Selective Heating Research Articles

NiCoAl-Based Monolithic Catalysts for the N2O Intensified Decomposition: A New Path towards the Microwave-Assisted Catalysis

Nitrous oxide (N2O) is considered the primary source of NOx in the atmosphere, and among several abatement processes, catalytic decomposition is the most promising. The thermal energy necessary for this reaction is generally provided from the external side of the reactor by burning fossil fuels. In the present work, in order to overcome the limits related to greenhouse gas emissions, high heat transfer resistance, and energy losses, a microwave-assisted N2O decomposition was studied, taking advantages of the microwave’s (MW) properties of assuring direct and selective heating. To this end, two microwave-susceptible silicon carbide (SiC) monoliths were layered with different nickel–cobalt–aluminum mixed oxides. Based on the results of several characterization analyses (SEM/EDX, BET, ultrasound washcoat adherence tests, Hg penetration technique, and TPR), the sample showing the most suitable characteristics for this process was reproduced in the appropriate size to perform specific MW-assisted catalytic activity tests. The results demonstrated that, by coupling this catalytic system with an opportunely designed microwave heated reactor, it is possible to reach total N2O conversion and selectivity of a highly concentrated N2O stream (50 vol%) at T = 550 °C, the same required in the conventionally heated process to remove N2O from a less concentrated gas stream (20 vol%).

Challenges in unconventional catalysis

Catalysis science and technology increased efforts recently to progress beyond conventional "thermal" catalysis and face the challenges of net-zero emissions and electrification of production. Nevertheless, a better gaps and opportunities analysis is necessary. This review analyses four emerging areas of unconventional or less-conventional catalysis which share the common aspect of using directly renewable energy sources: (i) plasma catalysis, (ii) catalysis for flow chemistry and process intensification, (iii) application of electromagnetic (EM) fields to modulate catalytic activity and (iv) nanoscale generation at the catalyst interface of a strong local EM by plasmonic effect. Plasma catalysis has demonstrated synergistic effects, where the outcome is higher than the sum of both processes alone. Still, the underlying mechanisms are complex, and synergy is not always obtained. There is a crucial need for a better understanding to (i) design catalysts tailored to the plasma environment, (ii) design plasma reactors with optimal transport of plasma species to the catalyst surface, and (iii) tune the plasma conditions so they work in optimal synergy with the catalyst. Microfluidic reactors (flow chemistry) is another emerging sector leading to the intensification of catalytic syntheses, particularly in organic chemistry. New unconventional catalysts must be designed to exploit in full the novel possibilities. With a focus on (a) continuous-flow photocatalysis, (b) electrochemical flow catalysis, (c) microwave flow catalysis and (d) ultrasound flow activation, a series of examples are discussed, with also indications on scale-up and process industrialisation. The third area discussed regards the effect on catalytic performances of applying oriented EM fields spanning several orders of magnitude. Under well-defined conditions, gas breakdown and, in some cases, plasma formation generates activated gas phase species. The EM field-driven chemical conversion processes depend further on structured electric/magnetic catalysts, which shape the EM field in strength and direction. Different effects influencing chemical conversion have been reported, including reduced activation energy, surface charging, hot spot generation, and selective local heating. The last topic discussed is complementary to the third, focusing on the possibility of tuning the photo- and electro-catalytic properties by creating a strong localised electrical field with a plasmonic effect. The novel possibilities of hot carriers generated by the plasmonic effect are also discussed. This review thus aims to stimulate the reader to make new, creative catalysis to address the challenges of reaching a carbon-neutral world.

Immunological consequences of CD91 Single Nucleotide Polymorphisms in patients with sarcomas

