A Very Stable High Throughput Taylor Cone-jet in Electrohydrodynamics

Designing Dual-Responsive Drug Delivery Systems: The Role of Phase Change Materials and Metal-Organic Frameworks

Stimuli-responsive drug delivery systems (DDSs) offer precise control over drug release, enhancing therapeutic efficacy and minimizing side effects. This review focuses on DDSs that leverage the unique capabilities of phase change materials (PCMs) and metal-organic frameworks (MOFs) to achieve controlled drug release in response to pH and temperature changes. Specifically, this review highlights the use of a combination of lauric and stearic acids as PCMs that melt slightly above body temperature, providing a thermally responsive mechanism for drug release. Additionally, this review delves into the properties of zeolitic imidazolate framework-8 (ZIF-8), a stable MOF under physiological conditions that decomposes in acidic environments, thus offering pH-sensitive drug release capabilities. The integration of these materials enables the fabrication of complex structures that encapsulate drugs within ZIF-8 or are enveloped by PCM layers, ensuring that drug release is tightly controlled by either temperature or pH levels, or both. This review provides comprehensive insights into the core design principles, material selections, and potential biomedical applications of dual-stimuli responsive DDSs, highlighting the future directions and challenges in this innovative field.

Oscillation Dynamics of Dielectric Polymer Droplets during Electrohydrodynamic Jetting in a Wide Range of Viscosities

The electrohydrodynamic (EHD) jetting of fluids is used for several applications such as inkjet printing, atomization of analyte in mass spectrometry, liquid metal alloy ion sources, and electrospinning of polymer fibers. Historically, the bulk of research has focused on nonviscous, highly conductive fluids which are most suitable for EHD spray and printing, while there is relatively little experimental work on EHD jetting of highly viscous liquid dielectrics. We studied the dynamics of oscillation and pulsating jetting from a suspended drop of polydimethylsiloxane (PDMS) polymers in an electric field, with particular attention to the viscosity dependence of the oscillation period and meniscus elongation and contraction time over a wide viscosity range (102-105 cSt). The reported results could help the appropriate design of EHD processes and may open new possibilities for the rheological characterization of liquid polymers using small volumes at the scale of nanoliters.

Personalised Medicine and the Potential Role of Electrospinning for Targeted Immunotherapeutics in Head and Neck Cancer

Advanced head and neck cancer (HNC) is functionally and aesthetically destructive, and despite significant advances in therapy, overall survival is poor, financial toxicity is high, and treatment commonly exacerbates tissue damage. Although response and durability concerns remain, antibody-based immunotherapies have heralded a paradigm shift in systemic treatment. To overcome limitations associated with antibody-based immunotherapies, exploration into de novo and repurposed small molecule immunotherapies is expanding at a rapid rate. Small molecule immunotherapies also have the capacity for chelation to biodegradable, bioadherent, electrospun scaffolds. This article focuses on the novel concept of targeted, sustained release immunotherapies and their potential to improve outcomes in poorly accessible and risk for positive margin HNC cases.

Perspectives of nanofibrous wound dressings based on glucans and galactans - A review

Wound healing is a complex and dynamic process that needs an appropriate environment to overcome infection and inflammation to progress well. Wounds lead to morbidity, mortality, and a significant economic burden, often due to the non-availability of suitable treatments. Hence, this field has lured the attention of researchers and pharmaceutical industries for decades. As a result, the global wound care market is expected to be 27.8 billion USD by 2026 from 19.3 billion USD in 2021, at a compound annual growth rate (CAGR) of 7.6 %. Wound dressings have emerged as an effective treatment to maintain moisture, protect from pathogens, and impede wound healing. However, synthetic polymer-based dressings fail to comprehensively address optimal and quick regeneration requirements. Natural polymers like glucan and galactan-based carbohydrate dressings have received much attention due to their inherent biocompatibility, biodegradability, inexpensiveness, and natural abundance. Also, nanofibrous mesh supports better proliferation and migration of fibroblasts because of their large surface area and similarity to the extracellular matrix (ECM). Thus, nanostructured dressings derived from glucans and galactans (i.e., chitosan, agar/agarose, pullulan, curdlan, carrageenan, etc.) can overcome the limitations associated with traditional wound dressings. However, they require further development pertaining to the wireless determination of wound bed status and its clinical assessment. The present review intends to provide insight into such carbohydrate-based nanofibrous dressings and their prospects, along with some clinical case studies.

