Polyurethane Substrate Research Articles

Application of 3D printing technology for green synthesis of Fe2O3 using ABS/TPU/chlorella skeletons for methyl orange removal.

Photocatalysis is widely acknowledged as an efficient and environmentally friendly method for treating dye-contaminated wastewater. However, the utilization of powdered photocatalysts presents significant challenges, including issues related to recyclability and the potential for secondary pollution. Herein, a novel technique based on 3D printing for the synthesizing of iron oxide (Fe2O3) involving chlorella was presented. Initially, chlorella powders were immobilized within acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) substrate plastics using melt extrusion technology. Subsequently, these composite materials were transformed into ABS/TPU/chlorella skeletons (ATCh40), through fused deposition molding (FDM) technology. The integration of Fe2O3 onto the ATCh40 (ATCh40-Fe2O3) skeletons was accomplished by subjecting them to controlled heating in an oil bath. A comprehensive characterization of the synthesized materials confirms the successful growth of Fe2O3 on the surface of 3D skeletons. This strategy effectively addresses the immobilization challenges associated with powdered photocatalysts. In photocatalytic degradation experiments targeting methyl orange (MO), the ATCh40-Fe2O3 skeletons exhibited a remarkable MO removal rate of 91% within 240 min. Under conditions where the pH of MO solution was maintained at 3, and the ATCh40-Fe2O3 skeletons were subjected to a heat treatment in a 150 °C blast drying oven for 2 hours, the degradation rate of MO remained substantial, achieving 90% removal after 6 cycles. In contrast, when the same synthetic procedure was applied to ABS/TPU (AT) skeletons, the resulting product was identified as α-FeOOH. The MO removal rate by the AT-α-FeOOH skeletons was considerably lower, reaching only 49% after 240 min. This research provided a practical approach for the construction of photocatalytic devices through the use of 3D printing technology.

Stretchable photosensors with InN nanowires operating at a wavelength of 1.3 μm.

Stretchable photosensors, which operate in the wavelength window of 1.3 μm, were fabricated with InN nanowires (NWs) and graphene to serve as a light-absorbing medium and carrier channel, respectively. Specifically, the stretchable photosensors were fabricated by transferring InN NWs embedded in graphene layers onto polyurethane substrates pre-stretched at the strain levels of 10, 20, 30, 40, 50, and 60%. An InN-NW photosensor fabricated at the pre-strain level of 50% and stretched at the strain of 50% produces a photocurrent of 0.144 mA, which corresponds to 76.2% of that (0.189 mA) measured in the released state. The photocurrent and photoresponsivity of the photosensor measured after 1000 cyclic-stretching tests are comparable to those measured before stretching. The performance of the stretchable photosensors was largely unaffected by parameters such as the relative humidity and duration of operation (up to 30 days), indicating that the devices operate very stably.

Autonomous Self-Healable, Ag Nanowire-Polymer Composite Flexible Electrode for Underwater Sensors

The development of self-healing electrodes tailored for underwater wearable sensors is paramount to broaden their applications in aquatic environments. However, autonomous self-healing of flexible electrodes, which encompasses both mechanical and electrical performance, remains a formidable challenge. Here, we present the development of a self-healing flexible electrode (AgNW–FPU), incorporating Ag nanowires (AgNWs) and a fluorine functionalized polyurethane (FPU) substrate. The FPU polymer was designed by systematically adjusting the dynamic bonds and chain mobility to achieve fast self-healing speed and efficiency. Higher dynamic bond content and good chain mobility led to the highest self-healing speed, both in air and underwater. The introduction of a fluorinated side chain enhanced hydrophobicity, further improving underwater self-healing. The AgNW–FPU electrode demonstrated fast underwater self-healing, driven by capillary bridges and enhanced contact between fractured nanowires. The AgNW-FPU electrodes were employed in a capacitive pressure sensor, showcasing its potential for underwater sensing applications.

Largely Improving the Output Performance of Stretchable Triboelectric Nanogenerators via Thermo-Compressive Technology.

