Microwave Thermal Effect Research Articles

A Tumor-Homing Nanoframework for Synergistic Microwave Tumor Ablation and Provoking Strong Anticancer Immunity Against Metastasis.

Microwave thermotherapy (MT) is a clinical local tumor ablation modality, but its applications are limited by its therapeutic efficacy and safety. Therefore, developing sensitizers to optimize the outcomes of MT is in demand in clinical practice. Herein, we engineered a special nanoframework (i.e., FdMI) based on a fucoidan-decorated zirconium metal-organic framework incorporating manganese ions and liquid physisorption for microwave tumor ablation. The monodisperse nanoframework exhibited both microwave thermal effects and microwave dynamic effects, which could effectively kill cancer cells by efficient intracellular drug delivery. Through fucoidan-mediated targeting of P-selectin in the tumor microenvironment (TME), the FdMI effectively accumulated in tumor regions, leading to significant eradication of orthotropic triple-negative breast cancer (TNBC) and aggressive Hepa1-6 liver tumors by the synergistic effects of microwave thermotherapy/dynamic therapy (MT/MDT). The eradication of primary tumors could activate systemic immune responses, which effectively inhibited distant TNBC tumors and lung metastasis of Hepa1-6 liver tumors, respectively. This work not only engineered nanoparticle sensitizers for tumor-targeted synergistic MT/MDT but also demonstrated that nanocarrier-based microwave tumor ablation could stimulate antitumor immunity to effectively inhibit distant and metastatic tumors, demonstrating the high potential for effectively managing advanced malignant tumors.

Microwave Hyperthermia Technology Based on Near‐Field Focused Metasurfaces: Design and Implementation

AbstractThis paper presents a near‐field focused metasurface design method for microwave hyperthermia. Utilizing full‐wave electromagnetic simulation, a novel dual‐layer metasurface unit with the following characteristics is developed: transmission efficiency higher than −1 dB, adjustable transmission phase from 0° to 360°, and insensitivity to the polarization and incident angle of the incoming wave. Leveraging phase compensation theory, the units at different positions in the array to achieve near‐field focusing functionality is meticulously designed. To further optimize transmission efficiency, the transmission phase of the central unit of the metasurface to 76° is tuned. When applying this near‐field focused metasurface to microwave hyperthermia, the electromagnetic and thermal effects in biological tissues is conducted simulations and experiments to analyzed. The results demonstrate that the proposed metasurface can effectively focus microwave energy, achieving efficient microwave transmission in pork tissue and generating localized high temperatures in the target area. This research introduces new design concepts and implementation strategies for the development of microwave hyperthermia technology.

Microwave catalytic and thermal effects of Ti3C2Tx/ZnO–PPy enhanced by interfacial polarization for rapid treatment of MRSA-induced osteomyelitis

Deep-seated osteomyelitis caused by bacterial infection, particularly methicillin-resistant Staphylococcus aureus (MRSA) infection, poses a significant challenge to treatment. In this study, we propose the utilization of a composite microwave (MW)-responsive polypyrrole-modified titanium carbide/zinc oxide (Ti3C2Tx/ZnO–PPy) heterostructure as a potential therapeutic option for MRSA-infected osteomyelitis. In vitro and in vivo experiments show that Ti3C2Tx/ZnO–PPy can effectively treat MRSA-induced osteomyelitis under MW irradiation, which is attributed to the enhanced in situ release of MW heat and reactive oxygen species (ROS). Density functional theory and MW network vector analysis further reveal that under MW irradiation, Ti3C2Tx/ZnO–PPy generates free electrons that move freely within the heterogeneous interface formed by Ti3C2Tx and ZnO, thereby enhancing the accumulation of charges. These charges combine with adsorbed oxygen at the interface to produce ROS. Furthermore, augmented dipole polarization induced by the functional groups on the surface of Ti3C2Tx and the interfacial polarization between Ti3C2Tx and ZnO contribute to good impedance matching and a favourable attenuation constant in the Ti3C2Tx/ZnO–PPy composite, resulting in superior MW thermal properties. Moreover, the polypyrrole-modified composite shows excellent biocompatibility. This efficient antimicrobial system with MW irradiation is expected to offer a viable approach to the management of osteomyelitis.