Overflow Control for Sustainable Development by Superwetting Surface with Biomimetic Structure

Liquid flowing around a solid edge, i.e., overflow, is a commonly observed flow behavior. Recent research into surface wetting properties and microstructure-controlled overflow behavior has attracted much attention. Achieving controllable macroscale liquid dynamics by manipulating the micro-nanoscale liquid overflow has stimulated diverse scientific interest and fostered widespread use in practical applications. In this review, we outline the evolution of overflow and present a critical survey of the mechanism of surface wetting properties and microstructure-controlled liquid overflow in multilength scales ranging from centimeter to micro and even nanoscale. We summarize the latest progress in utilizing the mechanisms to manipulate liquid overflow and achieve macroscale liquid dynamics and in emerging applications to manipulate overflow for sustainable development in various fields, along with challenges and perspectives.

Fabrication of a New, Low-Cost, and Environment-Friendly Laccase-Based Biosensor by Electrospray Immobilization with Unprecedented Reuse and Storage Performances

The fabrication of enzyme-based biosensors has received much attention for their selectivity and sensitivity. In particular, laccase-based biosensors have attracted a lot of interest for their capacity to detect highly toxic molecules in the environment, becoming essential tools in the fields of white biotechnology and green chemistry. The manufacturing of a new, metal-free, laccase-based biosensor with unprecedented reuse and storage capabilities has been achieved in this work through the application of the electrospray deposition (ESD) methodology as the enzyme immobilization technique. Electrospray ionization (ESI) has been used for ambient soft-landing of laccase enzymes on a carbon substrate, employing sustainable chemistry. This study shows how the ESD technique can be successfully exploited for the fabrication of a new promising environment-friendly electrochemical amperometric laccase-based biosensor, with storage capability up to two months without any particular care and reuse performance up to 63 measurements on the same electrode just prepared and 20 measurements on the one-year-old electrode subjected to redeposition. The laccase-based biosensor has been tested for catechol detection in the linear range 2-100 μM, with a limit of detection of 1.7 μM, without interference from chrome, cadmium, arsenic, and zinc and without any memory effects.

Fabrication of crystalline submicro-to-nano carbon wire for achieving high current density and ultrastable current

Crystalline carbon nanowire arrays were fabricated taking advantage of near-field electrospinning and stress decyanation. A novel fabrication method for carbon nanowires with radii ranging from ~2.15 µm down to ~25 nm was developed based on implementing nitrogen pretreatment on the silica surface and then aligning polymer nanofibers during near-field electrospinning at an ultralow voltage. Stress decyanation was implemented by subsequently pyrolyzing a polymer nanofiber array on the silica surface at 1000 °C for 1 h in an N₂ atmosphere, thus obtaining a crystalline carbon nanowire array with a nanostructured surface. Various crystalline nanostructures were fabricated on the nanowire surface, and their electrochemical performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Crystalline carbon wires with diameters ranging from micrometers to submicrometers displayed carbon nanoelectrode-like behavior with their CV curve having a sigmoidal shape. A highly crystalline carbon nanowire array showed distinct behavior, having a monotonically increasing straight line as its CV curve and a semicircular EIS spectrum; these results demonstrated its ultrastable current, as determined by electron transfer. Furthermore, nanocrystalline-structured carbon wires with diameters of ~305 nm displayed at least a fourfold higher peak current density during CV (4000 mA/m²) than highly crystalline carbon nanowires with diameters of ~100 nm and porous microwires with diameters of ~4.3 µm.