Abstract Tumor immunosurveillance is critically dependent on several immune cell types and proteins including CD91. CD91 is expressed on the surface of antigen presenting cells (APCs) and binds a select few heat shock proteins (HSPs) released by dying tumor cells. These HSPs carry tumor antigens and initiate anti-tumor immune responses in de novotumors. We have previously shown among multiple sarcoma types, osteosarcomas are poorly infiltrated by T cells and poorly immune edited. This correlates with reduced expression of CD91 on the surface of intratumoral APCs. CD91 is a highly polymorphic gene within the human population. Over 3500 single nucleotide polymorphisms (SNPs) have been identified, despite the relatively high conservation of CD91 throughout evolution. We have identified 155 of these SNPs within our sarcoma patient population, 11 of which are exonic and non-synonymous. We analyzed the immunologic data we obtained from patients with non-synonymous SNPs to patients with normal CD91 protein sequences. In addition, we used the computational modeling programs SIFT and PolyPhen-2 to predict the effects of these mutations on CD91 protein folding. SNPs rs746886209 and rs758644665 were indicated by both SIFT and PolyPhen-2 to have deleterious effects on CD91 folding and patients with these mutations had below average immune infiltration. While these data are currently correlative, we have developed an in vitromodel to obtain proof of concept.

Powder Bed Fusion via Machine Learning-Enabled Approaches

Powder bed fusion (PBF) applies to various metallic materials used in the metal printing process of building a wide range of complex parts compared to other AM technologies. PBF process has several variants such as DMLS (direct metal laser sintering), EBM (electron beam melting), SHS (selective heat sintering), SLM (selective laser melting), and SLS (selective laser sintering). For PBF to reach its maximum potential, machine learning (ML) algorithms are used with suitable materials to achieve goals cost-effectively. Various applications of neural networks, including ANNs, CNNs, RNNs, and other popular techniques such as KNN, SVM, and GP were reviewed, and future challenges were discussed. Some special-purpose algorithms were listed as follows: GAN, SeDANN, SCNN, K-means, PCA, etc. This review presents the evolution, current status, challenges, and prospects of these technologies in terms of material, features, process parameters, applications, advantages, disadvantages, etc., to explain their significance and provide an in-depth understanding of the same.

Biochemical and in silico evaluation of a recombinant, glucose tolerant, and highly thermostable β-glucosidase from Thermococcus radiotolerans DSM-15228

Backgroundβ-glucosidase (EC 3.2.1.21) catalyzing the β-glycosidic linkages in polysaccharides is a ubiquitous enzyme with great importance in biofuel and other industries. Enzyme inhibition by glucose has been considered as the major hurdle in the practical applications of this enzyme. Therefore, there has been a continuous search for novel β-glucosidase with high glucose tolerance and stability at industrial temperature. In the present study, recombinant of β-glucosidase from Thermococcus radiotolerans has been produced and characterized. ResultsThe enzyme was overexpressed in Escherichia coli strain BL21 (DE3) codon plus RIPL and purified by selective heat denaturation, ethanol precipitation and anion exchange chromatography. Purified enzyme displayed a band on SDS-PAGE with a molecular weight of 50 kDa. Optimum enzyme activity was found at pH 5, and 85°C, it retained more than 46% activity when incubated at 100°C for 5 min and exhibited 80% activity in the presence of 800 mM glucose. Km and Vmax values of the purified enzyme were found as 16.3 mM of pNPG and 25.8 µ moles per min. Molecular docking studies have shown a strong binding affinity of pNPG with the enzyme active site consisting of Glu365, Asn266, and Trp295 as major the active site amino acids. MD simulation analysis has shown a significantly high stability of enzyme active site and high potential of enzyme substrate complex formation. ConclusionsThe novel characteristics such as relatively low Km value, extremely high-temperature stability and tolerance of high glucose concentration advocate the enzyme as a potential candidate for the industrial applications.How to cite: Albalawi H, Altayeb HN, Iftikhar S, et al. Biochemical and in silico evaluation of a recombinant, glucose tolerant, and highly thermostable β-glucosidase from T. radiotolerans DSM-15228. Electron J Biotechnol 2023; 64. https://doi.org/10.1016/j.ejbt.2023.03.002.

Reduced graphene oxide catalytically enhances the rate of cyanate ester curing under variable frequency microwave heating

AbstractThe curing of Lonza Primaset PT‐30 novolac cyanate ester resin and EPON 826 bisphenol‐A diglycidyl ether were investigated using convective thermal heating and variable frequency microwave (VFM) heating. The addition of 1 part per hundred reduced graphene oxide (r‐GO) to PT‐30 novolac cyanate ester increased the VFM cure rate compared to thermal heating. Curing it at 160°C for 240 min with VFM heating resulted in a 55% degree of cure compared to a 26% degree of cure with thermal heating. This observed VFM rate enhancement is due to selective microwave heating of the r‐GO particles in the resin resulting in increased r‐GO catalytic activity toward cyanate ester curing. It is both a thermal and catalytic effect, the latter of which is absent when r‐GO is added to a bisphenol‐A diglycidyl ether resin with o‐phenylenediamine hardener. Impurities present in the PT‐30 matrix do not appear to contribute to its overall cure kinetics, nor do they participate in the observed VFM rate enhancement.

