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Endoscopic surgery is an effective and common clinical practice for chronic sinusitis. Nasal packing materials are applied in nasal surgery to prevent hemorrhage and promote wound healing. In this study, a degradable polyurethane foam dressing is successfully developed as a promising nasal packing material with good biocompatibility and antibacterial capability. Specifically, quaternized chitosan (QCS) serves as the crosslinker instead of polyols to offer polyurethane foam (PUF-QCS) antibacterial capability. The PUF-QCS2.0 % (with 2.0 wt% QCS) exhibits satisfactory liquid absorption capacity (19.4 g/g), high compressive strengths at both wet (14.5 kPa) and dry states (7.7 kPa), and a good degradation rate (8.3 %) within 7 days. Meanwhile, PUF-QCS2.0 % retains long-term antibacterial activity for 7 days and kills 97.3 % of S. aureus and 91.8 % of E. coli within 6 hours in antibacterial testing. Furthermore, PUF-QCS2.0 % demonstrates a positive hemostatic response in the rabbit nasal septum mucosa trauma model by reducing hemostatic time over 50.0 % and decreasing blood loss up to 76.1 % compared to the commercial PVA nasal packing sponge. Importantly, PUF-QCS also exhibits a significant antibacterial activity in nasal cavity. This nasal packing material has advantages in post-surgery bleeding control and infection prevention. The performance of a nasal packing sponge requires good mechanical properties, fast and high liquid absorption rate, effective degradability and strong antibacterial activity. These features are helpful for improving the postoperative recovery and patient healing. However, integrating these into a single polyurethane foam is a challenge. In this study, quaternized chitosan (QCS) is synthesized and used as a chain extender and antibacterial agent in preparing a degradable polyurethane foam (PUF-QCS) dressing. PUF-QCS undergoes partial degradation and exhibits effective broad-spectrum antibacterial activity in 7 days. The reduction of postoperative bleeding and infection observed in the animal experiment further demonstrates that the PUF-QCS developed here outperforms the existing commercial nasal packing materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Water-induced electricity generators (WIEGs) utilize water to generate electricity owing to the electrokinetic interactions between water molecules and nanomaterials. Improving charge carrier density and maintaining a stable concentration gradient are keys to enhancing the performance of the WIEGs. Herein, asymmetric polypyrrole (PPy) coated fabrics are prepared via chemical vapor deposition polymerization followed by partial deposition of a silicone resin to create hydrophobic and hydrophilic regions. A water-segregated connection (WSC) mode is developed for the WIEG (WCS-WIEG) with a pair of Fe electrodes, which demonstrates 36% and 34% improvement in voltage and current compared to the closed circuit connection mode due to the ion accumulation on the electrical double layer (EDL). When doped with FeCl 3 , the voltage, peak current density, and power density of the WCS-WIEG are further enhanced to 0.90 V, 1625 μA cm−3, and 360 μW cm−3, respectively. The high performances of the WCS-WIEG are attributed to the synergetic effect of the WSC mode, ion doping, and redox reaction on electrodes. Moreover, the FeCl 3 doped WCS-WIEG possesses excellent stability in long-term operation and demonstrates the ability to charge capacitors and drive a calculator or LED directly. This work provides new insights into the design and ion doping approach for developing WIEGs. [Display omitted] • A water-segregated connection (WSC) mode is developed for water-induced electricity generation. • The WSC mode demonstrates significant performance improvement compared to the closed circuit connection mode. • When doped with FeCl 3 , the binding energy calculated by DFT and power density are further enhanced. [ABSTRACT FROM AUTHOR]