A comprehensive kinetic study on low-GHG hydrogen production from microwave-driven methane pyrolysis

The present study focuses on the cogeneration of hydrogen (H2) and solid carbon from microwave-driven methane pyrolysis in a fluidized bed of carbon pellets. Numerical simulations using a coupled gas-solid chemistry approach reveal that introducing microwave thermal effects improves methane conversion rate, H2 selectivity, and carbon deposition rate. The chemical pathways analysis divulges that once the leading reaction for decomposing CH4 into H2, i.e., CH4+H ↔ CH3+H2, is completed, the C2H2 deposition mechanism onto the carbon pellets is the dominant pathway for the solid carbon production, indicating almost no carbon black (i.e., nanoparticles) formation. Carbon pellets provide abundant surface area for the conversion of C2H2 to H2, enhancing H2 selectivity in the resulting products. More importantly, the importance of more complex molecules, such as polycyclic aromatic hydrocarbons, greatly diminishes when using carbon pellets in the pyrolysis process, implying that smaller kinetic mechanisms are equally effective and desirable.

Microwave assisted black phosphorus-based core-shell composites with synergistic antibacterial and osteogenic ability for bone tissue repair

In clinics, repairing bone tissue with methicillin-resistant Staphylococcus aureus (MRSA) infections and bone defects remains a remarkable challenge. This study designs new core-shell composites of PMP/PVA (Fe3O4@APNs based on magnesium phosphate cement/Fe3O4@APNs-VAN-PLGA microspheres-agarose hydrogel). With Fe3O4@APNs (Phytic acid dodecasodium exfoliated BPNs (APNs) modified with Fe3O4) as an enhanced microwave (MW) sensitizer, the PMP/PVA system exhibits outstanding MW thermal performance. Under MW irradiation, the PMP/PVA exerts dual antibacterial activity through the MW thermal effect (MTE, quickly increased to 68.7 ± 2.4 °C in 5 min at 2.45 GHz, 10 W/cm2) and MW-triggered chemotherapy (CTH, in vitro: 99.98 ± 0.02 % (MRSA), 99.43 ± 0.73 % (E. coli); in vivo: 99.98 ± 0.02 %), which possesses antibacterial ability in vitro and anti-infective effects in vivo with low toxicity and side effects. In addition, PMP/PVA possesses biodegradability with Ca2+, Mg2+, and PO43− released, which not only facilitates the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSC) in vitro but also promotes new bone formation for bone defect sites with chronic osteomyelitis in vivo (the implantations were gradually replaced with a large area of new bone without apparent cortical reactions). Therefore, PMP/PVA with dual antibacterial activity, osteogenic performance, and low toxicity ability can potentially repair bone tissue with MRSA infections and refractory bone defects. The proposed system is promising for bone tissue repair of chronic osteomyelitis with bone defects.

Polysaccharide- and protein-based edible films combined with microwave technology for meat preservation

To reduce food-borne bacterial infection caused by food spoilage, developing highly efficient food packing film is still an urgent need for food preservation. Herein, microwave-assisted antibacterial nanocomposite films CaO2@PVP/EA/CMC-Na (CP/EC) were synthesized using waste eggshell as precursor, egg albumen (EA) and sodium carboxymethylcellulose (CMCNa) as matrix by casting method. The size of CaO2@PVP (CP) nanoparticles with monodisperse spherical structures was 100–240 nm. When microwave and CP nanoparticles (0.05 mg/mL) were treated for 5 min, the mortality of E. coli and S. aureus could reach >97 %. Under microwave irradiation (6 min), the bactericidal rate of 2.5 % CP/EC film against E. coli and S. aureus reached 98.6 % and 97.2 %, respectively. After adding CP nanoparticles, the highest tensile strength (TS) and elongation at break (EB) of CP/EC film reached 19.59 MPa and 583.43 %, respectively. At 18 °C, the proliferation of bacterial colonies on meat can be significantly inhibited by 2.5 % CP/EC film. Detailed characterization showed that the excellent meat preservation activity was due to the synergistic effect of dynamic effect generated by ROS and thermal effect of microwave. This study provides a promising approach for the packaging application of polysaccharide- and protein-based biomass nanocomposite antibacterial edible films.