Implementation of Thinned Array Synthesis in Hyperthermia Treatment Planning of 434 MHz Phased Array Breast Applicator Using Genetic Algorithm

Genetic algorithm-based array thinning technique is investigated in this paper to study the performance of our 18-element 434 MHz phased array breast applicator when driven by reduced number of active antennas. Selective power deposition ability was assessed for 18, 15, 12, and 9 active antennas on 25 patient models with varying characteristics. The average hotspot to target quotient of 18-, 15-, 12-, and 9-antenna excitation in 25 patient models was 1.18, 1.09, 1.09, and 1.13, respectively. The average temperature in 50% tumor volume for 18-, 15-, 12-, and 9-antenna excitation was 42.42 °C, 42.48 °C, 42.49 °C, and 42.48 °C, respectively. The temperature induced in tumor and healthy tissues is similar for varying number of active channels. However, the amount of power consumed was 25.2%, 53.9%, 97.9% higher for 15, 12, 9 active antennas compared to the filled array. Antenna array with 12 active elements was chosen as the optimal combination as it provided selective tumor heating with good tradeoff between number of channels and power consumption. The heating ability of the thinned array was assessed for 50% reduction in the number of active antennas on patient derived heterogeneous breast phantoms for five tumor target locations. The good agreement between simulated and measured thermal distributions demonstrate the selective heating ability of our phased array applicator for 50% reduction in hardware resources. The study outcome enables us to realize a cost-effective hyperthermia treatment delivery system.

Alternating magnetic field improved NiFe@MoS2 monolayer diatomic site catalyst for overall water splitting

Further uprating the catalytic activities of diatomic active sites while maintaining the atomic loading and diatomic coordination by external stimulation is a promising way to break the bottleneck in the improvement of diatomic site catalysts (DASCs). Herein, the as-prepared NiFe@MoS2 DASCs treated by external high-frequency alternating magnetic field (AMF) further expedite the alkaline water electrolysis process with a superior cell voltage of 1.576 V to afford a current density of 10 mA cm−2 than that treated without AMF (1.652 V). Theoretical simulation by COMSOL Multiphysics helps visualize the increase in temperature locally around the diatomic active sites, qualitatively revealing the magnetic heating effect that originates from the anchored magnetic Ni and Fe atoms. The selective magnetic heating of bifunctional diatomic active site proposed in this work can broaden horizons and endow another dimension in the design of highly efficient catalysts toward various complicated energy-related reactions.

Zebra-inspired stretchable, biodegradable radiation modulator for all-day sustainable energy harvesters.

Recent advances in passive radiative cooling systems describe a variety of strategies to enhance cooling efficiency, while the integration of such technology with a bioinspired design using biodegradable materials can offer a research opportunity to generate energy in a sustainable manner, favorable for the temperature/climate system of the planet. Here, we introduce stretchable and ecoresorbable radiative cooling/heating systems engineered with zebra stripe-like patterns that enable the generation of a large in-plane temperature gradient for thermoelectric generation. A comprehensive study of materials with theoretical evaluations validates the ability to accomplish the target performances even under external mechanical strains, while all systems eventually disappear under physiological conditions. Use of the zebra print for selective radiative heating demonstrates an unexpected level of temperature difference compared to use of radiative cooling emitters alone, which enables producing energy through resorbable silicon-based thermoelectric devices. The overall result suggests the potential of scalable, ecofriendly renewable energy systems.

