Ethanol Bath Research Articles

Development of the drop Freezing Ice Nuclei Counter (FINC), intercomparison of droplet freezing techniques, and use of soluble lignin as an atmospheric ice nucleation standard

Abstract. Aerosol–cloud interactions, including the ice nucleation of supercooled liquid water droplets caused by ice-nucleating particles (INPs) and macromolecules (INMs), are a source of uncertainty in predicting future climate. Because INPs and INMs have spatial and temporal heterogeneity in source, number, and composition, predicting their concentration and distribution is a challenge requiring apt analytical instrumentation. Here, we present the development of our drop Freezing Ice Nuclei Counter (FINC) for the estimation of INP and INM concentrations in the immersion freezing mode. FINC's design builds upon previous droplet freezing techniques (DFTs) and uses an ethanol bath to cool sample aliquots while detecting freezing using a camera. Specifically, FINC uses 288 sample wells of 5–60 µL volume, has a limit of detection of −25.4 ± 0.2 ∘C with 5 µL, and has an instrument temperature uncertainty of ± 0.5 ∘C. We further conducted freezing control experiments to quantify the nonhomogeneous behavior of our developed DFT, including the consideration of eight different sources of contamination. As part of the validation of FINC, an intercomparison campaign was conducted using an NX-illite suspension and an ambient aerosol sample from two other drop freezing instruments: ETH's DRoplet Ice Nuclei Counter Zurich (DRINCZ) and the University of Basel's LED-based Ice Nucleation Detection Apparatus (LINDA). We also tabulated an exhaustive list of peer-reviewed DFTs, to which we added our characterized and validated FINC. In addition, we propose herein the use of a water-soluble biopolymer, lignin, as a suitable ice-nucleating standard. An ideal INM standard should be inexpensive, accessible, reproducible, unaffected by sample preparation, and consistent across techniques. First, we compared lignin's freezing temperature across different drop freezing instruments, including on DRINCZ and LINDA, and then determined an empirical fit parameter for future drop freezing validations. Subsequently, we showed that commercial lignin has consistent ice-nucleating activity across product batches and demonstrated that the ice-nucleating ability of aqueous lignin solutions is stable over time. With these findings, we present lignin as a good immersion freezing standard for future DFT intercomparisons in the research field of atmospheric ice nucleation.

One-step electrochemical deposition leading to superhydrophobic matrix for inhibiting abiotic and microbiologically influenced corrosion of Cu in seawater environment

Finding efficient ways to prohibit abiotic and microbiologically influenced corrosion is a critical task for metal serving in harsh seawater environment. In this paper, originated from the biomimetics principle, a lotus leaf inspired superhydrophobic matrix composed by Fe-myristic acid compound is prepared on copper surface. The preparation is realized by a facile electrodeposition approach based on a coordination-deposition mechanism, which leads to porous structure composed of hydrophobic compound from an ethanol bath via a single step. The dependent relationship between wettability and electrodeposition conditions including electrodeposition potential and time is revealed. Sophisticated techniques including scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier Transform infrared spectroscopy are employed to characterize the matrix morphology and composition. Scanning Kelvin probe and other electrochemical methods show that superhydrophobic matrix improves the corrosion resistance capability of copper in different environments including atmosphere, natural seawater and salt spray, illustrating that superhydrophobic matrix endows high abiotic corrosion inhibition to the underneath Cu metal. The inhibition efficiency of Cu by superhydrophobic coating can reach 99.85 % after immersion in seawater for 28 days. For achieving high prohibition effect to the corrosion induced by microbes, the bio-adhesion inhibition is one prerequisite. The as-obtained superhydrophobic matrix is confirmed to prohibit the representative diatoms and sulfate reducing bacteria (SRB) to grow onto metal surface due to the limited anchoring sites and the low surface energy. Superhydrophobic matrix exhibits excellent corrosion resistance in harsh SRB suspension, demonstrating a prominent role to combat microbiologically influenced corrosion in seawater environment.