Stretchable triboelectric nanogenerators (TENGs) are widely applied in wearable and implantable electronics, smart medical devices, and soft robots. However, it is still a challenge to produce stretchable TENGs with both exceptional elasticity and output performance, which limits their application scope. In this work, high-performance stretchable TENGs are developed through a thermo-compression(TC) fabrication process. In particular, a poly(vinylidene fluoride) film is compactly bound to the elastic thermoplastic polyurethane substrate, which inherits excellent stretchability with a strain of up to 815%. Furthermore, owing to the large surface area, tight contact, and effective vertical transport of tribo-induced charges between the coupled fibrous tribo-layer and soft substrate, the TC composite film-based TENGs exhibit a greater output (2-4 times) than unlaminated film-based TENGs. Additionally, the broad universality of this method is proven using various tribo- and substrate materials. The proposed technology provides a novel and effective approach to conjointly boost the output and stretchability of TENGs, showing encouraging application prospects in self-powered wearable and flexible electronics.

Modular vertically-integrated skin patch for biosignal measurements

This paper presents research on a novel and modular vertically-integrated wearable skin patch for biosignal measurements. The flexible patch consists of a disposable skin-contacting electrode layer and a durable electronics part. The durable part is designed to include a printed re-chargeable battery, a solar cell, electronics for the measurement of electrocardiogram (ECG), galvanic skin response, acceleration, temperature and humidity and a covering visually appealing jewellery-like functional crystal layer for decoration and user interaction. The patch can store measurement data and transmit it to a mobile phone via a bluetooth low-energy radio. Integration process is developed for the vertical stacking that limits the skin-patch area to achieve a desirable form factor. The sensing electrodes are printed on stretchable thermoformable polyurethane substrate with vias through the substrate to couple skin-contacting electrodes to the upper functional layers. A removable adhesive layer between the disposable and durable parts is developed to enable separating the two parts after wear and then to couple the durable part with a new disposable part. The patch is tested on body for ECG sensing.

Sensitivity enhancement through geometry modification of 3D printed conductive PLA-based strain sensors

PurposeThe purpose of this study is to increasing the gauge factor, reducing the hysteresis error and improving the stability over cyclic deformations of a conductive polylactic acid (CPLA)-based 3D-printed strain sensor by modifying the sensing element geometry.Design/methodology/approachFive different configurations, namely, linear, serpentine, square, triangular and trapezoidal, of CPLA sensing elements are printed on the thermoplastic polyurethane substrate material individually. The resistance change ratio of the printed sensors, when loaded to a predefined percentage of the maximum strain values over multiple cycles, is recorded. Finally, the thickness of substrate and CPLA and the included angle of the triangular strain sensor are evaluated for their influences on the sensitivity.FindingsThe triangular configuration yields the least hysteresis error with high accuracy over repeated loading conditions, because of its uniform stress distribution, whereas the conventional linear configuration produces the maximum sensitivity with low accuracy. The thickness of the substrate and sensing element has more influence over the included angle, in enhancing the sensitivity of the triangular configuration. The sensitivity of the triangular configuration exceeds the linear configuration when printed at ideal sensor dimensional values.Research limitations/implicationsThe 3D printing parameters are kept constant for all the configurations; rather it can be varied for improving the performance of the sensor. Furthermore, the influences of stretching rate and nozzle temperature of the sensing material are not considered in this work.Originality/valueThe sensitivity and accuracy of CPLA-based strain sensor are evaluated for modification in its geometry, and the performance metrics are enhanced using the regression modelling.

