Display omitted
•Recycled fibers from car tire waste developed successfully into rubber aerogels•Aerogels have low density, highly porous but are much stiffer than Styrofoam•MTMS coating converts ...completely their hydrophobicity to super hydrophobicity•Excellent sound adsorption, high flexibility and low thermal conductivity•Versatile rubber aerogels are for several high-value engineering applications
For the first time, recycled car tire fibers (RCTF) shredded from car tire waste are developed successfully into a novel material, a rubber aerogel, using polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinkers through a cost-effective freeze-drying method. Its structure and main physical properties are investigated comprehensively for high-value applications, such as heat and sound insulation of buildings and oil spill spilling clean up. The rubber aerogel has ultra-low density (ρa = 0.035 – 0.145 g/cm3) and high porosity (Φavg = 84.31–96.20 %). With a simple but effective coating method with methoxytrimethylsilane (MTMS), both the interior and exterior of the whole rubber aerogel surface can be well coated, and the coated aerogel exhibits a super-hydrophobicity with a water contact angle of up to 134.4°. The rubber aerogel exhibits excellent heat insulation properties (Kavg = 0.035 – 0.047 W/m.K), very good thermal stability up to 500 °C, and significantly-enhanced rigidity up to a Young modulus of Eavg = 458.12 kPa, much larger than that of commercial Styrofoam. The rubber aerogel shows very good durability as it springs back to its original shape after compression tests. The rubber aerogel has a noise reduction coefficient (NRC) of 0.41 and performs approximately 10% better than commercial sound foam absorber at 2000–3000 Hz. The maximum oil absorbtion capacity of the rubber aerogel in this work is 19.3 g/g, very competitive to commercial sorbents. The fabrication method can also be scaled up for several other industrial applications, not limited to sound, heat and sorbent applications.
Abstract Particle-based methods have been increasingly attractive for solving biofluid flow problems, because of the ease and flexibility in modeling complex structure fluids afforded by the methods. ...In this review, we focus on popular particle-based methods widely used in red blood cell (RBC) simulations, including dissipative particle dynamics (DPD), smoothed particle hydrodynamics (SPH), and lattice Boltzmann method (LBM). We introduce their basic ideas and formulations, and present their applications in RBC simulations which are divided into three classes according to the number of RBCs in the simulation: a single RBC, two or multiple RBCs, and RBC suspension. Furthermore, we analyze their advantages and disadvantages. On weighing the pros and cons of the methods, a combination of the immersed boundary (IB) method and some forms of smoothed dissipative particle hydrodynamics (SDPD) methods may be required to deal effectively with RBC simulations.
The effectiveness of nanoparticles (NP) in nanomedicine depends on their ability to extravasate from vasculature towards the target tissue. This is determined by their permeability across the ...endothelial barrier. Unfortunately, a quantitative study of the diffusion permeability coefficients (P
) of NPs is difficult with in vivo models. Here, we utilize a relevant model of vascular-tissue interface with tunable endothelial permeability in vitro based on microfluidics. Human umbilical vein endothelial cells (HUVECs) grown in microfluidic devices were treated with Angiopoietin 1 and cyclic adenosine monophosphate (cAMP) to vary the P
of the HUVECs monolayer towards fluorescent polystyrene NPs (pNPs) of different sizes, which was determined from image analysis of their fluorescence intensity when diffusing across the monolayer. Using 70 kDa dextran as a probe, untreated HUVECs yielded a P
that approximated tumor vasculature while HUVECs treated with 25 μg/mL cAMP had P
that approximated healthy vasculature in vivo. As the size of pNPs increased, its P
decreased in tumor vasculature, but remained largely unchanged in healthy vasculature, demonstrating a trend similar to tumor selectivity for smaller NPs. This microfluidic model of vascular-tissue interface can be used in any laboratory to perform quantitative assessment of the tumor selectivity of nanomedicine-based systems.
Display omitted
•Modify rPET aerogel by silicone ceramic coating and (3-aminopropyl)triethoxysilane.•Rigidity of aerogel structure increase up to 124.8 kPa and hydrophobicity of 144.7°.•Enhanced ...thermal stability of up to 600 °C, thermal insulation of 31.8–34.9 mW/m·K.•CO2 adsorption capacity of the rPET aerogel enhance up to 300% with 0.44 mmol CO2/g.
