Solvent-free Fabrication Research Articles

Fusion Bonding Technique for Solvent-Free Fabrication of All-Solid-State Battery with Ultrathin Sulfide Electrolyte.

For preparing next-generation sulfide all-solid-state batteries (ASSBs), the solvent-free manufacturing process has huge potential for the advantages of economic, thick electrode, and avoidance of organic solvents. However, the dominating solvent-free process is based on the fibrillation of polytetrafluoroethylene, suffering from poor mechanical property and electrochemical instability. Herein, a continuously solvent-free paradigm of fusion bonding technique is developed. A percolation network of thermoplastic polyamide (TPA) binder with low viscosity in viscous state is constructed with Li6PS5Cl (LPSC) by thermocompression (≤5MPa), facilitating the formation of ultrathin LPSC film (≤25µm). This composite sulfide film (CSF) exhibits excellent mechanical properties, ionic conductivity (2.1 mS cm-1), and unique stress-dissipation to promote interface stabilization. Thick LiNi0.83Co0.11Mn0.06O2 cathode can be prepared by this solvent-free method and tightly adhered to CSF by interfacial fusion of TPA for integrated battery. This integrated ASSB shows high-energy-density feasibility (>2.5 mAh cm-2 after 1400 cycles of 9200 h and run for more than 10 000 h), and energy density of 390 Wh kg-1 and 1020 Wh L-1. More specially, high-voltage bipolar cell (≥8.5V) and bulk-type pouch cell (326 Wh kg-1) are facilely assembled with good cycling performance. This work inspires commercialization of ASSBs by a solvent-free method and provides beneficial guiding for stable batteries.

Solvent free fabrication and thermal tuning of copper oxide-zirconium dioxide nanocomposite for enhanced photocatalytic efficacy

Recently, several methods has been used for the synthesis of bimetal oxide nanocomposite, however, very few studies are available on the solvent free mechanochemical synthesis of nanomaterials. In this study, mortar and pestle assisted fabrication of copper oxide-zirconium dioxide nanocomposite (CuO–ZrO2 NC) was carried out and was calcined at 300, 600 and 900 °C. The variation in crystallographic parameters was examined through x-ray diffraction (XRD) and the crystallite size was found to be gradually increased with increasing calcination temperature. The morphological changes with increasing calcination temperature were traced during scanning electron microscopy (SEM) analysis. The percentage elemental composition was verified through energy dispersive x-ray (EDX) spectroscopy whereas the functional group analysis was done through Fourier transform infrared (FTIR) spectroscopy, where the intensity of peaks assigned to hydroxyl moiety decreased with increasing calcination temperature. The CuO–ZrO2 NCs were used as a photocatalysts for the degradation of the Fluorescein in the presence of solar light and highest photodegradation (77.27%) was noticed for the CuO–ZrO2 NC calcined at 900 °C.

Solvent-free fabrication of mechanically durable superhydrophobic film with regular hollow structures for passive cooling

Solvent-free fabrication of mechanically durable superhydrophobic film with regular hollow structures for passive cooling

Solvent-Free Fabrication of Anisotropic Microparticles with Precise 3D Shape Control Using Dipping-Based Micromolding.

We present an innovative solvent-free micromolding technique for rapidly fabricating complex polymer microparticles with three-dimensional (3D) shapes utilizing a surface tension-induced dipping process. Our fabrication process involves loading a photocurable solution into micromolds through mold dipping. The loaded solution, induced by surface tension, undergoes spatial deformation upon mold removal caused by surface forces, ultimately acquiring an anisotropic shape before photopolymerization. Results show that the amount of photocurable solution loaded depends on the degree of capillary penetration, which can be adjusted by varying the dipping time and mold height. It enables the production of polymer particles with precisely controlled 3D shapes without diluting them with volatile organic solvents. Sequential micromolding enables the spatial stacking of the polymer domain through a bottom-up approach, facilitating the creation of complex multicompartmental microparticles with independently controlled compartments. Finally, we demonstrated the successful simultaneous conjugation of multiple model-fluorescent proteins through the biofunctionalization of microparticles, indicating functional stability and effective conjugation of hydrophilic molecules such as proteins. We also extend our capacity to create bicompartmental microparticles with distinct functionalities in each compartment, revealing spatially controlled functional structures. In summary, these findings demonstrate a straightforward, rapid, and reliable method for producing highly uniform complex particles with precise control over the 3D shape and compartmentalization, all accomplished without the use of organic solvents.

