Polyurethane Nanofibers Research Articles

Strain-insensitive fiber sensors bioinspired by spider silk with a multilevel helical structure

The emergence of wearable electronics has greatly stimulated the exploration of fibers due to their inherent wearing comfort. However, the manufacturing of conductive fibers with both exceptional mechanical strength and stable conductive properties remains a formidable challenge. Inspired by the helical structure of spider silk, we propose a strain-insensitive conductive fiber with a multilevel helical structure by helically arranging carbon fibers on the surface of helical polyurethane nanofibers, which is further employed in the fabrication of fiber sensors. The resulting fibers demonstrate outstanding strain stability with a resistance change rate (ΔR/R0) of less than 0.09 when the strain reaches 100% and a resistance change rate below 0.3 at the 200% strain level, significantly outperforming previous reports. Through experimental investigations and computational analysis, we elucidate that the underlying mechanism of the superior conductive performance and stability is attributed to the redundant helical structures and polyurethane nanofiber core layer contraction. Moreover, the fiber devices fabricated on the basis of our strain-insensitive conductive fibers exhibit distinguished performance in various health-related physiological signal monitoring tasks, such as respiration heat monitoring, voice recording, and electrochemical detection of sweat constituents.

Ion-exchange formation of Ag2CO3-Ag3PO4 binary nanostructure on electrospun polyurethane nanofibers for enhanced photocatalytic degradation and antibacterial activities

In this study, a hybrid Ag2CO3-Ag3PO4/PU NFs membrane was prepared by electrospinning followed by ion-exchange methods. The obtained samples were characterized by SEM, EDS, XRD, and IR techniques. The Ag2CO3-Ag3PO4/PU NFs membrane composite exhibited excellent photocatalytic performance (100 % of the dye removal within 70 min) towards the degradation of methylene blue (MB) under visible light irradiation. This remarkable performance was mainly due to the efficient separation of the photogenerated charge carriers. In addition, the composite showed good antibacterial performance against Salmonella typhimurium and Staphylococcus aureus. The results obtained from the photocatalytic and antibacterial studies showed that the prepared material can be proposed as a multifunctional material in wastewater treatment and environmental applications.

Coaxial Nanofiber Binders Integrating Thin and Robust Sulfide Solid Electrolytes for High‐Performance All‐Solid‐State Lithium Battery

AbstractTo access the theoretically high energy density of sulfide‐based all‐solid‐state lithium batteries (ASSLBs), a thin and robust sulfide electrolyte membrane is essential. Given the pivotal role of binder in preserving the structural integrity and interfacial stability of sulfide electrolytes upon cycling, it is desired to integrate binding capability, toughness, and stiffness into one binder, yet remains difficult. Herein, this challenge is addressed using a nanofiber‐reinforced strategy in the solvent‐free dry‐film process. A coaxial polyvinylidene poly(vinylidene fluoride‐co‐hexafluoropropylene) @ thermoplastic polyurethane (PVDF‐HFP@TPU) nanofiber binder is embedding into a Li6PS5Cl (LPSCl) matrix to obtain a sulfide thin‐layer (LPSCl‐P@T). During hot calendering of the sulfide‐binder mixture, the PVDF‐HFP shell layer melts and tightly binds LPSCl particles. The underlying TPU core layer, which maintains the fibrous structure, reinforces the structural stability of the membrane. Particularly, the fiber‐matrix connection is improved with the assistance of the molten PVDF‐HFP, collectively contributing to the effective dissipation of the mechanical stress. Controlled fusion of the core‐shell nanofiber also leads to enhanced interfacial anchoring of the cathode and electrolyte. The assembled cells with LPSCl‐P@T deliver stable cycling performances. The PVDF‐HFP@TPU nanofiber binder overcomes the long‐existing incompatible problems between binder toughness and stiffness, and shows promises in developing high‐performance sulfide‐based ASSLBs.