Millions of tons of plastic are produced annually, but less than 10% are reported to be recycled. This work sets out to transform environmental plastic (polyethylene terephthalate – PET) waste into aerogels for high-value engineering applications, primarily to enhance the monetary incentive in recycling plastics. Coating techniques, using silicone ceramic (SCC) and (3-aminopropyl)triethoxysilane (APS, or APTES) solutions, are successfully devised to enhance the thermal stability and CO2 adsorption capability of rPET aerogel. The rPET/SCC aerogel exhibits improved thermal stability (up to 600 °C), enhanced thermal insulation (thermal conductivity Kavg = 31.8–34.9 mW/m·K), hydrophobic characteristics (up to 144.7° in contact angle) and enhanced rigidity (Young modulus Eavg = 4.5–124.8 kPa), while maintaining an ultra-low density (ρa = 14–62 g/cm3) and a high porosity (Φavg = 95.6–99.0%). Moreover, the amine-functionalised rPET aerogel achieves a CO2 adsorption capacity of up to 0.44 mmol CO2/g, superior to several commercial physio-sorbents. These promising results obtained demonstrate that the rPET aerogel is a versatile material suitable for a wide variety of high-value engineering applications, including thermal insulation and direct CO2 capture applications.
Display omitted
•rPET-silica aerogels are successfully developed from plastic bottle waste.•Ultra-low thermal conductivity and high thermal stability.•Very low compressive Young’s Modulus and very ...soft.•Fabrication method can be scaled up for industrial applications.
Recycled polyethylene tetraphalate (rPET) fiber–silica aerogels are successfully developed from rPET fibers obtained from PET plastic bottle waste and tetraethoxysilane (TEOS). The rPET – silica aerogels are prepared through a direct gelation of silica on PET. rPET fibers are treated with dichloromethane to partially dissolve the fibers. The fibers are then dipped and allow to swell in TEOS/ethanol mixture, with the pH controlled to 2.5 using HCl to promote hydrolysis. After the acid hydrolysis, the pH was controlled to 7 with an ammonium hydroxide solution (NH4OH) to promote condensation. The surface modification is carried out in a trimethylchlorosilane (TMCS)/n-hexane solution and washed with n-hexane to dry at room temperature to prevent shrinkage. The developed rPET – silica aerogels exhibit super-hydrophobicity with an average water contact angle of 149.9°. Their thermal conductivity is approximately 0.037 W/m K. They have a very low compressive Young’s Modulus (0.95–4.19 kPa) and hence very soft. By utilizing rPET fibers, this work provides an alternative method of recycling PET plastic wastes which ultimately helps in reducing its detrimental impact to the environment. The developed aerogels can be used in several industrial applications such as heat insulation, filtering, sound insulation and absorption.
•Viscoelastic effects on three-dimensional bubble rising in a wide range of Galilei and Eötvös numbers have been studied.•Relation between bubble deformation and negative wake for different ...Weissenberg number and viscosity ratio has been discussed.•A pulsating bubble rising velocity at high elasticity has been reported.•We have also characterized the bubble breakup in its tail due to the strong extensional flow.
The rise of a deforming air bubble of fixed volume surrounded by viscoelastic liquids is investigated by an adaptive direct numerical technique coupled with the volume-of-fluid method. The effects of the Weissenberg number (characterizing the strength of elasticity in the flow) and the viscosity ratio on the three-dimensional bubble dynamics have been studied and identified in a wide range of Galilei (Ga) and Eötvös (Eo) numbers, which measure gravitational force over viscous and surface tension forces, respectively. Our results demonstrate that the deformed bubble shape is not a strong predictor of the jump in the rise velocity in different flow regimes; and we verify that in highly elastic flows, the negative wake is mainly responsible for the rising velocity jump, consistent with previous experimental findings. The viscoelasticity induces a cusp shape at large Eo, while the increase in the rising velocity diminishes with a fattened bubble shape. By probing the polymeric conformational state and stresses, it is further indicated that the strain in the fluid is associated with the shear induced by the rising bubble, which produces the release of the elastic stress, giving rise to a fluid downward motion to form the negative wake. Interestingly, we first observe that when Ga is large enough the bubble undergoes a pulsating rising velocity in highly elastic flows due to the vortex shedding in the distant wake region. Moreover, since the development of viscoelastic stresses is closely correlated with the shear-strain response, a larger polymer deformation is seen to be formed at the bubble trailing edge for modest surface tension, which affects the balance between the extensional flow and the shear stresses on the tail interface, leading to the bubble breakup to form a satellite tail.
