Thermoplastic Polyurethane Nanofibers Research Articles

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.

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

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

Stretchable, flexible, and breathable MXene/dopamine/thermoplastic polyurethane nanofiber membrane with outstanding strain sensing and electromagnetic interference shielding performances

Outstanding strain sensing and electromagnetic interference (EMI) shielding performances are two important indicators for high-performance nanofiber membrane in flexible wearable electronic device. Here, simple electrospinning was employed to prepare the nanofiber membrane of thermoplastic polyurethane (TPU) as substrate. Then high-performance nanofiber membrane was developed by synthesizing dopamine on TPU nanofibers to form poly-dopamine (PDA) coatings (named PT) and ultrasonically loading MXene on PT (labeled MPT). Specifically, TPU substrate provides flexibility and breathability, PDA coating improves the adhesion between MXene and TPU, and MXene contributes to strain sensing and EMI shielding performances. Owing to the PDA coatings, MPT nanofiber membrane has outstanding EMI shielding efficiency (EMI SE) of 69.86 dB at 150 μm thickness and an absolute effective shielding value of 8383.33 dBcm2g−1. The combination of PDA with MXene improves the EMI SE of the MPT membrane by ∼ 1.6 times compared to other TPU-based membrane. MPT strain sensor exhibits great sensing performance with a remarkable detection threshold of 0.1%, strain coefficient of up to 2600, broad working range of 200%, and rapid response/recovery time (77/186 ms). Meanwhile, MPT strain sensor also shows remarkable ability to real-time monitor human health/motion, such as joint bending, breathing, speaking and heart rate, which makes significant contributions in the field of smart medicine. This nanofiber membrane can provide a universal strategy for the development of intelligent wearable medical devices.

Multifunctional combined drug-loaded nanofibrous dressings with anti-inflammatory, antioxidant stress and microenvironment improvement for diabetic wounds.

The treatment of diabetic wounds remains a formidable clinical challenge worldwide. Because of persistent inflammatory reaction, excessive oxidative stress, cell dysfunction, poor blood microcirculation and other microvascular complications, diabetic wounds often fall into inflammatory circulation and are difficult to heal, making patients confront the risk of amputation. In this study, silver complex nanoparticles with Resina Draconis extract and Rhodiola rosea L. extract were loaded in situ onto thermoplastic polyurethane nanofibers to develop a multifunctional electrospun nanofiber wound dressing with excellent mechanical properties, superior water absorption and breathability, good coagulation promoting activity, strong antibacterial performance and antioxidant properties. This wound dressing could effectively enhance the migration and proliferation of fibroblasts, reduce the increased thickness of regenerated epidermis caused by diabetes, and the high expression and high lipid peroxidation levels of IL-1 β, IL-6, TNF α, iNOS and MMP-9, and raise the low expression of VEGF, which shows great potential to accelerate the wound healing of diabetic mouse models. The wound healing rate reached about 87.92%, close to the non-diabetic group. Our findings suggest a breakthrough in diabetic wound care, offering a viable solution to a long-standing medical shackle.

Flexible and breathable iontronic tactile sensor with personal thermal management ability for a comfortable skin-attached sensing application

Wearable sensors are tightly attached on skin of different body parts for physiological monitoring and motion detection. In addition to sensing performance and flexible formation, maintaining of the normal mass microexchange between the covered skin and external environment with appropriate thermal dissipating ability for a comfortable wearing is highly important. Herein we report the design and fabrication of a new type of flexible and breathable tactile sensor with unique personal thermal management ability. The sensor adopts a supercapacitive iontronic sensing structure with microstructures by sandwiching one porous polyurethane/ionic liquid sponge with two electrospun thermoplastic polyurethane/MXene nanofiber electrodes for an enhanced sensitivity (∼105.77 kPa−1). In addition, the intrinsic elastic nature of polymers endows the whole device with excellent mechanical flexibility and the fabric and porous internal open-ended structure of substrates provide well air and moisture permeability (∼48 mm s−1) to maintain a normal thermal dissipating ability (∼1 ℃ lower than that covered by airtight film) without causing skin redness or inflammation. Furthermore, highly solar-reflective (∼0.98) silica microparticles are incorporated into the emissive (∼0.94) thermoplastic polyurethane nanofibers to achieve an effective passive cooling effect in the outdoor scene (∼ 3 ℃ lower than that covered by fabric clothes). The developed flexible and breathable tactile sensor as well as its design and fabrication strategy provide a promising route to develop advanced wearable electronics with unique personal thermal management ability for a comfort skin-attached sensing application.