Green and solvent-free fabrication of conductive halloysite–polythiophene nanocomposites for the removal of organic pollutants from aqueous media

Abstract Toxic pharmaceutical pollutants, such as nicotine, represent a significant threat to natural water sources due to their continuous discharge. To address this issue, clay minerals and their composites have demonstrated exceptional adsorptive and remedial capabilities for wastewater purification. This research focused on developing green clay-polymeric adsorbents for the efficient removal of pharmaceutical pollutants from industrial wastewater. The synthesis involves creating halloysite nanotube–polythiophene nanocomposites through a green and cost-effective method using vapour polymerization and a solvent-free, ball-milled technique for the adsorptive removal of nicotine from wastewater. The investigation evaluates the impacts of preparation, modification and environmental conditions on the adsorptive performance of these clay-based nanocomposites compared to pure polythiophene. The polymerization process was evaluated by varying the vapour polymerization holding time for a fixed amount of oxidant (FeCl3) and halloysite nanotube (HNT) to investigate the impacts of monomer vapour exposure time on the polymerization of nanocomposites. Following the characterization of the synthesized adsorbents using various methods, the study investigated the impacts of various parameters (e.g. adsorbent dosage, pH and contact time) on the adsorption capabilities of the materials on a laboratory scale. The results revealed that the incorporation of HNT improved the adsorbing performance of nanocomposites. The pH, absorbent concentration and contact time directly affect nicotine adsorption. Significantly, halloysite–polythiophene 3 with a 2 h polymerization duration demonstrated the maximum adsorption efficacy of 78.94% at pH 10 after a 24 h contact time. The environmentally friendly halloysite-based nanocomposite shows promising potential as an effective adsorbent for pharmaceutical pollutant (nicotine) removal from aquatic environments.

Solvent-free fabrication of pore-filling cation-exchange membranes for highly efficient desalination

The traditional route for ion-exchange membrane fabrication usually involves complex procedures that require substantial quantities of organic solvents and optionally undergo post-modification utilizing strong base or acid. Here, we develop a completely green route for cation-exchange membrane fabrication via a simple soaking pore-filling polymerization method using water as the sole solvent. The resulting pore-filling cation-exchange membranes (PFCEMs) exhibited high ion exchange capacity, moderate water uptake, robust mechanical properties, low area resistance (1.3 Ω cm2) and high limiting current density (181 mA cm−2), leading to superior performance for salt desalination. Benefiting from the superior electrochemical properties, PFCEM achieved an ideal desalination rate of 93.4 %, which was comparable to that of the flagship commercial Neosepta CMX membrane (91.5 %). In addition, the low membrane cost and satisfactory long-term stability of the PFCEMs indicated promising features for their scale-up in industrial production and applications.

Paintable Silicone-Based Corrugated Soft Elastomeric Capacitor for Area Strain Sensing.

Recent advances in soft polymer materials have enabled the design of soft machines and devices at multiple scales. Their intrinsic compliance and robust mechanical properties and the potential for a rapid scaling of the production process make them ideal candidates for flexible and stretchable electronics and sensors. Large-area electronics (LAE) made from soft polymer materials that are capable of sustaining large deformations and covering large surfaces and are applicable to complex and irregular surfaces and transducing deformations into readable signals have been explored for structural health monitoring (SHM) applications. The authors have previously proposed and developed an LAE consisting of a corrugated soft elastomeric capacitor (cSEC). The corrugation is used to engineer the directional strain sensitivity by using a thermoplastic styrene-ethylene-butadiene-styrene (SEBS). A key limitation of the SEBS-cSEC technology is the need of an epoxy for reliable bonding of the sensor onto the monitored surface, mainly attributable to the sensor's fabrication process that comprises a solvent that limits its direct deployment through a painting process. Here, with the objective to produce a paintable cSEC, we study an improved solvent-free fabrication method by using a commercial room-temperature-vulcanizing silicone as the host matrix. The matrix is filled with titania particles to form the dielectric layer, yielding a permittivity of 4.05. Carbon black powder is brushed onto the dielectric and encapsulated with the same silicone to form the conductive stretchable electrodes. The sensor is deployed by directly painting a layer of the silicone onto the monitored surface and then depositing the parallel plate capacitor. The electromechanical behavior of the painted silicone-cSEC was characterized and exhibited good linearity, with an R2 value of 0.9901, a gauge factor of 1.58, and a resolution of 70 με. This resolution compared well with that of the epoxied SEBS-cSEC reported in previous work (25 με). Its performance was compared against that of its more mature version, the SEBS-cSEC, in a network configuration on a cantilever plate subjected to a step-deformation and to free vibrations. Results showed that the performance of the painted silicone-sCEC compared well with that of the SEBS-cSEC, but that the use of a silicone paint instead of an epoxy could be responsible for larger noise and the under-estimation of the dominating frequency by 6.7%, likely attributable to slippage.