In this paper, we carried out an investigation of the dynamics of an air bubble rising in viscoelastic liquids with increasing volumes via volume-of-fluid based direct numerical simulations (DNS) ...with local adaptive mesh refinement techniques. The exponential Phan-Thien Tanner (EPTT) model is adopted for describing the rheological behaviours of the shear-thinning viscoelastic fluid. The well-known jump discontinuity in the terminal rise velocity at a critical bubble volume is captured, which agrees qualitatively with the experimental observation in the literature. On this basis, the numerical simulations have been performed for different rheological properties in wider flow regimes, providing new insights into the local flow field and the stress distribution around the deformable rising bubbles. A characteristic dimensionless regime map has also been proposed to distinguish the peculiar behaviours of a bubble rising in viscoelastic fluids at different Galilei (Ga) and Eötvös (Eo) numbers. We found that at low Ga and low Eo numbers, the large elastic stresses concentrate in the small region near the bubble’s trailing end, leading to the formation of bubble cusp. The appearance of the negative wake is the main reason for the velocity jump to occur. However, for higher Ga of 10, the viscous forces become less dominating. The fluctuations of the polymeric stresses are substantially intensified with increasing bubble volume, and large bubbles experience a pulsating rising velocity with oscillation shapes. On the other hand, at intermediate Ga and high Eo of 10, the modest surface tension induces a cap with a thin skirt trailing the bubble main body at early times. Due to the polymer stretching, the strong extensional flow behind the small bubble eventually forces the bubble tail to break up. The above analyses on the bubble dynamics at constant Morton (Mo) numbers facilitate the extrapolation of the volume effects at different flow regimes and, therefore, will guide the applications in the future.
•EPTT is used to describe shear-thinning viscoelasticity, agreeing with experiments.•3D DNS results provide new insights into the flow physics around rising bubbles.•Negative wake is the main reason for velocity jump to occur for supercritical bubbles.•An oscillatory motion appears with increasing volume when inertia is significant.•Extensional flow behind bubbles determines tail breakup for modest surface tension.
Appropriate surface patterns on polymer membranes have been demonstrated to have a strong effect on improving the permeability and anti-fouling ability. Herein, for the first time we have developed a ...surface-patterned alumina ceramic membrane with gradient porous structure using a novel 3D-printing technology. The well-controllable surface-patterned alumina membrane was fabricated by use of 3D-printable ceramic ink through a layer-by-layer coating on a porous substrate, after which the designed patterns were made on the membrane surface by 3D printing the same ink. The 3D-printed line-patterned membrane showed a notable increase in steady flux and a significantly enhanced antifouling ability, especially when the printed lines were perpendicular to the feed flow direction, as evaluated by our experimental and computational fluid dynamics simulation results. Fouling mechanisms were similar between different feed flow directions and evolved from the pore constriction or intermediate pore blocking towards cake filtration. The distance and height of the 3D-printed lines was also revealed to have influences on the fouling performance. Together with the advantages of easily designed structures and a rapid design-to-fabrication process using 3D-printing technology, this study provides an effective new approach to fabricate the advanced ceramic membranes with fouling mitigation for wastewater treatment.
•3D-printed surface-patterned ceramic membranes was developed by a single sintering process.•Surface-patterned ceramic membranes enhance permeation and significantly retarded fouling.•Anti-fouling ability is dependent on the feed flow direction with respect to printed line patterns.•Fouling performance is affected by the key parameters of printed patterns.•Breakthrough in development of antifouling ceramic membrane using 3D printing technology.
PDF