Investigating the Effect of Microwave Induction on the Polymerization Rate of Polycarboxylate Superplasticizers.

As a transmission medium and heating energy, microwave is widely favored due to its high efficiency, strong selectivity, and easy control. Here, the effects of different heating methods (conventional thermal induction (CI) and microwave induction (MI)) on the polymerization rate of polycarboxylate superplasticizer (PCE) were investigated. Compared with CI, MI significantly boosted the polymerization rate (by approximately 51 times) and markedly decreased the activation energy (Ea), from 46.83 kJ mol-1 to 35.07 kJ mol-1. The polar of the monomers and initiators in the PCE synthesis contributes to varying permittivities and loss factors under the microwave field, which are influenced by their concentration and reaction temperature. The insights gained from the microwave thermal effects and the micro-kinetics of the PCE polymerization system are able to propose theoretical underpinnings for the industrial-scale application of microwave induction polymerization, potentially steering the synthesis of polymer materials towards a more efficient and cleaner process.

Dielectric and Magnetic Composites of Fe3O4@APNs for Superior Microwave Thermal Effect.

As for the deep tissue infections of chronic osteomyelitis, antibiotics are hard to deliver into the infected bone tissue, which makes it difficult to be cured completely in clinic. Microwave has strong penetration, and the medium can produce a good bactericidal effect through the microwave thermal effect (MTE). Here, a new microwave sensitizer (Fe3O4@APNs) was prepared and evaluated. Black phosphorus nanosheets modified with phytic acid dodecasodium (APNs) were fabricated by a liquid-phase exfoliation method that exhibited good water oxygen stability. A complex with Fe3O4 compound and APNs (Fe3O4@APNs) was formed by an ultrasonic mixing process, which showed excellent MTE (quickly increased to 53.5 °C in 5 min at 2.45 GHz, 10 W/cm2) via dielectric versus magnetic loss (reflect loss value of -5.94 dB at 2.45 GHz). The Fe3O4@APNs microwave sensitizer developed in this study has an outstanding in vitro antibacterial effect and might show promise for the treatment of chronic osteomyelitis enabled by local tissue heating via the MTE.

Direct decomposition of hydrogen sulfide through microwave-induced discharge of graphitized bio-char

Direct decomposition of hydrogen sulfide (H2S) can be used to obtain high-purity hydrogen, thereby avoiding the waste of hydrogen resources by traditional Claus process. Microwave-induced discharge with spherical bio-char for H2S decomposition is proposed. The bio-char was treated by graphitization modification in presence of microwave heating and iron additive. The influences of graphitization parameters including iron loading and microwave irradiation time on the bio-char graphitization degree were studied. Subsequently, the modified bio-char was applied to induce microwave discharge, and the effects of graphitization parameters on discharge performance were discussed. Lastly, the attention was paid to investigate catalytic effect of microwave-induced discharge with the modified bio-char for H2S decomposition. The results showed the best graphitization degree of bio-char was achieved at iron loading of 6 mmol/g and microwave irradiation time of 60 min. The improvement of bio-char graphitization degree enhanced discharge intensity, thus promoting bed temperature. Microwave discharge exhibited a favorable catalytic effect on H2S decomposition, with initial and ending conversions at 97.4% and 83.2% in a two-hour test, respectively, because of synergistic effect of microwave discharge effect, microwave thermal effect and catalytic activity of the modified bio-char.

Microwave heating of coal slime based on multi-physics field simulations: Regulating waveguide port size and sample radius to improve microwave utilization efficiency