Organic solvent-free fabrication of thin film polyamide/zeolitic imidazolate framework membranes for removal of dyes from water

Thin film composite (TFC) polyamide (PA) membranes in combination with zeolitic imidazolate frameworks (ZIF), such as ZIF-8 and ZIF-93, have been fabricated using a novel approach based on vapor phase interfacial polymerization (VIP). These membranes have been investigated for nanofiltration (NF) of aqueous solutions of organic dyes, such as Rose Bengal (RB, 1017 Da), Sunset Yellow (SY, 452 Da) and Acridine Orange (AO, 265 Da). The preparation of the PA layer by VIP technique avoids the use of any organic solvent that is typically required in the conventional PA synthesis. Both ZIF-8 and ZIF-93 were initially synthesized using conventional procedures (methanol-based route) and incorporated to the PA layer in two different configurations: i) thin film nanocomposite with ZIF embedded within the PA film, and ii) bilayer membranes with a layer of ZIF between the support and the PA layer. The synthesis of ZIF-93 using a water-based route was developed for the bilayer configuration allowing for an organic solvent-free fabrication of PA/ZIF-93 bilayer VIP-TFC. These membranes showed the highest water permeances of 2.6, 3.4 and 2.2 L m-2h−1 bar−1 for RB, SY and AO, respectively. As compared to the control membrane VIP-TFC, this represents permeance increases of 69–117% and maintains high (greater than 99%) rejection of all the organic dyes. Membrane characterization demonstrated that the permeance enhancement for bilayer PA/ZIF-93 VIP-TFCs is related to an improved hydrophilicity, higher surface roughness and thinner selective layers. The prepared membranes demonstrated excellent cycle stability, maintaining their initial water permeance and dye rejection throughout 34 h of long-term operation, and being able to operate across the entire pH range studied (pH 3 to 9) without any detrimental effects on performance.

Solvent-free lithium iron phosphate cathode fabrication with fibrillation of polytetrafluoroethylene

Fabricating electrode for lithium-ion batteries (LiBs) with solvent-free (SF) procedure can save energy and improve electrochemical performance simultaneously. Polymer fibrillation is one of the most promising SF procedures due to its feasibility for upscale production. The hardness of lithium iron phosphate (LFP) impedes its SF fabrication with polytetrafluoroethylene (PTFE) fibrillation. In this study, we successfully expanded PTFE fibrillation for SF LFP electrode fabrication with the help of carbon nanotubes (CNTs). CNTs increase the conductivity of electrode, and act as matrix for LFP particles to ensure relative displacement to further fibrillate PTFE to form self-supporting electrode film when the dry mixture was hot rolled. The SF LFP/hard carbon full cells were fabricated and demonstrated comparable electrochemical performance to slurry casting (SC) fabricated LFP electrode. The initial coulombic efficiency (ICE) of full cell increased to more than 95% after prelithiation.