Application of microwave in manufacturing technology: A review

In todays world due to wide experimentation of materials and wider application in various field and with introduction of reduced production or manufacturing costs, and processing lead times, newly developed processing technology is what is required with these advantages. The newly developed processing techniques should be such that it should be widely acceptable for all types of materials including metals, non-ferrous metals, non-metals etc. Such processing methods are many but microwave processing is one of the fastest and latest emerging manufacturing technology that has found new application in material joining, casting, heat treatment, cladding, sintering, machining and drilling. In comparison to other conventional processes, microwave processing of materials not only enhances the mechanical properties but also redues the defects and has certain economical advantage in power and time savings. In comparison to conventional processes, microwave processing due to hybrid and selective heating, the parts produced has more uniform, axial, cellular and homogeneous type of structure is obtained. It has found application in not only in food processing industry but wide application has been found in manufacturing industry. Though other processes are available in the industries like electric furnace and ohmic resistance heating but the microwave due to its properties like penetration radiation, controllable electric field distribution, rapid heating, selective heat, self limit reactions with advantage of lower environmental impact has been extensively used for industrial and material processing applications. This work describes the review focusses on technological advancement of microwave processing of materials and their application in manufacturing applications in industries.

Investigation of mechanical properties of microwave welded SS304-SS202 lap joints

The joint between dissimilar materials is always challenging to develop through traditional techniques due to the different properties of the parent materials. However, a novel non-traditional route of joining similar and dissimilar materials through energy conversion and absorption has been developed called SMHH (selective microwave hybrid heating). It has gained much attention due to its unique heating abilities. In the present work, the lap joint between SS202-SS304 is developed through SMHH placing nickel powder as an interlayer. The lap joint was characterized mechanically through shear tests and microhardness. Since the sheared area of the joint is large, it is challenging to achieve a good joint. Thus, to develop a solid joint, laser surface texturing (LST) was introduced to the joining surfaces, and the joints were characterized. After LST was introduced, a fully diffused joint interlayer region was observed through scanning electron microscopy (SEM). The EDS results confirmed the complete metallurgical bonding occurred by the diffusion of elements across the weld zone. From the XRD spectrum, the formation of intermetallic compounds like FeNi, FeNi3, C3Fe7, and M23C6 were identified at the joint region. The mean microhardness of 355 ± 10 HV was determined at the joint region of lap joints with LST. A lap joint with LST exhibits 217 MPa of shear strength, which is significantly higher than the joints without LST. Fractography of the shear failure specimens pointed out that partial heating of the interlayer caused incomplete bonding of the base metal and interlayer for without LST lap joints. However, mixed mode failure of SS202 near the overlap region of the LST lap joint occurred. It is concluded that the addition of LST on the lap joint has made a colossal impact on enhancing joint strength and intermetallic bonding. In addition, temperature-time profiling was studied to understand the heating mechanism involved in SMHH using thermocouples.

Selective Infrared Neural Inhibition Can Be Reproduced by Resistive Heating

ObjectivesSmall-diameter afferent axons carry various sensory signals that are critical for vital physiological conditions but sometimes contribute to pathologies. Infrared (IR) neural inhibition (INI) can induce selective heat block of small-diameter axons, which holds potential for translational applications such as pain management. Previous research suggested that IR–heating-induced acceleration of voltage-gated potassium channel kinetics is the mechanism for INI. Therefore, we hypothesized that other heating methods, such as resistive heating (RH) in a cuff, could reproduce the selective inhibition observed in INI. Materials and MethodsWe conducted ex vivo nerve-heating experiments on pleural-abdominal connective nerves of Aplysia californica using both IR and RH. We fabricated a transparent silicone nerve cuff for simultaneous IR heating, RH, and temperature measurements. Temperature elevations (ΔT) on the nerve surface were recorded for both heating modalities, which were tested over a range of power levels that cover a similar ΔT range. We recorded electrically evoked compound action potentials (CAPs) and segmented them into fast and slow subcomponents on the basis of conduction velocity differences between the large and small-diameter axonal subpopulations. We calculated the normalized inhibition strength and inhibition selectivity index on the basis of the rectified area under the curve of each subpopulation. ResultsINI and RH showed a similar selective inhibition effect on CAP subcomponents for slow-conducting axons, confirmed by the inhibition probability vs ΔT dose-response curve based on approximately 2000 CAP measurements. The inhibition selectivity indexes of the two heating modalities were similar across six nerves. RH only required half the total electrical power required by INI to achieve a similar ΔT. SignificanceWe show that selective INI can be reproduced by other heating modalities such as RH. RH, because of its high energy efficiency and simple design, can be a good candidate for future implantable neural interface designs.