Wet-adaptive Strain Sensor Based on Hierarchical Core-sheath Yarns for Underwater Motion Monitoring and Energy Harvesting

Bifunctional flexible electronics with motion monitoring and energy harvesting have broad application prospects in day-to-day activities of human society. Nevertheless, conventional electronics are difficult to adapt to the wear comfortability and anti-sensing interference properties in wet environments. Herein, a wet-adaptive spandex/graphene@cotton/polyurethane yarn (SGCPY) sensor is fabricated with excellent sensing and triboelectric performance, which comprises core layer of spandex fibers, middle layer of graphene@cotton sensing fibers and outer layer of spindle-knotted polyurethane nanofibers. Benefiting from its unique structure, as-prepared SGCPY sensor exhibits high mechanical properties (~80%), superhydrophobic performance (>130°), good strain sensitivity (1.82) and fatigue resistance (12000 cycles) even under water condition. The usage of the SGCPY sensor is demonstrated for the stable monitoring of human body motions and human-machine interaction in both air and water environments. When SGCPY sensor weave as plain fabric, the textile also can convert various mechanical energy into electric power for driving electronic device, showing a maximum voltage of ~3.9V and ~0.7V with solid-solid and liquid-solid contact. This work fosters the in-depth study of textile-based electronics for underwater applications and highlights the promising prospects of multi-functional flexible electronics based on textiles.

Toward the design of highly waterproof‐breathable electrospun nanofiber membrane based on π–π interactions

AbstractWaterproof and breathable nanofiber membranes are highly desirable for protective textiles; however, the practical application of nanofiber membranes is limited by fluorine‐containing material addition or complicated post‐treatment. Herein, we reported unique fluorine‐free polyurethane (PU)/poly(styrene‐b‐s‐b‐styrene) (SBS) nanofiber membranes by a facile direct electrospinning. Owing to the addition of SBS, the hydrophobicity, waterproofness, and mechanical properties of PU nanofiber membranes were dramatically enhanced. Furthermore, the highly interconnective channels were constructed after the introduction of SBS into the PU nanofiber membrane, which resulted in enhanced breathability. The enhancement in the comprehensive performance of the PU/SBS composite nanofiber membrane might be attributed to the π–π interactions between SBS and PU. By adjusting the concentration of the PU/SBS, fluorine‐free PU/SBS nanofiber membranes were optimized systematically, exhibiting satisfactory waterproofness (hydrostatic pressure, 47.4 kPa), acceptable breathability (water vapor transition rate, 5.6 kg m−2 d−1), and outstanding mechanical properties (breaking strength, 5.7 MPa; breaking elongation, 387.9%). The PU/SBS‐14 nanofiber membrane is ideal for wearable textiles, especially for outdoor protective clothing, wound dressings, and medical gowns.

An enclosed solid-liquid triboelectric nanogenerator based on Janus-type TPU nanofibers

Various environmental factors such as high humidity, rain, snow, and other conditions restrict the practical use of triboelectric nanogenerator (TENG). Herein, Janus-type thermoplastic polyurethane (TPU) nanofiber films with good hydrophobicity were fabricated by side-by-side electrospinning. The output performance of TENG based on Janus-type TPU nanofiber films was much higher than that made of normal TPU nanofiber films. A flexible enclosed TENG was prepared that maintained its output performance regardless of external humidity. What’s more, liquid metal gallium (Ga) was injected into the enclosed TENG and used as the tribo-material. The addition of Ga to the enclosed TENG increased its output performance to reach a peak voltage of 282 V and current of 6.0 μA. The enclosed TENG was able to power light-emitting diodes (LEDs) even when immersed in water, demonstrating its potential for using under high-humidity conditions.

Multifunctional ultraelastic helical conductive yarn for motion detection and human-machine interaction

Featured with intrinsic lightweight, great flexibility, and easy integration into functional textiles or devices, the stretchable conductive fiber has attracted much attention in the realm of wearable electronics. However, the conductive fibers encounter a troublesome “trade-off” between high conductivity and large elasticity under large deformation, which restricts their widespread applications. Herein, we designed a multifunctional highly elastic helical conductive yarn (HCY) by electrospinning polyurethane (PU) nanofibers, polydopamine (PDA)-assisted silver nanoparticles (AgNPs) deposition and over-twisting. The introduction of a PDA mediated layer fosters strong bond between the conductive AgNPs and the elastic PU nanofibers matrix, showcasing robust structural stability and electrical performance. The hierarchically interlocked conductive structure confers high electrical conductivity to the stretchable HCY, enabling it to withstand large mechanical deformation, which achieves good recoverability within a range of 700 %, great durability (40000 times at deformation of 200 %) and maximum conductive tensile elongation up to 1200 %. Furthermore, the HCY also features excellent Joule-heating ability, great antibacterial performance, and functions as a rapid-response strain sensor (GFmax = 9.82), which is ideal for detecting human motion and enhancing human–machine interactions. This work provides a new path for developing advanced stretchable conductive materials, which is of great significance for versatile ultraelastic wearable electronic devices.

