Gunnar Seide

Bio: Gunnar Seide is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Fiber & Medicine. The author has an hindex of 13, co-authored 33 publications receiving 414 citations.

Novel Carbon Nanotube/Cellulose Composite Fibers As Multifunctional Materials.

Abstract: Electroconductive fibers composed of cellulose and carbon nanotubes (CNTs) were spun using aqueous alkaline/urea solution. The microstructure and physical properties of the resulting fibers were investigated by scanning electron microscopy, Raman microscopy, wide-angle X-ray diffraction, tensile tests, and electrical resistance measurements. We found that these flexible composite fibers have sufficient mechanical properties and good electrical conductivity, with volume resistivities in the range of about 230-1 Ohm cm for 2-8 wt % CNT loading. The multifunctional sensing behavior of these fibers to tensile strain, temperature, environmental humidity, and liquid water was investigated comprehensively. The results show that these novel CNT/cellulose composite fibers have impressive multifunctional sensing abilities and are promising to be used as wearable electronics and for the design of various smart materials.

Spinnability and Characteristics of Polyvinylidene Fluoride (PVDF)-based Bicomponent Fibers with a Carbon Nanotube (CNT) Modified Polypropylene Core for Piezoelectric Applications.

Abstract: This research explains the melt spinning of bicomponent fibers, consisting of a conductive polypropylene (PP) core and a piezoelectric sheath (polyvinylidene fluoride). Previously analyzed piezoelectric capabilities of polyvinylidene fluoride (PVDF) are to be exploited in sensor filaments. The PP compound contains a 10 wt % carbon nanotubes (CNTs) and 2 wt % sodium stearate (NaSt). The sodium stearate is added to lower the viscosity of the melt. The compound constitutes the fiber core that is conductive due to a percolation CNT network. The PVDF sheath's piezoelectric effect is based on the formation of an all-trans conformation β phase, caused by draw-winding of the fibers. The core and sheath materials, as well as the bicomponent fibers, are characterized through different analytical methods. These include wide-angle X-ray diffraction (WAXD) to analyze crucial parameters for the development of a crystalline β phase. The distribution of CNTs in the polymer matrix, which affects the conductivity of the core, was investigated by transmission electron microscopy (TEM). Thermal characterization is carried out by conventional differential scanning calorimetry (DSC). Optical microscopy is used to determine the fibers' diameter regularity (core and sheath). The materials' viscosity is determined by rheometry. Eventually, an LCR tester is used to determine the core's specific resistance.

Structure, properties, and phase transitions of melt‐spun poly(vinylidene fluoride) fibers

Abstract: Three different experimental techniques were used to study structural phase transitions in melt-spun poly(vinylidene fluoride) fibers, which were produced with different process parameters and processed in the draw-winding process at different temperatures and draw ratios. The fibers are examined with the help of wide-angle X-ray diffraction at elevated temperatures, differential scanning calorimetry with stochastic temperature modulation, and dynamic mechanical analysis. An oriented mesophase and deformed crystal structures can be observed in all fibers and assigned to the mechanical stress occurring in the processes. Furthermore, several phase transitions during melting and two mechanical relaxation processes could be detected. The observed transitions affect the crystal geometry, the orientation distribution, anisotropic thermal expansion, and the mechanic response of the fiber samples. The relaxation processes can be related with an increasing amount of crystalline β-phase in fibers drawn at different temperatures. The detailed information about phase transitions and the related temperatures are used to produce fibers with an extended amount of β-phase crystallites, which are responsible for piezoelectric properties of the material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Influence of process parameters on filament distribution and blending quality in commingled yarns used for thermoplastic composites

Abstract: A prospective method for manufacturing thermoplastic composites involves commingling to produce hybrid yarn consisting of two components: reinforcement fibres and thermoplastic matrix. In this work...

Polyethylene-based carbon fibers by the use of sulphonation for stabilization

Abstract: Polyethylene has great potential as an alternative material for carbon fiber production. Polyethylene can be processed in the economic melt spinning process. These precursors are prepared for the subsequent process step of carbonization by using chemical stabilization (sulphonation). The strategy is to adjust these precursor properties by the melt spinning process, thus resulting in a precursor, which can be stabilized sufficiently by sulphonation. The objective is to find the correlation between precursor properties and the results of the sulphonation. In this paper, the chemical stabilization is described and the results of the chemical stabilization are discussed. The novelty in this paper is that the results of the sulphonation are brought in correlation with the precursor properties. It can be shown that the filament diameter and the polymer structure (e.g., the crystallinity) of the precursor have an influence on the sulphonation process.

Nanocellulose, a Versatile Green Platform: From Biosources to Materials and Their Applications

Abstract: With increasing environmental and ecological concerns due to the use of petroleum-based chemicals and products, the synthesis of fine chemicals and functional materials from natural resources is of great public value. Nanocellulose may prove to be one of the most promising green materials of modern times due to its intrinsic properties, renewability, and abundance. In this review, we present nanocellulose-based materials from sourcing, synthesis, and surface modification of nanocellulose, to materials formation and applications. Nanocellulose can be sourced from biomass, plants, or bacteria, relying on fairly simple, scalable, and efficient isolation techniques. Mechanical, chemical, and enzymatic treatments, or a combination of these, can be used to extract nanocellulose from natural sources. The properties of nanocellulose are dependent on the source, the isolation technique, and potential subsequent surface transformations. Nanocellulose surface modification techniques are typically used to introduce e...

