Excellent Thixotropy Research Articles

Rheology and buildability of sustainable 3D printed magnesium potassium phosphate cement composites incorporating MgO-SiO2-K2HPO4

MKPCs with unique advantage of superior strength, excellent durability and high thixotropy provides alternative binder for 3D printing. The acid-base reaction between dead burnt MgO and K2HPO4 is intense and the retarding effect is limited in practical cases. This paper presents the investigation of MKPCs incorporating MgO-SiO2-K2HPO4 binders prepared with dead burnt MgO, soluble phosphate (K2HPO4•3 H2O) and silica fume (SF). The effects of magnesium-to-phosphate (M/P) mass ratio, SF and slag ratios on rheological properties and the printability were tailored and setting time reached to 50 min by increasing the alkaline environment of the solution. In addition, the pozzolanic activity of SF and slag were synergistically motivated and thus promoted the precipitation of K-struvite, MgSiO3 and C-(A)-S-H hydrates. Two-stage Athix values were calculated to describe the structuration rate. It is confirmed excellent thixotropy was dominated by early-age physical re-flocculation and later-age cement hydration. Although the structure deformation increased significantly as SF content increased, the beneficial effect of SF content on the increase of strength is significantly important than that of adverse effect on the buildability. Slag powder and fine aggregate were incorporated to make the binders more “printable”. A cylinder with 16 layers on optimum mixture was printed without deformation.

Fabrication of edible inks for 3D printing as a dysphagia food: An emerging application of bigels

With the increasing prevalence of swallowing difficulties among the elderly, 3D printing technology has emerged as a promising approach to create attractive and appetitive dysphagia diets. This study focused on synthesizing bigels composed of beeswax oleogel (OG) and gellan gum hydrogel (HG) to explore their potential for 3D printing dysphagia diets. The ratio of OG to HG plays a pivotal role in determining the gel network structure, rheological properties, and water distribution of the bigels, thereby influencing their suitability as 3D printing ink. Notably, a bicontinuous structure achieved with an OG to HG ratio of 1:1 (sample 1-1) imparted desirable properties for 3D printing, including moderate shear-thinning behavior, ensuring smooth extrusion, excellent thixotropy for maintaining structural integrity, and adequate storage modulus for self-supporting during printing. These were indicated by lower flow index (n value) of 0.18, longer time respond to the applied stress (λ value) of 9.51 ± 0.32 s, higher creep recovery rate of 55.51 ± 1.36%, thixotropic recovery rate up to 93.23 ± 0.72%, and uniform moisture distribution across semi-bound water and free water with ratio of 56.94 to 43.06, compared to bigels with OG-in-HG and HG-in-OG structures. Evaluation of the 3D printed bigels through the International Dysphagia Diet Standardization Initiative (IDDSI) confirmed that sample 1-1 (classified as Level 5-Minced and Moist) was suitable for individuals with swallowing difficulties. This study provides new insights into developing visually appealing dysphagia diet using 3D printing.

High-Temperature, Salt-Resistant, and High-Strength-Controlled Consolidated Resin Slurry for Fracture Plugging during Oil and Gas Well Drilling

Summary The temperature and pressure of deep and ultradeep plugging are gradually increasing, resulting in higher requirements for the performance of plugging materials. In this study, a resin slurry plugging system that can be used to plug lost channels of fractures of different scales in the process of oil and gas exploitation was prepared, and the factors affecting the consolidation of the system under different conditions were studied. The resin slurry plugging system was initially consolidated in 2 hours and completely consolidated in 6–9 hours. It exhibited good viscosity recovery ability and excellent thixotropy characteristics of shear thinning and static thickening, which help realize strong residence and plugging in the fracture. The resin slurry plugging system prepared with 200 000 mg/L salinity water could still achieve good consolidation at 140°C, and the consolidating strength was higher than 5.0 MPa. In addition, the 7.10-MPa consolidation strength of the resin slurry plugging system with aging at 140°C for 15 days could satisfy the long-term plugging needs. Furthermore, the pressure-bearing plugging capacity and degradability of the resin slurry plugging system were investigated. The resin slurry plugging system could be fully filled in the steel wedge-shaped fractured core at 140°C, and the pressure-bearing plugging capacity was up to 13.07 MPa. The resin slurry plugging system could achieve a strong residence in the sand-filling pipe model, forming a high-strength plugging layer, and the pressure-bearing plugging capacity could reach 10.73 MPa. The acid dissolution degradation rate at 140°C was 97.69%, indicating a low degree of damage to the reservoir and meeting the requirements for subsequent plug removal. The excellent properties of the resin slurry plugging system, such as high temperature, high salt resistance, and pressure plugging, provide a new solution for plugging lost formations of fracture cave carbonate rocks.