Thermosetting polyimide (PI) foams (PIFs) are usually synthesized through chemical foaming; however, this approach is environmentally toxic, and it is difficult to regulate the cell structure, remold the foam, and increase the foam compressive strength. The development of microcellular PIFs with ultrahigh compressive strength and high volume expansion ratio remains a challenge. Herein, thermoplastic PI with a branched structure and flexible ether bonds was synthesized through solution polymerization, and microcellular thermoplastic PIFs (TPIFs) with ultrahigh strength were fabricated via supercritical-carbon-dioxide foaming using 2,4,6-triamino pyrimidine (TAP) as a chain-extender monomer. Subsequently, a lattice model of a closed tetrakaidecahedral cell was used to clarify the relation between the foam compressive strength and polymer cell structure. Experimental results indicate that the optimal thermal imidization temperature is 230 °C and that the resulting branched structure considerably improves viscoelasticity, flame retardancy, and foaming performance. A TAP content of 0.75 g results in branched-structure TPIFs with a mean cell size of 16.8 μm. Notably, at high temperatures and pressures, the compressive strength of TPIFs with 0.75 g TAP is more than nine times of that of TPIFs without TAP. Increasing the TAP content beyond 0.75 g results in a crosslinked structure. Backward differentiation shows that TPIF compression is constant at 0.14–0.18 in the [0,0,1] lattice direction. The proposed physical foaming method is environment-friendly and can sustainably produce TPIFs with a high volume expansion ratio, an adjustable microcellular structure, and outstanding mechanical properties. [Display omitted] • Branched thermoplastic polyimide (TPI) synthesized via solution polymerization. • TPI offers superb flame resistance and recyclability for fireproofing. • Microcellular TPI foams are fabricated by supercritical CO 2 foaming. • TPI foams exhibit uniform structure and strong compressive strength. • Lattice model clarifiies the relationship between compressive strength and polymer cell structure. [ABSTRACT FROM AUTHOR]

Polyimide foams (PIFs), renowned as some of the best materials for excellent performance in harsh temperature environments, have been developed to meet the increasing demands of high-tech industries. A state-of-the-art review of advanced PIFs research was conducted, covering the general research profiles and trends, institutions and scholars, major journals, research categories, and application fields through a bibliometric analysis of publications.Research on polyimide-based foam has increased approximately 30-fold over the past 40 years. One hundred forty-two research institutions from 20 countries have conducted research related to PIFs. Literature co-citation analysis reveals that the knowledge base of the PIFs research field primarily focuses on chemical synthesis foaming. This spotlight on engineering applications systematically describes the synthesis mechanisms, various typical fabrication methods, and the microstructure of PIFs. The advantages and disadvantages of this methods have been compared. Representative functions and corresponding mechanism models, which include thermal, mechanical, sensing, electromagnetic, flame retardant, oil-water separation, and other fields, have been outlined. This review offers insights into the technological development prospects and opportunities. Finally, the arduous tasks and challenges of PIFs research are summarized, providing valuable guidance for researchers interested in this field. [Display omitted] • A state-of-the-art review of PIFs research through bibliometric analysis • The synthesis mechanism, fabrication methods, and the microstructure of PIFs were systematically described. • Representative functions and the corresponding mechanism models were concluded • Provided information on the technological development prospects and opportunities • The arduous tasks and challenges of PIFs were summarized [ABSTRACT FROM AUTHOR]

Developing novel absorbent materials targeting high-efficiency, low-energy-consumption, and environmental-friendly oil spill cleanup is still a global issue. Porous absorbents endowed with self-heating function are an attractive option because of that they are able to in-situ heat crude oil and dramatically reduce oil viscosity for efficient remediation. Herein, we facilely prepared an eco-friendly multifunctional bacterial cellulose/MXene aerogel (P-SBC/MXene aerogel) for rapid oil recovery. Thanks to excellent full solar spectrum absorption (average absorbance = 96.6 %), efficient photo-thermal conversion, and superior electrical conductivity (electrical resistance = 36 Ω), P-SBC/MXene aerogel exhibited outstanding photothermal and electrothermal capabilities. Its surface temperature could quickly reach 93 °C under 1.0 kW/m2 solar irradiation and 124 °C under 3.0 V voltage respectively, enabling effective heat transfer toward spilled oil. The produced heat significantly decreased crude oil viscosity, allowing P-SBC/MXene aerogel to rapidly absorb oil. By combining solar heating and Joule heating, P-SBC/MXene aerogel connected to a pump-assisted absorption device was capable of achieving all-weather crude oil removal from seawater (crude oil flux = 630 kg m−2 h−1). More notably, P-SBC/MXene aerogel showed splendid outdoor crude oil separation performance. Based on remarkable crude oil/seawater separation ability, the versatile aerogel provides a promising way to deal with large-area oil spills. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Higher quenching temperature and longer quenching period facilitate SC crystal formation. • The addition of deionized water to the solvent effectively enhances the formation of SC crystals. • The introduction of carbon nanotubes (CNTs) as a nucleating agent significantly impacts SC crystals formation. The formation of stereo-complex crystals (SC) in porous poly (lactic acid) (PLA) material is intricately linked with improving its comprehensive properties. In this work, the effects of process conditions, solvent composition and additional nucleating agent on SC crystals during the fabrication of porous PLA through thermally-induced phase separation method were studied. Crystallization behavior of SC crystals during the pore-forming process is systematically investigated, revealing that higher quenching temperature and longer quenching period facilitate the formation of SC crystals. Additionally, the addition of deionized water to the solvent effectively enhances SC crystals formation by reducing solution viscosity and prolonging the phase separation time. The highest crystallinity of SC crystals (X SC) can be achieved, reaching 30.6%, when the water content is controlled at 1.6%. Furthermore, the introduction of carbon nanotubes (CNTs) as a nucleating agent exhibits a pronounced effect on the formation of SC crystals. When incorporating a 3 wt% content of CNTs, X SC reaches its peak value at 37.7%. This work is helpful to provide reference for improving mechanical properties and heat resistance of porous PLA, thereby expanding its potential outdoor applications. [ABSTRACT FROM AUTHOR]