Preparation and characterization of superhydrophobic PVDF/HMSNs hybrid membrane for CO2 absorption

Superhydrophobic polyvinylidene fluoride (PVDF) membranes were prepared via incorporated with hydrophobic modified SiO2 nanoparticles (HMSNs). Results demonstrated that HMSNs in the dope induced precipitation of PVDF, mainly by solid-liquid demixing in ethanol bath. The fabricated superhydrophobic PVDF/HMSNs hybrid membrane was showed uniformly skinless comprising of PVDF spherical microparticles. During preparation, the HMSNs attach onto the PVDF microsphere surfaces as-formed micro-nano structures, which was important for imparting membrane superhydrophobicity. Therefore, the water contact angle of PVDF/HMSNs hybrid membrane was 155° as the mass ratio of HMSNs with PVDF matrix was 0.15:1 when ethanol coagulation bath was used. Since the proposed modification allowed HMSNs migration onto PVDF spherical microparticles surfaces during the exchange between solvent and non-solvent, the hydrophobicity of internal surface of membrane pores and channels was also enhanced. This feature successfully inhibited the liquid intrusion into membrane pores, and guaranteed a stable anti-wettability over a long period. The absorption flux was 2.34 mmol m−2 s−1 for prewetted as the mass ratio of HMSNs with PVDF matrix was 0.15:1 with a fluid flow rate of 240 mL min−1, 3.3 times higher than the prewetted pristine PVDF membrane. These results show that PVDF/HMSNs hybrid membranes are ideal candidates for application in CO2 absorption.

Establishment of HPLC-RID method for the determination of soluble sugars in peanut seed

<p indent=0mm>Edible peanut is one of the important directions of peanut breeding in China and even in the world. However, the lack of efficient detection method of soluble sugar content related to edible quality in peanut kernel limits the progress of edible peanut breeding. In this study, a method of extracting soluble sugar from peanut kernel by 80% ethanol and water bath was established. The method simplified the pre-treatment steps of samples and speeded up the extraction progress compared with the GB method. The accuracy and repeatability tests showed that this method had high repeatability accuracy and effectiveness. Then, the samples extracted by this method and GB method were both tested by HPLC-RID, it was found that the soluble sugar in mature peanut kernel was mainly sucrose, with little glucose and fructose in 20 peanut varieties. There were no significant differences between these two methods. The results of 20 peanut varieties using the method and GB method showed that the sucrose content ranged from <sc>16.19 mg g^-1</sc> to <sc>83.81 mg g^-1,</sc> <sc>15.60 mg g^-1</sc> to <sc>81.38 mg g^-1,</sc> and with an average of <sc>30.41 mg g^-1,</sc> <sc>30.20 mg g^-1.</sc> In summary, the results not only further verified the practicability of the method established in this study, but also showed that there was a huge difference in the sucrose content between these peanut varieties.

Bioprocess-inspired preparation of silica with varied morphologies and potential in lithium storage

As one of the most delicate bioprocesses in nature, biosilicification is closely related to biosilica with various morphologies, and has provided abundant inspiration to materials synthesis. In the present study, to explore the biosilica formation process and fabricate silica with an exquisite microstructure for lithium-ion battery (LIB) electrodes, a bacterial phage (M13) is used as a biotemplate to synthesize silica with diverse morphologies: cylinders, hexagonal prisms, assemblies of smaller cylinders and nanowires. A facile ethanol bath method is conducted to coat the nanowires with nitrogen-containing carbon and carbon-coated SiO2 nanowires with mesochannels (C@msSiO2NWs) are first used as anode materials for LIBs. Attributed to the uniform carbon coating and parallel mesochannel structure, the electronic conductivity and capacity to accommodate volume variations were significantly improved. In the electrochemical performance test, the composites calcined at 750 °C (C@msSiO2NWs-750) show an impressive capacity of 653 mA h g−1 at a current density of 500 mA g−1 and stability (1000 cycles). In view of the electrochemical test outcomes, the preparation of a sophisticated structure with an outstanding potential is easily achieved via a biomimetic strategy.