Thermo-mechanical characterization of electrospun polyurethane/carbon-nanotubes nanofibers: a comparative study

Creating ultrathin, mountable fibers from a wide range of polymeric functional materials has made electrospinning an adequate approach to producing highly flexible and elastic materials. In this paper, electrospinning was utilized to produce thermoplastic polyurethane (TPU) nanofibrous membranes for the purpose of studying their thermal and mechanical properties. Towards a study of the effects of fiber orientation and multi-walled carbon nanotubes (MWCNTs) as a filler on both mechanical and thermal characteristics of electrospun TPU mats, an experimental comparison was held between unidirectional and randomly aligned TPU and TPU/MWCNTs nanofibrous structures. The incorporation of MWCNTs into randomly oriented TPU nanofibers resulted in a significant increase in Young's modulus (E), from 3.9 to 7.5 MPa. On the other hand, for unidirectionally spun fibers, Young's modulus increased from 17.1 to 18.4 MPa upon the addition of MWCNTs. However, dynamic mechanical analysis revealed a different behavior. The randomly oriented specimens exhibited a storage modulus with a significant increase from 180 to 614 MPa for TPU and TPU/MWCNTs mats, respectively, and a slight increase from 119 to 143 MPa for unidirectional TPU and TPU/MWCNTs mats, respectively. Meanwhile, the loss modulus increased with the addition of MWCNTs from 15.7 to 58.9 MPa and from 6.4 to 12 MPa for the random and aligned fibers, respectively. The glass transition values for all the mats fell in the temperature range of – 60 to − 20 °C. The thermal degradation of the membranes was not significantly affected by the addition of MWCNTs, indicating that the mixing of the two constituents did not change the TPU’s polymer structure and that the TPU/MWCNTs nanocomposite exhibited stable thermal degradation properties.

Adsorption and Removal of Composite Contaminants in Water Using Thermoplastic Polyurethane Nanofiber Membranes with Polydopamine–Polyethyleneimine Coatings

Dye wastewater containing bisphenol A (BPA) and dyes as pollutants has not been adequately studied. Our previous study revealed that thermoplastic polyurethane (TPU) nanofiber membranes (NFMs) modified by the addition of polyethyleneimine (PEI) and polydopamine (PDA) satisfactorily adsorb dyes. Herein, we first optimized the synthesis conditions for such membranes, noting a PEI/PDA monomer ratio of 2:2 and a deposition time of 48 h to be optimal. Experiments using these membranes revealed that binary systems containing BPA and the dyes (Congo red (CR), Eosin yellow (EY), or sunset yellow (SY)) exhibit three adsorption behaviors. CR and BPA compete with each other for adsorption sites, decreasing the maximum adsorption capacity (Qmax) for CR 208.3 mg/g (in a monomeric system) to 182.4 mg/g. The adsorption rates for CR and BPA decreased from 0.002 min−1 and 0.331 min−1 in the monomeric systems to 8.37 × 10−4 min−1 and 0.072 min−1, respectively, in the binary CR–BPA system, exhibiting antagonistic effects. When EY and BPA coexisted, Qmax for EY increased from 60.0 (monomeric) to 71.9 mg/g, whereas that for BPA increased from 35.6 to 43.2 mg/g, showing a synergistic effect due to the possible bridging effect. The adsorption sites for SY and BPA are independent of each other. The novelty of this study is the finding that PDA/PEI-TPU NFMS exhibited high adsorption capacity for dyes and BPA in binary composite systems and PDA/PEI-TPU NFMs showed different adsorption patterns for three dye–BPA binary composite systems. The preparation of PDA/PEI-TPU NFMs and the investigation of the adsorption mechanism for dye–BPA binary composite systems are not only of theoretical importance but also provide experimental and data support for practical applications.