High sensitivity flexible piezoelectric nanogenerator based on multi‐layer piezoelectric composite fiber for human motion energy harvesting

AbstractIn this study, a piezoelectric nanogenerator (PENG) based on multilayer composite fiber had good and stable piezoelectric output performance, which could realize biomechanical energy collection and human movement monitoring. The polyvinylidene fluoride‐hexafluoryl propylene (P(VDF‐HFP)) composite fiber doped with MXene was used as a promising piezoelectric functional layer (MPFP). By electrospinning, P(VDF‐HFP) composite fiber was constructed by alternating electrospinning with polyurethane (TPU) nanofibers layer by layer. The adoption of MXene as a functional filler promoted the transformation of P(VDF‐HFP) from α to piezoelectric β‐crystal, the piezoelectric β‐crystal content of P(VDF‐HFP) increased, and the dielectric properties and polarization levels were enhanced. At the same time, the multi‐layer structure design improved the piezoelectric sensitivity and mechanical properties of the composite fiber, and the composite fiber was more flexible and had longer tensile strain. With excellent dielectric and mechanical properties, 3MPFP/TPU/3MPFP/TPU multilayer composite fibers showed piezoelectric sensitivity of 10.88 V/kPa. Under the action of palm pressing, the PENG generated an open circuit voltage of 25 V, and the voltage signal of the device under different motion forms had specific characteristics such as peak value, frequency, and shape, which could be used to realize the analysis of human motion forms. This study provided an efficient, simple, and creative new idea for the application of flexible energy storage electronic devices, PENGs, and piezoelectric sensors.

Enhancing of antibacterial activity of Polyurethane (TPU) nanofiber using green extracted Zinc Oxide (ZnO NPs) and Graphene Oxide (GO NPs)

Enhancing of antibacterial activity of Polyurethane (TPU) nanofiber using green extracted Zinc Oxide (ZnO NPs) and Graphene Oxide (GO NPs)

Enhanced thermoregulation performance of knitted fabrics using phase change material incorporated thermoplastic polyurethane and cellulose acetate nanofibers

AbstractNanofibers act as carriers in systems containing functional materials produced via electrospinning method. By this way, it is possible to transport functional materials with polymer nanofibers, besides having a large surface area compared to their volume, the encapsulation process, which includes complex preparation processes, is eliminated here, and functional materials such as phase‐change materials (PCMs) can be conveniently integrated directly into the carrier material by electrospinning method. The resulting nanofiber membrane can also be used in combination with textile fabrics. This study aims to develop PCM containing nanofibrous membrane coated knitted fabric structures with heat regulation capabilities. Two types of PCMs, hexadecane and octadecane loaded into thermoplastic polyurethane (TPU) and cellulose acetate (CA) nanofibers, directly electrospun on cotton (CO), cotton/polyester (CO/PES), cotton/acrylic (CO/PAC) knitted fabrics for thermoregulation. These nanofiber‐coated fabrics were characterized by scanning electron microscopy (SEM) and differential scanning colorimetry (DSC), and their comfort properties were evaluated by water vapor and air permeability tests and compared with a commercial microcapsule impregnated fabric. According to DSC results, PCM incorporated CA nanofibers had better heat storage capacity than TPU nanofibers and microcapsule applied fabrics. Although PCM‐loaded CA nanofibers may not block airflow as effectively as TPU nanofibers, when a proper coating is achieved air permeability can be decreased to 21.70 L/m2/s, along with a heat storage capacity of 26.38 J/g and still having permeability to water vapor (%40).Highlights Phase change materials were integrated directly to the carrier material by electrospinning PCM integrated nanofiber coating reduced air permeability PCM integrated nanofiber coating did not block water vapor permeability Electrspun cellulose acetate +PCM coating had better heat storage capacity