High-efficiency nanodelamination of NiCoLDHs with hydroquinone as intercalator in universal solvent and physical treatments

Nanodelamination and controlled stripping of two-dimensional materials are important ways to realize the release of the performance of nano-functional materials. This work shows that hydroquinone (HQ) intercalated nickel-cobalt hydroxides (NiCoLDHs) have been nanodelaminated in different solvents (water, ethanol, ethanol/water, and toluene) and physical treatment (ultrasonic bath, magnetic stirring, and hydrothermal). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction techniques (XRD), Fourier transform infrared (FT-IR), thermal analyses (DSC-TGA), and Brunauer-Emmett-Teller (BET) were used to characterize the structures of all the samples. The results show that nanodelamination of the treated NiCoLDHs-HQ samples with three kinds of physical treatment in different solvents reduces the intensity of the characteristic d001 reflections and moves to the smaller angle, indicating that the HQ is an effective nanodelamination intercalation agent. Microstructure and BET analysis also demonstrate that NiCoLDHs achieve high-efficiency nanodelamination driven by HQ in ethanol and ultrasonic bath than that of other in solvents and physical treatment. This significant delamination effect is mainly attributed to the interaction between hydroquinone and NiCoLDHs or solvent, and this delamination strategy provides a new method for efficient application of 2D material as electrode, catalyst, or polymer/clay nanocomposites.

Wet-spinning of magneto-responsive helical chitosan microfibers.

Helical structures can be found in nature at various length scales ranging from the molecular level to the macroscale. Due to their ability to store mechanical energy and to optimize the accessible surface area, helical shapes contribute particularly to motion-driven processes and structural reinforcement. Due to these special features, helical fibers have become highly attractive for biotechnological and tissue engineering applications. However, there are only a few methods available for the production of biocompatible helical microfibers. Given that, we present here a simple technique for the fabrication of helical chitosan microfibers with embedded magnetic nanoparticles. Composite fibers were prepared by wet-spinning and coagulation in an ethanol bath. Thereby, no toxic components were introduced into the wet-spun chitosan fibers. After drying, the helical fibers had a diameter of approximately 130 µm. Scanning electron microscopy analysis of wet-spun helices revealed that the magnetic nanoparticles agglomerated into clusters inside the fiber matrix. The helical constructs exhibited a diameter of approximately 500 µm with one to two windings per millimeter. Due to their ferromagnetic properties they are easily attracted to a permanent magnet. The results from the tensile testing show that the helical chitosan microfibers exhibited an average Young’s modulus of 14 MPa. By taking advantage of the magnetic properties of the feedstock solution, the production of the helical fibers could be automated. The fabrication of the helical fibers was achieved by utilizing the magnetic properties of the feedstock solution and winding the emerging fiber around a rotating magnetic collector needle upon coagulation. In summary, our helical chitosan microfibers are very attractive for future use in magnetic tissue engineering or for the development of biocompatible actuator systems.

Lifetime of a single bubble on the surface of a water and ethanol bath

The time a single bubble stays on a liquid bath surface depends on deterministic drainage. However, for pure water, stochastic local disturbances also affect bubble death. For binary systems like water/alcohol mixtures (WAM), preferential evaporation of one component is crucial. We examine stochastic and deterministic effects on WAM bubble lifetime statistically using an automated bubble generator. The bubble lifetime probability density and the increase in its average with ethanol concentration depends on stabilizing Marangoni stresses arising from evaporation-induced heterogeneities.

Short Exposure to Moderate Concentration of Alcohol During Embryonic Development Does Not Alter Gross Morphology in Zebrafish.

