into account in such investigations. Here, a self-designed and...

Composites of textile fabrics and 3D-printed layers have been investigated thoroughly during the last decade. Usually, material extrusion such as the fused deposition modeling (FDM) technique is used to build such composites, revealing challenges in preparing form-locking connections between both materials due to the highly viscous polymer melt, wh...

Possibilities to perform 3D printing directly on textile fabrics have been investigated intensively during the last decade. Usually, fused deposition modeling (FDM) printing with often inexpensive 3D printers is applied in these experiments. Several studies revealed the influence of textile fabrics, FDM polymers and printing parameters, indicating...

The idea of 3D printing on textile fabrics was first mentioned around 10 years ago and has been investigated in detail since. Originally aimed at opening new design possibilities, combining 3D printing with textile substrates has shifted towards a new method to prepare composites with defined mechanical and other physical properties. The main probl...

The third SmartTecStyle conference 2024 will be held online from December 11-12, 2024, organized by ITES (Institute for Technical Energy Systems) at Bielefeld University of Applied Sciences and Arts, Germany. International speakers from academia and industry will present recent results of research and development. The registration is free of charg...

Tissue engineering is based on combining cells with suitable scaffolds and growth factors. Recently, bone tissue engineering has been especially investigated deeply due to a large number of bone-related diseases. One approach to improve scaffolds is based on using piezoelectric materials as a way to influence the growing bone tissue by mechanical s...

When nanomaterials meet textiles, innovative new materials meet successful conventional fiber-based materials. This Special Issue will present comprehensive research outlining progress in the field of nanomaterials and textiles-the application of nanomaterials to improve the performance of textiles or initiate even new functional properties. This i...

The exchange bias (EB) is a unidirectional magnetic anisotropy that is found in structures containing exchange-coupled ferromagnetic/antiferromagnetic interfaces. The EB usually manifests as a horizontal shift of the hysteresis after cooling the system through the Néel temperature of the antiferromagnet in the presence of an external magnetic field...

Special Issue Information Dear Colleagues, The environmental issues caused by various industries need to be regulated or overcome. Due to the waste generated during production or the product life cycle, the fashion industry has been focused on sustainability in recent years. Product recycling presents a good alternative for the fashion industry. I...

Microalgae can be used for various applications, such as food, cosmetics or biofuel production. Usually they are cultivated in bioreactors, which makes harvesting and processing strenuous. Growing them adhering on a surface, i.e. as a biofilm, can reduce these problems. On the other hand, introducing substrates into bioreactors may cause additional...

The air permeability of a textile fabric belongs to the parameters which characterize its potential applications as garments, filters, airbags, etc. Calculating the air permeability is complicated due to its dependence on many other fabric parameters, such as porosity, thickness, weaving parameters and others, which is why the air permeability is u...

Textiles are often used to protect people from cold environments. While most garments are designed for temperatures not far below 0 °C, very cold regions on the earth near the poles or on mountains necessitate special clothing. The same is true for homeless people who have few possibilities to warm up or workers in cooling chambers and other cold e...

Magnetic micro and nano sensors can be used in a broad variety of applications, e.g., for navigation, automotives, smartphones and also for health monitoring. Based on physical effects such as the well-known magnetic induction, the Hall effect, tunnel magnetoresistance and giant magne-toresistance, they can be used to measure positions, flow, press...

Algae-based biopolymers can be used in diverse energy-related applications, such as separators and polymer electrolytes in batteries and fuel cells and also as microalgal biofuel, which is regarded as a highly renewable energy source. For these purposes, different physical, thermochemical, and biochemical properties are necessary, which are discuss...

Magnetic nanofibers were prepared by electrospinning polymer/metal solutions of poly(acrylonitrile) (PAN) with magnetite (Fe3O4) nanoparticles. At a mass ratio of PAN:magnetite of 2:1, the total solid content in the dimethyl sulfoxide (DMSO) solution was varied between 15 wt.% and 25 wt.%, which represents the limits of the spinnable range. The res...

Statistical summary 3T3 Swiss albino mouse cells are often used in biotechnological applications. These cells can grow adherently on suitable surfaces. In our study, they were grown on different titanium substrates, comparing commercially available titanium sheets of grade 1 and grade 2, respectively, with Ti64 which was 3D printed with different p...