Benefitting from the wearability, ductility and portability, flexible and stretchable strain sensors display a more extensive field of applications than traditional sensors in terms of medical diagnosis, smart home, environmental monitoring and so on. However, the critical sensing performances, such as sensitivity, sensing range, stability and detection limit of flexible strain sensors still need to be improved. Microstructural optimization has been considered as an efficient strategy for tuning the performances. In this work, a carbon nanotubes (CNTs)/carbon black (CB)/thermoplastic polyurethane (TPU) fibrous film (CCTF) is prepared through electrospinning, spraying and ultrasonic anchoring technique. Synergetic conductive layers by combining CNTs/CB and CB are constructed on both sides of CCTF. In virtue of the optimization of microstructures and the synergetic conductive network, the obtained CCTF possesses an ultrawide response range (up to 500 % strain), high sensitivity (gauge factor, GF up to 1516), short response/recovery time (80/80 ms), low detection limit (0.05 % strain), favorable sensing stability and long-term durability. CCTF with excellent strain sensing performances is assembled as a strain sensor, which accounts for full range human biological signal acquisition, including joint movements, muscle tension, and facial micro-expressions. This paper provides a certain reference significance for the preparation and fabrication of next-generation flexible strain sensors with high performances. A flexible strain sensor based on carbon nanotubes (CNTs)/carbon black (CB)/thermoplastic polyurethane (TPU) film (CCTF) is fabricated through electrospinning, spraying and ultrasonic anchoring technologies. CCTF possesses excellent sensing performance due to the optimization of the microstructure, achieving a wide sensing range (up to 500 % strain), high sensitivity (GF up to 1516), low detection limit (0.05 % strain), and short response/recovery time (80/80 ms). [Display omitted] • A fibrous strain sensor with synergetic conductive networks of CNTs/CB and CB is fabricated. • The sensor possesses both a wide sensing range (500 % strain) and high sensitivity (GF up to 1516). • Low detection limit (0.05 % strain) and short response/recovery time have also been achieved. • The sensor is demonstrated to precise full range human biological signal acquisition. [ABSTRACT FROM AUTHOR]

Nowadays, passive radiative cooling (PRC) has being attracted intensive attention because it can realize cooling effect without consuming any energy. Unfortunately, fabricating polymer film with radiative cooling effect by a facile, continuous and environmentally friendly method is still a large challenge. In this study, high density polyethylene (HDPE)/polyvinyl oxide (PEO) film were first fabricated by melt extrusion casting method, and polyethylene film composed of directional microfibrils (PFCDM) were finally obtained after selective dissolution of PEO phase in deionized water at 70 °C. The as-prepared PFCDM shows higher average solar reflectivity of 85.17% in the visible range and stronger average mid-infrared emissivity of 82.04% within the atmospheric window. It shows a sub-ambient cooling of 23.28 °C during the day and 3.1 °C at night, suggesting that it has a remarkable PRC performance. Moreover, the as-prepared PFCDM has outstanding wearability and self-cleaning property, showing promising potential of personal thermal management. This study proposes a facile but environmentally friendly method for fabricating PFCDM, paving a new way to develop wearable PRC film following the concept of thermoplastic polymers "functionalized" processing. [Display omitted] • PFCDM was efficiently prepared via melt extrusion casting and water leaching. • PFCDM shows remarkable passive radiative cooling performance. • PFCDM has higher day and night cooling power. • PFCDM has outstanding wearability and self-cleaning property. [ABSTRACT FROM AUTHOR]