Dual conductive network enables mechanically robust polymer composites with highly electrical and thermal conductivities

Thermally and electrically conductive polymer composites (CPCs) have been widely used in smart and flexible electronics; however, huge challenges remain in simultaneously improving the electrical and thermal conductivity of CPCs while maintaining the satisfactory mechanical properties including sufficient strength and toughness. In this study, we propose an effective interfacial regulation approach to fabricate CPCs with a dual conductive network through decoration of Ag nanoparticles (AgNPs) onto the polyurethane (PU) nanofibers containing graphite nanoplatelets (GNPs), followed by hot-pressing. Rigid GNPs expand the PU nanofiber network, facilitating Ag precursor adsorption, while subsequent hot-pressing eliminates the big channels and pores inside nanofiber composite membranes and hence greatly enhance their mechanical properties. After hot-pressing, the synergistic dual conductive network with greatly reduced thermal and electrical contact resistance leads to significant improvements in both thermal and electrical conductivity (up to 27.71 W (m K)−1 and 1.87 × 106 S/m, respectively). Moreover, the mechanically robust CPCs with exceptional durability possess superior Joule heating performance at low voltages and heat dissipation capability. This study provides inspiration for designing highly thermally and electrically conductive CPCs with potential applications as flexible thermal interface materials.

Enhanced Antibacterial Activity of Clindamycin Using Molecularly Imprinted Polymer Nanoparticles Loaded with Polyurethane Nanofibrous Scaffolds for the Treatment of Acne Vulgaris.

Acne vulgaris, a prevalent skin condition, arises from an imbalance in skin flora, fostering bacterial overgrowth. Addressing this issue, clindamycin molecularly imprinted polymeric nanoparticles (Clin-MIP) loaded onto polyurethane nanofiber scaffolds were developed for acne treatment. Clin-MIP was synthesized via precipitation polymerization using methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), and azoisobutyronitrile (AIBN) as functional monomers, crosslinkers, and free-radical initiators, respectively. MIP characterization utilized Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) before being incorporated into polyurethane nanofibers through electrospinning. Further analysis involved FTIR, scanning electron microscopy (SEM), in vitro release studies, and an ex vivo study. Clin-MIP showed strong antibacterial activity against S. aureus, with inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 0.39 and 6.25 μg/mL, respectively. It significantly dropped the bacterial count from 1 × 108 to 39 × 101 CFU/mL in vivo and has bactericidal activity within 180 min of incubation in vitro. The pharmacodynamic and histopathology studies revealed a significant decrease in infected animal skin inflammation, epidermal hypertrophy, and congestion upon treatment with Clin-MIP polyurethane nanofiber and reduced pro-inflammatory cytokines (NLRP3, TNF-α, IL-1β, and IL-6) conducive to acne healing. Consequently, the recently created Clin-MIP polyurethane nanofibrous scaffold. This innovative approach offers insight into creating materials with several uses for treating infectious wounds caused by acne.

All-Fiber Flexible Electrochemical Sensor for Wearable Glucose Monitoring.

Wearable sensors, specifically microneedle sensors based on electrochemical methods, have expanded extensively with recent technological advances. Today's wearable electrochemical sensors present specific challenges: they show significant modulus disparities with skin tissue, implying possible discomfort in vivo, especially over extended wear periods or on sensitive skin areas. The sensors, primarily based on polyethylene terephthalate (PET) or polyimide (PI) substrates, might also cause pressure or unease during insertion due to the skin's irregular deformation. To address these constraints, we developed an innovative, wearable, all-fiber-structured electrochemical sensor. Our composite sensor incorporates polyurethane (PU) fibers prepared via electrospinning as electrode substrates to achieve excellent adaptability. Electrospun PU nanofiber films with gold layers shaped via thermal evaporation are used as base electrodes with exemplary conductivity and electrochemical catalytic attributes. To achieve glucose monitoring, gold nanofibers functionalized by gold nanoflakes (AuNFs) and glucose oxidase (GOx) serve as the working electrode, while Pt nanofibers and Ag/AgCl nanofibers serve as the counter and reference electrode. The acrylamide-sodium alginate double-network hydrogel synthesized on electrospun PU fibers serves as the adhesive and substance-transferring layer between the electrodes. The all-fiber electrochemical sensor is assembled layer-by-layer to form a robust structure. Given the stretchability of PU nanofibers coupled with a high specific surface area, the manufactured porous microneedle glucose sensor exhibits enhanced stretchability, superior sensitivity at 31.94 μA (lg(mM))-1 cm-2, a broad detection range (1-30 mM), and a significantly low detection limit (1 mM, S/N = 3), as well as satisfactory biocompatibility. Therefore, the novel electrochemical microneedle design is well-suited for wearable or even implantable continuous monitoring applications, thereby showing promising significant potential within the global arena of wearable medical technology.