Fabrication of conformal antenna by 3D printing of recycled thermoplastic polyurethane on fabric

In this study, a recycled thermoplastic polyurethane (TPU) substrate was 3D printed on cotton-lycra fabric (CLF) using the fused filament fabrication (FFF) method to create a microstrip patch antenna (MPA) following the sustainable development goal (SDG) (with a special focus on the industry, innovation, and infrastructure). Some recent studies have highlighted that the FFF process may be employed for required alterations in infill structure, and density, to provide accurate dimensional features for MPA (for wearable applications). It has been reported that for wearable applications, the conformal design of MPA is one of the major requirements. But hitherto little has been reported on the process capability of FFF for the conformability of MPA. This study highlights the process capability of FFF by considering the strain and strain hardening coefficient (SHC) of the MPA substrate, leading to a conformal antenna, which may be further used in wearable applications (at different bending positions without disturbing the antenna performance). Further, the MPA was designed and simulated at a resonating frequency (Rf) of 4.9 GHz using high-frequency structural simulation (HFSS) software, which shows the bending of MPA at a radius of 30 mm, 40 mm, 50 mm, and 60 mm resulted in Rf of 4.81 GHz, 4.81 GHz, 4.81 GHz, and 4.82 GHz respectively which lies in the range and shows the conformability of the designed MPA at different bending positions.

The effect of lignin-based polyols on the properties of polyurethane coatings

The aim of this research was to replace petroleum-based polyols with polyols made from lignin and nano-lignin in the production of polyurethane coatings. Lignin and nano-lignin were first reacted with either diethylenetriamine or ethylenediamine. Subsequently, they were modified with propylene carbonate. The lignin- and nano-lignin-derived polyols replaced the conventional acrylic polyol in the production of polyurethane coatings. The results of Fourier transform infrared analysis showed that urethane, isothiocyanate and strong C–N bonds were formed in nano-lignin-based polyurethanes. Moreover, the surface adhesion test of the lignin-based polyurethane coating showed that with increasing lignin content, the adhesion strength of the coating decreased. Mixing lignin nanoparticles into the polyurethane substrate caused the adhesion strength to rise from 1.67 to 4.52 MPa. An increase in the amino nano-lignin content of oil-based polyol of up to 7% improved the curing of the coating and increased the scratch resistance to more than 5 kg. The results showed that lignin from a mechanical pulping process has a direct effect on reducing the smoothness and the glossiness of polyurethane coatings.

Highly Stretchable, Highly Sensitive, and Antibacterial Electrospun Nanofiber Strain Sensors with Low Detection Limit and Stable CNT/MXene/CNT Sandwich Conductive Layers for Human Motion Detection

With the rise of the concept of “Internet of Everything”, the development of wearable sensing devices is growing rapidly. Among them, crack-based strain sensors have received much attention due to their high sensitivity. However, the application of crack-based strain sensors has been limited by the relatively narrow sensing range. Here, a sandwich structure of a CNT/MXene/CNT sensing layer was realized on the flexible thermoplastic polyurethane substrate prepared by electrospinning, followed by layer-by-layer vacuum filtration. The two stable carbon nanotube (CNT) layers broaden the sensing range, and the strain sensor exhibits excellent sensing range (390%) and stability (3000 tensile tests). The strain sensor also shows excellent sensitivity (GF = 2159.5), low detection limit (0.05%), and fast response time (∼50 ms). The sensor is responsive to different movements when being applied to human motion detection, and the smart wearable device based on the strain sensor shows excellent performance in gesture language recognition. In addition, the antibacterial property of the conductive material inherently facilitates the wider application of the strain sensors.

Highly Stretchable and Flexible Electrospinning‐Based Biofuel Cell for Implantable Electronic

AbstractWith the emerging demand of implantable microelectronics, it essentially requires the fully integrated and reliable power supplies. The study reports a stretchable and flexible electrospinning‐based glucose/O2 biofuel cell with glucose oxidase bioanode, Pt/C cathode and thermoplastic polyurethane substrate, which is capable for adapting to the various stresses and strains caused by individual movement. The rigid benzene rings and elastic chain segments of thermoplastic polyurethane ensure its superior tensile property. Furthermore, the stable covalent connections between the activated carbon nanotubes (CNTs‐COOH) and glucose oxidase inside 3D thermoplastic polyurethane network are established by amide reaction to ensure the rapid direct electron transfer of bioanode and stable power output of device in flexible environments. The biofuel cell exhibits an open circuit voltage of 0.575 V, and high‐power density of 57 µW cm−2 in 5 mM glucose. Moreover, the power‐generation properties of implantable biofuel cell keep steady, and its power density exhibits limited fluctuations on the dorsum of rat when bending, stretching, and twisting in 28 days. There is no obvious local inflammation or systemic abnormalities in rats. It satisfies the impressive biocompatible requirement, demonstrating the promising potential of electrospinning‐based biofuel cell as a robust self‐sustained power source for implantable electronics.