Long-Lasting Thixotropic Natural Polymeric Hydrogel Based on Silk Nanofibrils.

Hydrogels are considered to be ideal biomedical materials as their physical properties are similar to the physiological tissue environment. In particular, thixotropic hydrogels have received increasing attention from researchers because of their injectability. Herein, a simple and rapid method was developed for the preparation of a regenerated silk fibroin (RSF) hydrogel with long-lasting and excellent thixotropy. The thixotropic RSF hydrogel was readily formed by ultrasonic treatment of the pretreated RSF solution for 2 min followed by incubation at 40 °C for 10 min. The storage modulus of the RSF hydrogels recovered to more than 90% of the original value within 20 s after withstanding 1000% shear strain. By avoiding complicated chemical or physical treatments and by addition of crosslinking agents and/or other chemical components, the obtained RSF hydrogels maintained excellent biocompatibility. Hence, the cells implanted inside the hydrogel can grow and proliferate normally. By virtue of ultrasonic treatment during the preparation, functional nanoparticles can be uniformly dispersed in the RSF solution to prepare RSF-based hybrid hydrogels with various functions. As an application example, hydroxyapatite (HAP) with osteoinductivity was mixed with RSF solution to prepare the RSF/HAP hybrid hydrogel. The RSF/HAP hybrid hydrogel maintained biocompatibility and thixotropy of the original RSF hydrogel and promoted osteoblastic differentiation of cells owing to the addition of HAP. Therefore, the RSF hydrogel prepared in this work has a strong application prospect in the biomedical field including, but not limited to, bone repair.

Fabrication of fat-reduced water-in-oil emulsion and the application in 3D printing

Water-in-oil (W/O) emulsion is promising to design fat-reduced foods for 3D printing. In this study, oleogel-based W/O emulsion containing 65% water fraction was prepared by sunflower wax (SW, 1.0 wt%) and soybean phosphatidylethanolamine (SP, 0.5 wt%) with stability exceeding 30 days. Besides reducing interfacial tension, from X-ray diffraction and rheological results, SP was considered co-oleogelator to change the crystal habit of SW to enhance the external SW-based oleogel structure. The strong external oleogel structure was not only good for reducing droplets movements to improve physical stability, but facilitating the molding and supporting abilities of the emulsion gel in 3D printing. Based on rheological measurements, the emulsion gels were shown improved printing performance with SP increasing: extrusion (shear-thinning behavior), recovery (excellent thixotropy), and self-supporting (sufficient storage modulus and deformation resistance). In 3D printing, the emulsion gels with growing SP were displayed better shape retention and allowed printing the designs with more delicate and vivid features. This study provided new insight for W/O emulsion formation using natural ingredients for 3D printing to create fat-reduced foods.

Joint‐Inspired Liquid and Thermal Conductive Interface for Designing Thermal Interface Materials with High Solid Filling yet Excellent Thixotropy (Adv. Funct. Mater. 14/2023)

Contact Thermal Resistance In article number 2214071, Kai Wu, Qiang Fu, and co-workers report a joint-inspired interfacial engineering strategy by employing liquid metal to the surface of rigid alumina, which improves material's thermal conductivity and thixotropy. This method will inspire development of high-performance polymer-based thermal interface materials for future advanced electronics.