Several studies have demonstrated translational potential of the zebrafish in modeling fetal alcohol spectrum disorders (FASDs), including the less severe forms of this disease. Short exposure to even low doses of alcohol during embryonic development has been shown to disrupt behavior, alter neurochemistry, and expression of neuronal markers and glial cell phenotypes in zebrafish. However, no study to date has systematically analyzed the potential morphological effects of the short- and low-dose embryonic alcohol exposure regimen used before with zebrafish to model milder forms of human FASD. In this study, we use this previously used embryonic alcohol exposure regimen. We immerse intact zebrafish eggs of AB strain and of a genetically variable wild-type population for 2 h into 1% or 0% (vol/vol) ethanol bath at one of five developmental stages (8, 16, 24, 32, or 40 h postfertilization). At 8 days postfertilization, we quantify body length and width and eye diameter of the larvae. We report nonsignificant effects of embryonic alcohol exposure used at all developmental stages in both populations of zebrafish. Our results confirm that visual perception or motor function is unlikely to have contributed to previously reported behavioral abnormalities resulting from embryonic alcohol exposure in zebrafish.

QCM Sensors Combining Highly Nanostructured Metal-Blacks Sublayers and Active Self-Assembled Monolayers

Introduction Quartz Crystal Microbalance (QCM) sensors are characterized by many potential applications. They are being widely used as biosensors, in pharmacological applications, for combustion control, environmental pollution monitoring, etc. [1]. Regardless the specific application, the recognition resolution of quartz chips is usually determined and restrained according to the Sauerbray equation (For example for 10 MHz QCM, the change of resonance frequency in 1 Hz corresponds to 4.4 ng/cm2 of adsorbed mass per surface). This fact is crucial mainly for gas sensor application where we need to detect concentration down to ppm or even ppb levels. However, there are some possibilities on how to enhance the QCM sensor properties and amplify their sensitivity, for instance by increasing the specific surface area of QCM electrodes, and thus providing more bonding sites for the analyte [2]. In this contribution, we propose a novel method that uses nanostructured materials called metal-blacks as a sublayer for the increase of active sensor surface, in combination with self-assembled monolayers (SAMs) that serves as a receptor layer. Metal-Blacks Metal-blacks – MBs are highly nanoporous and nanostructured materials with a large surface area. Their name originates in black colour, caused by the absorption of incident light on their surface. The incident light penetrates into the pores and channels where it undergoes multiple reflections in cavities and where it is almost completely absorbed. Due to the very large surface area, MBs are ideal materials for enhancement of QCM gas sensors properties [3]. Experimental The nanostructured layers of black gold (BAu) and black palladium (BPd) were prepared by evaporation from a tungsten boat at an elevated pressure of 200 Pa. Prepared layers of MBs were then characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SAMs of zinc octacarboxylphthalocyanine ZnPc(COOH)8 were prepared by two-step grafting method, where ZnPc(COOH)8 is covalently bonded to the molecule of aminothiophenol, which serves as an surface anchor via its gold/palladium-sulfur bond. The preparation procedure was as follows. At first, the QCM electrodes with MB layers were degreased in a sonicated ethanol bath during a few minutes and then dried under a nitrogen flow. Second, the QCM samples were cleaned by UV-ozone treatment and immediately immersed into 10-4 M solution of aminothiophenol in ethanol/DMF solvent for 24h. Third, after the 24h incubation time, the samples were moved into 10-4 M solution of the macrocycles and left there for another 24h. In the end, the samples were carefully rinsed with the solvent to eliminate adsorbed molecular overlayers and subsequently washed with ethanol in order to remove solvent residues and dried under nitrogen flux.Once prepared, QCM sensor impedance spectra were obtained by impedance analyzer Agilent 4294A. Responses towards different analytes (EtOH, CH4, H2O, NO2, toluene, acetaldehyde) were measured in a glass chamber that enables the measurement of up to 6 sensors at the same time. Sensors were measured at a constant gas flow and room temperature. The sensor resonant frequencies were measured by oscillattor circuits in connection with an NI PCI-6602 card used as a precise counter Results and Conclusions In this contribution, we have proved that highly nanoporous and nanostructured materials (such as metal-blacks), which have a large specific surface area, provide more binding sites for analytes and, hence, increase the response of the QCM sensors. As an example measurement, we present the response of QCMs with BAu towards ethanol vapours (Fig. 1). The curves illustrate that the response of the sensor with the BAu electrode is 10-times bigger than the one of the standard QCM (152Hz/15Hz). For the combined layer (BAu + ZnPc(COOH)8), the response amplification is not so large but it is still significant. In this case, the response is 3-times bigger than the one from the QCM with ZnPc(COOH)8 only (without BAu). However, in contrast with QCM with just bare BAu, the surface modification with SAMs layers influences the sensor selectivity. The combined layers of MBs and SAMs then result in a selective sensor with increased sensitivity. According to the presented results metal-blacks are promising materials that can significantly boost the sensitivity of QCM sensors and still preserve the selectivity of its active layers.