Flexible transparent electromagnetic interference (EMI) shielding films in visual windows are crucial for the innovation of optoelectronic devices, but the challenge of balancing light transmittance and EMI shielding effectiveness (SE) still exists. Herein, this work described a flexible transparent MXene@SWNTs/PC film with a hierarchical conductive layer that was fabricated via an alternating rotation spraying method. The multi-scale hierarchical structure configured with 1D SWNTs and 2D MXene endow the obtained film with good comprehensive properties, i. e, low sheet resistance of 32.8 Ω/sq at 56.1% light transmittance, thus causing a satisfactory EMI SE of 20.8 dB. Moreover, the transparent shielding films exhibit remarkable flexibility, which can maintain steady EMI SE after 1000 continuous bending cycles. More importantly, the low sheet resistance and high light absorption capacity of hybrid conductive layer facilitate the transparent shielding film with low-voltage-driven electric heating effect and outstanding photothermal conversion ability, respectively, ensuring the normal operation under extreme cold condition. The combination of good light transmittance, satisfactory EMI shielding performance, and multi-source thermal response enables MXene@SWNTs/PC film to have great potential as a transparent shielding film in emerging optoelectronic devices. A multifunctional MXene@SWNTs/PC film with hierarchical structure prepared via an alternating rotation spraying process, integrating capabilities of light transmittance, EMI shielding, and multi-source thermal response together. [Display omitted] [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) inherently shows the distinct brittleness at room temperature, which is a major drawback limiting its practical applications. Great efforts have been done to improve the toughness by adding high content of flexible polymers or low content of nanoparticles, which is often at the expense of tensile strength. In this work, supertoughened PLA blend with high elongation at break (247.7%) containing low content of poly(ethylene oxide) (PEO) (8%) was directly fabricated by melt extrusion method. Interestingly, its tensile strength and modulus are only slightly decreased (<25%). The reasons for the balanced mechanical property can be understood as follows: I) The increasing mobility of amorphous chains of PLA due to the plasticizing effect of PEO. II) The strengthening effect of mesophase can hinder tensile strength to be severely sacrificed. III) The rod-like PEO phase can initiate more crazes and further prevents them from developing into cracks, allowing effective energy dissipation. This study proposes a facile but efficient strategy to fabricate PLA blends containing low content of PEO with balanced mechanical property, which would provide a clue for toughening other brittle thermoplastics. [Display omitted] • PLA blend with balanced mechanical property is directly prepared by melt extrusion. • A low content of PEO can realize the supertoughness of PLA. • The tensile strength and modulus are only slightly decreased. • Mesophase and rod-like phase morphology are keys to supertoughness. [ABSTRACT FROM AUTHOR]

To get strong and anti-freezing hydrogel with multiple contact and non-contact sensing performance, a facial method is proposed in this work using multiple physical bonding crosslinking and glycerol (GL) immersing strategy. The obtained hydrogels show a tensile stress at break of 5.4 MPa, an elongation at break of 1420 %, and a compression strength of 12.2 MPa at 80 % strain. Additionally, benefiting from the GL immersing the hydrogel shows superior anti-freezing (no ice formation at −60 °C) and water retention ability (water loss less than 17 % after storing at 50 °C for 7 h). Furthermore, the volume resistance of hydrogels exhibits excellent responses against humidity, temperature, strain, and stress. The variation of the resistance against temperature can be well described by the Arrhenius equation with an activation energy of 501.3 meV, verifying a band-gap dominated diffusion hopping conductive mechanism of the hydrogel. The sufficient humidity and temperature responses make the hydrogel applicable as a non-contact sensor, and the wide temperature strain sensing (−40 to 50 °C) and stress sensing capability ensures that the hydrogel can be used as a contact sensor, ensuring that the hydrogel can be used as perfect flexible sensor for monitoring human motion and physiological signals. [Display omitted] • Strong and anti-freezing hydrogel with multiple sensing performance is obtained. • The hydrogel is prepared using multiple physical bonding crosslinking and glycerol immersing strategy. • The resistance variation against temperature is described by the Arrhenius equation with an activation energy of 501.3 meV. [ABSTRACT FROM AUTHOR]