Organic solvent-free constructing of stable zeolitic imidazolate framework functional layer enhanced by halloysite nanotubes and polyvinyl alcohol on polyvinylidene fluoride hollow fiber membranes for treating dyeing wastewater

In this study, zeolitic imidazolate framework (ZIF-8)/polyvinylidene fluoride (PVDF) loose nanofiltration (NF) hollow fiber membranes were fabricated by constructing ZIF-8 functional layer on the PVDF supporting membranes based on the vacuum-assisted assembly process. The ZIF-8 synthesis was completed in a water system, and the synthesized ZIF-8 suspension was directly added to polyvinyl alcohol (PVA) and halloysite nanotubes (HNTs) aqueous solution system without drying to prepare the casting solution, which could solve the agglomeration and poor dispersion problem of ZIF-8 particles. In addition, the embedded HNTs and the loaded PVA among the ZIF-8 layer could improve the bonding strength between the ZIF-8 layer and the supporting membranes. After constructing ZIF-8 functional layer, the pore size of supporting membranes decreased from more than 300 nm to several nanometers. Furthermore, the water contact angle reduced from 91.1° to 54.2°. Applied to treat dye wastewater, the prepared ZIF-8/PVDF membranes maintained high dye rejection (˃99.0 %) for Congo red (CR), but low salt rejection for NaCl (about 2 %). In addition, the flux could reach 21.6 L m-2h−1 after continuous filtration 360 min, exhibiting a potential for treating the dye/salt wastewater. In particular, there were no organic solvents used in the work, which provided a promising idea for solvent-free fabrication of loose NF membranes.

Synthesis and Structure of 2-Hydroxypropyl Methacrylate-Capped Isophorone Diisocyanate and Poly(Propylene Glycol) Urethane Mixtures and the Properties of their UV-Cured Co-Networks with Isobornyl Methacrylate

Polyurethane acrylate prepolymers with different contents of HIPIH and HIH were synthesized via reacting excessive isophorone diisocyanate (IPDI) with poly(propylene glycol) (PPG) and then end-capping with 2-hydroxypropyl methacrylate (HPMA) in isobornyl methacrylate (IBOMA). After the addition of the photoinitiator PI 1173, the resulting prepolymer resins were irradiated by UV light to form cured materials. The structures of the prepolymers were confirmed by 1H NMR, FT-IR, and GPC. SEM analyses proved that no obvious phase separation was observed within the cured sample. As the content of HIH increased, the viscosity of the prepolymers increased slightly. In addition, the gel content, solvent resistance, Shore hardness, Young's modulus, and the tensile strength of the cured films increased, whereas the elongation at break decreased gradually. The volume shrinkage of the cured samples ranged between 4.5% and 4.8%. DMA analyses showed that the Tgs of the cured samples increased as more HIH structures existed. TGA analyses revealed that the cured samples had high thermal stability. This solvent-free fabrication process was simple, convenient, and controllable. By simply regulating the contents of HIPIH and HIH in the prepolymers, the performances of the cured materials could be adjusted to a wide range.

Solvent-free fabrication of photothermal polypyrrole-coated sulfur particles for solar steam generation

The use of solar heat to produce steam holds great potential in terms of solving drinkable freshwater scarcity worldwide. However, the fabrication of low-cost, large-scale photothermal materials remains difficult; existing multi-step processes use toxic solvents. Here, a solvent-free and facile synthetic process is presented: we coat sulfur (S) with polypyrrole (PPY), then use PPY-coated S (S-PPY) as a photothermal layer for solar steam generation. We demonstrate an excellent solar steam evaporation rate (2.13 kg m-2h−1 at 1 Sun light intensity; efficiency 88.92 %). The use of inexpensive and abundant S as a substrate for PPY photothermal composites will find many energy-conversion applications as welll as water purification and desalination via solar steam generation.

Solvent-Free Fabrication of Thick Electrodes in Thermoplastic Binders for High Energy Density Lithium-Ion Batteries.

The rapid development of electric vehicles has generated a recent demand for high energy density lithium-ion batteries (LIBs). One simple, effective way to enhance energy density of LIBs is to increase the thickness of electrodes. However, the conventional wet process used to fabricate thick electrodes involves the evaporation of large amounts of organic solvents, which causes an inhomogeneous distribution of conductive additives and binders. This weakens the mechanical and electrochemical network between active materials, resulting in poor electrochemical performance and structural degradation. Herein, we introduce a new strategy to produce homogeneous thick electrodes by using a dry, solvent-free process. Instead of using a conventional PVDF (polyvinylidene fluoride) binder, we employed a phenoxy resin as the binder in dry process for the first time. This thermoplastic binder exhibits better ductile properties than PVDF in the way that it generates a uniform network structure that connects the active materials during the hot press process. This enables the production electrochemically stable electrodes without using organic solvents, which record capacity retention rates of 73.5% over 50 cycles at a 40 mg/cm2 of thick electrodes. By contrast, thick electrodes produced with a PVDF binder via wet processing only have a capacity retention rate of 21.8% due to rapid structural degradation.

