Ultrasonic Atomization Research Articles

Alginate-based ‘nano-micro’ hybrid matrices developed using ultrasonic atomization for Co-delivery of chemotherapeutic drugs against superficial tumors

Cancer has remained a life-threatening condition, with about 9.6 million deaths globally, despite the advancements and research in therapeutic approaches. Several chemotherapeutic agents are available which can reduce the size of tumors but have non-specific adverse effects on surrounding cells and the propensity to cause the formation of multi-drug resistant tumors. This report investigates a novel and facile method of ultrasonic atomization for the synthesis of Doxorubicin (Dox) loaded chitosan and Piperine (Pip) loaded Poly lactide-co-glycolide (PLGA) nanoparticles (Dox-Ch-NP, Pip-PLGA-NP). Further co-encapsulate these drug-loaded nanoparticles in hybrid alginate microspheres (HAM) using the same technique. The nanoparticles and microspheres were analyzed for size and morphology by DLS, SEM, TEM and CLSM. In vitro studies were performed to determine encapsulation efficiency, drug release and cell cytotoxicity. For the in-vivo evaluation of this co-delivery vehicle Swiss Albino Mice were used. The ultrasonic atomization process led to the development of Dox-Ch-NP (50–150 nm), Pip-PLGA-NP (50–200 nm) and HAM (5 μm). The encapsulation efficiency was 32% and 67% in the case of Dox-Ch-NP and Pip-PLGA-NP, respectively. Sustained in vitro release of both drugs was achieved for 15 days. MTT-based cell cytotoxicity assay shows 88% cell viability in HEK-293 and 51% in HeLa cells after 24Hrs of treatment with HAM. The in-vivo study suggested 93% of tumor reduction with Dox-Ch-NP treatment, 75% reduction with Pip-PLGA-NP treatment While 100% reduction in tumor volume after 15 days of treatment completion. The in-vivo study also showed higher and faster tumor volume reduction in co-delivered drugs via HAM than in single drug-loaded nanoparticles. The results indicate the successful formulation of multi-drug hybrid carriers which can aid in generating an efficient anti-tumor therapeutic regimen for localized tumors with reduced chances of occurrence of multi-drug resistant tumors.

Dynamics of the spontaneously accelerative equatorial expansion of a droplet in a high-intensity acoustic standing wave field

This work reports an investigation of the acoustically induced accelerated deformation of drops in high-intensity acoustic standing wave fields generated by a single-axis acoustic levitator. The dynamic characteristics of droplet deformation are obtained and discussed based on high-speed visualization and in-house Python codes. Based on the actual physical characteristics, the finite element method numerical model has been developed for intercoupling the sound field and flow field, allowing for bidirectional feedback between the drop shape and the acoustic wave. The experimental results indicate that during the deformation process of droplets, their equatorial radius expands at an increasing speed without artificially increasing the sound field intensity. The simulation shows that the acoustic radiation suction acting on the equator dominates droplet deformation. Furthermore, there is a kind of positive feedback loop between the acoustic radiation pressure (pr) amplitude at the drop’s equator and the aspect ratio (AR) during the deformation period. It is confirmed that this causes the spontaneous accelerated expansion of the droplet’s equator. In addition, the functional relationship between pr at the drop’s equator and the AR has been obtained through theoretical derivation, which is consistent with the simulation results. Finally, the critical Bond number (Ba,s) of the rim instability is also obtained. This work provides deeper insights into contactless liquid manipulation and ultrasonic atomization technology applications.

Potentials of Ultrasonically Atomized Cored Wires for Powder Metallurgy and Additive Manufacturing

Abstract Powder production for additive manufacturing is currently mainly done by inert gas atomization. A new process is the production of low-oxygen and highly spherical metal powders by ultrasonic atomization from a wire or rod feedstock. As a crucible-free process and because of an electric arc as an energy source, even materials with a high liquidus temperature up to 1800 °C can be processed. A limitation of this technique can be found in the continuous processing of high-strength materials, like martensitic hardenable tool steels, from a stiff wired feedstock because of the limited feed ability. This paper investigates the possibility of processing high-strength steel powder using cored wire as the starting material for the ultrasonic atomization process to circumvent the feeding problem of high-strength materials. Thereby, two carbon martensitic hardenable hot work tool steels with a carbon content of 0.12 wt. % and 0.4 wt. % are considered as reference materials. After the atomization process with varying parameters, powders are characterized concerning their morphology, chemical composition, phases formed, and related powder properties. In addition to flowability, the bulk density are also determined. Based on these results, a conclusion will finally be given on the suitability of ultrasonically atomized powders for additive manufacturing and fast sintering techniques.