Microwave pyrolysis, a promising green-processing technology with high efficiency and low consumption, is particularly applicable in the pyrolysis of solid waste fuels such as coal slime. The microwave thermal effect plays an imperative role in the pyrolysis process. Low microwave utilization efficiency in single-mode microwave cavities is caused by the irregular field intensity distribution, and since of the high manufacturing costs of the equipment, it is unclear the relationship between waveguide port size, microwave field intensity distribution, and the temperature of sample. In this study, the effects of different waveguide port sizes and sample radius on the heating characteristics of coal slime were investigated using COMSOL Multiphysics software to construct a coupled multiphysics finite-element model. Moreover, the effects of the radius of the coal slime on the microwave utilization efficiency. The results demonstrated that only two types of wave distribution were found within the cavity, α and β, under the size of the waveguide port. The field intensity distribution in the β-type cavity was uniform, which prompted the sample temperature from 176 °C to 657 °C and microwave utilization efficiency from 10.16 % to 33.87 %. The maximum microwave utilization efficiency was increased from 33.87 % to 67.22 % by adjusting the radius of the sample at the optimal port size. The efficiency of the microwaves was maximized when the width-to-height ratio of the waveguide is 70:65 and the sample radius is 30–35 mm, and the sample temperature was maintained in a more desirable range. From the findings of this study, both the waveguide port size and sample radius are essential influencing factors in determining the sample temperature and microwave energy utilization efficiency during the heating of coal slime.

Damage properties of basaltic rocks under multilevel stress loading and microwave irradiation

The deterioration of mechanical strength and damage characteristics of rock under microwave is the primary focus in evaluating the applicability of microwave-efficient rock-breaking technology. This study analyzed the mechanical strength deterioration and damage characteristics of basalt under microwave irradiation and performed an X-ray digital radiography (DR) image analysis of the damage process of basalt under a multilevel stress loading (MSL) path. The research results show that basalt with a large porosity had a better thermal effect on microwave irradiation and significantly enhanced the resistance to deterioration. The microwave thermal effect of polar minerals is critical to plastic failure behavior. This study also proposes a rock damage characteristic evaluation model based on X-ray DR image quantitative analysis and X-ray absorption dose threshold segmentation. The image analysis model can accurately describe the evolution process of rock damage characteristics. A modified model for basalt damage characteristic analysis is provided. The elastic–plastic damage model based on the Cast3M finite element software was compared with the proposed damage model based on X-ray DR images. The calculated results show that the change in the damage zone was consistent with the damage crack propagation process of basalt. Therefore, the proposed damage evaluation model can provide guidance for the scientific evaluation of the adaptability of microwave-assisted tunnel boring machine (TBM) efficient rock-breaking technology.

Decoupling thermal effects and possible non-thermal effects of microwaves in vacuum evaporation of glucose solutions

Microwave vacuum evaporation (MVE) is a promising alternative to conventional methods. However, the mechanisms underlying its efficiency remain elusive. In this study, the effects of microwaves on glucose solutions were investigated via molecular dynamics (MD) simulations and experimental studies to elucidate possible microwave non-thermal and thermal effects, respectively. MD simulations on energy-related parameters, interfacial properties, and molecular migration indicated that a microwave electric field of 10 5 V/m could not influence water evaporation behavior at a constant temperature of 90 °C, validating the absence of non-thermal effects in the MVE of glucose solutions. Meanwhile, superheating was not observed in this study during microwave heating at atmospheric pressure or in vacuum. High-intensity microwaves enabled the solution to reach its boiling point rapidly and remarkably induced an intensified film boiling during MVE, thereby shortening the evaporation time. Therefore, the high efficiency of MVE may be attributed to the thermal effects of strong microwaves. • Thermal effects and possible non-thermal effects during MVE were studied. • Non-thermal effects were not observed during microwave evaporation at 10 5 V/m. • 10 9 V/m-z and 10 9 V/m-x microwaves accelerated and impeded evaporation, respectively. • Superheating did not occur during microwave heating with solution agitation.

Investigating the role of microwave thermal and non-thermal effects on WO3-graphene oxide composite synthesis.

The effects of microwave-assisted synthesis on the morphology and crystalline structure of WO3-graphene oxide (GO) composites have been investigated. Using two different microwave reactors, evidence supports that thermal and non-thermal effects significantly influence the properties of the synthesized materials. The findings reveal that the microwave cavity geometry affects how the microwaves are "delivered" to the reactional cavity as a function of time; it also orientates the growth process of the WO3 particles. Consequently, the crystalline structure and morphology are affected. As a result, the WO3-GO composites produced using a CEM reactor exhibit a rounded shape and hexagonal phase of WO3, besides enhanced reduction of GO. Whereas the composites made using an Anton-Paar reactor are composed of sheets and flowers of WO3 with hexagonal, triclinic and/or WO3 hydrate structures and cause a lower reduction on the GO.

