Highlights
The sensors displayed high sensitivity (8962.7), fast response time (60 ms), outstanding stability and durability (> 10,000 cycles) and widely workable stretching range (0–160%).
A ...theoretical approach was used to analyze mechanical property, and a model based on tunneling theory was modified to describe the relative change of resistance.
Two equations were proposed and offered an effective but simple approach to analyze the change of number of conductive paths and distance of adjacent conductive particles.
In recently years, high-performance wearable strain sensors have attracted great attention in academic and industrial. Herein, a conductive polymer composite of electrospun thermoplastic polyurethane (TPU) fibrous film matrix-embedded carbon black (CB) particles with adjustable scaffold network was fabricated for high-sensitive strain sensor. This work indicated the influence of stereoscopic scaffold network structure built under various rotating speeds of collection device in electrospinning process on the electrical response of TPU/CB strain sensor. This structure makes the sensor exhibit combined characters of high sensitivity under stretching strain (gauge factor of 8962.7 at 155% strain), fast response time (60 ms), outstanding stability and durability (> 10,000 cycles) and a widely workable stretching range (0–160%). This high-performance, wearable, flexible strain sensor has a broad vision of application such as intelligent terminals, electrical skins, voice measurement and human motion monitoring. Moreover, a theoretical approach was used to analyze mechanical property and a model based on tunneling theory was modified to describe the relative change of resistance upon the applied strain. Meanwhile, two equations based from this model were first proposed and offered an effective but simple approach to analyze the change of number of conductive paths and distance of adjacent conductive particles.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Highlights
Ni-MXene/MF foam is synthesized via an electrostatic assembly and dip-coating process.
The “micro-capacitor” structure of Ni/MXene and the 3D porous structure of MF endow the foam ...excellent impedance matching and wave absorption performance.
The excellent heat insulation, infrared stealth, and flame-retardant performances are achieved.
The development of multifunctional and efficient electromagnetic wave absorbing materials is a challenging research hotspot. Here, the magnetized Ni flower/MXene hybrids are successfully assembled on the surface of melamine foam (MF) through electrostatic self-assembly and dip-coating adsorption process, realizing the integration of microwave absorption, infrared stealth, and flame retardant. Remarkably, the Ni/MXene-MF achieves a minimum reflection loss (RL
min
) of − 62.7 dB with a corresponding effective absorption bandwidth (EAB) of 6.24 GHz at 2 mm and an EAB of 6.88 GHz at 1.8 mm. Strong electromagnetic wave absorption is attributed to the three-dimensional magnetic/conductive networks, which provided excellent impedance matching, dielectric loss, magnetic loss, interface polarization, and multiple attenuations. In addition, the Ni/MXene-MF endows low density, excellent heat insulation, infrared stealth, and flame-retardant functions. This work provided a new development strategy for the design of multifunctional and efficient electromagnetic wave absorbing materials.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Superhydrophobic polymer foams are a good candidate for oil absorption because of their lightweight and tunable porosity and have promising applications in the long-term application of oil–water ...separation. However, developing a facile and green strategy to fabricate pure polymer foams with superhydrophobicity and eco-friendliness for large-scale oil–water separation remains a challenge. Here, a facile template-free water-assisted thermally impacted phase separation approach combined with skin peeling for the fabrication of superhydrophobic and eco-friendly pure poly(lactic acid) (PLA) foam for oil–water separation is proposed for the first time. The PLA foam with special micro- and nanostructures possesses a water contact angle of 151°, and the maximum saturated adsorption capacity is 31.5 g/g. More importantly, during the continuous oil–water pumping experiment, the foam has an efficiency of 98% and could maintain for more than 15 h, showing a promising prospect for cleaning large-scale oil pollution.
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IJS, KILJ, NUK, PNG, UL, UM
A flexible, biocompatible, nitrile butadiene rubber (NBR)-based strain sensor with high stretchability, good sensitivity, and excellent repeatability is presented for the first time. Carbon black ...(CB) particles were embedded into an NBR matrix via a dissolving-coating technique, and the obtained NBR/CB composite was coated with polydopamine (PDA) to preserve the CB layer. The mechanical properties of the NBR films were found to be significantly improved with the addition of CB and PDA, and the produced composite films were noncytotoxic and highly biocompatible. Strain-sensing tests showed that the uncoated CB/NBR films possess a high sensing range (strain of ∼550%) and good sensitivity (gauge factor of 52.2), whereas the PDA/NBR/CB films show a somewhat reduced sensing range (strain of ∼180%) but significantly improved sensitivity (gauge factor of 346). The hysteresis curves obtained from cyclic strain-sensing tests demonstrate the prominent robustness of the sensor material. Three novel equations were developed to accurately describe the uniaxial and cyclic strain-sensing behavior observed for the investigated strain sensors. Gloves and knee/elbow covers were produced from the films, revealing that the signals generated by different finger, elbow, and knee movements are easily distinguishable, thus confirming that the PDA/NBR/CB composite films can be used in a wide range of wearable strain sensor applications.