Error Correction and Reanalysis of the Vibration Analysis of a Piezoelectric Ultrasonic Atomizer to Control Atomization Rate

Dynamic mesh atomizers have been widely used in various fields because of their compact structure, low energy consumption, and low production costs. The finite element method is an important technique to analyze the factors affecting the atomization performance of dynamic mesh atomizers. However, at present, there is a lack of decisive solutions to the basic problems of boundary setting in terms of the simulation and vibration displacement characteristics of atomizers under different vibration modes. In this paper, two errors were found in the Vibration Analysis of a Piezoelectric Ultrasonic Atomizer to Control Atomization Rate paper written by Esteban Guerra-Bravo et al. in 2021. First, in the finite element analysis, the boundary condition of the atomizing sheet was set to be fixed, which is inconsistent with the actual support situation and seriously affects the vibration of the atomizing sheet. Second, in the simulation result, from the first mode to the third mode, the growth rate of the maximum displacement at the center of the atomizing sheet was as high as 77.12%, even up to 221.05%, which is inconsistent with the existing vibration theory. In view of these errors, in this paper, the working principle of dynamic mesh atomizers is analyzed and the vibration equation of the atomizing sheet under peripheral simple support is derived. Through comparison with the literature, it was proven that the boundary setting and vibration displacement of the atomizing sheet in the original paper are unreasonable. By measuring the atomizing rate of the atomizing sheet under different boundary conditions, it was proven that the peripheral freedom of the atomizing sheet should be greater than or equal to 1, namely, peripheral freedom or peripheral simply supported. The vibration displacement theory was used for the simulation, and the relationship between the vibration displacement and resonant frequency of the atomizing sheet under peripheral simple support was measured. It was found that with the increase in the resonance frequency, the maximum displacement of vibration modes with only nodal circles was larger than that of the other vibration modes, and the maximum displacement increased slightly with the increase in the number of nodal circles by about 0.98%.

Optimising aerosol jet printing of collagen inks for enhanced piezoelectricity and controlled surface potential

Collagen is a highly versatile protein used in tissue engineering constructs and as a model piezoelectric biomaterial. The piezoelectricity of collagen can be enhanced through the alignment of collagen domains and fibres, although most fabrication techniques used to form dense collagenous constructs do not allow for significant collagen alignment. The use of aerosol jet printing (AJP) mitigates the limitations of using soluble collagen inks for bioprinting or extrusion-based 3D printing, particularly if microfibrillar collagen suspensions are used as a cost-effective and scalable ink source. In this work, Type I and Type II microfibrillar collagen from different anatomical sources were successfully deposited using AJP with two different atomisation methods, namely pneumatic-AJP (p-AJP) and ultrasonic-AJP (u-AJP). The printing parameters were optimised for their piezoelectric amplitude and surface potential. Fourier transform infrared spectra of the films revealed that ultrasonic atomisation did not cause notable denaturation of collagen, although the process resulted in the fractionation and preferential deposition of the oligomeric and gelatinous components within the slurry. The printed collagen samples displayed a piezoelectric response that was four times higher than the values obtained from drop-cast collagen films, and their surface potential was found to be positively correlated to the roughness of the films which can be controlled through the mode of atomisation. These results indicate the ability to enhance and control the piezoelectricity and surface potential using p-AJP and u-AJP, which offers a promising physical modulation technique to tailor cell adhesion, proliferation or differentiation for collagen-based tissue engineering constructs.

Multifunctional Ultrasmall Theranostic Nanohybrids Developed by Ultrasonic Atomizer for Drug Delivery and Magnetic Resonance Imaging.