Electrospinning can be used to prepare nanofiber mats from diverse polymers, polymer blends and embedded nanoparticles. Especially nanofiber mats from biopolymers promote cell growth for wound healing, tissue engineering or other biotechnological applications. These materials, however, are often not stable at high temperatures, which makes steriliz...

The exchange bias (EB) is a unidirectional anisotropy that occurs, e.g., upon field-cooling ferromagnet/antiferromagnet systems. In many material systems, the EB field is reduced from one hysteresis loop to the next measurement. This so-called training effect (TE) has been investigated in experiments and by means of theoretical efforts by many rese...

Planning long-term space missions, investigating growth of edible plants and fungi is of utmost importance. To investigate the behavior of plants or mushrooms in microgravity, the situation is usually simulated by using a clinostat on which the objects under investigation are slowly rotated around an axis perpendicular to the direction of gravity,...

Textiles are used by humans for many purposes, from clothing to technical applications such as geotextiles, agrotextiles, or medical textiles. However, in addition to their importance, textiles are also responsible for various types of environmental pollution along the entire textile chain, from production, transport and trade to daily use to their...

Textiles are used by humans for many purposes, from clothing to technical applications such as geotextiles, agrotextiles, or medical textiles. However, in addition to their importance, textiles are also responsible for various types of environmental pollution along the entire textile chain, from production, transport and trade to daily use to their...

Exchange bias (EB) is a unidirectional anisotropy caused by interface coupling between a ferromagnet and an antiferromagnet. It causes a preferential direction of magnetization in the ferromagnet, which manifests as a shift of the hysteresis loop along the magnetic field axis. Here, we demonstrate a large EB of over 1000 Oe at 20 K in a twinned Co(...

Microelectromechanical systems (MEMS) combine electrical and mechanical functions and are nowadays broadly applied in many technology fields, often as sensors or actors [...]

A first limited approach for the automated production of crocheted fabrics was introduced in 2019. However, the knowledge on crocheted fabrics is very scarce and only few technical applications are presented in the literature. To provide a basis for possible future technical applications, the general tensile properties of crocheted fabrics are expl...

Electrospinning enables producing nanofibers or nanofiber mats from diverse polymers, polymer blends or polymers with embedded nanoparticles. Depending on the technology used, even core–shell structures or Janus fibers can be created. Such nanofibers can be applied in a broad range of fields, from biotechnology and biomedicine to filters and batter...

Nanofibers are currently among the most researched nanomaterials in materials science. Various high-resolution microscopy techniques are used for morphological investigations, with the diameter as primary characteristic. Since methodological factors influencing the diameter distribution are usually ignored, numerical values can hardly be compared a...

Electrospun nanofiber mats have a high specific surface area and very small pores which can be tailored by the spinning process. They are thus highly suitable as filters for small particles and molecules, such as organic dyes. On the other hand, they are usually very thin and thus have low mechanical properties. As a potential reinforcement, myceli...

Electrocardiogram (ECG) signals are often measured for medical purposes and in sports. While common Ag/AgCl glued gel electrodes enable good electrode skin contact, even during movements, they are not comfortable and can irritate the skin during long-term measurements. A possible alternative is textile electrodes, which have been investigated exten...

SAŽETAK: Obućarski proizvodi kao predmeti koji se koriste u našem životu imaju dugu istoriju vezanu za njihovu proizvodnju. Oni su prošli kroz razne promene praćene tehnološkim napretkom koji se dešavao tokom godina. Uprkos ovim promenama, u poređenju sa drugim industrijama, industrija obuće i dalje ostaje proizvodnja zasnovana na ljudskom radu. Ne...

Stab-resistant clothing has been used for centuries by soldiers. Today, it is also used by policemen and other people in dangerous jobs or situations. While chain-mail or metal inserts in protective vests are heavy and uncomfortable, lightweight and bendable alternatives are currently the subject of investigation. Special textile fabrics offer a ce...

Nanofiber mats can be electrospun by different techniques, usually subdivided into needle-based and needleless. The latter allow for producing large-area nanofiber mats, e.g., with a width of 50 cm and lengths of several meters, if electrospinning proceeds for several hours, depending on the required thickness. Even spinning smaller samples, howeve...

