CO2 Bubbles Research Articles

Development of alginate macroporous hydrogels using sacrificial CaCO3 particles for enhanced hemostasis

Polymeric hydrogels have increasingly garnered attention in the field of hemostasis. However, there remains a lack of targeted development and evaluation of non-dense polymeric hydrogels with physically incorporated pores to enhance hemostasis. Here, we present a facile route to macroporous alginate hydrogels using acid-induced CaCO3 dissolution to provide Ca2+ for alginate gelation and CO2 bubbles for subsequent macropore formation. The as-prepared pore structure in the hydrogels and its formation mechanisms were characterized through microscopic imaging and nitrogen adsorption/desorption tests. Functional analyses revealed that the macroporous hydrogels exhibited improved rheology, blood absorption, coagulation factor delivery, and platelet aggregation. Ultimately, the introduction of pores significantly enhanced the hemostatic effectiveness of alginate hydrogels in vivo, as demonstrated in rat tail amputation and liver injury models, leading to a reduction in blood loss of up to 77 % or a decrease in bleeding time of up to 88 %. Notably, hydrogels with higher porosity achieved with a CaCO3 to alginate ratio of 40 % outperformed those with lower porosity in the aforementioned properties. Furthermore, these improvements were found to be biocompatible and elicited minimal inflammation. Our findings underscore the potential of a simple porous hydrogel design to enhance hemostasis efficacy by physically incorporating macropores.

Experimental study of interfacial mass transfer from single CO2 bubbles ascending in stagnant water

The study focuses on the interfacial mass transfer from single CO2 bubbles with initial diameter in the range of 0.7−3.0 mm in a vertical column with stagnant deionized water. The objective is to enhance the understanding of the intricate phenomena involved in interfacial mass transfer by examining the individual effects of the liquid-side mass transfer coefficient and the bubble size. The liquid-side mass transfer coefficient is found in this study to be influenced by both the initial bubble diameter and on the bubble age, i.e., the time the bubble is exposed to the liquid influences the obtained liquid-side mass transfer coefficient. Existing literature suggests that bubbles of diameter <2−3 mm behave as rigid spheres with immobile interface and reduced internal gas circulation, which negatively impact the interfacial mass transfer. The results obtained from this study show that the maximum value of the liquid-side mass transfer coefficient is obtained for bubbles of diameter 2.1−2.3 mm. For bubbles with a mean diameter ≤1.4 mm, the mean liquid-side mass transfer coefficient decreases with decreasing mean bubble diameter. A Lagrangian model description is used with various correlations for the liquid-side mass transfer coefficients to perform numerical simulations of the change in bubble volume during the bubble rise. The existing correlations for the liquid-side mass transfer coefficient give very different simulation results and fail to accurately capture the transient evolution of the bubble as it exposes to the mass transfer phenomenon and hydrostatic pressure gradient. The correlation for the liquid-side mass transfer coefficient proposed by Clift et al. (1978) is modified in this work, and the experimentally obtained data are well predicted by the new modified correlation.

Study of direct alloying of steels by carbon reduction of Cr2O3 under vacuum

Currently, steel is mainly alloyed by adding ferrochrome alloys in the production of chromium-containing steels. However, the production of ferrochrome consumes a lot of electricity and produces a large number of additional products that are extremely harmful to the environment. For the consideration of the above problems, the experiment studied the reduction behavior of Cr2O3 using carbon powder as the reductant under different ambient pressures, different reductant dosages, and different initial oxygen contents in the molten steel. The results show that CO bubbles can be formed by decreasing the air pressure and increasing the amount of reductant, thus the reduction rate and reduction efficiency of Cr2O3 can be increased. It was found that the ambient air pressure mainly affected the reduction rate of Cr2O3, and the fastest reduction rate of Cr2O3 was found in vacuum environment. The reductant dosage has great influence on the reduction rate, reduction efficiency, density and size of inclusions of Cr2O3. Addition of carbon powder with a carbon-to-oxygen molar ratio of 2 will significantly improve the reduction rate of Cr2O3. The yield of [Cr] in steel can reach more than 95 %. In addition, the density of inclusions in steel is stabilized below 0.2/mm−2. The addition of carbon powder with nc:no ≤ 1.0 significantly reduces the reduction rate of Cr2O3 due to the decrease of carbon concentration in the steel. The density of inclusions in steel also increased significantly up to 210.4/mm−2. The initial oxygen content in the molten steel had little effect on the reduction of Cr2O3. However, the reduction rate of Cr2O3 is lower in steel with high oxygen concentration than in steel with low oxygen concentration. Under the optimum reduction conditions-nc:no = 2.0, initial oxygen content of 3 × 10−4, and ambient air pressure of 50 Pa. The yield of [Cr] in steel can reach 96.85 %, the total oxygen content can be reduced to 1.6 × 10−5, the density of inclusions is 0.04/mm−2, and the size of inclusions is below 1.8 μm.