Enhancing cellular affinity for skin disorders: Electrospun polyurethane/collagen nanofiber mats coated with phytoceramides

Although the use of thermoplastic polyurethane (Tpu) nanofiber mats as wound dressings is of great interest due to their mechanical properties, they are hindered by their poor wettability and bioavailability. In this study, we aimed to improve the cellular affinity of Tpu nanofiber mats for skin disorders by incorporating extracted collagen (Col) from tendons and physically mixed with a layer of phytoceramides (Phyto) to produce TpuCol@X-Phyto mats in which the weight % of Phyto relatively to the weight of the solution was X = 0.5, 1.0, or 1.5 wt% via facile electrospinning approach. The collective observations strongly indicate the successful incorporation and retention of Phyto within the TpuCol architecture. An increase in the Phyto concentration decreased the water contact angle from 69.4° ± 3.47° to 57.9° ± 2.89°, demonstrating improvement in the hydrophilicity of Tpu and binary blend TpuCol nanofiber mats. The mechanical property of 1.0 wt% Phyto aligns with practical requirements owing to the presence of two hydroxyl groups and the amide linkage likely contributing to various hydrogen bonds, providing mechanical strength to the channel structure and a degree of rigidity essential for transmitting mechanical stress. The proliferation of human skin fibroblast (HSF) peaked significantly 100 % with TpuCol@X-Phyto mats coated for X =1.0 and 1.5 wt% of Phyto. Electrospun scaffolds with the highest Phyto content have shown the lowest degree of hemolysis, demonstrating the high level of compatibility between them and blood. The TpuCol@1.5Phyto mat also demonstrated higher efficacy in antibacterial and antioxidant activities, achieving a rate of DPPH radical scavenging of 83.3 % for this latter property. The most notable wound closure among all tested formulations was attributed to higher Phyto. Thus, the developed TpuCol@1.5Phyto nanofiber formula exhibited enhanced healing in an in vitro epidermal model.

Bi-layered polyurethane nanofiber patches with asymmetrical surface prevent postoperative adhesion and enhance cardiac repair

The adhesion between heart and chest post-operation raises a significant challenge for the application of cardiac patches due to its severe influences on the recovery of heart function and increased risk of re-treatment. Anabatic inflammatory response and increased oxidative stress aggravate the damage to heart functions. Herein, a multi-functional cardiac patch was manufactured by successive electrospinning of two types of novel selenium-containing polyurethanes (PU), followed by click grafting of poly (ethylene glycol) (PEG) molecules on the top layer. This patch possessed dual-functions of postoperative anti-adhesion and anti-oxidative stress for efficient therapy post myocardial infarction (MI). The high redox reactivity of diselenium bonds were introduced into the main chains of PU, which reduced the level of reactive oxygen species (ROS) and modulated the inflammatory environment, alleviating the synechia formation simultaneously. The cardiac patch could effectively resist fibroblast adhesion, regulate the expression of vinculin and tissue-type plasminogen activator (t-PA), and inhibit the synechia formation. Meanwhile, it also restored significantly the heart function post MI by decreasing the local inflammation, facilitating less collagen formation, and improving cell signal transduction and angiogenesis. Collectively, this novel patch achieved anti-adhesion and therapeutic effect synergistically, bringing advancement in cardiac patch design and potential for translation of medicinal devices.