The increasing development and application of wireless devices and systems that radiate electromagnetic waves makes electromagnetic interference (EMI) shielding more and more important in everyday life. In practice, rigid EMI shields are the most commonly used ones. However, for humans or in automotive and aviation applications, flexible, drapable...

Possibilities of direct 3D printing on textile fabrics have been investigated with increasing intensity during the last decade, leading to composites which can combine the positive properties of both parts, i.e., the fast production and lateral strength of textile fabrics with the flexural strength and point-wise definable properties of 3D printed...

Exchange bias (EB) is a unidirectional anisotropy occurring in exchange-coupled ferro-magnetic/antiferromagnetic systems, such as thin films, core-shell particles, or nanostructures. In addition to a horizontal shift of the hysteresis loop, defining the exchange bias, asymmetric loops and even vertical shifts can often be found. While the effect is...

Combining 3D printing, especially fused deposition modelling (FDM) as a material extrusion technique, with textile fabrics can lead to full-layer composites as well as partly reinforced textiles with different mechanical properties at different positions. While the combination of both techniques enables the production of new kinds of objects differ...

Air permeability is used to characterize textile fabrics with respect to their usability as a garment or filter, airbag or parachute. It depends on the fabric's porosity, air voids in the fabric, yarn specifications, thickness and other parameters, making it hard to calculate it reliably from other parameters. At the same time, measuring air permea...

Electrospun nanofiber mats are nowadays often used for biotechnological and biomedical applications, such as wound healing or tissue engineering. While most studies concentrate on their chemical and biochemical properties, the physical properties are often measured without long explanations regarding the chosen methods. Here, we give an overview of...

Electrospun nanofiber mats are usually applied in fields where their high specific surface area and small pore sizes are important, such as biotechnology or filtration. Optically, they are mostly white due to scattering from the irregularly distributed, thin nanofibers. Nevertheless, their optical properties can be modified and become highly import...

Atomic force microscopy (AFM) belongs to the high-resolution surface morphology investigation methods. Since it can, in many cases, be applied in air, samples can more easily be inspected than by a scanning electron microscope (SEM). In addition, several special modes exist which enable examination of the mechanical and other physical parameters of...

Electrospun nanofiber mats were coated with a thin magnetic layer, the magnetization in which is shown by fields of small arrows. Measuring this magnetization and its reversal under a varied external magnetic field is performed by a magneto-optical method, as shown by the impinging and reflected green laser beams. The paper reports for the first ti...

3D printing on textile fabrics has been investigated intensively during the last years. A critical factor is the adhesion between the printed polymer and the textile fabric, limiting the potential areas of application. Especially safety-related applications, e.g. stab-resistant textile/polymer composites, need to show reliable adhesion between both...

Low-cost sensors and single circuit boards such as Arduino and Raspberry Pi have increased the possibility of measuring biosignals by smart textiles with embedded electronics. One of the main problems with such e-textiles is their washability. While batteries are usually removed before washing, single-board computers and microcontrollers, as well a...

Shielding of instruments and humans from electromagnetic interference (EMI) has become increasingly important during the last decades due to more and more machines and devices radiating electromagnetic waves. While several applications can use rigid shields, more flexibility is enabled by developing bendable, drapable, ideally even stretchable EMI...

Additive manufacturing, also named 3D printing, can be used to create objects from diverse polymers, metals, and other materials in diverse shapes and dimensions. If special physical or chemical properties are necessitated, using corresponding feedstock enables varying such properties in a broad range. Besides choosing a suitable base material, oft...

Stab-resistant garments have been used for centuries, utilizing metals, paper, or polymeric structures, often inspired by natural structures such as scales. Nowadays, stab-resistant vests or vest inserts are used by police and security personnel, but also by bus drivers, ambulance officers, and other people who are empirically often attacked on dut...

--- Engineering Proceedings --- Three-dimensional printing belongs to the emerging technologies of our time. An important aspect regarding the potential applications of 3D-printed objects is their dimensional accuracy. Especially in the case of the most often used fused deposition modeling (FDM) technique, dimensional differences between the digita...