Air bag-embedded MIL-101(Fe) metal-organic frameworks for an amplified tumor microenvironment activation loop through strategic delivery of iron ions and lentinan.

Background: Iron-based nanocarriers have demonstrated potential in redirecting tumor associated macrophages (TAMs) polarization towards the M1 phenotype, critical for activating the tumor microenvironment (TME) in triple negative breast cancer (TNBC). However, their real-world effectiveness is curtailed by insufficient Fe2+/3+ exposure and the absence of suitable synergists in tumors. Methods: We introduce an air bag-embedded iron-based MIL-101 metal-organic frameworks (MOFMIL-101(Fe)) for igniting the TME in TNBC through bubble-driven tumoral codelivery of Fe2+/3+ and lentinan. This system, named HM/Ef/LNT-MOFMIL-101(Fe), features nano-sized MOFMIL-101(Fe) as the core, embedded NaHCO3 as a pH-triggered air bag, electrostatically-adsorbed lentinan forming the inner shell, and a shield shell with 4T1&red blood cell hybrid membrane. Results: HM/Ef/LNT-MOFMIL-101(Fe) can mitigate non-specific capture in the bloodstream but respond to the acidic tumor milieu, rapidly generating a burst of CO2 bubbles to disassemble MOFMIL-101(Fe). Upon entering tumors, lentinan-induced interferon-γ (IFN-γ) enable Fe2+/3+ facilitating an enhanced ferroptosis and Fenton-like reaction, pushing TAMs towards M1 polarization via the "IFN-γ-ferroptosis-ROS-Caspase-3" pathway. Moreover, HM/Ef/LNT-MOFMIL-101(Fe) increases the infiltration of T lymphocytes and decreases regulatory T cells. These cascading immune responses synergistically foster a loop of amplified TME activation based on TAMs M1 polarization, showcasing notable advancements in anticancer effectiveness and promise for various combination therapies. Conclusion: This study utilizes an "embedded air-bag" strategy to achieve strategic codelivery of Fe2+/3+ and lentinan, providing a new tool for engineering the TME.

Through-Space Electrochemiluminescence Reveals Bubble Forces at Remote Phase Boundaries.

Several groups have reported on the curious chemistry and reaction acceleration in confined volumes. These complex multiphase systems most closely resemble natural processes, and new measurement tools are necessary to probe chemistry in such environments. Generally, electrochemiluminescence (ECL) reports on processes immediately near (within a few micrometers) the electrode surface. Here, we introduce through-space ECL, reporting on dynamics of processes far away (100s of μm) from the electrode surface. We achieved this by collecting reflected ECL light. During the heterogeneous oxidation of C2O42- in an aqueous phase adjacent to a 1,2-dichlorethane droplet, CO2 accumulates in the 1,2-dichloroethane droplet. Upon buildup, we demonstrate that a CO2 bubble forms in the nonaqueous phase and is surprisingly trapped at the water|1,2-dichloroethane interface and continues to grow. The co-oxidation of tris(bipyridine)ruthenium(II) in the aqueous phase lights up the electrode surface and reflects off the edges of the bubble, revealing the bubble growth over time even when the bubble is fractions of a millimeter from the surface. We extend our results to quantifying bubble forces at the water-oil interface at remote distances from the electrode surface.

CO2-Responsive Water-Soluble Conjugated Polymers as a Multifunctional Fluorescent Probe for Bioimaging Applications.