Novel Graphene Transfer Method to Silicone and its Sensing Application on Porous PDMS

In this work, we demonstrate a simple and sensitive parallel-plate capacitive pressure sensor fabricated on biocompatible, weather durable, elastic composite silicone and polyurethane substrate with porous polydimethylsiloxane (PDMS) dielectric made through a mixture of water as spacers. This sensor comprised a graphene electrode, which was developed through novel chemical vapor deposition on copper with hot press transfer process. The sensitivity of the sensor exhibits a positive correlation with the dielectric porosity. In addition, this device exhibits fast response time and wide dynamic window for applications. The highest sensitivity of 3.01 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> at 20% water concentration in PDMS for the dynamic range of 0–40 kPa was achieved with a response time of 0.25 s and detection resolution of 0.4 pF.

Intrinsically Stretchable Organic Solar Cells without Cracks under 40% Strain

AbstractIntrinsically stretchable organic solar cells (IS‐OSCs) have been recently spotlighted for their omnidirectional stretchability, seamless integrability to any surface, and facile fabrication. Due to these attributes, IS‐OSCs are ideal off‐grid power sources, especially for wearable electronics in real‐life. However, under human body elongation as high as ≈40%, cracks in IS‐OSCs are considered inevitable, and the origin of the mechanical failure is rarely identified. Herein, the crack‐initiation and the propagation mechanism are first clarified. Based on this, a crack‐free substrate/transparent electrode platform for stretchable electronics is also suggested. A double‐locking scheme, which reinforces the physical/chemical adsorption within the most mechanically fragile layer, a poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and also with thermoplastic polyurethane substrate, is introduced. As a result, the crack‐onset strain of double‐locked IS‐OSCs surpasses 40%, while that of pristine ones is less than 20%. The IS‐OSCs with the double‐locked system exhibits an efficient power conversion efficiency of 10.2%, and the absence of cracks allows the IS‐OSCs to maintain 79.7% of the initial PCE at 40% strain.

Strontium-Cobaltite-Based Perovskite (SrCoO3) for Solar-Driven Interfacial Evaporation Systems for Clean Water Generation.

Solar-driven evaporation technology is often used in areas with limited access to clean water, as it provides a low-cost and sustainable method of water purification. Avoiding salt accumulation is still a substantial challenge for continuous desalination. Here, an efficient solar-driven water harvester that consists of strontium-cobaltite-based perovskite (SrCoO3) anchored on nickel foam (SrCoO3@NF) is reported. Synced waterways and thermal insulation are provided by a superhydrophilic polyurethane substrate combined with a photothermal layer. The structural photothermal properties of SrCoO3 perovskite have been extensively investigated through state-of-the-art experimental investigations. Multiple incident rays are induced inside the diffuse surface, permitting wideband solar absorption (91%) and heat localization (42.01 °C @ 1 sun). Under 1 kW m-2 solar intensity, the integrated SrCoO3@NF solar evaporator has an outstanding evaporation rate (1.45 kg/m2 h) and solar-to-vapor conversion efficiency (86.45% excluding heat losses). In addition, long-term evaporation measurements demonstrate small variance under sea water, illustrating the system's working capacity for salt rejection (1.3 g NaCl/210 min), which is excellent for an efficient solar-driven evaporation application compared to other carbon-based solar evaporators. According to the findings of this research, this system offers significant potential for producing fresh water devoid of salt accumulation for use in industrial applications.