- - - published in Applied Research (Wiley) - - - The hysteresis loops of magnetic samples can be measured by magneto-optical Kerr effect (MOKE), while magnetic force microscopy (MFM) is used to depict domain walls or spatially resolved magnetization orientation in magnetic nanostructures or thin films. Both methods are commonly applied on thin fil...

Magnetic nanofibers belong to the geometries which are intensively investigated in simulations and experiments due to their unique magnetic properties, varying in their lengths, cross-sections, and bending radii. Besides basic research of different magnetization reversal processes and magnetization dynamics in bent nanofibers, these structures are...

Three-dimensional printing enables building objects shaped with a large degree of freedom. Additional functionalities can be included by modifying the printing material, e.g., by embedding nanoparticles in the molten polymer feedstock, the resin, or the solution used for printing, respectively. Such composite materials may be stronger or more flexi...

This new Special Issue of Materials entitled “3D/4D Printing Application for Shape Memory Materials” aims to publish original and review papers dealing with basic and applied research on this emerging technology [...]

Highlights Magnetic single droplet and four-droplet spheres systems were examined with respect to their energy landscapes For thin oxide layers, the numbers of extrema are similar to spheres without coating For an oxide coated system, the maximum packing density is increased by 12%, as compared to the non-coated system Improved magnetic memory syst...

Magnetic nanoparticles can be embedded in electrospun nanofibers and other polymeric matrices to prepare magnetic composites with defined magnetic and mechanical properties. Metal-oxide nanoparticles, such as magnetite or nickel-ferrite, are of special interest since they do not need a coating to avoid oxidation. Like other nanoparticles, these met...

While fused deposition modeling (FDM) and other relatively inexpensive 3D printing methods are nowadays used in many applications, the possible areas of using FDM-printed objects are still limited due to mechanical and thermal constraints. Applications for space, e.g., for microsatellites, are restricted by the usually insufficient heat resistance...

--- Applied Research --- Graphical Abstract Phase change memory (PCM) belongs to the non-volatile solid-state memory techniques. Data are stored by setting each cell to a low-resistance (crystalline) or a high-resistance (amorphous) state. While fast switching and multi-level data storage are advantageous, writing currents and data retention still...

- - - published in Technologies - - - Electrospinning is often investigated for biotechnological applications, such as tissue engineering and cell growth in general. In many cases, three-dimensional scaffolds would be advantageous to prepare tissues in a desired shape. Some studies thus investigated 3D-printed scaffolds decorated with electrospun...

With a steadily increasing number of machines and devices producing electromagnetic radiation, especially, sensitive instruments as well as humans need to be shielded from electromagnetic interference (EMI). Since ideal shielding materials should be lightweight, flexible, drap-able, thin and inexpensive, textile fabrics belong to the often-investig...

--- Textiles 2022, 2(2), 265-274 --- The electrocardiogram (ECG) is one of the most commonly measured biosignals. In particular, textile electrodes allow for the measuring of long-term ECG without skin irritation or other discomforts for the patient. Such textile electrodes, however, usually suffer from insufficient or unreliable skin contact. Thus...

As the electron transport layer of dye-sensitized solar cells (DSSCs), the photoanode is an important component that affects photoelectric conversion efficiency (PCE). The commonly used material titanium dioxide (TiO2) is difficult to prepare as nanostructures with large specific surface area, which affects dye loading and electrolyte diffusion. He...

Magnetic nanoparticles can be used for medical and other purposes, but can also be integrated in polymeric or other nonmagnetic matrices of diverse shapes, for example, thin-films or fibers. In the latter case, it may be important how the magnetic nanoparticles are distributed in the matrix, a topic which is often not taken into account when such c...

Keratin is one of the most important protein materials and can act as a sustainable biopolymer for manifold applications. This paper reports on a sustainable extraction method for keratin from wool fiber materials. The use of this extracted keratin for polymer film preparation and preparation of nano-composite materials by electrospinning is invest...

Atomic force microscopy (AFM) is one of the microscopic techniques with the highest lateral resolution. It can usually be applied in air or even in liquids, enabling the investigation of a broader range of samples than scanning electron microscopy (SEM), which is mostly performed in vacuum. Since it works by following the sample surface based on th...