We describe important progress in the synthesis and development of gas-responsive water-soluble conjugated polymers (WSCPs) with potential as multifunctional fluorescent materials for biomedical imaging and probes. A water-soluble WSCP (I-PT) composed of a hydrophobic fluorescent polythiophene backbone and a hydrophilic imidazole side chain was successfully prepared through a facile and efficient two-step synthetic route. Owing to the repulsive force between the hydrophilic and hydrophobic segments and the highly sensitive carbon dioxide (CO2)- and nitrogen (N2)-responsive imidazole groups in its structure, I-PT can spontaneously self-assemble into spherical-like nanoparticles in an aqueous environment, and thus exhibits unique light absorption and fluorescence properties as well as rapid responsiveness to CO2 and N2. In addition, its structure, optical absorption/fluorescence behavior, and surface potential can be quickly turned on and off through alternating cycles of CO2 and N2 bubbling and exhibit controllable cyclic switching stability, thereby allowing effective manipulation of its hierarchical structure and chemical-physical characteristics. More importantly, a series of in vitro cell experiments confirmed that, compared to the significant cytotoxicity of pristine and N2-treated I-PT nanoparticles, CO2-treated I-PT nanoparticles exhibit extremely low cytotoxicity in normal and cancer cells and undergo greatly accelerated cellular uptake, resulting in a significant increase in the intensity and stability of their fluorescence signal in the intracellular environment. Overall, this newly discovered CO2/N2-responsive system provides new insights to effectively enhance the biocompatibility, cellular internalization, and intracellular fluorescence characteristics of WSCPs and holds great potential for biomedical imaging/sensing applications.

Computational Insights into a CO2-Responsive Emulsion Prepared Using the Superamphiphile Assembled by Electrostatic Interactions.

The superamphiphiles exhibit broad prospects for fabricating stimuli-responsive emulsions. Because the superamphiphiles are assembled via noncovalent interactions, they have the advantage of fast response and high efficiency. Recently, a series of switchable emulsions using CO2-responsive superamphiphiles have been developed, which extends the applications of CO2-responsive materials in widespread field. However, there is still a lack of fundamental understanding on the switching mechanism related to the assembled structure of superamphiphiles at the oil-water interface. We employed molecular dynamics (MD) simulations to investigate the reversible emulsification/demulsification process of a responsive emulsion system stabilized by a recently developed responsive superamphiphile (BTOA), which consists of oleic acid (OA) and cationic amine (named 1,3-bis(aminopropyl)tetramethyldisiloxane, BT). The simulation results present the morphologies in both the emulsion and demulsification states. It is found that the ionized OA- and the protonated BT+ together form an adsorption layer at the oil-water interface. The hydrophobic parts of BT+ are inserted into the adsorption layer, and the two amine groups contact the water phase. This adsorption layer reduces the interfacial tension and stabilizes the emulsion. After the bubbling of CO2, the surfactants were fully protonated to OA and BT2+. Because of the changes in the molecular polarity, OA and BT2+ entered the oil and water phases, respectively, resulting in demulsification. The structural and dynamical properties were analyzed to reveal the different intermolecular interactions that were responsible for the reversible reversibility of the emulsion. The observations are considered to be complementary to experimental studies and are expected to provide deeper insights into studies on developing responsive materials via supramolecular assemblies.

CO2 bubbling pretreatment to remove the inhibition of lime disinfection wastewater in a swine manure anaerobic digestion system

Under the African swine fever epidemic, the extensive use of lime disinfectants has seriously inhibited anaerobic digestion (AD). In this study, the subject was swine manure containing lime disinfectant wastewater. The research set up a carbon dioxide (CO2) bubbling pretreatment device before it entered AD to explore the effect of breaking the inhibition of lime disinfectant. The results showed that the initial pulmonary hypertension (pH) of 11.0 and CO2 bubbling time of 8 h had the best effect, which could reduce calcium ion (Ca2+) by 73.0%, and the biogas production of the batch AD test increased by 28 times. In the continuous AD test, the Ca2+ of CK increased to 7.67 g/L, while the S1 pretreated by CO2 bubbling stabilized at 2.6 g/L, the biogas production in S1 was 112.4% higher than in CK. CO2 bubbling pretreatment reduces the concentration of Ca2+ in swine by utilizing the combination of exogenous CO2 and Ca2+, breaking the inhibitory effect on AD, and thereby improving the performance of the AD system. The test used CO2 in biogas to break the inhibition of lime disinfectants on AD, which was a convenient and feasible pretreatment process.