Theranostic nanoparticulate systems (TNPs) have shown potential in addressing problems related to spatial localization and temporally controlled release of drugs with the capabilities of real-time imaging to evaluate the progress of therapy. The current study reports the ultrasonic atomization-led synthesis of in vitro and in vivo evaluations of ultrasmall chitosan-based theranostic nanohybrid formulations with encapsulated doxorubicin (DOX) and iron-oxide magnetic nanoparticles. The nanohybrid particles are characterized using transmission electron microscopy, powder X-ray diffraction, FTIR, DOX encapsulation efficiency, in vitro release, cellular uptake, and toxicity. These formulations were also tested for the capability of invivo tumor reduction and simultaneous magnetic resonance imaging using Swiss albino mice. Ultrasonic atomizer-led synthesis resulted in chitosan-magnetic nanohybrids (CMNPs) having sizes of 15 ± 3 nm which comprise MNP of 10 ± 3 nm. The encapsulation of DOX in CMNP was around 25%, resulting in an 80% sustained release over 10 days at pH 5 and 7. CMNP was also found to be an efficient DOX delivery vehicle tested on cancer cells (HeLa). The CMNPs were able to reduce the tumor volume by 60% in 15 days. The inherent magnetic property and nanoscale size of CMNPs also provided for enhanced contrast efficiency in magnetic resonance imaging of tumors. Thus, such multifunctional theranostic nanoparticles can be an efficient tool for targeted diagnostic and therapeutic success.

DEVELOPMENT OF ULTRASONIC SPRAYER FOR AIRCRAFT OILS ANALYSIS BY MICROWAWE PLASMA COMPLEX

One of the critical components of microwave plasma complex, which determines metrological and diagnostic parameters of the appliance, is a device for ultrasonic atomization and supply of a lubricating oil sample to spectra excitation source (SES). The main problem was the development of atomizer construct, which makes it possible to increase its resource for failure and reduce influence associated with the brand of analyzed lubricating aviation oils on size of sol droplets. The article presents requirements for the parameters of generated sol sputtering system during microwave plasma measurements, and also describes the search for the optimal sputter construct. Several constructs of ultrasonic nebulizers have been analyzed using the ANSYS 19.0 academic software package. The proposed construct is based on the principle of double spraying. An assessment of the effect of lubricating oil viscosity on the size of sol droplets was carried out and a method was described to reduce this effect.

A new Al-Cu alloy for LPBF developed via ultrasonic atomization

Wrought 2xxx aluminum alloys are difficult to process by laser powder bed fusion (LPBF) because of the hot cracking susceptibility caused by their large solidification range. Although several studies on Ti and Zr additions to 2xxx Al-Cu alloys show improved processability in LPBF, only few explore the addition of alternative alloying elements such as Cr and Fe. There is thus little knowledge on the ability of these elements to avoid hot cracking. In the present work, a new Al-Cu alloy with Ti, Cr and Fe additions is put forward and the mechanisms impeding hot cracking formation are analyzed. (Al, Cr)3Ti_L12 precipitates are formed during the solidification process, promoting heterogenous nucleation and grain refinement. Cr not only contributes to solid solution strengthening but also supports the stabilization of the Al3Ti metastable cubic phase. The addition of near-eutectic Fe decreases the solidification range, further reducing the susceptibility for hot cracking. Nano-hardness mapping reveals the solidification path of the alloy, with higher values associated with the highly dense areas of precipitates forming at the melt pool boundaries. A novel printable alloy with hardness values exceeding those of existing Al alloys for LPBF was designed.

Preparation and evaluation of injectable microsphere formulation for longer sustained release of donepezil.