Electrospraying as a Technique for the Controlled Synthesis of Biocompatible PLGA@Ag2S and PLGA@Ag2S@SPION Nanocarriers with Drug Release Capability

Ag2S nanoparticles are near-infrared (NIR) probes providing emission in a specific spectral range (~1200 nm), and superparamagnetic iron oxide nanoparticles (SPION) are colloidal systems able to respond to an external magnetic field. A disadvantage of Ag2S NPs is the attenuated luminescent properties are reduced in aqueous media and human fluids. Concerning SPION, the main drawback is the generation of undesirable clusters that reduce particle stability. Here, we fabricate biocompatible hybrid nanosystems combining Ag2S NPs and SPION by the electrospraying technique for drug delivery purposes. These nanostructures are composed of poly(lactic-co-glycolic acid) (PLGA) as the polymeric matrix in connection with both Ag2S NPs and SPIONs. Initially, we fabricate a hybrid colloidal nanosystem composed of Ag2S NPs in connection with PLGA (PLGA@Ag2S) by three different routes, showing good photoluminescent (PL) properties with relatively high average decay times. Then, we incorporate SPIONs, obtaining a PLGA polymeric matrix containing both Ag2S NPs and SPION (PLGA@Ag2S@SPION). Interestingly, in this hybrid system, the location of Ag2S NPs and SPIONs depends on the synthesis route performed during electrospraying. After a detailed characterization, we demonstrate the encapsulation and release capabilities, obtaining the kinetic release using a model chemotherapeutic drug (maslinic acid). Finally, we perform in vitro cytotoxicity assays using drug-loaded hybrid systems against several tumor cell lines.

Bio-electrospraying assessment toward in situ chondrocyte-laden electrospun scaffold fabrication

Electrospinning has been widely used to fabricate fibrous scaffolds for cartilage tissue engineering, but their small pores severely restrict cell infiltration, resulting in an uneven distribution of cells across the scaffold, particularly in three-dimensional designs. If bio-electrospraying is applied, direct chondrocyte incorporation into the fibers during electrospinning may be a solution. However, before this approach can be effectively employed, it is critical to identify whether chondrocytes are adversely affected. Several electrospraying operating settings were tested to determine their effect on the survival and function of an immortalized human chondrocyte cell line. These chondrocytes survived through an electric field formed by low needle-to-collector distances and low voltage. No differences in chondrocyte viability, morphology, gene expression, or proliferation were found. Preliminary data of the combination of electrospraying and polymer electrospinning disclosed that chondrocyte integration was feasible using an alternated approach. The overall increase in chondrocyte viability over time indicated that the embedded cells retained their proliferative capacity. Besides the cell line, primary chondrocytes were also electrosprayed under the previously optimized operational conditions, revealing the higher sensitivity degree of these cells. Still, their post-electrosprayed viability remained considerably high. The data reported here further suggest that bio-electrospraying under the optimal operational conditions might be a promising alternative to the existent cell seeding techniques, promoting not only cells safe delivery to the scaffold, but also the development of cellularized cartilage tissue constructs.

Viscosity Effect on the Electrospray Characteristics of Droplet Size and Distribution

Electrostatic spraying is a method of atomizing a fluid using a high voltage as an atomization auxiliary device, and various spraying modes exist according to experimental parameters and viscosity. A maximum of 11 spray modes were identified according to the changes in the applied voltage and flow rate. To produce fine droplets and a uniform size, which are the advantages of electrostatic spraying, in this experiment, the Sauter mean diameter (SMD) and SMD distribution were evaluated in each spray mode of electrostatic spraying. By comparing the other spray modes with the cone jet mode, it was confirmed that the maximum difference of the SMD was less than 1.5 times and the standard deviation of the rotated and pulsed jets was 2.5 times or more. In the cone shape range, the SMD and SMD distribution according to the applied voltage confirmed that the droplet size was the smallest in the middle of the cone jet mode, and the droplet distribution was also narrow. In the cone jet mode, the droplet size increased linearly with the viscosity and flow rate. In addition, the droplet distribution range was distinctive depending on the type of fluid. In the case of the relationship between the droplet size and current, it was proven that the higher the viscosity, the higher the current value for the same SMD; furthermore, the difference in the current-SMD increase rate was insignificant. Through experiments, this work presents experimental data of SMD, SMD distribution, and current-SMD in electrostatic spray experiments under various conditions.