A bubble-enhanced lanthanide-doped up/down-conversion platform with tumor microenvironment response for dual-modal photoacoustic and near-infrared-II fluorescence imaging

As an important tumor diagnosis strategy in precision medicine, multimodal imaging has been widely studied. However, the weak imaging signal with low spatial resolution and the constant signal of lack of specific activation severely limit its disease diagnosis. Herein, a bubble-enhanced lanthanide-based up/down-conversion platform with tumor microenvironment response for dual-mode imaging, LDNP@DMSN-Au@CaCO3 nanoparticles (named as LDAC NPs) were successfully developed. Combining the advantages of photoacoustic imaging (PAI) and the second near-infrared window (NIR-II) fluorescence imaging (FI), significantly improved the accuracy of diseases diagnosis. LDAC NPs with flower-like structure were synthesized through the encapsulation of uniform lanthanide-doped nanoparticles (NaYbF4:Ce,Er@NaYF4 named LDNPs) with dendritic mesoporous silica (DMSN). The gold nanoparticles (Au NPs) were then in situ grown on the surface of DMSN and the surface were finally coated with a layer of calcium carbonate (CaCO3). Under the excitation of the 980 nm laser, LDNPs showed strong emission of NIR-II at 1550 nm due to the doping of Ce and Er ions, showcasing excellent spatial resolution and deep tissue penetration characteristics, while the resulting visible light emission (540 nm) enables Au NPs to generate PAI signals with the aid of LDNPs via the fluorescence resonance energy transfer effect. In acidic tumoral environment, CaCO3 layer could produce CO2 microbubbles, and the PAI signals of LDAC NPs could be further enhanced with the generation of CO2 bubbles due to the bubble cavitation effect. Simultaneously, the NIR-II FI of LDAC NPs was self-enhanced with the degradation of the CaCO3. This intelligent nanoparticle with stimulus-activated dual-mode imaging capability holds great promise in future precision diagnostics.

A review of mechanisms influencing stable rheology complex Pickering foams for carbon utilization & storage in subsurface formations

While CO2 foams have been utilized for tertiary oil recovery and carbon collection, utilization, and storage for quite some time, but due to foam instability, the storage efficiency and enhanced oil recovery (EOR) of this method have been less efficient. Pickering foam represents a complex fluid made of CO2 bubbles stabilized by nanoparticles in water (NPs). This approach considerably enhances EOR and CO2 storage performance. The various mechanisms influencing the stabilization of a foam by an NPs have also been discussed. As a CO2 foam enhancer, NPs improve the foam layer & interfacial dilatational viscoelasticity and dynamic CO2 storage. Incorporating NPs on the foam lamella inhibits foam bubble disintegration and enhances foam’s durability. The novelty of the work lies in the concise explanation of various mechanisms influencing the success of Pickering foams in this role. A stable CO2 foam when injected into a heterogeneous porous media causes a larger areal sweep, even under adverse shear conditions and regains initial rheological profile, once shear is withdrawn, and the improved CO2 storage contributed to a boost in sweep efficiency, enabling the collection of larger amounts of oil.

Bioinspired controllable CaCO3 synthesis from solid waste by an “all in one” amino acid-in strategy: Implication for CO2 mineralization

CO2 mineralization suffers from extensive consumption of acidic/alkaline reagents due to the limited kinetics, which necessitates the development of an atom/energy-efficient process. An “all in one” reagent amino acid-based Ca2+ leaching-CO2 mineralization process inspired by biomineralization was proposed. This study explored the interactions between amino acids and Ca leaching, CaCO3 pre-nucleation, nucleation, and growth by investigating the evolution of Ca concentration, solution turbidity and CaCO3 morphology in complex CFA. Promising Ca2+ leaching efficiencies were observed, being 51.1 %, 34.2 %, and 21.0 % for glycine (Gly), L-alanine (Ala), and L-arginine (Arg), respectively, negatively correlated with their pI but positively correlated with their bonding energy with Ca2+. These amino acids ultimately led to a CaCO3 production of Gly (114.8 g/kg) > Ala (78.2 g/kg) > Arg (54.5 g/kg) from CFA. Gly leachate remained transparent (1.23 NTU) in the first 3 min of CO2 bubbling even though the solution was supersaturated and then got turbid suddenly (6508.75 NTU in 10 min) as continued CO2 bubbling, indicating the inhibition of Gly on CaCO3 nucleation. Observations using Cryo-SEM confirm the presence of abundant CaCO3 nanoparticles in the early stages of mineralization, which later assemble into vaterite crystal particles with a sub-structure and coalesce into larger particles in Gly and Ala. Meanwhile, Arg inhibited calcite growth along the C-axis, leading to the formation of thin, blocky-like particles. Furthermore, 0.010 ∼ 0.027 mmol/g amino acids are occluded into the CaCO3, stabilizing the metastable vaterites and imparting thermal stability, which was believed to be associated with this multistep pathway involving a transient prenucleation cluster, nanoparticle precursor formation, and particle–particle coalescence.