Addressing water pollution issues is directly related to green sustainable development. In this work, a heterostructure polyurethane-based (PU) sponge was prepared by a facile "dip-adhere" strategy to achieve simultaneous and efficient removal of oils and dyes from water. This innovatively designed sponge comprises two functional layers. The hydrophobic/lipophilic octadecylamine-molybdenum disulfide coated PU sponge (ODA-MoS 2 @PU) layer exhibits excellent sorption capacity, ranging from 37.35 to 63.52 times its own weight, for eight organic solvents (DMSO, isopropanol, n-hexane, petroleum ether, n-butanol, glycol, acetone, xylene) and five oils (soybean oil, olive oil, gasoline, diesel, and lubrication). Furthermore, it exhibits robust stability in extreme environments and maintains a high separation efficiency (99 % after 50 separations). The photocatalytic/superhydrophilic polydopamine-molybdenum disulfide coated PU sponge (PDA-MoS 2 @PU) layer demonstrates great photocatalytic degradation efficiency for dyes (96.80 % for methylene blue and 97.39 % for methyl orange). Consequently, the heterostructure PU sponge holds application potential in environment remediation. [Display omitted] • A dual-functional heterostructure sponge was prepared. • Continuous oil-water separation was realized with the oil-gathering device. • The simultaneous treatment of removing oils and dyes was achieved. [ABSTRACT FROM AUTHOR]

For smart devices, there is a growing demand for multi-functional soft actuators, nevertheless, well-developed actuators always respond to single stimulus, and it is still challenging to achieve the application diversity standards. Herein, a bidirectional multi-stimuli responsive soft actuator based on Ti 3 C 2 T X MXene-cellulose nanowhiskers (CNWs)-polyvinyl alcohol (PVA)/polydimethylsiloxane (PDMS) multilayer membranes is proposed (MXCP-P). By grafting CNWs onto MXene nanosheets, a freestanding composite film with gradient layered structure was prepared. Due to the hygroscopicity among MXene nanosheets, increased interlayer space is in favor of adsorption/desorption of water molecules, causing invertible shape change and humidity-driven deformation with a rapid response. Based on high photothermal conversion capacity of MXene and large difference of coefficient of thermal expansion between PDMS and MXene, the MXCP-P achieves an ultra-large amplitude and fast response driven by natural light. A Venus flytrap soft robot is constructed with good actuation behaviors. The MXCP-P film was employed as actuators in the opera of The Male Phoenix Pursui from Han Dynasty and in shadow puppetry "Monkey King Subdus the White-Bone Demon" of China, both exhibiting excellent performances towards humidity and light stimuli synchronously. This paper inspires a new strategy for multi-stimuli responsive soft bionic robots and intelligent traditional shadow play. MXCP-P based multi-stimuli responsive flexible actuator was fabricated, showing improved mechanical properties and bidirectional bending characteristics. In addition to its application in traditional fly traps and rolling robots, the MXCP-P actuator is also employed to develop traditional Chinese opera culture, such as "The Male Phoenix Pursui" and "Shadow puppetry". [Display omitted] [ABSTRACT FROM AUTHOR]

Polyimide foams (PIFs) are usually synthesized by solution polymerization, followed by chemical foaming to prepare thermosetting foam. In this research, lightweight microcellular thermoplastic polyimide foams (TPIFs) were fabricated via a novel two-step foaming approach using supercritical carbon dioxide (scCO 2) as a blowing agent. The poly(amic acid) (PAA) and polyester ammonium salt (PEAS) precursor solutions were synthesized with pyromellitic dianhydride (PMDA) as dianhydride reagents and polyether amine Jeffamine D230 as aliphatic diamine reagent via blending and solution polymerization, respectively. The solution polymerization process demonstrated a higher molecular weight and superior formability than the blending process. The optimum thermal imidization temperature of 200 °C was optimized via the thermal and rheological property analysis. The cell morphology and mechanical properties of the TPIFs could be turned by varying the saturation time, foaming pressure, and imidization temperature. At a thermal imidization temperature of 200 °C, the TPIFs exhibited a branched structure with a small mean cell diameter (123.78 μm), and a high compressive strength (0.4 MPa) under 10 % strain at high temperature and pressure, which was more than ten times that of the TPIFs with thermal imidization temperature of 130 °C. This research provides a feasible method for producing high volume expansion ratio TPIFs with adjustable microcellular structures and outstanding mechanical properties. [Display omitted] • Poly(amic acid) and polyester ammonium salt precursor were synthesized by blending and solution polymerization, respectively. • Adding a flexible linkage provided the torsional capacity of the chain segment, and improved its flexibility. • Microcellular TPI foams were fabricated via a novel two-step foaming approach using supercritical CO 2 as a blowing agent. • The branched molecular structure was favourable for improving cell uniformity and mechanical properties. [ABSTRACT FROM AUTHOR]