Joint‐Inspired Liquid and Thermal Conductive Interface for Designing Thermal Interface Materials with High Solid Filling yet Excellent Thixotropy

AbstractFor advanced thermal interface materials (TIMs), massive inorganic addition for high isotropic thermal conductivities conflicts with suitable rheological viscosity for low contact thermal resistance. Traditional strategies rarely resolve such a contradiction, and it remains an academic and industrial challenge. Herein, inspired by the structure and function of the bone joint, a best‐of‐both‐worlds approach is reported that endows a standard polydimethylsiloxane/alumina (PDMS/Al2O3) TIM with simultaneously enhanced rheological mobility and thermal conductivity. It is conducted by employing morphology‐controllable gallium‐based liquid metal (LM) to the surface of Al2O3by a scalable mechanochemical process. At the typical polymer‐LM‐Al2O3interface, LM droplets with low cohesive energy can release the freedom for macromolecular chain relaxation and reduce the viscosity, successfully allowing the high‐loading TIMs (79 vol.%) to keep the thixotropic state and effectively reducing its contact thermal resistance with a copper substrate by 65%. At the same time, adjacent LMs merge to thermally bridge separate Al2O3particles, which facilitates the interfacial thermal conduction and enhances the thermal conductivity from 5.9 to 6.7 W m−1 K−1. Along with additional electrical insulation, this filler modification strategy is believed to inspire others to develop high‐performance polymer‐based TIMs for future advanced electronics.

Extrusion-based 3D printing of high internal phase emulsions stabilized by co-assembled β-cyclodextrin and chitosan

β-cyclodextrin (β-CD) modified by chitosan (CS) via electrostatic interactions and hydrogen bonds was used to fabricate high internal phase emulsions (HIPEs) for food 3D printing. The most promising ink for 3D printing was screened among HIPEs stabilized by polysaccharide complexes at CS concentrations of 0.08–0.40 wt% and pH values of 3–7. The β-CD/CD complexes formed by 1.20 wt% β-CD and 0.32 wt% CS at pH 5 possessed proper wettability and interfacial tension, forming an interfacial membrane, which could offer sufficient electrostatic repulsion and steric barrier against the coalescence of emulsion droplets. Rheological an analysis indicated that HIPE stabilized by β-CD/CS complexes at 0.32 wt% CS and pH 5 has good printing potential in three stages of 3D printing: extrusion (shear-thinning behavior), recovery (excellent thixotropy), and self-supporting (sufficient storage modulus and yield stress). Subsequently, 3D printing results of plane and stereo models also demonstrated that HIPE stabilized by these complexes possessed the best printability. This study obtained food-grade inks with outstanding extrudability, recoverability and self-supporting properties by a simple and easy method, providing ideas and guidance for applying polysaccharide-based HIPEs in 3D printing. • Developed β-cyclodextrin/chitosan complexes formed by physical interactions. • Prepared high internal phase emulsions possessed uniform and stable droplets. • The rheology of emulsions was controlled by CS concentrations and pH values. • The emulsion had outstanding extrudability and printability in food 3D printing.

Construction of 3D printable Pickering emulsion gels using complexes of fiber polysaccharide-protein extracted from Haematococcus pluvialis residues and gelatin for fat replacer

Structural fat replacers that can meet the requirements of various forms of reduced-fat foods are essential for the application of fat replacement, and emulsion gels emerge as a potential alternative for fat replacers. In this study, fiber polysaccharide-protein extracted from Haematococcus pluvialis residues (FPHRs) formed FPHRs-Gelatin complexes with gelatin. Fourier transformed infrared spectroscopy confirmed the formation of hydrogen bonds between FPHRs and gelatin, the secondary structure order of the protein was enhanced. Three-phase contact angle determination showed that the contact angle of FPHRs-Gelatin complexes was 104°–114°. By exploring the effect of FPHRs concentration, gelatin concentration, and oil-water ratio on the emulsion gels, the Pickering emulsion gels were formed when the FPHRs and gelatin concentration were 2 wt% and 3 wt%, respectively. What's more, these emulsion gels had shear thinning phenomenon, low frequency dependence as well as excellent thixotropy when the oil-water ratio was 0.6, which indicated that they had strong structural support and great recovery capacity to be used as 3D printed materials. The 3D objects printed by the FPHRs-Gelatin complexes emulsion gels had superior print resolution and shape fidelity. This study provides a new type of emulsion gel with structure that can be used as an ideal fat replacer in food processing, the construction of a new 3D emulsion gel material is of great significance for broadening the applications of gelatin-based gels and microalgal food.