Visual experimental study of nanofluids application to promote CO2 absorption in a bubble column

The addition of dispersed-phase nanoparticles in the liquid phase can enhance the gas–liquid transfer process as the suspended nanoparticles affect the transfer process inside the fluid through micro-disturbance or micro-convection effects. In this paper, a high-speed digital camera was used to visualize the bubble behavior of CO2 in pure water and nanofluids to examine the effects of CO2 gas flow rate, nanoparticle solid content and type on the bubble behavior in the fluids. The CO2 absorption performance in three water-based nanofluids were compared in a bubbler. And the mass transfer characteristics during CO2 bubble absorption and the reasons for the enhanced gas–liquid mass transfer effect of nanoparticles were analyzed. The results showed that the presence of nanoparticles affected the formation process of bubbles in the fluid, shortened the bubble detachment time, reduced the detachment diameter, effectively increased the gas–liquid contact area, and improved the bubbles detachment frequency. The system with MCM-41 corresponded to a higher overall mass transfer coefficient. Uncalined MCM-41 contained surfactant which enhanced foaming behavior in water. This prevented the transfer of CO2 to some extent, and the CO2 absorption by uncalined MCM-41/H2O was 5.34% higher than that by pure water. Compared with SiO2 nanoparticles with the same particle size and the same composition, MCM-41 had a higher adsorption capacity and better hydrophilicity due to its larger specific surface area and rich porous structure, which was more favorable to accelerate the collision between nanoparticles and CO2 bubbles to cause micro-convection. Under the condition of 0.1% (mass) solid content, the enhancement of CO2 absorption process by MCM-41 nanoparticles was more significant and improved by 16.9% compared with pure water.

ZIF-67 hybridization and boron doping to enhance the photo-electrocatalytic properties of g-C3N4

Photo-electrocatalysis is a growing field, and cobalt-based metal-organic frameworks (Co-MOFs) are attracting much interest because of their porous nature, high surface area, and malleable structure. This study investigated the photo-electrocatalytic properties of g-C3N4 and boron-doped-g-C3N4 when hybridized with cobalt-based MOF (ZIF-67). In this work, we describe the preparation of novel g-C3N4/ZIF-67 and B-g-C3N4/ZIF-67 composites by poly-condensation and co-condensation methods, respectively. ZIF-67 hybridization caused a decrease in the band gap energy of g-C3N4 due to changes in the crystalline structure and size. EIS results indicated that only B-g-C3N4/ZIF-67 showed a response to light irradiation. At the same time, both B-g-C3N4/ZIF-67 and g-C3N4/ZIF-67 demonstrated sufficient light response when the potential applied was increased to -1.2 V vs. NHE in LSV analyses. CO2 reduction to ethanol was performed for 3 hours at -1 V vs. NHE under continuous light irradiation and CO2 bubbling for each catalyst. Ethanol production rates were recorded as 10.024, 12.0168, 30.7230, and 32.1096 μmol/cm2.h for g-C3N4, B-g-C3N4, g-C3N4/ZIF-67, and B-g-C3N4/ZIF-67, respectively.