Enhancing the dechlorination of CuCl residue using a microwave sulfation-roasting method: Process optimization and mechanism investigation

Spent CuCl residue produced from zinc hydrometallurgy is a typical toxic and hazardous solid waste as well as a secondary resource owing to its high contents of chlorine and valuable metals (Pb, Cu, Zn). The removal of chlorine from the CuCl residue and recycling of valuable metals are critical issues for the copper slag resource treatment process. In this study, a novel method of microwave sulfation-roasting under an oxygen atmosphere is used to improve the dechlorination process, and various parameters, such as roasting temperature, duration, sulfuric acid concentration, and liquid/solid ratio, are optimized. First, according to thermodynamic calculations, the addition of H2SO4 can significantly decrease both the roasting temperature and time needed for microwave oxidation-roasting. The dechlorination experimental results reveal that the dechlorination rate of the CuCl residue is as high as 91.91% under a temperature of 250 °C, holding time of 120 min, sulfuric acid concentration of 70%, and liquid-solid ratio of 1.42. The microstructure, chemical composition, and phase changes of the CuCl residue before and after roasting are characterized using scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray fluorescence and X-ray diffraction; further, the mass contents of the main elements in the roasting product and tail gas absorption solution are determined by chemical analysis, Evidently, the selective heating property of microwaves produces more holes and cracks in the copper slag, which can provide a new reaction channel for H2SO4 and CuCl slag reactions, and almost all CuCl in the copper slag is completely removed by transformation into CuO, CuSO4 and Cu2O(SO4). Simultaneously, a large number of gas by-products produced in the dechlorination process, such as SO2 and Cl2, can be absorbed by the NaOH solution. Therefore, no pollution is generated in the environment. These findings illustrate that microwave sulfation-roasting is an effective method for promoting the treatment and recycling of CuCl waste residues.

The EGFR C797S Mutation Confers Resistance to a Novel EGFR Inhibitor CLN-081 to EGFR Exon 20 Insertion Mutations

IntroductionEGFR exon 20 insertion mutations account for 5% to 10% of EGFR-mutated NSCLC. CLN-081 (formerly known as TAS6417), a novel covalent EGFR tyrosine kinase inhibitor, exhibits pan-mutation selective efficacy, including exon 20 insertions, in the clinical setting. Nevertheless, some patients may not respond to CLN-081 and resistance to CLN-081 may emerge over time in others. MethodsWe exposed Ba/F3 cells transduced with EGFR exon 20 insertions (Y764_V765 insHH or A767_S768insSVD) to increasing concentrations of CLN-081 to generate resistant cells and then subjected their complementary DNA to sequencing to identify acquired mutations. We then evaluated effects of small molecules on engineered Ba/F3 cells on the basis of proliferation assays, Western blotting, and xenograft models. ResultsAll CLN-081 resistant clones harbored the EGFR C797S mutation. Ba/F3 cells with C797S (Ba/F3-C797S) were resistant to EGFR tyrosine kinase inhibitors targeting EGFR exon 20 insertion mutations, including CLN-081. Pimitespib, a selective heat shock protein 90 inhibitor, induced apoptosis in Ba/F3-C797S cells in vitro and inhibited growth of Ba/F3-C797S tumors in vivo. Ba/F3 cells with A763_Y764insFQEA-C797S remained sensitive to erlotinib. ConclusionsWe conclude that the EGFR C797S mutation confers resistance to CLN-081. Our preclinical data suggest a potential small molecule to overcome CLN-081 resistance, which may benefit patients with lung cancer with EGFR exon 20 insertions.

Low-cost, high-density Mn–Co spinel coatings for stainless steel interconnect via efficient microwave heating

The high preparation cost and poor density of spinel coatings for stainless steel interconnect have always been puzzling conundrums for the solid oxide fuel cell stack developers. Herein, the microwave heating technology for fabricating Mn–Co spinel coating is developed to address these issues. We designed a device spontaneously providing reducing atmospheres and realized the low-cost, high-efficiency reduction of Mn–Co spinel via microwave heating. Dense coatings (MnO + Co) are formed on the steel surface at ∼1100 °C. The excellent density is related to the melting of Co particles induced by microwave selective heating. At initial, microwave heating is dominated by dipolar polarization, interfacial polarization, and natural resonance. After forming metallic Co, conductive loss and the lens effect further accelerate the reduction process. High-quality spinel coatings are formed during the subsequent oxidation at 800 °C, exhibiting an extremely low area-specific resistance increase rate.