Graphene-decorated polyurethane nanofiber membrane flexible sensor with different fiber orientation

Electrospun polyurethane (PU) nanofiber membranes offer desirable properties such as large strain, good resilience, light weight, good air permeability, and good adhesion to the skin; as a result, they have a unique advantage in the development of flexible sensors. To explore the application of conductive graphene (Gr)/PU nanofiber membranes in the field of strain sensing and to study the influence of the nanofiber orientation structure on the sensing performance of nanofiber sensors, electrospinning technology was adopted to prepare PU nanofiber membranes with different fiber orientations by adjusting the rotating speed of the receiving drum. Gr/PU nanofiber membranes were prepared as strain-resistance sensors, their strain-resistance sensing performance was analyzed, and the membranes were used to monitor human motion and air vibrations. The results showed that the orientation of the nanofibers in the PU nanofiber membranes could be improved by increasing the rotation speed of the receiving drum. Gr/PU nanofiber sensors have good sensing linearity, sensitivity, and stability; an increase in fiber orientation also increases sensor sensitivity, and the sensitivity factor can reach more than 200 at 50 % strain. Sensors with a low detection threshold and high detection sensitivity, which can be used for large-scale motion monitoring of human joints and small-range motion monitoring of air vibrations, have potential applications in wearable human motion health monitoring and other fields.

Preparation of CNT/CNF/PDMS/TPU Nanofiber-Based Conductive Films Based on Centrifugal Spinning Method for Strain Sensors.

Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their use in harsh environments. In this paper, a novel method is proposed to fabricate flexible conductive films via centrifugal spinning to generate thermoplastic polyurethane (TPU) nanofiber substrates by employing carbon nanotubes (CNTs) and carbon nanofibers (CNFs) as conductive fillers. These fillers are anchored to the nanofibers through ultrasonic dispersion and impregnation techniques and subsequently modified with polydimethylsiloxane (PDMS). This study focuses on the effect of different ratios of CNTs to CNFs on the film properties. Research demonstrated that at a 1:1 ratio of CNTs to CNFs, with TPU at a 20% concentration and PDMS solution at 2 wt%, the conductive films crafted from these blended fillers exhibited outstanding performance, characterized by electrical conductivity (31.4 S/m), elongation at break (217.5%), and tensile cycling stability (800 cycles at 20% strain). Furthermore, the nanofiber-based conductive films were tested by attaching them to various human body parts. The tests demonstrated that these films effectively respond to motion changes at the wrist, elbow joints, and chest cavity, underscoring their potential as core components in strain sensors.

Energy harvesting with thermoplastic polyurethane nanofiber mat integrated with functionalized multiwalled carbon nanotubes

Energy harvesting with thermoplastic polyurethane nanofiber mat integrated with functionalized multiwalled carbon nanotubes

Polyurethane Nanofiber Polymer: preparation, production, characterization and properties

Polyurethane Nanofiber Polymer: preparation, production, characterization and properties

Mechanically robust and electrically conductive nanofiber composites with enhanced interfacial interaction for strain sensing

Electrically conductive fiberfibre/fabric composites (ECFCs) are competitive candidates for use in wearable electronics. Therefore, it is essential to develop mechanically robust ECFC strain sensors with sensing performance. In this study, MXene assembly and hot-pressing were combined to prepare strong yet breathable ECFCs for strain and temperature sensing. Hydrogen bonding between MXene and polyurethane (PU) and ultrasonication-induced interfacial sintering were responsible for MXene nanosheets assembly on the PU nanofibers. MXene decoration made PU nanofibers electrically conductive, resulting in a conductive network. Hot-pressing improved interface adhesion among the conductive nanofibers. Thus, the mechanical properties of the nanofiber composites, including tensile strength, toughness and fracture energy, were enhanced. The nanofiber composites exhibited surface stability and durability. When the nanofiber composites were used as strain sensors, they showed breathability with a linear resistance response ranging from 1 % to 100 % and cycling stability. In addition, they produced stable sensing signals over 1000 cycles when a notch was present. They could also monitor temperature variations with a negative temperature coefficient (−0.146 %/°C). This study provides an interfacial regulation method for the preparation of multi-functional nanofiber composites with potential applications in flexible and wearable electronics.