One-step solvent-free fabrication of superhydrophobic cellulose powder with reversible wettability

Superhydrophobic cellulose-based products show tremendous potential applications in both industries and researches owing to their inherent biodegradability, non-toxicity, and cost-effectiveness. However, previous studies mainly focused on superhydrophobic cellulose bulk materials rather than universal cellulose powder. Though some methods have been proposed for preparing superhydrophobic cellulose powder, their fabricating processes involve plenty of high-toxic organic solvents. In this work, we proposed a facile one-step solvent-free method to prepare superhydrophobic cellulose powder. The modified cellulose powder shows not only superhydrophobicity but also reversible wettability. Moreover, the superhydrophobic cellulose shows immense UV resistance by enduring 60 h UV radiation. The superhydrophobic cellulose powder-coated cotton fabric could separate oil/water mixture with high efficiency and reusability. This work provides a green method to produce superhydrophobic cellulose powder which can be used as a raw material for sophisticated multifunctional material fabrication in future.

Self-shrinking soft demoulding for complex high-aspect-ratio microchannels

Microchannels are the essential elements in animals, plants, and various artificial devices such as soft robotics, wearable sensors, and organs-on-a-chip. However, three-dimensional (3D) microchannels with complex geometry and a high aspect ratio remain challenging to generate by conventional methods such as soft lithography, template dissolution, and matrix swollen processes, although they are widespread in nature. Here, we propose a simple and solvent-free fabrication method capable of producing monolithic microchannels with complex 3D structures, long length, and small diameter. A soft template and a peeling-dominant template removal process are introduced to the demoulding process, which is referred to as soft demoulding here. In combination with thermal drawing technology, microchannels with a small diameter (10 µm), a high aspect ratio (6000, length-to-diameter), and intricate 3D geometries are generated. We demonstrate the vast applicability and significant impact of this technology in multiple scenarios, including soft robotics, wearable sensors, soft antennas, and artificial vessels.

Doping Mechanism of Perovskite Films with PbCl2 Prepared by Magnetron Sputtering for Enhanced Efficiency of Solar Cells.

The last decade has witnessed a rapid growth of perovskite solar cells extended from mesoporous to planar architecture as well as from solution processing to solvent-free fabrication. The preparation of perovskite films by solvent-free method still presents significant challenges, such as the difficulty of film preparation by multiple evaporation sources in vapor deposition and the immaturity of the sputtered method. Here, we present a planar perovskite solar cell fabricated by solvent-free magnetron sputtering without the assistance of the mesoporous TiO2 layer, and lead chloride (PbCl2) was mechanically milled into the target of methylammonium lead halides (MAPbI3) to improve the quality of perovskite film by regulating the crystallization process with the Cl element. Furthermore, the internal reason for the effect of different PbCl2 doping contents on the trap density of perovskite films was also investigated in detail. These lead to an improved power conversion efficiency of planar heterojunction perovskite solar cells up to 17.10%, which is the highest efficiency recorded for the sputtered perovskite solar cells so far. The stability of resulting solar cells has also been significantly improved by exploring the doping mechanism of perovskite films with PbCl2 in detail, showing great research and application prospect.

Development of High Refractive Index Polydimethylsiloxane Waveguides Doped with Benzophenone via Solvent-Free Fabrication for Biomedical Pressure Sensing

We present the fabrication and characterization of elastomeric optical waveguides, to be used for the manufacture of a conformable, water-resistant, and cost-effective pressure sensor that is amenable to the development of smart wearable health monitoring devices. To achieve this goal, high-sensitivity polydimethylsiloxane waveguides with a rectangular cross-section were fabricated. A new up-doping procedure, to tailor the refractive index of the ensuing waveguides, was experimentally developed using benzophenone additives. With this method we demonstrated a high refractive index change (up to +0.05) as a linear function of the benzophenone doping concentration. Propagation losses of about 0.37 dB/cm in the visible range and a high sensitivity to transverse compression of 0.10%/dB optical power loss were measured. It was also shown that one can further control the refractive index of the waveguide core and cladding regions through proper selection of the polydimethylsiloxane base to curing agent mixing ratio.