Thermal Effects of Microwaves in Contaminated Soil Remediation

Thermal Effects of Microwaves in Contaminated Soil Remediation

Microwave Assisted Biodiesel Production Using Heterogeneous Catalysts

As a promising renewable fuel, biodiesel has gained worldwide attention to replace fossil-derived mineral diesel due to the threats concerning the depletion of fossil reserves and ecological constraints. Biodiesel production via transesterification involves using homogeneous, heterogeneous and enzymatic catalysts to speed up the reaction. The usage of heterogeneous catalysts over homogeneous catalysts are considered more advantageous and cost-effective. Therefore, several heterogeneous catalysts have been developed from variable sources to make the overall production process economical. After achieving optimum performance of these catalysts and chemical processes, the research has been directed in other perspectives, such as the application of non-conventional methods such as microwave, ultrasonic, plasma heating etc, aiming to enhance the efficiency of the overall process. This mini review is targeted to focus on the research carried out up to this date on microwave-supported heterogeneously catalysed biodiesel production. It discusses the phenomenon of microwave heating, synthesis techniques for heterogeneous catalysts, microwave mediated transesterification reaction using solid catalysts, special thermal effects of microwaves and parametric optimisation under microwave heating. The review shows that using microwave technology on the heterogeneously catalysed transesterification process greatly decreases reaction times (5–60 min) while maintaining or improving catalytic activity (>90%) when compared to traditional heating.

Study the synergism of microwave thermal and non-thermal effects on microbial inactivation and fatty acid quality of salmon fillet during pasteurization process

Microwave processing is a combined treatment of thermal and non-thermal effects on microorganisms and food ingredients. There may exist synergism between these two types of effects. The objective of this study was to explore the synergism of microwave thermal (i.e. temperature) and non-thermal effects on microbial inactivation and on fatty acids quality of pasteurized salmon fillets. Water bath processes with same time-temperature profiles and same microbial inactivation intensity were designed as control. Results showed that the microwave non-thermal effect on microbial inactivation was significantly (P < 0.05) enhanced by increasing temperatures. Compared with the microbial inactivation of thermal effect, the inactivation efficiency of microwave non-thermal effect increased from 22.18% to 35.25% while final temperatures of samples increased from 84 °C to 100 °C. Furthermore, with the same microbial inactivation intensity of 7.5-log CFU/g, microwave process retained better fatty acids quality in consideration of significantly higher (P < 0.05) PUFAs (especially for ARA, EPA and DHA) than those with water bath treatments. These results demonstrated that high temperatures could bring significant enhancement on microwave non-thermal effect, and microwave processing could provide better bacteria control and meanwhile retain higher product quality due to the synergism of microwave thermal and non-thermal effects.

Study of Microwave-Induced Ag Nanowire Welding for Soft Electrode Conductivity Enhancement

Silver nanowire (AgNW)-coated thin films are widely proposed for soft electronics application due to their good conductivity, transparency and flexibility. Here, we studied the microwave welding of AgNW-based soft electrodes for conductivity enhancement. The thermal effect of the microwave to AgNWs was analyzed by dispersing the nanowires in a nonpolar solution, the temperature of which was found to be proportional with the nanowire diameters. AgNWs were then coated on a thin film and welded under microwave heating, which achieved a film conductivity enhancement of as much as 79%. A microwave overheating of AgNWs, however, fused and broke the nanowires, which increased the film resistance significantly. A soft electrode was finally demonstrated using the microwave-welded AgNW thin film, and a 1.13 µA/mM sensitivity was obtained for glucose sensing. Above all, we analyzed the microwave thermal effect on AgNWs to provide a guidance to control the nanowire welding effect, which can be used for film conductivity enhancement and applied for soft and bio-compatible electrodes.