Stabilizing performance of montmorillonite on fish gelatin-monascorubins system by labyrinth effect

Natural monascorubins could be used in various fields but are unstable under heat, pH, etc., with limited application. Fish gelatin could disperse monascorubins, which could be further stabilized by montmorillonite. Effect of montmorillonite was studied by CIElab color, zeta potential, particle sizes, SEM, contact angle, antibacterial activity, thermal/chemical resistance, and the stabilizing mechanism was explored by FTIR, XRD, Raman and molecular simulation. Montmorillonite effectively strengthened gelatin-monascorubin system by labyrinth effect based on hydrogen bond, host-guest interaction and complexation, thereby reducing sizes with nano structure and increasing specific surface area, antibacterial activity and thermal/chemical stability. High-content montmorillonite made the nanocomplex system to have outstanding shear-thinning behavior, excellent thixotropy and proper yield stress, and to illustrate potential as edible inks. This nanocomplex system performed well in handwriting and massive screen printing, with great surface fastness. Structure based on fish gelatin and montmorillonite indicates promise in dispersing and stabilizing functional materials with broad industrial application value.

Experimental Research on Cationic Surfactants in the Drag Reduction of Water Injection Pipeline

Summary To achieve the throughput increase and drag reduction of the water injection pipeline for offshore oil fields, this paper takes the cationic surfactant solution as the research object and explores the feasibility of applying the additive drag reduction technology to the water injection pipelines through the rheological test and drag reduction simulation device. The experimental results show that the cetyltrimethylammonium chloride (CTAC) selected initially has excellent thixotropy, and the viscosity recovery rate within 300 seconds can reach more than 97%. In addition, CTAC/NaSal (sodium salicylate) solution has strong oil resistance and salt tolerance. As the oil concentration increases from 0 to 6,000 ppm, the viscosity only decreases by 8.24%; as the salt concentration increases from 0 to 6,000 ppm, the maximum viscosity growth rate is 87.08%. Furthermore, the CTAC/NaSal has good temperature resistance, which enhances with the increase of concentration. The recommended concentration of drag reducer is 400 ppm, and the maximum drag reduction rate, throughput increase rate, pressure drop reduction rate is 74.19, 76.76, and 67.99%, respectively. Therefore, the CTAC/NaSal solution has broad application prospects in the drag reduction of water injection pipelines.

Chitosan-reinforced PHB hydrogel and aerogel monoliths fabricated by phase separation with the solvent-exchange method

The poly(3-hydroxybutyrate) (PHB) organogel monoliths were prepared by nonsolvent-induced phase separation (NIPS). The NIPS-derived organogels were solvent-exchanged with chitosan (CS) solution, resulting in the successful loading of CS into PHB hydrogel. With increasing the CS content, the as-prepared composite hydrogels became syringe injectable with excellent thixotropy due to the increase in the gel network's hydrophilicity. The hydrogels were successfully freeze-dried into PHB/CS composite aerogels, which exhibited remarkably improved compressive modulus/collapse strength of 1.6 MPa/159 kPa compared to 0.5 MPa/31 kPa for pure PHB aerogels. The effect of CS on gel crystallization and structure was also investigated. The amphiphilic PHB/CS hydrogels effectively entrapped both hydrophilic/cationic doxorubicin (DOX) and hydrophobic/anionic indomethacin (IDM). The drug release behavior depended on the charge interactions between drugs and CS. The accelerated DOX release in acidic condition from injected hydrogels owing to the charge repulsion shows potential for a controlled and localized cancer therapy.

Study on the characteristics of grinding fluid in extrusion grinding machining

Extrusion grinding machining (EGM) has become a key technology in the post-processing of micro-hole in the injector nozzle. In this paper, the pure slurry prepared from organic bentonite and the pure slurry after adding abrasive as experimental objectives, and the correlation performance has been carried out. Results showed that both pure slurry and slurry abrasive have good shear thinning characteristics, belong to pseudoplastic non-Newtonian fluid, and their rheological properties obey the power-law model. The pure slurry after stirring and shearing can restore the reticular structure in a short time, which proves that it has excellent thixotropy and meets the conditions of circulating processing of grinding fluid. In addition, the pure slurry and slurry abrasive also have good sedimentation stability, suspension capacity, and dispersion properties.