High-performance triboelectric nanogenerators based on TPU/mica nanofiber with enhanced tribo-positivity

As a promising energy harvesting technology, triboelectric nanogenerator (TENG) has brought a leap forward to the development of self-powered systems. Many materials, especially inorganic non-metallic materials, proved to possess excellent triboelectric property, have rarely been practically used due to their fragility and rigidity. Here, fragile and rigid mica with strong triboelectric positivity is exfoliated into 2D nanosheets and electrospun into flexible and stretchable thermoplastic polyurethane (TPU) nanofibers for high-performance TENGs. Paired with polyvinylidene fluoride/MXene (PVDF/MXene) nanofibers, the transferred charge of the TENG with TPU/mica nanofibers significantly enhanced to 82.4 nC from 38.6 nC due to the enhanced tribo-positivity. Kelvin probe force microscopy (KPFM) measurements of single pure TPU and TPU/mica nanofibers showed mica apparently enhanced the positive electrostatic surface potential (ESP) of TPU. The mean peak ESP of pure TPU nanofiber was about 194 mV, while it was increased to 218 mV on the regions of TPU/mica nanofiber without mica nanosheets aggregation and 305 mV on the regions where mica nanosheets aggregated. The power density of the TENG with TPU/mica nanofiber reached 1458 mW/m2, exhibiting a 16-fold enhancement compared with the one based on pure TPU nanofiber. A thin and flexible TENG was fabricated and conformally worn on a wrist and palm for body motion monition and object gripping sorting. This work proposed high-performance triboelectric nanogenerators based on TPU/mica nanofibers and a general approach to effectively utilize rigid and fragile materials with excellent triboelectric property for making triboelectric layers.

Flexible Sensors Array Based on Frosted Microstructured Ecoflex Film and TPU Nanofibers for Epidermal Pulse Wave Monitoring

Recent advances in flexible pressure sensors have fueled increasing attention as promising technologies with which to realize human epidermal pulse wave monitoring for the early diagnosis and prevention of cardiovascular diseases. However, strict requirements of a single sensor on the arterial position make it difficult to meet the practical application scenarios. Herein, based on three single-electrode sensors with small area, a 3 × 1 flexible pressure sensor array was developed to enable measurement of epidermal pulse waves at different local positions of radial artery. The designed single sensor holds an area of 6 × 6 mm2, which mainly consists of frosted microstructured Ecoflex film and thermoplastic polyurethane (TPU) nanofibers. The Ecoflex film was formed by spinning Ecoflex solution onto a sandpaper surface. Micropatterned TPU nanofibers were prepared on a fluorinated ethylene propylene (FEP) film surface using the electrospinning method. The combination of frosted microstructure and nanofibers provides an increase in the contact separation of the tribopair, which is of great benefit for improving sensor performance. Due to this structure design, the single small-area sensor was characterized by pressure sensitivity of 0.14 V/kPa, a response time of 22 ms, a wide frequency band ranging from 1 to 23 Hz, and stability up to 7000 cycles. Given this output performance, the fabricated sensor can detect subtle physiological signals (e.g., respiration, ballistocardiogram, and heartbeat) and body movement. More importantly, the sensor can be utilized in capturing human epidermal pulse waves with rich details, and the consistency of each cycle in the same measurement is as high as 0.9987. The 3 × 1 flexible sensor array is employed to acquire pulse waves at different local positions of the radial artery. In addition, the time domain parameters including pulse wave transmission time (PTT) and pulse wave velocity (PWV) can be obtained successfully, which holds promising potential in pulse-based cardiovascular system status monitoring.

Strain-adjustable reflectivity of polyurethane nanofiber membrane for thermal management applications

Passive radiative cooling technologies are highly attractive in pursuing sustainable development. However, current cooling materials are often static, which makes it difficult to cope with the varying needs of all-weather thermal comfort management. Herein, a strategy is designed to obtain flexible thermoplastic polyurethane nanofiber (Es-TPU) membranes via electrospinning, realizing reversible in-situ solvent-free switching between radiative cooling and solar heating through changes in its optical reflectivity by stretching. In its radiative cooling state (0% strain), the Es-TPU membrane shows a high and angular-independent reflectance of 95.6% in the 0.25–2.5 μm wavelength range and an infrared emissivity of 93.3% in the atmospheric transparency window (8–13 μm), reaching a temperature drop of 10 °C at midday, with a corresponding cooling power of 118.25 W/m2. The excellent mechanical properties of the Es-TPU membrane allows the continuous adjustment of reflectivity by reversibly stretching it, reaching a reflectivity of 61.1% (ΔR = 34.5%) under an elongation strain of 80%, leading to a net temperature increase of 9.5 °C above ambient of an absorbing substrate and an equivalent power of 220.34 W m−2 in this solar heating mode. The strong haze, hydrophobicity and outstanding aging resistance exhibited by this scalable membrane hold promise for achieving uniform illumination with tunable strength and efficient thermal management in practical applications.