In this study, donepezil-loaded PLGA and PLA microspheres (Dp-PLGA-M/Dp-PLA-M) and Dp-PLA-M wrapped in a polyethylene glycol-b-polycaprolactone (PC) hydrogel (Dp-PLA-M/PC) were prepared to reduce the dosing frequency of injections to treat Alzheimer's disease patients. Dp-PLGA-M and Dp-PLA-M with a uniform particle size distribution were repeatably fabricated in nearly quantitative yield and with high encapsulated Dp yields using an ultrasonic atomizer. The injectability and in vitro and in vivo Dp release, biodegradation, and inflammatory response elicited by the Dp-PLGA-M, Dp-PLA-M, and Dp-PLA-M/PC formulations were then compared. All injectable formulations showed good injectability with ease of injection, even flow, and no clogging using a syringe needle under 21-G. The injections required a force of <1N. According to the biodegradation rate of micro-CT, GPC and NMR analyses, the biodegradation of Dp-PLA-M was slower than that of Dp-PLGA-M, and the biodegradation rate of Dp-PLA-M/PC was also slower. In the Dp release experiment, Dp-PLA-M sustained Dp for longer compared with Dp-PLGA-M. Dp-PLA-M/PC exhibited a longer sustained release pattern of two months. In vivo bioavailability of Dp-PLA-M/PC was almost 1.4 times higher than that of Dp-PLA-M and 1.9 times higher than that of Dp-PLGA-M. The variations in the Dp release patterns of Dp-PLGA-M and Dp-PLA-M were explained by differences in the degradation rates of PLGA and PLA. The sustained release of Dp by Dp-PLA-M/PC was attributed to the fact that the PC hydrogel served as a wrapping matrix for Dp-PLA-M, which could slow down the biodegradation of PLA-M, thus delaying the release of Dp from Dp-PLA-M. Dp-PLGA-M induced a higher inflammatory response compared to Dp-PLA-M/PC, suggesting that the rapid degradation of PLGA triggered a strong inflammatory response. In conclusion, Dp-PLA-M/PC is a promising injectable Dp formulation that could be used to reduce the dosing frequency of Dp injections.

A miniature atomization-air-cooled heat sink for electronic chips

With the continuous development of information technology and electronic components, the heat dissipation needs of electronic chips are constantly increasing. A miniature atomization-air-cooled heat sink for electronic chips (MAHSEC) is presented. The combination of cooling fan and piezoelectric ultrasonic atomizer improves the utilization of micro droplets, which makes the MAHSEC simple in structure and excellent in heat dissipation performance. The prototype of MAHSEC is designed and fabricated. The atomization characteristics and heat dissipation performance of MAHSEC are measured by experiments. Experimental results indicate that the atomization amount increases with the increase of voltage, and the optimal driving frequency is 110 kHz. Under the driving voltage of 70Vpp and driving frequency of 110 kHz, MAHSEC reduces the temperature of electronic chips from 143 °C to 45.8 °C, which demonstrates that MAHSEC has excellent thermal management performance.

In-Situ polymerized polypyrrole Janus cotton fabric for Solar-driven water evaporation in Textile-dying wastewater

Herein, a Janus cotton fabric (JCF) with polypyrrole (PPy) layer was prepared through one-side ultrasonic atomization deposition followed by the in-situ polymerization. The PPy layer was robust on the fabric and showed excellent light absorbance ability (∼99%). And the JCF with 60 min one-side deposition (JCF-60) showed good photothermal conversion ability with the vapor generation rate of 1.45 kg m−2h−1 and the photothermal conversion efficiency of 91.0% in dyed water purification. It can be expected to large scale applications in solar-driven water evaporation.

Performance enhancement of modified solar distillers using synthetic nanocomposites, reflectors, cover cooling, and ultrasonic foggers: Experimental approach

This work aimed to develop the thermo-economic performance of solar still (SS) via various additives. On the one hand, to improve the thermophysical properties of the basin saline water, two nanocomposites were utilized in the modified SSs (MSSs). In MSS1, chitosan @ graphene oxide (Cs@GO) was used, whereas chitosan @ nickel oxide (Cs@NiO), was provided in MSS2. The concentration influence on the yield was investigated considering three ratios (0.1, 0.2, and 0.3 wt%). The selected concentration (0.3 wt%) was used for the upcoming cases being better than others. At this weight ratio, the yield was augmented by 72.7, and 57.5 % for MSS1, and MSS2, respectively, compared to CSS. In the first case (Case I), a glass lid cooling unit was attached to the MSSs to boost the condensation rate. In the second case (Case II), top and bottom external reflectors were fixed on the MSSs. Then, Case III contained both cover cooling and reflectors. In addition to these enhancers, ultrasonic atomizers were placed on the basin of MSSs in Case IV. In each experiment, both MSS1 and MSS2 were simultaneously compared to conventional SS (CSS). All cases showed good thermo-economic performances. The best performance was obtained, especially in terms of yield, from MSS1 in Case IV, at which the production, energy, and exergy efficiencies were improved by 113.72, 96, and 167.62 %, respectively.