Elastic Modulus of a Carbonized Layer on Polyurethane Treated by Ion-Plasma

Nanocoatings formed by various plasma and chemical methods on the surface of polymeric materials have unique properties. However, the applicability of polymeric materials with nanocoatings under specific temperature and mechanical conditions depends on the physical and mechanical properties of the coating. The determination of Young's modulus is a task of paramount importance since it is widely used in calculations of the stress-strain state of structural elements and structures in general. Small thicknesses of nanocoatings limit the choice of methods for determining the modulus of elasticity. In this paper, we propose a method for determining the Young's modulus for a carbonized layer formed on a polyurethane substrate. For its implementation, the results of uniaxial tensile tests were used. This approach made it possible to obtain patterns of change in the Young's modulus of the carbonized layer depending on the intensity of ion-plasma treatment. These regularities were compared with regularities of changes in the molecular structure of the surface layer caused by plasma treatment of different intensity. The comparison was made on the basis of correlation analysis. Changes in the molecular structure of the coating were determined from the results of infrared Fourier spectroscopy (FTIR) and spectral ellipsometry.

Stretchable and Flexible Snake Skin Patterned Electrodes for Wearable Electronics Inspired by Kirigami Structure

AbstractHerein, snake‐skin‐patterned electrodes, with high versatility and excellent biocompatibility, are developed by combining the Kirigami structure and biomimicry. The snake‐skin electrode has excellent stretchability owing to the integration of the Kirigami structure and patterning. The snake skin patterns are optimized through finite element analysis (FEA) simulations to determine the most stretchable pattern structure. Based on the FEA results, we fabricated the optimal pattern on a polyurethane (PU) substrate by sputtering the AgPdCu alloy target. Even at high strains of 30% and 50%, the electrode exhibits much better stretchability compared with the electrode without the snake skin pattern. The best stretchable electrode exhibits a resistance change (ΔR) of less than 1.5 when it is severely stretched at up to 50% strain. Additionally, the dynamic stretching fatigue test, reveals that it exhibits stable conductivity, thus proving the effectiveness of using snake‐skin pattern for stretchable electrodes. The bending, rolling, folding and twisting tests confirm that the electrode has outstanding flexibility, too. A wearable temperature sensor with a snake‐skin‐patterned electrode exhibits stable and highly sensitive temperature sensing properties. In addition, light emitting diodes connected to the stretchable electrode exhibits stable brightness despite severe deformation of the electrodes.

Sputtering of micro-carbon-silver film (μC-Ag) for endotracheal tubes to mitigate respiratory infections

Polyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (μC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the μC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using species S. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that μC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.

Fabrication of Screen-Printed Electrodes Modified by Hydrothermal MnO2 Microflowers and Carbon for Electrochemical Sensors in Copper Ions Detection

Porous MnO2 microflowers with a hexagonal crystalline structure were facilely prepared at a low hydrothermal temperature of 90°C, without using any template or capping agent. The as-prepared MnO2 only presented an excellent detection ability for copper (II) by a square wave anodic stripping voltammetry in the presence of super P carbon black as conducting agent, and Nafion as binder. In the present work, to evaluate the detection ability of copper (II) in the MnO2 microflowers, chips of screen-printed electrodes (SPEs) having a polyurethane substrate, a silver working electrode, a carbon counter electrode, and a silver pseudoelectrode, were designed. Then, the SPEs chips were modified with MnO2 microflowers and/or super P carbon and used as electrochemical sensors for the detection of copper (II) present in water sources. From the measured results, the fabricated sensors with excellent copper detection in a linear range from 0.625 nM to 15 nM (R2 = 0.9737), and a low detection limit (0.5 nM), high sensitivity (214.05 μA/cm2 nM), and rapid response (180 s) demonstrated high application potential for electrochemical sensors in the detection of copper in water resources.