A nano-structured bilayer asymmetric wettability textile for efficient personal thermal and moisture management in high-temperature environments

In recent years, climate change has led to extremely hot weather conditions in many parts of the world, which not only causes large amount of energy consumption for building space cooling, but also poses a great threat to the health and safety of people outdoors. A wearable textile that could simultaneously maximizing thermal insulation, facilitating evaporative cooling, and enhancing radiative cooling would play an important role for outdoor personal thermal and moisture management in high-temperature environments. However, developing such a textile with a relatively simple structure remains a huge challenge. Herein, a bilayer asymmetric wettability cooling membrane (BAWCM) textile composed of banana trees cellulose aerogel membrane (BTCAM) and thermoplastic polyurethane nanofibers doped with zinc oxide nanoparticles (ZnO-NPs/TPU) is prepared by freeze-drying and subsequent electrospinning. The BAWCM textile has good thermal insulation performance, thereby reducing heat input when the ambient temperature is higher than the human body temperature. Meanwhile, the textile possesses a high reflectance of 91.3 % in the 0.37–2.5 μm wavelength range and an infrared emissivity of 90.2 % in the 8–13 μm wavelength range. In outdoor test, it is demonstrated that the BAWCM textile can be as large as 9.3 °C cooler than cotton under direct sunlight. More importantly, the textile can effectively achieve directional perspiration to accelerate evaporative cooling, preventing sticky and hot sensation. Through the integration of excellent thermal insulation, enhanced radiative cooling, and continuous sweat wicking-drying capability, this novel textile exhibits significantly improved personal thermal and moisture management performances in high-temperature environments.

Investigation of conductive printed thermoplastic polyurethane nanofibers to detect the clogging of air filters

Recently, air pollution attracted many worries because of its high number of deaths per year. To solve the problem, the industries are trying to fabricate the giant air filtration system for public areas. However, the clogging of air filters should be detected in real-time to change or clean them. E-textile is a very fascinating field, which is often used in medical, safety, military and clogging detection applications. These components are integrated into soft textile materials according to their usage requirements. One of the most attractive textile structures is the nanofibers due to their advantageous properties such as porosity, lightweight, and high surface area. To have conductive nanofiber-based membrane sensors, two in situ electrical conductivity principles using conductive particles and surface conductivity, such as immersion and printing methods are recommended. In this research, the thermoplastic polyurethane (TPU) nanofibers’ membranes are produced using an electrospinning system and the carbon ink was printed on the surface of nanofibers to apply in textile sensors applications. SEM images showed the uniform structure of the nanofibers and the porosity of the system even after printing. The electromechanical properties of printed membranes demonstrated the change of electrical resistance under stretch. Conclusively, these conductive membranes could be employed as strain sensors to detect the small changes in the output airflow indicated the possible clogging of air filters.

Electrically assisted solution blow spinning of PVDF/TPU nanofibrous mats for air filtration applications.

In this study, pure polyvinylidene fluoride (PVDF), pure thermoplastic polyurethane (TPU), and PVDF/TPU blend nanofibers (1:3, 2:2, 3:1 ratios) were produced via electrically assisted solution blow spinning for air filtration applications. Scanning electron microscopy (SEM) analysis was conducted to investigate the diameters and morphology of nanofibers. The filtration performance of nanofibrous mats was examined by air filtration test with challenging with 0.26 ± 0.07 μm salt particles. Moreover, the flexibility and strength of the samples were determined via tensile tests. Results showed that pure TPU nanofibers had better mechanical properties, while pure PVDF nanofibers showed better filtration performance. However, 3PVDF/1TPU nanofibrous sample had high filtration efficiency (98.86%) close to pure PVDF (99.85%) and better flexibility (32.80% elongation) compared to pure PVDF (11.64% elongation).