Constructing 3D hierarchical CNTs/VO2 composite microspheres with superior electromagnetic absorption performance

To achieve efficient electromagnetic wave absorption (EWA) performance with requirements of low density and thin thickness, three-dimensional (3D) hierarchical CNTs/VO2 composite microsphere was successfully synthesized though an ultrasonic atomization process in this work. The phase composition, morphology, EWA performance and corresponding mechanism were investigated. The VO2 microspheres (MS) was obtained via the complete reduction of V2O5 by oxalic acid, and the introduced CNTs were uniformly distributed around VO2 MS. The addition of CNTs both improved the impedance matching and provided multiple attenuation modes. The highly conductive CNTs enhanced conductivity further increasing conductance loss. Moreover, heterogeneous interfaces formed between CNTs and VO2 phase generated strong polarization loss. Furthermore, the construction of 3D structure not only benefited the stability of structure but also extended the paths of EW reflection and scattering thus consuming more EW energy. With the synergistic effect of favorable impedance matching and attenuation ability, the excellent EWA performance was achieved that the minimum reflection loss was −58.2 dB with the effective absorption bandwidth of 3.94 GHz in X band. This research plays a significant guiding role in structural construction and optimization of EW absorber.

Effect of Hypochlorous Acid on Blepharitis through Ultrasonic Atomization: A Randomized Clinical Trial.

To evaluate the efficacy and safety of eyelid hygiene using topical 0.01% hypochlorous acid (HOCL) through ultrasonic atomization after 2 weeks in patients with blepharitis. Randomized controlled trial. Patients with blepharitis were randomized into two groups: topical 0.01% HOCL through ultrasonic atomization (HOCL group, 42 eyes) or eyelid scrubs (control group, 37 eyes). Patients in both groups received warm compresses twice daily and topical 0.5% levofloxacin three times a day. Primary outcomes were the ocular surface disease index scores (OSDI), lid margin redness, lid margin abnormalities, meibum expressibility, meibum quality, and noninvasive breakup time after 2 weeks. Secondary outcomes were conjunctiva redness, corneal fluorescein staining, and tear meniscus height. A questionnaire of treatment adherence with a free response section was administered to confirm patient compliance and comments. Sixty-seven participants participated in this study. Both groups show an improvement in all primary outcomes, while statistically significant improvements in OSDI, lid margin redness, lid margin abnormality, meibum expressibility and quality are only limited to the HOCL group after 2 weeks of treatment (p < 0.05, p < 0.05, p < 0.001, p < 0.001 and p < 0.001, respectively). Subgroup analysis in HOCL reveals that only the change in lid margin abnormality and meibum expressibility in the mild-moderate meibomian glands loss patients at baseline has a statistically significant difference p < 0.05). Multiple linear regression shows that the improvement in OSDI is negatively associated with meibum expressibility score at the baseline (95% CI [-28.846, -1.815], p = 0.028). The patient compliance is 7.1 ± 2.0 in the HOCL group and 7.1 ± 1.8 in the control group (p > 0.05). No adverse events are reported. Topical 0.01% HOCL through ultrasonic atomization is a tolerable and effective eyelid hygiene treatment for blepharitis.