Development of Cellulose-Reinforced Polyurethane Coatings: A Novel Eco-Friendly Approach for Wind Turbine Blade Protection

Wind energy is considered a clean energy source and is predicted to be one of the primary sources of electricity. However, leading-edge erosion of wind turbine blades due to impacts from rain drops, solid particles, hailstones, bird fouling, ice, etc., is a major concern for the wind energy sector that reduces annual energy production. Therefore, leading-edge protection of turbine blades has been an important topic of research and development in the last 20 years. Further, there are critical issues related to the amount of waste produced, including glass fiber, carbon fiber, and various harmful volatile organic compounds in turbine fabrication and their end-of-life phases. Hence, it is vital to use eco-friendly, solvent-free materials and to extend blade life to make wind energy a perfect clean energy source. In this study, cellulose microparticles (CMP) and cellulose microfibers (CMF) have been used as fillers to reinforce water-based polyurethane (PU) coatings developed on glass fiber reinforced polymer (GFRP) substrates by a simple spray method for the first time. Field emission scanning electron microscopy images show the agglomerated particles of CMP and fiber-like morphology of CMF. Fourier transform infrared spectra of CMP, CMF, and related coatings exhibit associated C–H, C=O, and N–H absorption bands of cellulose and polyurethane. Thermal gravimetric analysis shows that CMP is stable up to 285 °C, whereas CMF degradation is observed at 243 °C. X-ray photoelectron spectroscopy of C 1s and O 1s core levels of CMP, CMF and related coatings show C–C/C–H, C–O, C–OH, and O–C=O bonds associated with cellulose structure. The solid particle erosion resistance properties of the coatings have been evaluated with different concentrations of CMP and CMF at impact angles of 30° and 90°, and all of the coatings are observed to outperform the PU and bare GFRP substrates. Three-dimensional (3D) profiles of erosion scans confirm the shape of erosion scars, and 2D profiles have been used to calculate volume loss due to erosion. CMP-reinforced PU coating with 5 wt.% filler concentration and CMF-reinforced PU coating with 2 wt.% concentration are found to be the best-performing coatings against solid particle erosion. Nanoindentation studies have been performed to establish a relation between H3/E2 and the average erosion rate of the coatings.

Kinetics and Mechanism of Electroless Silver Deposition on a Polyurethane Substrate at Moderate to High Concentration of Metal Precursor and Reductant

Kinetics and Mechanism of Electroless Silver Deposition on a Polyurethane Substrate at Moderate to High Concentration of Metal Precursor and Reductant

Biodegradation of polyester polyurethane by Cladosporium sp. P7: Evaluating its degradation capacity and metabolic pathways

Microorganisms capable of decomposing polyurethane (PU) and other plastics have the potential to be used in bio-recycling processes. In this study, 20 PU-degrading strains were isolated, including 11 bacteria and 9 fungi, using a synthesized poly(1,4-butylene adipate)-based PU (PBA-PU) as the screening substrate. Three PU substrates with increasing structure complexities were used for a thorough evaluation of microbial degradation capacity: Impranil® DLN-SD, PBA-PU film and PU foam waste. After 4 days, the best fungal PBA-PU degrader, Cladosporium sp. P7, could degrade 94.5% of Impranil® DLN-SD. After 28 days of cultivation, 32.42% and 43.91% of solid PBA-PU film was converted into soluble small molecules when used as the sole carbon source or in a medium with other co-carbon sources, respectively. Accordingly, the weight loss of PU foam waste after 15 days was 15.3% for the sole carbon condition and 83.83% for the co-carbon conditions. Furthermore, PBA-PU was used for metabolic pathway analysis because of its known composition and chemical structure. Six metabolites were identified during the degradation process of PBA-PU, including adipic acid (AA), 1,4-butanediol (BDO), and 4,4’-methylenedianiline (MDA), which can also be used as the sole carbon source to grow the fungal strain P7, resulting in the discovery of two MDA metabolites during the cultivation processes. Based on the presence of these eight metabolites, we hypothesized that PBA-PU is first depolymerized by the fungal strain P7 via ester and urethane bond hydrolysis, followed by intracellular metabolism and mineralization of the three monomers to CO2 and H2O.