Protein aggregates nucleate ice: the example of apoferritin

Abstract. Biological material has gained increasing attention recently as a source of ice-nucleating particles that may account for cloud glaciation at moderate supercooling. While the ice-nucleation (IN) ability of some bacteria can be related to membrane-bound proteins with epitaxial fit to ice, little is known about the IN-active entities present in biological material in general. To elucidate the potential of proteins and viruses to contribute to the IN activity of biological material, we performed bulk freezing experiments with the newly developed drop freezing assay DRoplet Ice Nuclei Counter Zurich (DRINCZ), which allows the simultaneous cooling of 96 sample aliquots in a chilled ethanol bath. We performed a screening of common proteins, namely the iron storage protein ferritin and its iron-free counterpart apoferritin, the milk protein casein, the egg protein ovalbumin, two hydrophobins, and a yeast ice-binding protein, all of which revealed IN activity with active site densities &gt; 0.1 mg−1 at −10 ∘C. The tobacco mosaic virus, a plant virus based on helically assembled proteins, also proved to be IN active with active site densities increasing from 100 mg−1 at −14 ∘C to 10 000 mg−1 at −20 ∘C. Among the screened proteins, the IN activity of horse spleen ferritin and apoferritin, which form cages of 24 co-assembled protein subunits, proved to be outstanding with active site densities &gt; 10 mg−1 at −5 ∘C. Investigation of the pH dependence and heat resistance of the apoferritin sample confirmed the proteinaceous nature of its IN-active entities but excluded the correctly folded cage monomer as the IN-active species. A dilution series of apoferritin in water revealed two distinct freezing ranges, an upper one from −4 to −11 ∘C and a lower one from −11 to −21 ∘C. Dynamic light scattering measurements related the upper freezing range to ice-nucleating sites residing on aggregates and the lower freezing range to sites located on misfolded cage monomers or oligomers. The sites proved to persist during several freeze–thaw cycles performed with the same sample aliquots. Based on these results, IN activity seems to be a common feature of diverse proteins, irrespective of their function, but arising only rarely, most probably through defective folding or aggregation to structures that are IN active.

Sample Preparation Method of Scanning and Transmission Electron Microscope for the Appendages of Woodboring Beetle.

This report described sample preparation methods that scanning and transmission electron microscope observations, demonstrated by preparing appendages of the woodboring beetle, Chlorophorus caragana Xie & Wang (2012), for both types of electron microscopy. The scanning electron microscopy (SEM) sample preparation protocol was based on sample chemical fixation, dehydration in a series of ethanol baths, drying, and sputter-coating. By adding Tween 20 (Polyoxyethylene sorbitan laurate) to the fixative and the wash solution, the insect body surface of woodboring beetle was washed more cleanly in SEM. This study's transmission electron microscopy (TEM) sample preparation involved a series of steps including fixation, ethanol dehydration, embedding in resin, positioning using fluorescence microscopy, sectioning, and staining. Fixative with Tween 20 enabled penetrate the insect body wall of woodboring beetle more easily than it would had been without Tween 20, and subsequently better fixed tissues and organs in the body, thus yielded clear transmission electron microscope observations of insect sensilla ultrastructures. The next step of this preparation was determining the positions of insect sensilla in the sample embedded in the resin block by using fluorescence microscopy to increase the precision of target sensilla positioning. This improved slicing accuracy.