Selective H2 Evolution and CO2 Absorption in Electrolysis of Ethanolamine Aqueous Solutions

Selective H2 evolution and CO2 absorption in several ethanolamine aqueous solutions are comparatively investigated using a new electrolysis reactor. H2 bubbles are generated from a cathode in any ethanolamine electrolyte, and its experimental gas evolution rates are correlated by Faraday’s first rule. No or smaller amounts of CO2 and N2 bubbles than stoichiometric ones are generated on an anode through the reaction between hydroxide ions and ethanolamine ones. No CO or O2 is observed in the system exhaust, and most of the CO2, along with N2, is still absorbed in ethanolamine aqueous solutions with the addition of KOH and/or HCOOH under high pH conditions. Variations of the concentrations of coexisting ions dissolved in the electrolytes of mono- or tri-ethanolamine (MEA or TEA) and ethylenediamine (EDA) solutions with CO2 absorption are calculated using the equilibrium constants to relate the concentrations of solute ions. Electric resistivities of the ethanolamine aqueous solutions are correlated by the pH value and are analyzed in terms of equilibrium constants among the concentrations of coexisting ions. Conditions of the MEA electrolyte to achieve high-performance electrolysis is discussed for selective H2 generation.

Effect of the Temperature on Interfacial Properties of CO2/H2 Mixtures Contacting with Brine and Hydrophilic Silica by Molecular Dynamics Simulations.

Underground H2 storage (UHS) is a promising technology to achieve large-scale, long-term H2 storage. Using CO2 as a cushion gas to maintain the pressure of the reservoir and withdraw stored H2 in the saline aquifer simultaneously enables the implementation of UHS and underground CO2 storage (UCS). The difference in the molecular properties of CO2 and H2 leads to distinct interfacial behavior when in contact with the brine and rock, thereby affecting the flow patterns and trapping mechanisms of gases in geological formations. Accurate prediction of the interfacial properties of CO2, H2, and the mixtures when interacting with brine and rock is crucial to minimizing the uncertainties in UHS and UCS projects. In this study, molecular dynamics (MD) simulations are performed to predict the interfacial tension, surface excess, bubble evolution, and contact angle of CO2, H2, and the mixtures at 10 MPa and 300-400 K. The MD results show that the interaction of CO2 with H2O and hydrophilic silica is considerably stronger than that of H2. The interfacial tension reduces linearly with the temperature in H2-dominated mixture systems, and the surface adsorption of H2 can diminish in a CO2-dominated system or at high-temperature conditions. The hydrophilic silica is more CO2-wet than H2-wet, and the attached CO2 bubble is more easily disconnected. Ions and the temperature play different roles in the contact angle.

A novel constant pressure control method for nucleation boiling of CO2/lubricant in molecular dynamics simulation

Conventional molecular dynamics simulations of nucleation boiling typically employ the fixed volume method, resulting in a non-constant pressure during the boiling process. In this paper, we propose an additional pressure control method, placing a cover plate at the top of the liquid phase to achieve liquid phase pressure control during boiling. The novel method yields a pressure control error within ±5 %. CO2 and CO2/PEC4 lubricating oil mixture are used to investigate the differences in heat transfer characteristics between non-constant and constant pressure nucleation boiling. Furthermore, the effect of PEC4 lubricating oil on CO2 nucleation boiling under a fixed pressure condition is explored. The results show that both the bubble nucleation and growth time of CO2 and the CO2/PEC4 mixture are prolonged under constant pressure. This causes a compression in CO2 molecular spacing, thereby reducing CO2 diffusion and mass transfer capabilities. Heat transfer from the solid to the liquid, and within the liquid itself, is diminished, while the distribution of PEC4 molecules within the liquid phase becomes more even. The migration rate of PEC4 molecules in the liquid phase slows down. Under the constant pressure model, PEC4 increases the mass transfer resistance of CO2. As the lubricant mass fraction rises, The nucleation and growth rate of CO2 bubbles decline. In comparison to CO2, PEC4 molecules exhibit a stronger interaction energy with the Cu wall surface. During boiling, some PEC4 molecules accumulate on the Cu surface, forming an oil film that impedes the direct contact between CO2 molecules and the Cu wall.

Early Planet Formation in Embedded Disks (eDisk). X. Compact Disks, Extended Infall, and a Fossil Outburst in the Class I Oph IRS43 Binary

We present the first results from the Early Planet Formation in Embedded Disks Atacama Large Millimeter/submillimeter Array Large Program toward Oph IRS43, a binary system of solar mass protostars. The 1.3 mm dust continuum observations resolve a compact disk, ∼6 au radius, around the northern component and show that the disk around the southern component is even smaller, ≲3 au. CO, 13CO, and C18O maps reveal a large cavity in a low-mass envelope that shows kinematic signatures of rotation and infall extending out to ∼2000 au. An expanding CO bubble centered on the extrapolated location of the source ∼130 yr ago suggests a recent outburst. Despite the small size of the disks, the overall picture is of a remarkably large and dynamically active region.