Unraveling the electron transfer rates of highly crystalline carbon nanowires with surface oxides

In the development of glassy carbon fiber toward graphene fiber, highly crystalline carbon wires have attracted attention. More importantly, a charge cannot be accommodated at the surface of highly oriented pyrolytic graphite as it would be in a metal. In this work, we demonstrate that enhancing the decyanation reaction rate and reducing the nanowire diameter to below the crystallite size (≲50 nm) greatly contribute to the microstructure transformation of carbon from low crystalline glassy carbon to crystalline micro-structure. Using silica surfaces to limit the shrinkage of electrospun nanofibers during oxidation and carbonization, enhances the conversion of alcohol groups to normal carbonyl groups on the surface of the carbon wires derived from PAN fibers deposited with near field electrospinning (NFES). Cyclic voltammograms (CVs) on the carbon nanowires reveal that the enhancement of alcohol groups to normal carbonyl groups slows down the rapid electron transfer on glassy carbon electrodes. Using electrochemical impedance spectroscopy (EIS), we also establish that the electron transfer on the surface of highly crystalline carbon nanowires almost completely depends on the presence of oxygen groups. The highly crystalline structure of nanoscale carbon wires with a large amount of normal carbonyl groups exhibits an ultra-low electron transfer rate (less than 1.2 μm s^-1), showing the ability to make the charges reside on the highly crystalline carbon nanowires. The straight line in CV allows for EIS measurements at high alternating current voltages, improving upon the non-linearity of traditional electrochemical cells by overcoming the stochastic errors and the lower signal-to-noise ratio for ultra-sensitive biomolecule detection (≤25 mV). The latter could spur the development of a new generation of electrochemical cells and biomedical signal measurements.

Exploration of Bioengineered Scaffolds Composed of Thermo-Responsive Polymers for Drug Delivery in Wound Healing

Innate and adaptive immune responses lead to wound healing by regulating a complex series of events promoting cellular cross-talk. An inflammatory response is presented with its characteristic clinical symptoms: heat, pain, redness, and swelling. Some smart thermo-responsive polymers like chitosan, polyvinylpyrrolidone, alginate, and poly(ε-caprolactone) can be used to create biocompatible and biodegradable scaffolds. These processed thermo-responsive biomaterials possess 3D architectures similar to human structures, providing physical support for cell growth and tissue regeneration. Furthermore, these structures are used as novel drug delivery systems. Locally heated tumors above the polymer lower the critical solution temperature and can induce its conversion into a hydrophobic form by an entropy-driven process, enhancing drug release. When the thermal stimulus is gone, drug release is reduced due to the swelling of the material. As a result, these systems can contribute to the wound healing process in accelerating tissue healing, avoiding large scar tissue, regulating the inflammatory response, and protecting from bacterial infections. This paper integrates the relevant reported contributions of bioengineered scaffolds composed of smart thermo-responsive polymers for drug delivery applications in wound healing. Therefore, we present a comprehensive review that aims to demonstrate these systems' capacity to provide spatially and temporally controlled release strategies for one or more drugs used in wound healing. In this sense, the novel manufacturing techniques of 3D printing and electrospinning are explored for the tuning of their physicochemical properties to adjust therapies according to patient convenience and reduce drug toxicity and side effects.

Detecting and targeting neurodegenerative disorders using electrospun nanofibrous matrices: current status and applications