3D printed gellan gum/graphene oxide scaffold for tumor therapy and bone reconstruction

Compared with traditional tissue engineering scaffold processing methods, 3D printing technology has obvious advantages in achieving high structural complexity, flexibility and specific patient needs. Printing ink materials with both high printability and biocompatibility remains a major challenge. Herein, a hydrogel bio-ink with excellent thixotropy and recovery properties was prepared by combining gellan gum (GG) and graphene oxide (GO) for extrusion 3D printing. The GG/GO scaffold constructed by 3D printing has a regular and connected porous structure, which maintains high fidelity with the model. Cell proliferation and attachment in the printed 3D curcumin-loaded scaffold revealed that the bifunctional GG/GO/Cur scaffold could inhibit human osteosarcoma cell line (MG-63) growth significantly and induce tumor cell death effectively in vitro. Simultaneously, the scaffold could support the attachment and proliferation of mouse osteoblast cell (MC3T3). Therefore, the functional GG/GO/Cur scaffold is expected to be used to repair the bone defects induced by surgery and kill the possibly residual tumor cells at the same time to achieve the purpose of tumor therapy and bone reconstruction.

Rheological parameters, thixotropy and creep of 3D-printed calcium sulfoaluminate cement composites modified by bentonite

The structural instability and poor thixotropy of three-dimensional (3D) printing of calcium sulfoaluminate (CSA) cement composites hinder their applicability in the construction field. In this study, the rheological parameters, thixotropy and creep of 3D-printed CSA cement composites containing bentonite are investigated based on shear-rate- and shear-stress-controlled protocols to achieve a stable three-dimensional structure and excellent thixotropy. Experimental results show that a stable 3D structure with excellent thixotropy can be achieved when the content of bentonite is 2%. In this case, the plastic viscosity and dynamic yield stress are lower than 2.50 Pa s and 645.54 Pa, respectively. The correlation between the rheological parameters and thixotropy of 3D-printed CSA cement composites suggests that the actual thixotropy can be predicted by the yield stress. Furthermore, the shear-stress-controlled protocol was implemented to simulate the effect of gravity and test different creep periods of 3D-printed CSA cement composites with bentonite. The improved static yield stress exhibited better effectiveness in resisting structural deformation over time.

Enhanced therapeutic effect of paclitaxel with a natural polysaccharide carrier for local injection in breast cancer

The side effect and inefficiency of paclitaxel (PTX) in clinic have became the major problem in field of cancer chemotherapy. The local drug delivery constructed by injectable hydrogel has been suggested as the alternative due to its superior properties such as tumor selectivity, minimally invasive administration and sustained drug release behavior. Polysaccharides have been commonly used as a gelling agent to construct injectable hydrogel due to its wide resources, biocompatibility and bioactive functions. Here, we reported an injectable drug carrier with enhanced therapeutic effect based on Pinus koraiensis polysaccharide (PKP). The interaction, morphology and mechanical properties were studied. Interestingly, gels exhibited excellent injectable property including rapid recovery time, excellent thixotropy ability and good rheological property after injection, and these special properties make them more suitable to be constructed as an injectable drug carrier. In addition, the biocompatibility of gel was demonstrated in terms of hemolysis analysis. PTX-loaded gel showed excellent tumor inhibition effect against 4T1 and MCF-7 breast cancer cell lines in vitro, and exhibited the significant tumor growth suppression and reduced systemic toxicity in vivo. The successful construction of PTX-loaded gel demonstrates that PKP can be used as a promising carrier in local drug delivery.

A self-assembled supramolecular natural product gel from liquidambaric acid in traditional Chinese medicine with inherent anti-inflammatory activity for drug delivery.

Self-assembled supramolecular gels as a soft material have received extensive attention due to their excellent physicochemical properties such as variability, multiple responsiveness and appropriate viscoelasticity. At present, many self-assembled gels with physicochemical functions are constructed as drug delivery systems and used for the treatment of diseases. However, self-assembled gel drug delivery systems having pharmacological functions remain almost unexplored. Here, we present an anti-inflammatory pharmacologically active gel drug delivery system consisting of direct self-assembled small molecule naturally-occurring compounds (self-assembled small molecule natural products, SSNPs) derived from traditional Chinese medicine. The system not only exhibits excellent thixotropy, good topical safety and sustained release, but also achieves superior inflammatory therapeutic effects both in vivo and in vitro. Compared to non-pharmacologically active drug delivery systems, this system can increase the in vivo anti-inflammatory activity of drugs by nearly two-thirds. More importantly, its therapeutic effect even reached 141.54% of OTC drugs. The successful construction of an anti-inflammatory pharmacologically active gel drug delivery system not only makes full use of the self-assembly properties and biological activity of natural products, but also provides an important reference for the development of pharmacologically active drug delivery systems using SSNPs in the future.