Innovative antibacterial electrospun nanofibers mats depending on piezoelectric generation

This paper introduces a new approach of testing piezoelectric nanofibers as antibacterial mat. In this work, both Polyvinylidene fluoride (PVDF) and PVDF embedded with thermoplastic polyurethane nanofibers are synthesized as nanofibers mat via electrospinning technique. Then, such mat is analyzed as piezoelectric material to generate electric voltage under different mechanical excitations. Furthermore, morphological and chemical characteristics have been operated to prove the existence of beta sheets piezoelectricity of the synthesized nanofibers mats. Then, the synthesized nanofibers surfaces have been cyclically stretched and exposed to bacteria specimen. It has been noticed that the generated voltage and the corresponding localized electric field positively affect the growth of bacteria and reduces the formation of K. penomenue samples bacteria colonies. In addition, the effect of both stretching frequency and pulses numbers have been studied on the bacteria count, growth kinetics, and protein leakage. Our contribution here is to introduce an innovative way of the direct impact of the generated electric field from piezoelectric nanofibers on the reduction of bacteria growth, without depending on traditional anti-bacterial nanoparticles. This work can open a new trend of the usability of piezoelectric nanofibers through masks, filters, and wound curing mats within anti-bacterial biological applications.

Different Adsorption Behaviors and Mechanisms of Anionic Azo Dyes on Polydopamine–Polyethyleneimine Modified Thermoplastic Polyurethane Nanofiber Membranes

Considering the notable mechanical properties of thermoplastic polyurethane (TPU), polydopamine–polyethyleneimine (PEI) -modified TPU nanofiber membranes (PDA/PEI-TPU NFMs) have been developed successfully for removal of anionic azo dyes. The adsorption capacity of PDA/PEI-TPU NFMs was evaluated using three anionic dyes: congo red (CR), sunset yellow (SY), and methyl orange (MO). Interestingly, it exhibited different adsorption behaviors and mechanisms of CR on PDA/PEI-TPU NFMs compared with SY and MO. With the decrease in pH, leading to more positive charges on the PDA/PEI-TPU NFMs, the adsorption capacity of SY and MO increased, indicating electrostatic interaction as a main mechanism for SY and MO adsorption. However, wide pH range adaptability and superior adsorption have been observed during the CR adsorption process compared to SY and MO, suggesting a synergistic effect of hydrogen bonding and electrostatic interaction, likely as a critical factor. The adsorption kinetics revealed that chemical interactions predominate in the CR adsorption process, and multiple stages control the adsorption process at the same time. According to the Langmuir model, the maximum adsorption capacity of CR, SY and MO were reached 263, 17 and 23 mg/g, respectively. After six iterations of adsorption–desorption, the adsorption performance of the PDA/PEI-TPU NFMs did not decrease significantly, which indicated that the PDA/PEI-TPU NFMs have a potential application for the removal of CR molecules by adsorption from wastewater.

Constructing synergistically strengthening-toughening 3D network bundle structures by stereocomplex crystals for manufacturing high-performance thermoplastic polyurethane nanofibers reinforced poly(lactic acid) composites

As one of the most promising biodegradable materials, poly(lactic acid) (PLA) is seriously restricted by its notorious inherent brittleness and weak heat distortion resistance. In this work, a novel and simple methodology is proposed using an eccentric rotor extruder (ERE) with a predominantly elongational flow field to manufacture high-performance engineered poly(L-lactic acid)/poly(D-lactic acid)/thermoplastic polyurethane nanofiber composites on an industrial scale. The oriented tough TPU nanofibers (TNFs), rigid integrated PLA hybrid crystals and their good interface compatibility produce a strengthening-toughening bundle structure. When the PDLA content reached 3 wt%, the bundle structures interlinked with each other to form a strengthening-toughening 3D network. This resulted in a high-performance engineered 80L/5D/15T nanofiber composite with super toughness of 74.1 kJ/m2, high strength of 47.3 MPa and superior Young's modulus of 1378 MPa, which are 28.6 times, 85% and 92.7%, respectively, compared with neat PLLA. Compared with those published literatures, the 80L/5D/15T nanofiber composite not only possesses super toughness (more than 28 times) but also maintains good strength (maintain 85%), additionally good heat distortion resistance was also obtained. The performance of 80L/5D/15T nanofiber composite was significantly superior in comparison with biodegradable plastics as well as petroleum-based non-degradable general-purpose plastics and engineering plastics, demonstrating its enormous potential as a substitute structural material in harsh environments. It is believed that the novel and industrial scale methodology opens new perspectives for manufacturing other high-performance engineered biodegradable materials.