SG-APSIC1085: Microbiological analysis concerning antimicrobial effect of atomized ionless hypochlorous acid water in a hospital environment

Objectives: We evaluated the disinfecting efficacy of atomized ionless hypochlorous acid water (CLFine) against pathogenic microorganisms in an isolation room. Methods: The study was conducted in an isolation room of Kurume University Hospital. CLFine with available chlorine concentrations of 40 ppm and 300 ppm as test substances and purified water as control were atomized with an ultrasonic atomizer (CLmistL). The 40 ppm and 300 ppm of CLFine were atomized at the atmospheric available chlorine concentrations of ~0.03 ppm and 0.1~0.2 ppm, respectively, and purified water was atomized in the same manner as CLFine. Petri dishes with Staphylococcus aureus, Bacillus cereus spores, Bacillus subtilis spores and Aspergillus ruber were allocated in the room, then CLFine or purified water was atomized. Sampling was performed at 3 and 5 hours after the start of atomization, and the bacterial counts were measured. The study was carried out either with air conditioning turned “on” or “off” because atmospherically available chlorine concentration is affected by ventilation. Results: When the air conditioning was turned on, purified water showed a slight reduction of bacterial counts by 0.9 log or less at 5 hours after the atomization. When CLFine was used, 40 ppm greatly reduced the counts of Staphylococcus aureus by 5.1~5.4 logs reduction at 5 hours after the atomization, but no distinctive efficacy was observed against other microorganisms. On the other hand, 300 ppm caused a significant reduction of the bacterial counts for all the microorganisms at 5 hours after the atomization (P &lt; .001 vs purified water). The same results were observed in the environment with the air conditioning turned off. Conclusions: Our data suggest that CLFine effectively disinfects pathogenic microorganisms and can contribute to maintaining the hygienic environment of hospital rooms. This study was funded as contracted research by NIPRO Corporation with the approval of the ethics committee (study no. 21229).

Collaborative printing and in-situ frontal curing of highly-viscous thermosetting composites

Rapid manufacturing of thermosets via frontal polymerization is very attractive for thermosetting composites due to the expected decarbonization and manufacturing flexibility with limited energy consumption; however, it is challenging for 3D printing and frontal curing of highly-viscous thermoset composites (e.g., >100,000 mPa.s at room temperature) because of the rheology requirement of the 3D printing process and limited pot life of frontal curable resin inks under elevated temperature, which is usually used to reduce the viscosity of inks. We report an in-situ combining materials-based 3D printing process for printing and in-situ frontal curing of highly viscous thermosets. Specifically, an ultrasonic atomizer sprays the curing agent solution during the printing process to achieve an in-situ mixing with the resin oligomers at a microscale level. Multiphysics simulation indicated the curing degree distribution through the thickness direction and a printing window is provided depending on the extrusion deposition rate, the deposition layer thickness, and the ultrasonic sprayer amplitude. Further experiments were carried out, and it was found that the frontal velocity increased, and the frontal temperature remained almost unchanged with the rise of the ultrasonic amplitude. The curing degree and curing uniformity were improved with the increase of the ultrasonic amplitude but decreased with the increase of the printing layer thickness. Samples with different ultrasonic amplitudes and extrusion layer thicknesses were printed, and their mechanical properties were tested. The tensile strength and Young's modulus of novolac epoxy resin reached 47.56 MPa and 2.19 GPa, respectively. The feasibility of this method for composite printing was demonstrated. At a 5 wt% loading of short fibers, the tensile strength and Young's modulus of as-printed composites reached 66.71 MPa and 3.65 GPa. This method provides a fast and energy-efficient way to manufacture highly viscous thermosets and their composites.

The effect of clinical face shields on aerosolized particle exposure.

Face shields protect healthcare workers (HCWs) from fluid and large droplet contamination. Their effect on smaller aerosolized particles is unknown. An ultrasonic atomizer was used to simulate particle sizes equivalent to human breathing and forceful cough. Particles were measured at positions correlating to anesthetic personnel in relation to a patient inside an operating theatre environment. The effect of the application of face shields on HCW exposure was measured. Significant reductions in particle concentrations were measured after the application of vented and enclosed face shields. Face shields appear to reduce the concentration of aerosolized particles that HCWs are exposed to, thereby potentially conferring further protection against exposure to aerosolized particles in an operating theatre environment.

A Novel Hydrophilic, Antibacterial Chitosan-Based Coating Prepared by Ultrasonic Atomization Assisted LbL Assembly Technique.