Fabrication of Zein/Pectin Hybrid Particle-Stabilized Pickering High Internal Phase Emulsions with Robust and Ordered Interface Architecture.

Diets containing partially hydrogenated oils (PHOs) expose the human body to trans fatty acids, thus endangering cardiovascular health. Pickering high internal phase emulsions (HIPEs) is a promising alternative of PHOs. This work attempted to construct stable Pickering HIPEs by engineering interface architecture through manipulating the interfacial, self-assembly, and packing behavior of zein particles using the interaction between protein and pectin. Partially wettable zein/pectin hybrid particles (ZPHPs) with three-phase contact angles ranging from 84° to 87° were developed successfully. ZPHPs were irreversibly anchored at the oil-water interface, resulting in robust and ordered interfacial structure, evidenced by the combination of LB-SEM and CLSM. This situation helped to hold a percolating 3D oil droplet network, which facilitated the formation of Pickering HIPEs with viscoelasticity, excellent thixotropy (>91.0%), and storage stability. Curcumin in HIPEs was well protected from UV-induced degradation and endowed HIPEs with ideal oxidant stability. Fabricated Pickering HIPEs possess a charming application prospect in foods and the pharmaceutical industry.

Nanoscale Laponite as a Potential Shale Inhibitor in Water-Based Drilling Fluid for Stabilization of Wellbore Stability and Mechanism Study.

Shale hydration is the main reason causing wellbore instability in oil and gas drilling operations. In this study, nanoscale laponite as a shale inhibitor was employed to stabilize wellbores. The inhibition property of laponite suspensions was evaluated by an immersion experiment, linear swelling measurement, and a shale recovery test. Then the shale inhibition mechanism was studied by using capillary suction time (CST) measurement, a thixotropy study, plugging performance evaluation, and related theoretical analysis. Evaluation experiment results showed that laponite had a better inhibition property than widely used inhibitors of potassium chloride (KCl) and poly(ester amine) (PA). The mechanism study revealed that integration of several factors strengthened the inhibition property of laponite suspensions. Laponite nanoparticles could plug interlayer spaces of clays by electrostatic interaction to reduce water invasion; the "house of cards" structure of laponite suspensions enables large CST values and low free water contents; the excellent thixotropy of a laponite nanofluid could allow a nanofilm to form in order to reduce water invasion into the formation; the nanoscale laponite particles could substantially reduce the shale permeability and form less porous surfaces. Furthermore, laponite could considerably decrease the filtrate volume of the drilling fluid, while KCl and PA had negative influences on the properties of the drilling fluid. This approach described herein might provide an avenue to inhibit shale hydration.

4D Printing of Robust Hydrogels Consisted of Agarose Nanofibers and Polyacrylamide.

Hydrogels combined with complex 3D shapes and robust mechanical properties are extremely desired soft platforms in the fields of biomaterials, recently, 4D printing has been developed to be further shaped to form required patterns. On the basis of the excellent thixotropy of Laponite and the thermal-reversible sol-gel transition of agarose and easy formation of nanofibers below 35 °C, a 4D printing hydrogel (4D Gel) was fabricated by in situ polymerizing acrylamide in the agarose matrix containing Laponite. The experimental results demonstrated that Laponite played an important role in the improvement of 4D printing, such as endowing the ink with shear-thinning behavior to extrude easily and excellent shape stability after printing. The mechanical properties of 4D Gel were unexpectedly higher than those of both agarose and polyacrylamide hydrogels. The 4D Gel showed the ability to further transform its shapes, and was used successfully to construct a whalelike hydrogel, which opened mouth and cocked tail by treating with an external force and then cooling, as well as the octopus like hydrogel with waved tentacles to seem to "come alive". This work opened a new avenue for creating more complex architectures than 3D with excellent properties, which is important in the macromolecule fields for the wide applications.