Ultra-fast preparing carbon nanotube-supported trimetallic Ni, Ru, Fe heterostructures as robust bifunctional electrocatalysts for overall water splitting

Rapid preparing unique carbon-based carriers via simple, low-cost and eco-friendly synthetic strategies benefits for the design of efficient catalysts and their commercial application. In this work, the Fe/C@CNT carrier that the carbon-coated Fe/Fe3C nanoparticles (iron-carbon heterostructure) uniformly growing on carbon nanotube (CNT) is obtained via the fast pyrolysis (only 3 min) of ferrocene on CNT with efficient microwave thermal effect. The unique heterostructure improves the dispersity and stability of Ni, Ru-based compounds on Fe/C@CNT carrier during the fast preparation progress of Ni-Ru@Fe/C@CNT catalyst and the subsequent catalytic reaction processes, and promotes the formation of efficient active sites for HER (Ru (0)) and OER (Ni (3 + )). Therefore, Ni-Ru@Fe/C@CNT shows robust bifunctional activity and enduring stability, and just needs the low overpotential about 32 mV and 246 mV to reach the current density of 10 mA cm−2 for HER and OER, respectively, which are better than the Ni-Ru-Fe@CNT using smooth CNT as carrier and even far superior to the commercial Pt/C and RuO2. More importantly, the whole preparation process of Ni-Ru@Fe/C@CNT is fast, simple and low-cost, providing a facile and environment friendly strategy to rapidly prepare efficient catalysts.

Investigation of smart water imbibition assisted with microwave radiation as a novel hybrid method of enhanced oil recovery

This research aims to investigate the efficiency of a new hybrid method of smart water imbibition assisted with microwave (MW) radiation. Some experiments including the contact angle measurement, attenuated total reflectance (ATR), zeta potential evaluation, oil viscosity measurement, and smart water imbibition were studied to find the effect of the MW radiation on the performance of the smart water imbibition. To capture the controlling mechanisms, it was essential to sustain the temperature in some of the MW treatments. Hence, the rock sections were treated by two methods of dry (MW treating the sections without immersion in the brine water) and immersed (MW treating the sections when they are immersed in the brine water) treatments. It was shown that the contact angle of an aged rock section could be reduced from 170° at the initial condition to almost 37° due to treating by smart water and the MW radiation. Divalent cations of Mg2+ and SO42- were discovered to be more efficient in the wettability improvement than Ca2+, and this fact was discussed in detail from thermodynamic and kinetic points of view. Also, it was found that the MW thermal effect is not the only reason for the wettability improvement and organic compound desorption, but also the MW treatment could destabilize the organic compounds on the rock surface through generating oscillating electric fields. This fact was confirmed by the results of the immersed MW treatment, where the contact angle reduction was found to be almost as efficient as the dry MW treatment. Based on the ATR spectrums, the MW radiation can desorb the polar and non-polar compounds in two different mechanisms of thermal desorption and destabilization caused by oscillating electric fields. Furthermore, it was shown that the oil viscosity was reduced due to temperature rising caused by the microwave treatment, but when the temperature of the oil sample reduced to the room temperature, the viscosity reduction was not observed. The oil viscosity, after the treatment for 2 min, with the radiation power of 20, 40, 60, 80, and 100 maximum power increased to 52.5, 53.1, 55.5, 54.2, and 53.1 cp, respectively. Finally, it was shown that the oil recovery was increased 9% during the MW radiation for 16 min in the smart water imbibition test. Based on the observed results in this research, it is concluded that the hybrid of smart water imbibition assisted with MW radiation could be considered as a novel EOR method resulting in more oil recovery.

Liquid‐phase‐induced synthesis of SiC rods by microwave heating

β-SiC rods were synthesized by microwave heating using activated carbon, boric acid, and tetraethoxysilane (TEOS) as raw materials. A sol–gel method was carried out to coat silicon dioxide (SiO2) on activated carbon and mix with boric acid. The mixed raw powders were pre-formed by uniaxial pressing into cylindrical pellets in the dimension of Φ 30 × 25 mm. The heating temperature was 1100 °C with different holding times of 10 min, 20 min, and 30 min, respectively. Techniques of XRD, SEM, DSC-TG were carried out to characterize samples. It was found that β-SiC rods can be prepared by microwave heating with the presence of liquid phase. Hybrid microwave thermal effects give rise to complicated physical and chemical reactions at high temperature. Microwave plasma and microwave coupling effects occurred due to the gases and liquid during the reaction. The growth of SiC is realized by the diffusion–precipitation mechanism. SiC rods are well formed under sufficient atomic diffusion on the surface and within the sample by self-coupling. Perfect homogeneous growth occurs with no stack fault appearing within prepared SiC rods.