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IJS, KILJ, NUK, PNG, UL, UM
We present a simple but accurate algorithm to calculate the flow and shear rate profile of shear thinning fluids, as typically used in biofabrication applications, with an arbitrary viscosity-shear ...rate relationship in a cylindrical nozzle. By interpolating the viscosity with a set of power-law functions, we obtain a mathematically exact piecewise solution to the incompressible Navier-Stokes equation. The algorithm is validated with known solutions for a simplified Carreau-Yasuda fluid, full numerical simulations for a realistic chitosan hydrogel as well as experimental velocity profiles of alginate and chitosan solutions in a microfluidic channel. We implement the algorithm in an easy-to-use Python tool, included as Supplementary Material, to calculate the velocity and shear rate profile during the printing process, depending on the shear thinning behavior of the bioink and printing parameters such as pressure and nozzle size. We confirm that the shear stress varies in an exactly linear fashion, starting from zero at the nozzle center to the maximum shear stress at the wall, independent of the shear thinning properties of the bioink. Finally, we demonstrate how our method can be inverted to obtain rheological bioink parameters in-situ directly before or even during printing from experimentally measured flow rate versus pressure data.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A novel physical model is proposed relating fiber diameter and its distribution to various process parameters. Power laws are derived taking into consideration, applied voltage, viscosity, charge ...density, surface tension, and jet splitting. It is recommended how researchers should analyze their data to separate various effects. In particular, it is possible to predict not only the fiber diameter but also its distribution.
A novel physical model is proposed relating fiber diameter and its distribution to various process parameters in electrospinning. The key approach is the separation of electrospinning into a flow‐dominated and a drying‐dominated regime, where jet splitting occurs at the transition from the one to the other regime.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To allow an efficient protection against viruses like the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), it is important to avoid their spreading by using filtering face pieces ...(FFP), which are categorized by different standards according to their filtration efficiency. In this study, we subjected six brands of FFP2 standard masks to three different conditions and subsequently analysed them for their filtration performance to evaluate potentials for reusability. The conditions comprised changes of temperature and air humidity, an exposure to isopropyl alcohol (IPA) and an autoclave sterilization. While four of six masks consisted of electrostatically treated melt blown non-wovens, two masks were fabricated using a nanofibrous multilayer system. Due to the absence of prior electrostatic treatment, the nano-masks did not show a significant change in filtration efficiency when discharged by IPA, unlike the melt blown nonwoven masks showing a significant decrease of filtration efficiency down to around 50% at a particle size of 0.3 μm. However, most melt blown masks maintained a sufficient filtration efficiency after all other treatments with even better results than the nanofibrous masks. This was particularly the case for the capacity to filter smallest particles/droplets with a size of around 0.1 μm, which is below the range of typical filtering standards and important for the retention of virally contaminated nano-aerosols or unattached viruses. After temperature/humidity variation and autoclave sterilization, melt blown masks were able to retain a filtration efficiency up to over 90% at 0.1 μm contrary to nano-masks showing a decrease down to around 70%. Based on their better filtration performance, lower price and potential reusability, we conclude that electret melt blown masks are the preferable type of FFP2 masks.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A model taking into consideration viscosity and evaporation is suggested to describe the spreading kinetics of struts in bioprinting. Scenarios resulting by complete and partial wetting are discussed ...and described. Applicable fit functions and predictive scaling laws are given, relating viscosity of bioinks, process parameters such as print speed and throughput to the strut width. The approach is primarily based on 1D spreading.
A model taking into consideration viscosity and evaporation is suggested to describe the 1D spreading kinetics of struts in bioprinting. Applicable fit functions and predictive scaling laws are given, relating viscosity of bioinks, process parameters such as print speed and throughput to the strut width. The approach is primarily based on 1D spreading, indicated by the figure.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
For decades, crude oil spills and oil wastewater have become the most problematic environmental pollution and damage to public health. Therefore, it is considerable to develop superhydrophobic ...polymer foam for separating oil from water with high selectivity and sorption capacity. Here, a new type of environmentally friendly pure polypropylene (PP) foam with superhydrophobicity is first time proposed with a particular coexistence of microspheres and microporous structure fabricated via an advanced solvent‐evaporation method. The PP foam exhibits exceptional superhydrophobic with a water contact angle of 151° and the maximum saturated adsorption capacity of 26 g g−1. After more than 15 h of cyclic continuous oil–water pumping experiment, it still maintains a high oil absorption efficiency of 98%, providing the basis for practical commercial applications. More importantly, the variation of hydrophobic properties is described by Flory–Huggins polymer solution theory and Huggins interaction parameters, and the optimal solution ratio range is predicted which provides a relevant theoretical basis for actual industrial production.
This work provides a superhydrophobicity polypropylene (PP) foam with a particular coexistence of microspheres and microporous structure fabricated via an advanced solvent‐evaporation method. Flory–Huggins polymer solution theory and Huggins interaction parameters are used to describe the variation of hydrophobic properties, and the optimal solution ratio range is predicted successfully.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Anisotropic ternary composites comprising poly(methy-methacrylate) (PMMA), carbon black (CB), and carbon nanotubes (CNTs) were extruded using a capillary rheometer and the electrical conductivities ...of the composites were measured and presented in a detailed contour plot covering a large range of filler fractions (up to 30 vol% CNTs, 20 vol% CB). A recent generic conductivity model for ternary composites was successfully validated using the conductivity measurements. When analyzing the conductivity measurements using four traditional definitions of 'synergy' between two conductive fillers, no clear synergetic effect was observed between CB and CNT. Also, when all the conductivity data for ternary CNT/CB composites from the existing literature was carefully gathered and analyzed, the number of confirmed occurrences of strong and convincing CNT/CB synergies was surprisingly low. Finally, a novel definition of synergy based on the physical aspect, in particular, its maximum, the 'synergasm', was defined in order to obtain a more precise instrument for revealing regions of potential synergy.
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