Dual precipitate simultaneous enhancement of tensile and fatigue strength in (FeCoNi)86Al7Ti7 high-entropy alloy fabricated using selective laser melting

Recent studies have indicated that precipitation-strengthened high-entropy alloys (HEAs) show superior mechanical performance and have been successfully fabricated by additive manufacturing. However, the lack of fatigue and fracture research has limited the engineering applications of additive manufacturing HEAs. This work explored a dual precipitation-strengthened (FeCoNi)86Al7Ti7 HEA with excellent tensile and fatigue strength, prepared through selective laser melting and heat treatment. Compared with the as-built samples, the tensile properties and fatigue endurance limit improved through aging by 48.7% and 30%, respectively. The strengthening mechanism and enhanced fatigue performance were clarified in detail. The improvement in fatigue strength was attributed to the improved resistance of the L12 and L21 precipitates. During deformation, the dislocation shear coherent L12 precipitates reduced slip band energy and inhibited slip band expansion, while the L21 particles acted as obstructions for further slip band propagation, severely limiting the rapid formation and propagation of crack growth. In-situ TEM cyclic tensile-tensile testing also clarified the fatigue crack growth behavior, demonstrating that crack deflection due to L21 precipitate obstruction slowed down the crack growth rate and efficiently promoted the closure of the microcrack tips. This work offers implications for a new strategy to develop additive manufacturing HEAs.

Polyvinyl chloride cooperates with biomass to assist in the directional conversion of N and Cl as NH3 and HCl to prepare clean fuel by low-temperature microwave heating

This work proposed an innovative integrated process to produce clean fuel. Waste polyvinyl chloride (PVC) was co-pyrolysis with biomass as a hydrogenation agent to enhance the conversion N of biomass to NH3 in the gaseous product by microwave heating. This work demonstrated the conditions suitable for the co-pyrolysis of PVC and the biomass (straw and rice husk, respectively) process based on the denitrification and dechlorination effects including indexes of N and Cl removal ratio and NH3 and HCl production ratio. The mass ratio of PVC to biomass (PVC: biomass), microwave heating power, active carbon (AC), and the pyrolysis temperature turned out to be significant factors for N and Cl removal and PVC: biomass and AC were also positive for converting N and Cl to NH3 and HCl. The optimum operating conditions were PVC: biomass 1:9, microwave heating power 500 W, active carbon 1.6 g, and heating temperature 300 °C. The mechanism could be primarily related to the volumetric and selective heating advantage of microwave heating, being attributed to producing abundant H radicals from PVC and promoting the hydrogenation reaction of biomass to remove N as NH3. Moreover, the denitrification and dechlorination effect differences between microwave heating and electric heating were studied to explore the microwave non-thermal heating effect. The amount of the N removal ratio and the NH3 production ratio by microwave heating was almost 5%–10% higher. The amount of the Cl removal ratio and the HCl production ratio was almost 10% and 7% higher than that by electric heating. The pyrolysis reaction enhancement and the better denitrification and dechlorination effect of microwave heating could be a result of specific microwave non-thermal effects in addition to the thermal effect, containing more uniform heat distribution and selective heating characteristics. The present work may provide a new viewpoint for the clean utilization of biomass and chlorinated plastic waste as a fuel and avoid HCl corrosion when treating the chlorinated plastic waste.

The selective heating effect of microwave irradiation on a binary mixture of water and polyethylene oxide: a molecular dynamics simulation approach.