Accelerable Self-Sintering of Solvent-Free Molybdenum/Wax Biodegradable Composites for Multimodally Transient Electronics.

Biodegradable conductive composites are key materials or components for printable transient electronics that can be fabricated in a low-cost and high-efficiency manner, thereby boosting their wide applications in biomedical engineering, hardware security, and environmental-friendly electronics. Continuous efforts in this area still lie in the development of strategies for highly conductive, safe, and reliable biodegradable conductive composite materials and devices. This paper introduces molybdenum/wax composites for multimodally printable transient electronics in which multiple transience modes including dissolution-induced degradation and thermally triggered degradation are available. Systematic experiments demonstrate several advantages and unique properties of this material system, including solvent-free fabrication, self-sintering behavior, and long-term and high conductivity via accelerable self-sintering treatment and rehealing capabilities. Notably, the immersion of molybdenum/wax composites in phosphate buffer solution can provide both positive effects (accelerated self-sintering-dominated) and negative effects (degradation-dominated) on their electrical conductivities. Mechanism analyses reveal the basis for balancing the degradation and accelerated self-sintering processes. The presented demonstrations foreshadow opportunities of the developed molybdenum/wax composites in rehealable electronics, on-demand smart transient electronics with multiple transience modes, and many other related unusual applications.

Solvent-Free Method for Defect Reduction and Improved Performance of p-i-n Vapor-Deposited Perovskite Solar Cells.

As perovskite-based photovoltaics near commercialization, it is imperative to develop industrial-scale defect-passivation techniques. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabricate metal-halide perovskite thin films. We demonstrate markably improved growth and optoelectronic properties for vapor-deposited [CH(NH2)2]0.83Cs0.17PbI3 perovskite solar cells by partially substituting PbI2 for PbCl2 as the inorganic precursor. We find the partial substitution of PbI2 for PbCl2 enhances photoluminescence lifetimes from 5.6 ns to over 100 ns, photoluminescence quantum yields by more than an order of magnitude, and charge-carrier mobility from 46 cm2/(V s) to 56 cm2/(V s). This results in improved solar-cell power conversion efficiency, from 16.4% to 19.3% for the devices employing perovskite films deposited with 20% substitution of PbI2 for PbCl2. Our method presents a scalable, dry, and solvent-free route to reducing nonradiative recombination centers and hence improving the performance of vapor-deposited metal-halide perovskite solar cells.

PET fabric treated with environmental-friendly phosphorus-based compounds for enhanced flame retardancy, thermal stability and anti-dripping performance

Poly (ethylene terephthalate) (PET) fabric is ubiquitous in daily life; however the flammability of PET poses a risk for fire events. In this work, a P, N and Si tri-element flame retardant was prepared containing synthetic flame retardant bis-phosphonomethyl-aminomethyl phosphonic acid (BPMAEPA) and 3-(trimethoxysilyl) propyl methacrylate (KH-570). The flame retardant was applied to PET fabric by the pad-dry-cure (PDC) process. The results showed that the limiting oxygen index (LOI) of the treated PET fabric could be increased to 33.5, and the melt-dripping was eliminated. The total heat release (THR) was significantly decreased during combustion because of the dual-phase flame retardant mechanism of the coatings. Moreover, the residue char was increased by 78%, and the CO 2 /CO ratio was decreased by 73% as determined by the cone calorimetry test. In addition, the amount of combustible products produced during the thermal decomposition process were effectively reduced. This work offers a novel methodology for the fabrication of flame retardant PET fabric with exceptional flame retardancy , thermal stability and anti-dripping performance. • An organic solvent-free fabrication of flame retardant PET fabric is proposed. • BPMAEPA with KH-570 preserves more molecular skeleton of PET fabric during combustion. • BPMAEPA with KH-570 increases the limit oxygen index of PET fabric from 21.0 to 33.5 • BPMAEPA with KH-570 reduces the comprehensive pyrolysis index from 25.6 to 10.6 • The flame retardant mechanism of phosphorus, nitrogen and silicon tri-elements is revealed.