Preventing oxide precipitation in selective wet etching of Si3N4 for 3D-NAND structure fabrication: The role of bubbles

Selective wet etching of Si3N4 is a critical process in the fabrication of 3D-NAND structures; however, it faces a oxide precipitation problem that significantly deteriorates the remaining structure morphology. A recent study by Kim et al.(Kim et al., 2022 [1]) showed that generating CO2 bubbles during the wet etching process efficiently solves the precipitation problem in the fabrication of a 128 multi-layer 3D-NAND structure. In this study, we numerically investigated the multiscale diffusive transport of oxides in the etching process via three different simplified simulations at different scales to reveal the underlying mechanism. We found that mass transport within the multilayer structures alone cannot contribute to the oxide precipitation behavior. Macroscopic transport from the wafer-etchant interface to the bulk must be considered since it contributes to a high oxide concentration at the wafer-etchant surface, which further increases the concentration within the trenches, leading to the precipitation problem. Through the conjecture oxide transport simulation, we found that the large bubbles generated from the reaction agitate the surrounding liquid and dramatically reduce the oxide concentration at the wafer-etchant surface by one order of magnitude, thereby solving the precipitation problem. Our findings clearly explain the experimental results reported by Kim et al. and will further benefit the development of process-intensification technologies in wet etching.

Targeted echogenic and anti-inflammatory polymeric prodrug nanoparticles for the management of renal ischemia/reperfusion injury

Ischemia/reperfusion (IR) injury is an inevitable pathological event occurring when blood is resupplied to the tissues after a period of ischemia. One of major causes of IR injury is the overproduction of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), which mediates the expression of various inflammatory cytokines to exacerbate tissue damages. The overproduced H2O2 could therefore serve as a diagnostic and therapeutic biomarker of IR injury. In this study, poly(boronated methacrylate) (pBMA) nanoparticles were developed as nanotheranostic agents for renal IR injury, which not only generate CO2 bubbles to enhance the ultrasound contrast but also provide potent preventive effects in a H2O2-triggered manner. The surface of pBMA nanoparticles was decorated with taurodeoxycholic acid (TUDCA) that binds P-selectin overexpressed in inflamed tissues. In the mouse model of renal IR injury, TUDCA-coated pBMA (T-pBMA) nanoparticles preferentially accumulated in the injured kidney and markedly enhanced the ultrasound contrast. T-pBMA nanoparticles also effectively prevented renal IR injury by scavenging H2O2 and suppressing the expression of inflammatory cytokines. Treatment progress of IR injury could be also monitored by echogenic T-pBMA nanoparticles. Given their targeting ability, excellent H2O2-responsiveness, anti-inflammatory activity and H2O2-triggered echogenicity, T-pBMA nanoparticles have excellent translational potential for the management of various H2O2-related diseases including IR injury.

Ultrarapid-Acting Microneedles for Immediate Delivery of Biotherapeutics.

Subcutaneous injection is a common administration route for rapid and efficient delivery of biotherapeutics. However, syringe-based injections usually require professional assistance and are associated with pain and potential risks of infections, thus leading to undesired patient compliance and poor life quality. Herein, we present an ultrarapid-acting microneedle (URA-MN) patch for immediate transdermal delivery of therapeutics in a minimally invasive manner. Effervescent agents are incorporated into the tip of URA-MN for rapid generation of CO2 bubbles upon insertion into the skin, immediately powering the biotherapeutics release within a few minutes. The release kinetics of diverse agents including liraglutide, insulin, and heparin from the URA-MN were evaluated in three different mouse models, and the rapid release of biotherapeutics and potent therapeutic effects were achieved with only 5-minute administration. Noteworthily, attributed to the short application duration and negligible residuals of MN matrix remaining in the skin, the URA-MN patch showed desirable biocompatibility after 6-week administration. This article is protected by copyright. All rights reserved.