In this study, we investigate the molecular mechanisms of a microwave-driven selective heating process by performing molecular dynamics simulations for three different systems including pure water, pure polyethylene oxide (PEO), and water-PEO mixed systems in the presence of a microwave with two different intensities of electric field such as 0.001 V Å-1 and 0.01 V Å-1 at a frequency of 100 GHz. First, from performing molecular dynamics simulations of CO and CO2 in the presence of the microwave, it is confirmed that the molecular dipole moment is responsible for the rotational motion induced by the oscillating electric field. Second, by analyzing the MD simulations of the pure water system, we discover that the dipole moment of water exhibits a time lag with respect to the microwave. During the heating process, however, the temperature, kinetic, and potential energies increase synchronously with the oscillating electric field of the microwave, showing that the heating of the water system is caused by the molecular reaction of water to the microwave. Comparing the water-PEO mixed system to the pure water and pure PEO systems, the water-PEO mixed system has a higher heating rate than the pure PEO system but a lower heating rate than the pure water system. Therefore, we conclude that heating the water-PEO mixed system is driven by water molecules selectively activated by microwave irradiation. We also calculate the diffusion coefficients of water molecules and PEO chains by describing their mean square displacements, demonstrating that the diffusion coefficients are increased in the presence of microwaves for both water and PEO in pure and mixed systems. Lastly, during the microwave heating process, the structures of the water-PEO mixed system are altered as a function of the intensity of electric field, which is mainly driven by the response of water molecules.

Digital Twins towards Microwave-assisted 3D Printing of Continuous Carbon Fiber Reinforced Composites

Microwave-assisted 3D printing based on the fused filament fabrication (FFF) method is an emerging technology to print lightweight continuous carbon fiber reinforced thermoplastics (CCFRP) at high speed. Different from traditional FFF, microwave offers selective and volumetric heating properties to melt thermoplastic materials instantaneously, and the microwave printing head and nozzle remain at room temperature. These advantages can increase the printing speed of CCFRP significantly, while the belt slippage of a printing bed is noticed during microwave-assisted 3D printing. The slippage of the moving belt happens because the cold nozzle moves at high speed and encounters resistance from the rough surface of the printed filament. To solve this problem, this paper presents a hierarchical digital twin (DT) framework, consisting of core and basic DTs, for the prevention of belt slippage induced printing malfunction. The core DTs use MATLAB Simscape multibody models to simulate the printing process virtually and the printing G-code is corrected before printing. In addition, an accelerometer installed on the printing bed is connected to the core DTs. Abnormal vibration signals due to belt slippage can be measured and communicated with core DTs for interrupting and correcting the process. By monitoring the temperature of the heated filament and the output microwave power, the service life of the nozzle and microwave cable are evaluated in the basic DTs.

Non-destructive processing of silver containing glass ceramic antibacterial coating on polymeric surgical mesh surfaces.

Surgical meshes composed of bioinert polymers such as polypropylene are widely used in millions of hernia repair procedures to prevent the recurrence of organ protrusion from the damaged abdominal wall. However, post-operative mesh infection remains a significant complication, elevating hernia recurrence risks from 3.6% to 10%, depending on the procedure type. While attempts have been made to mitigate these infection-related complications by using antibiotic coatings, the rise in antibiotic-resistant bacterial strains threatens their effectiveness. Bioactive glass-ceramics featuring noble metals, notably silver nanoparticles (AgNPs), have recently gained traction for their wide antibacterial properties and biocompatibility. Yet, conventional methods of synthesizing and coating of such materials often require high temperatures, thus making them impractical to be implemented on temperature-sensitive polymeric substrates. To circumvent this challenge, a unique approach has been explored to deposit these functional compounds onto temperature-sensitive polypropylene mesh (PP-M) surfaces. This approach is based on the recent advancements in cold atmospheric plasma (CAP) assisted deposition of SiO2 thin films and laser surface treatment (LST), enabling the selective heating and formation of functional glass-ceramic compounds under atmospheric conditions. A systematic study was conducted to identify optimal LST conditions that resulted in the effective formation of a bioactive glass-ceramic structure without significantly altering the chemical and mechanical properties of the underlying PP-M (less than 1% change compared to the original properties). The developed coating with optimized processing conditions demonstrated high biocompatibility and persistent antibacterial properties (>7 days) against both Gram-positive and Gram-negative bacteria. The developed process is expected to provide a new stepping stone towards depositing a wide range of functional bioceramic coatings onto different implant surfaces, thereby decreasing their risk of infection and associated complications.