To explore the potential applicability of chitosan (CTS), we prepared aldehyde chitosan (CTS-CHO) with chitosan and sodium periodate via oxidation reaction and then a chitosan-based hydrophilic and antibacterial coating on the surface of poly (lactic acid) (PLA) film was developed and characterized. The oxidation degree was determined by Elemental analyser to be 12.53%, and a Fourier transform infrared spectroscopy was used to characterize the structure of CTS-CHO. It was evident that CTS-CHO is a biocompatible coating biomaterial with more than 80% cell viability obtained through the Live/Dead staining assay and the alamarBlue assay. The hydrophilic and antibacterial CTS-CHO coating on the PLA surface was prepared by ultrasonic atomization assisted LbL assembly technique due to Schiff's base reaction within and between layers. The CTS-CHO coating had better hydrophilicity and transparency, a more definite industrialization potential, and higher antibacterial activity at experimental concentrations than the CTS coating. All of the results demonstrated that the ultrasonic atomization-assisted LbL assembly CTS-CHO coating is a promising alternative for improving hydrophilicity and antibacterial activity on the PLA surface. The functional groups of CTS-CHO could react with active components with amino groups via dynamic Schiff's base reaction and provide the opportunity to create a drug releasing surface for biomedical applications.

A Novel PLLA/MgF2 Coating on Mg Alloy by Ultrasonic Atomization Spraying for Controlling Degradation and Improving Biocompatibility.

Problems of rapid degradation and poor biocompatibility (endothelialization and hemocompatibility) limit magnesium (Mg) alloy's further applications in vascular stents. To solve these problems, a novel composite coating was designed on Mg alloy via a two-step method. First, a Mg alloy sample was immersed in hydrofluoric acid. Then, a poly-l-lactic acid (PLLA) coating was made by ultrasonic atomization spraying with 5 and 10 layers (referred to as PLLA(5)-HF-Mg and PLLA(10)-HF-Mg). Characterizations were analyzed from the microstructure, element distribution, and wettability. The degradation behavior was tested with an electrochemical test and immersion test. Endothelialization was investigated using human umbilical vein endothelial cells (HUVECs). Hemocompatibility was examined with a platelet adhesion test. The results showed that the PLLA coating could not only cover the surface, but also could permeate through and cover the holes on the MgF2 layer, mechanically locked with the substrate. Thus, the composite coating had higher corrosion resistance. The PLLA/MgF2 coating, especially on PLLA(10)-HF-Mg, enhanced HUVECs' viability and growth. While incubated with platelets, the PLLA/MgF2 coating, especially on PLLA(10)-HF-Mg, had the lowest platelet adhesion number and activity. Taken together, the novel PLLA/MgF2 coating controls Mg alloy's degradation by spraying different layers of PLLA, resulting in better endothelialization and hemocompatibility, providing a promising candidate for cardiovascular stents.

Performance enhancement of solar desalination using evacuated tubes, ultrasonic atomizers, and cobalt oxide nanofluid integrated with cover cooling

The water shortage crisis has been paid attention to and many efforts have been conducted to find proper and applicable solutions to it through developing desalination systems. Commonly, being simple in construction and easy operation, solar stills (SSs) have been developed to meet the freshwater need; especially, in arid areas. However, their productivity and efficiency improvement are still a challenge. Accordingly, the current work aimed to enhance the thermo-economic performance of a pyramid SS (PSS) by augmenting the evaporation and condensation processes. For obtaining high vapor generation, evacuated tubes and ultrasonic foggers were integrated into the developed PSS (DPSS) as a first case (DPSS-I), in which different operation times of the foggers were tested. Then, Co3O4 nanofluid (1.5 wt%) was added as a basin fluid in the second case (DPSS-II). Finally, in the third case (DPSS-III), a glass cooling was used for boosting the condensation rate. Besides the experiments, a complete thermo-economic performance analysis was done via calculating the energetic and exergetic efficiencies and freshwater cost (per liter). All these performance indicators of DPSS were compared to that of traditional PSS (TPSS). As resulted, integrating all the proposed additives (DPSS-III) could enhance freshwater production, energy efficiency, and exergy efficiency by 83.87%, 18.29% and 38.86%, respectively. Additionally, the production cost, per freshwater liter, was reduced by 11.61%. These results showed the applicability, sustainability, and feasibility of the proposed additives in the field of solar desalination, particularly SSs.