Development and characterization of lanolin incorporated electrospun nanofibers for nursing pads

In this study, to combine the biological properties of lanolin and the advantages of electrospun nanofiber mats for developing a potent topical wound dressing/nursing pads that includes lanolin, lanolin incorporated electrospun cellulose acetate (CA), polyethylene oxide (PEO), polyethylene oxide/chitosan (PEO/chitosan) and thermoplastic polyurethane (TPU) nanofibers were developed and characterized. Surface tension, viscosity and conductivity measurements of each polymer solution were carried out in order to characterize the spinning solutions. Lanolin addition did not affect the conductivity values but increase the viscosity of each spinning solution. According to the SEM images, smooth nanofiber surfaces were produced which could be appropriate for a top layer of a nursing pad. Slightly attached, thicker nanofibers could be seen from the TPU/Lanolin images. Similar to TPU nanofibers, CA nanofibers were smoother and thinner than CA/Lanolin nanofibers. Lanolin effected the uniformity of the PEO nanofibers, but it could be said that homogeneous distribution of lanolin was achieved. Characterization of these nanofiber membranes were also carried out with FTIR, DSC, swelling and weight loss analysis. Since TPU nanofibers were hydrophobic and the addition of lanolin made the nanofiber more hydrophobic, they did not show high swelling ratios. CA nanofibers swelled 610% due to their relatively hydrophilic nature and bulky structure. PEO nanofibers were totally dissolved in the water, a very thin layer remained for PEO-Chitosan/lanolin nanofibers. So, using electrospun CA and TPU nanofiber membranes for a nursing pad upper layer could be suitable. CA/lanolin nanofibers showed better hydrophilicity and swelling when compared to TPU nanofibers. On the other hand, TPU nanofibers are more elastic and durable with lower swelling.

A robust metal-organic framework nanofibrous membrane as filter for fast separation of cationic dyes from aqueous solution

• Bio-MOF-1@TPU NFM with robust mechanical properties was successfully fabricated. • Bio-MOF-1@TPU NFM can be used as a filter to separate cationic dye from aqueous solution. • Bio-MOF-1@TPU NFM exhibited fast filtration ability and stable reuse effect. • The separation process was based on the ion-exchange and monolayer adsorption mechanisms. A robust metal-organic framework (MOF) nanofibrous membrane (NFM) was successfully fabricated via electrospinning by employing thermoplastic polyurethane (TPU) as substrate and encapsulating anionic bio-MOF-1 into TPU nanofibers. Characterization with FT-IR, EDS and PXRD confirmed that the crystal structure of bio-MOF-1 maintained well in TPU nanofibers. Based on the ion-exchange mechanism, the as-prepared bio-MOF-1@TPU NFM can be used as a filter for efficient separation of cationic dyes from mixed dyes aqueous solution. Benefiting from the robust mechanical properties of TPU, the bio-MOF-1@TPU NFM can repeatedly withstand the suction filtration pressure without damage, resulting in a very fast dye separation process that completed within 70 s, and a very stable reuse effect that the removal efficiency of MB + was just 9.0 % less than that of the first filtration after five cycles of use. This work will be useful for the design of MOFs NFMs based on electrospinning applied to fast separating organic dyes from practical wastewater.

Flexible, stretchable, breathable and sweatproof all-nanofiber iontronic tactile sensor for continuous and comfortable knee joint motion monitoring

Running improperly for an extended period of time will induce irreversible damage to knee joints, which can bring about excruciating pains to joggers. Wearable sensors for continual knee-monitoring are highly recommended. However, conventional flexible sensors built on airtight substrates are inferior in comfort when wearing for lengthy durations. Herein, a highly flexible and stretchable iontronic tactile sensor is developed on an electrospun thermoplastic polyurethane nanofiber platform. The multilayered, intertwined, nanofiber network housing numerous micro-pores/channels endows the sensor with superior air permeability, sweat inertness, thermal dissipation ability, and biocompatibility, which allows for an extended, comfortable wearing experience. Accrediting the supercapacitive sensing mechanism and porous microstructure, a performance exhibiting a high sensitivity, wide detection range, rapid response, excellent stability and repeatability can be achieved. Pragmatically, a knee-sensor prototype was developed and demonstrated running in real-time and continuously: monitoring a single point of pressure with 3 individual sensor units attached to the rim of the knee and mapping the spatial pressure distribution with an array of sensors covering the whole knee. The health status of the knee could be properly diagnosed, which would be useful for warning of potential knee injuries or to better the form of exercisers.