Tuning from frustrated magnetism to superconductivity in quasi-one-dimensional KCr3As3 through hydrogen doping

We report the charge doping of KCr$_3$As$_3$ via H intercalation. We show that the previously reported ethanol bath deintercalation of K$_2$Cr$_3$As$_3$ to KCr$_3$As$_3$ has a secondary effect whereby H from the bath enters the quasi-one-dimensional Cr$_6$As$_6$ chains. Furthermore, we find that - contrary to previous interpretations - the difference between non-superconducting as-grown KCr$_3$As$_3$ samples and superconducting hydrothermally annealed samples is not a change in crystallinity but due to charge doping, with the latter treatment increasing the H concentration in the CrAs tubes effectively electron-doping the 133 compound. These results suggest a new stoichiometry KH$_x$Cr$_3$As$_3$, that superconductivity arises from a suppressed magnetic order via a tunable parameter and pave the way for the first charge-doped phase diagram in these materials.

Characteristics and Ice Nucleation Activity of Sugarcane Epiphytic and Endophytic Bacteria and Their Role in Host Frostbite

Sugarcane is one of the most important economic plants in tropical and subtropical regions worldwide, which is exposed to damage in cold condition. This study was conducted to characterize the epiphytic and endophytic bacteria and investigation of their role in ice nucleation activity and host frostbite. During the survey in spring and summer 2015, a total of 136 Gram-negative and Gram-positive bacterial strains were isolated from main sugarcane fields, especially Ahwaz sugarcane agro-industries in the south of Iran. According to phenotypic features and sequences of 16S rRNA encoding genes of sugarcane epiphytic and endophytic bacteria, they belonged to six families including Pseudomonadaceae, Xanthomonadaceae, Enterobacteriaceae, Sphingomonadaceae, Microbacteriaceae and Bacillaceae. Representatives of these families were identified as Pseudomonas fluorescens (Epi57-A4), Pseudomonas marginalis (strain Epi48-A17), Pseudomonas putida (strain Epi57-I6), Xanthomonas axonopodis strain (Endo57-A8), Stenotrophomonas maltophilia (strain Endo69-A6), Pseudomonas geniculata strain (Epi69-A4), Pantoea stewartii (strain Epi57-I8), Sphingomonas sp. (strain Epi48-A7), Microbacterium arborescens (strain Epi69-I1) and Bacillus sp. (strain Epi48-A8). The highest frequency of the tested bacterial strains was observed for Pseudomonadaceae and Xanthomonadaceae family members. Pseudomonas fluorescens strain Epi57-A4 and Pantoea stewartii strain Epi57-I8 showed ice nucleation activity in ethanol bath and caused frost damage on sugarcane seedlings in vitro. Amplification of Ice nucleation gene using degenerate inaprimers showed that only Pseudomonas fluorescens strain Epi57-A4 was ina+ gene, suggesting the potential of this gene to accelerate frosting in sugarcane during the cold condition.

3D Scaffolds of Polycaprolactone/Copper-Doped Bioactive Glass: Architecture Engineering with Additive Manufacturing and Cellular Assessments in a Coculture of Bone Marrow Stem Cells and Endothelial Cells.