Long-term stability belongs to the main problems of dye-sensitized solar cells (DSSCs), impeding their practical application. Especially the usually fluid electrolyte tends to evaporation, thus drying the cells if they are not perfectly sealed. While gelling the electrolyte with different polymers often reduces the efficiency, using a glycerol-base...

Stop marks are one of the most frequently occurring errors in warp-knitted fabrics. They become visible in a fabric each time a warp-knitting machine stops and restarts. Nevertheless, investigations of such stop marks are rarely found in scientific literature. Here, we report on time-dependent investigations of stop marks in warp-knitted fabrics. M...

COMMUNICATIONS IN DEVELOPMENT AND ASSEMBLING OF TEXTILE PRODUCTS - - - - - Microalgae can be used for diverse applications in research and industry. Several microalgae grow adhering to surfaces that are usually two-dimensional. A third dimension could increase the amount of microalgae adhering to a given area and can be offered by textile fabrics....

To measure biosignals constantly, using textile-integrated or even textile-based electrodes and miniaturized electronics, is ideal to provide maximum comfort for patients or athletes during monitoring. While in former times, this was usually solved by integrating specialized electronics into garments, either connected to a handheld computer or incl...

3D printing is nowadays used for many applications far beyond pure rapid prototyping. As tools to prepare custom-made objects which may be highly complex, different 3D printing techniques have emerged into areas of application where the mechanical, thermal, optical and other properties have to meet high requirements. Amongst them, applications for...

Carbon nanofibers are used for a broad range of applications, from nano-composites to energy storage devices. They are typically produced from electrospun poly(acrylonitrile) nanofibers by thermal stabilization and carbonization. The nanofiber mats are usually placed freely movable in an oven, which leads to relaxation of internal stress within the...

Electrospinning can be used to produce nanofiber mats containing diverse nanoparticles for various purposes. Magnetic nanoparticles, such as magnetite (Fe3O4), can be introduced to produce magnetic nanofiber mats, e.g., for hyperthermia applications, but also for basic research of diluted magnetic systems. As the number of nanoparticles increases,...

The emerging technology of 3D printing can not only be used for rapid prototyping, but will also play an important role in space exploration. Additive manufactured parts can be used in diverse space applications, such as magnetic shields, heat pipes, thrusters, etc. Three-dimensional printed parts offer reduced mass, high possible complexity, and f...

- - - COMMUNICATIONS IN DEVELOPMENT AND ASSEMBLING OF TEXTILE PRODUCTS - - - While shape memory alloys (SMAs) and shape memory polymers (SMPs) can already be found in diverse applications, shape memory textiles are less often used. Nevertheless, they are regularly investigated. Typical ways to produce shape memory textiles (SMTs) are introducing sh...

Asymmetric hysteresis loops can be found in exchange-bias systems in which a ferromagnet is exchange-coupled with an antiferromagnet. In purely ferromagnetic samples, such effects can occur due to undetected minor loops or thermal effects. While the exchange bias is long established in hard-disk read/write heads and diverse spintronics applications...

Magnetic nanofibers can be used for data transport and storage, especially related to the emerging field of neuromorphic computing. Domain walls in bent nanofibers can nucleate, e.g., due to rotating local magnetic fields. Their propagation through bent nanofibers, however, depends on the bending direction in correlation to the rotational orientati...

A growing population needs an expansion of agriculture to ensure a reliable supply of nutritious food. As a variable concept, vertical farming, becoming increasingly popular, can allow plant growth for local food production in the vertical sense on, e.g. facades in addition to the classical layered structure in buildings. As substrates, textile fab...

Combining textile fabrics with 3D printing has been investigated intensively during the last years. Mostly, research concentrated on the adhesion between both partners of the composite or on the new freedom of design, enabled by combining these techniques. Here, we present examinations of the influence of elastic 3D printed patterns on the elongati...

Magnetic force microscopy (MFM) belongs to the methods that enable spatially resolved magnetization measurements on common thin-film samples or magnetic nanostructures. The lateral resolution can be much higher than in Kerr microscopy, another spatially resolved magnetization imaging technique, but since MFM commonly necessitates positioning a cant...