Advanced Carbon for Flexible and Wearable Electronics.

Abstract: Flexible and wearable electronics are attracting wide attention due to their potential applications in wearable human health monitoring and care systems. Carbon materials have combined superiorities such as good electrical conductivity, intrinsic and structural flexibility, light weight, high chemical and thermal stability, ease of chemical functionalization, as well as potential mass production, enabling them to be promising candidate materials for flexible and wearable electronics. Consequently, great efforts are devoted to the controlled fabrication of carbon materials with rationally designed structures for applications in next-generation electronics. Herein, the latest advances in the rational design and controlled fabrication of carbon materials toward applications in flexible and wearable electronics are reviewed. Various carbon materials (carbon nanotubes, graphene, natural-biomaterial-derived carbon, etc.) with controlled micro/nanostructures and designed macroscopic morphologies for high-performance flexible electronics are introduced. The fabrication strategies, working mechanism, performance, and applications of carbon-based flexible devices are reviewed and discussed, including strain/pressure sensors, temperature/humidity sensors, electrochemical sensors, flexible conductive electrodes/wires, and flexible power devices. Furthermore, the integration of multiple devices toward multifunctional wearable systems is briefly reviewed. Finally, the existing challenges and future opportunities in this field are summarized.

Smart Textile-Integrated Microelectronic Systems for Wearable Applications

Abstract: The programmable nature of smart textiles makes them an indispensable part of an emerging new technology field. Smart textile-integrated microelectronic systems (STIMES), which combine microelectronics and technology such as artificial intelligence and augmented or virtual reality, have been intensively explored. A vast range of research activities have been reported. Many promising applications in healthcare, the internet of things (IoT), smart city management, robotics, etc., have been demonstrated around the world. A timely overview and comprehensive review of progress of this field in the last five years are provided. Several main aspects are covered: functional materials, major fabrication processes of smart textile components, functional devices, system architectures and heterogeneous integration, wearable applications in human and nonhuman-related areas, and the safety and security of STIMES. The major types of textile-integrated nonconventional functional devices are discussed in detail: sensors, actuators, displays, antennas, energy harvesters and their hybrids, batteries and supercapacitors, circuit boards, and memory devices.

Continuously prepared highly conductive and stretchable SWNT/MWNT synergistically composited electrospun thermoplastic polyurethane yarns for wearable sensing

Abstract: Highly conductive and stretchable yarns have attracted increasing attention due to their potential applications in wearable electronics. The integration of conductive yarns with large stretching capability renders the composite yarns with new intriguing functions, such as monitoring human body motion and health. However, simultaneously endowing the yarns with high conductivity and stretchability using an easily scalable approach is still a challenge. Here, highly conductive and stretchable yarns based on electrospun thermoplastic polyurethane (TPU) fiber yarns successively decorated with multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) were prepared by a combined electrospinning, ultrasonication adsorbing, and bobbin winder technique. The improved thermal stability of the SWNT/MWNT/TPU yarn (SMTY) indicated strong interfacial interactions between the CNTs and electrospun TPU fibers. The synergism between the successively decorated SWNTs and MWNTs significantly enhanced the conductivity of the TPU yarns (up to 13 S cm−1). The as-fabricated yarns can be easily integrated into strain sensors and exhibit high stretchability with large workable strain range (100%) and good cyclic stability (2000 cycles). Moreover, such yarn can be attached to the human body or knitted into textiles to monitor joint motion, showing promising potential for wearable electronics, such as wearable strain sensors.

Melt electrospinning today: An opportune time for an emerging polymer process

Abstract: Over the last decade, melt electrospinning has emerged as an alternative polymerprocessing technology to alleviate concerns associated with solvents in traditional elec-trospinning. This has resulted in the fabrication of ultrafine fibers from an increasing rangeof synthetic polymers and composite systems, to materials including ceramics, drivingnew applications in technical areas such as textiles, filtration, environment and energyas well as biomedicine. In this article, we review the significant advancements in theoret-ical modeling of the underlying physical principles, coupled with experimental validationusing a variety of technical devices and designs that allows well-controlled fiber formationusing optimized material and operating parameters. Innovative device designs are indi-cating avenues towards higher throughput of randomly collected melt electrospun fibersfor the production of commodity nonwoven substrates, similar to solution electrospinningand many other industrial fiber-forming processes. However, we identify a recent shift inperception towards melt electrospinning in the literature, where the adaptation of additivemanufacturing approaches to device designs enables precise fiber placement with filamentresolutions not yet demonstrated by more established melt-extrusion based direct writingtechnologies. New, highly ordered arrangements of ultrafine fibers with distinctive surfacetopology, encapsulating and sensing properties are opening new fields of application inareas such as drug delivery, biosensors and regenerative medicine as high performancematerials. The development of these materials is reviewed with an emphasis on an area ofcurrent research, where melt electrospun scaffolds are contributing to promising treatmentstrategies to regenerate or replace human tissue and for the new field of in vitro diseasemodels as well as humanized mice models.