The local delivery of Cu2+ from copper-doped bioactive glass (Cu-BaG) was combined with 3D printing of polycaprolactone (PCL) scaffolds for its potent angiogenic effect in bone tissue engineering. PCL and Cu-BaG were, respectively, dissolved and dispersed in acetone to formulate a moderately homogeneous ink. The PCL/Cu-BaG scaffolds were fabricated via direct ink writing into a cold ethanol bath. The architecture of the printed scaffolds, including strut diameter, strut spacing, and porosity, were investigated and characterized. The PCL/Cu-BaG scaffolds showed a Cu-BaG content-dependent mechanical property, as the compressive Young's modulus ranged from 7 to 13 MPa at an apparent porosity of 60%. The ion dissolution behavior in simulated body fluid was evaluated, and the hydroxyapatite-like precipitation on the strut surface was confirmed. Furthermore, the cytocompatibility of the PCL/Cu-BaG scaffolds was assessed in human bone marrow stem cell (hBMSC) culture, and a dose-dependent cytotoxicity of Cu2+ was observed. Here, the PCL/BaG scaffold induced the higher expression of late osteogenic genes OSTEOCALCIN and DLX5 in comparison to the PCL scaffold. The doping of Cu2+ in BaG elicited higher expression of the early osteogenic marker gene RUNX2a but decreased the expression of late osteogenic marker genes OSTEOCALCIN and DLX5 in comparison to the PCL/BaG scaffold, demonstrating the suppressing effect of Cu2+ on osteogenic differentiation of hBMSCs. In a coculture of hBMSCs and human umbilical vein endothelial cells, both the PCL/BaG and PCL/Cu-BaG scaffolds stimulated the formation of a denser tubule network, compared to the PCL scaffold. Meanwhile, only slightly higher gene expression of vWF was observed with the PCL/Cu-BaG scaffold than with the PCL/BaG scaffold, indicating the potent angiogenic effect of the released Cu2+.

Fabrication of fluffy shish-kebab structured nanofibers by electrospinning, CO2 escaping foaming and controlled crystallization for biomimetic tissue engineering scaffolds

Electrospun nanofibrous scaffolds are highly recognized in tissue engineering since they can mimic the structure of extracellular matrix (ECM). However, the nanofibers fail to resemble the three dimensional geometry of organs, and the surface nanotopography of collagen fibrils in ECM. In order to mimic the structure of ECM in both macroscale (3D geometry) and microscale (surface nanotopography), an ingenious approach was developed in this study. Electrospun nanofibers collected in ethanol bath was soaked in CO2 saturated ethanol and subsequently foamed in a water bath, due to the escaping of CO2 gas. This simple green method takes the advantage of solubility difference of carbon dioxide (CO2) in ethanol and water, and is applicable to different materials. The foamed fluffy polycaprolactone (PCL) nanofibrous scaffolds achieved a low bulk density of 0.041 g/cm3 and a high porosity of 95.3%. To resemble the surface nanotopography of ECM, shish-kebab structure was introduced onto the fluffy PCL nanofibers by controlled crystallization. The shish-kebab structures greatly enhanced the surface area of scaffolds from 6.9 m2/g for 2D PCL to 10.9 m2/g for 3D SK-PCL. In addition, 3T3 fibroblast cell culture results confirmed that the cells interacted strongly with the 3D fluffy nanofibers and migrated into the inner area of the scaffolds rapidly. Moreover, human fibroblast cell culture results confirmed further enhancement in cell attachment and proliferation on the fluffy shish-kebab structured nanofibrous scaffolds, which indicates the developed biomimetic 3D scaffolds have high potential to be used for 3D tissue regeneration.

Direct Write Assembly of Graphene/Poly(ε-Caprolactone) Composite Scaffolds and Evaluation of Their Biological Performance Using Mouse Bone Marrow Mesenchymal Stem Cells.

Scaffold and mesenchymal stem cell-based cartilage tissue engineering offers a favorable way for the repair and regeneration of injured cartilage. In this study, poly (ε-caprolactone) PCL scaffolds with grid-like structure having periodic lattice was manufactured by robocasting method in the presence of graphene nanoplatelets for cartilage tissue engineering applications. For this purpose, a PCL solution (20wt%) containing pristine graphene nanopowders in the form of platelets was prepared as printing ink and it was dispensed through a nozzle at room temperature to an ethanol bath at 4°C. The construction of porous scaffolds was made by a layer-by-layer assembly. Results revealed that graphene additions were not detrimental to deposition process and the structure of the resultant scaffolds. In vitro cell tests indicated that the prepared grid-like graphene/PCL composite scaffolds have good cytocompatibility and non-toxicity for mouse bone marrow mesenchymal stem cells. The stem cells attached and proliferated well on the scaffolds and they also demonstrated a chondrogenic differentiation in the absence of transforming growth factors.

A fibrous cellulose paste formulation to manufacture structural parts using 3D printing by extrusion

An optimized paste based on short natural cellulose fibers combined with carboxymethyl cellulose at a high dry content (42 wt.%) was implemented as a bio-based material for 3D printing by extrusion. The homogeneous paste exhibited a pronounced thinning behavior and yield stress; it was extruded using a screw extrusion-based direct ink writing system and could easily flow through a small nozzle. The optimized formulation enabled accurate additive manufacturing of parts using a natural air-drying process with or without an ethanol bath. We characterized the anisotropic shrinkage that occurred during the drying of 3D printed parts and proposed a compensation method to account for it. The obtained results emphasized that cellulose had a strong potential to be used as a raw material for 3D printing of cheap, lightweight, robust, and recyclable parts.

Fabrication of three-dimensional nanofibrous gelatin scaffolds using one-step crosslink technique

Electrospun nanofibers have been considered to be an ideal scaffold for tissue engineering, because of the extracellular-matrix-like structure and the well-controlled fabrication. Here, a new method was used to fabricate electrospun three-dimensional macroporous nanofibrous gelatin scaffolds in ethanol bath by one-step crosslink with glutaraldehyde. The mean diameter of the one-step crosslinked fibers was significantly smaller than that of the traditional two-step crosslinked fibers (p < 0.05), and scaffolds prepared by one-step crosslink were fluffy and porous. No significant difference was found in the degradation rates for both fibers within 14 days. After immersion in PBS for 14 days, numerous two-step crosslinked fibers merged together. By contrast, the morphology and macroporous structure of one-step crosslinked fibers showed no evident change and were generally maintained. Approximate crosslinking degrees of the two-step and one-step crosslinked gelatin fibers were 40% and 54%, respectively (p < 0.05). Results from fluorescence microscopy and hematoxylin-eosin staining showed that MC3T3-E1 subclone four cells were distributed more evenly and diversely in the one-step crosslinked fiber scaffolds. The one-step crosslinked fibers enhanced the proliferation and differentiation potential of MC3T3-E1 cells. Furthermore, one-step crosslinked fibers were beneficial in repairing defects in the skulls of rats. Thus, one-step crosslink by glutaraldehyde in ethanol bath is a cost-effective and simple method to fabricate three-dimensional macroporous nanofiberous scaffolds. This technique retains the morphology and structure of the gelatin fibers, and enhances the biological performance of scaffolds in vitro and in vivo.

Engineering of Removing Sacrificial Materials in 3D-Printed Microfluidics

Three-dimensional (3D) printing will create a revolution in the field of microfluidics due to fabricating truly three-dimensional channels in a single step. During the 3D-printing process, sacrificial materials are usually needed to fulfill channels inside and support the printed chip outside. Removing sacrificial materials after printing is obviously crucial for applying these 3D printed chips to microfluidics. However, there are few standard methods to address this issue. In this paper, engineering techniques of removing outer and inner sacrificial materials were studied. Meanwhile, quantification methods of removal efficiency for outer and inner sacrificial materials were proposed, respectively. For outer sacrificial materials, a hot bath in vegetable oil can remove 89.9% ± 0.1% of sacrificial materials, which is better than mechanics removal, hot oven heating, and an ethanol bath. For inner sacrificial materials, injecting 70 °C vegetable oil for 720 min is an optimized approach because of the uniformly high transmittance (93.8% ± 6.8%) and no obvious deformation. For the industrialization of microfluidics, the cost-effective removing time is around 10 min, which considers the balance between time cost and chip transmittance. The optimized approach and quantification methods presented in this paper show general engineering sacrificial materials removal techniques, which promote removing sacrificial materials from 3D-printed microfluidics chips and take 3D printing a step further in microfluidic applications.