Neurodegeneration is defined as the progressive atrophy and loss of function of neurons; it is present in neurodegenerative disorders such as Multiple Sclerosis, Alzheimer's, Huntington's, and Parkinson's diseases. The detection of such disorders is performed by various imaging modalities while their therapeutic management is quite challenging. Besides, the pathogenesis of neurodegenerative disorders is still under ongoing research due to complex and multi-factorial mechanisms. Currently, targeting the specific proteins responsible for neurodegeneration is of great interest to many researchers. Furthermore, nanotechnology-based approaches for targeting the affected neurons became an emerging field of interest. Nanostructures of various forms have been developed aiming to act as therapeutics for neurodegeneration, in which electrospun nanofibers seem to play an important role as biomedical products for both detection and management of the diseases. Electrospinning is an intriguing method able to produce nanofibers with a wide range of sizes and morphological characteristics. Such nanofibrous matrices can be delivered through different administration routes to target various diseases. In this review, the most recent advancements in electrospun nanofibrous systems that target or detect multiple neurodegenerative diseases have been enlightened and an introduction to the general aspects of neurodegenerative diseases and the electrospinning process has been made. Finally, future perspectives of neurodegeneration targeting were also discussed.

Dripping, jetting and tip streaming

Dripping, jetting and tip streaming have been studied up to a certain point separately by both fluid mechanics and microfluidics communities, the former focusing on fundamental aspects while the latter on applications. Here, we intend to review this field from a global perspective by considering and linking the two sides of the problem. First, we present the theoretical model used to study interfacial flows arising in droplet-based microfluidics, paying attention to three elements commonly present in applications: viscoelasticity, electric fields and surfactants. We review both classical and current results of the stability of jets affected by these elements. Mechanisms leading to the breakup of jets to produce drops are reviewed as well, including some recent advances in this field. We also consider the relatively scarce theoretical studies on the emergence and stability of tip streaming in open systems. Second, we focus on axisymmetric microfluidic configurations which can operate on the dripping and jetting modes either in a direct (standard) way or via tip streaming. We present the dimensionless parameters characterizing these configurations, the scaling laws which allow predicting the size of the resulting droplets and bubbles, as well as those delimiting the parameter windows where tip streaming can be found. Special attention is paid to electrospray and flow focusing, two of the techniques more frequently used in continuous drop production microfluidics. We aim to connect experimental observations described in this section of topics with fundamental and general aspects described in the first part of the review. This work closes with some prospects at both fundamental and practical levels.

Measuring Surface and Interfacial Tension In Situ in Microdripping Mode for Electrohydrodynamic Applications

Walking on water is made possible, at least for tiny insects, by molecular interaction at the interfaces of dissimilar materials. Impact of these interactions-surface tension (SFT) and, more broadly, interfacial tension (IFT)-is particularly evident at micro and nano sizescales. Thus, implications of walking on water can be significant for SFT or IFT (S/IFT)-driven nanofabrication technologies, such as electrohydrodynamic atomization (EHDA), in developing next generation biomimetic microphysiological systems (MPS) and drug delivery systems (DDS). However, current methods for estimating S/IFT, based on sessile drops or new surface formation on a ring or plate, are unsuitable for integration with EHDA assemblies used in electrospinning and electrospraying. Here, we show an in situ method for estimating S/IFT specifically devised for EHDA applications using signal processing algorithms that correlate the frequency and periodicity of liquid dispensed in EHDA microdripping mode with numerical solutions from computational fluid dynamics (CFD). Estimated S/IFT was generally in agreement with published ranges for water-air, 70% ethanol-air, chloroform-air, and chloroform-water. SFT for solutions with surfactants decreased with increasing concentrations of surfactant, but at relatively higher than published values. This was anticipated, considering that established methods measure SFT at boundaries with asymmetrically high concentrations of surfactants which lower SFT.

Electrospun nanofibers: A nanotechnological approach for drug delivery and dissolution optimization in poorly water-soluble drugs

Electrospinning is a novel and sophisticated technique for the production of nanofibers with high surface area, extreme porous structure, small pore size, and surface morphologies that make them suitable for biomedical and bioengineering applications, which can provide solutions to current drug delivery issues of poorly water-soluble drugs. Electrospun nanofibers can be obtained through different methods asides from the conventional one, such as coaxial, multi-jet, side by side, emulsion, and melt electrospinning. In general, the application of an electric potential to a polymer solution causes a charged liquid jet that moves downfield to an oppositely charged collector, where the nanofibers are deposited. Plenty of polymers that differ in their origin, degradation character and water affinity are used during the process. Physicochemical properties of the drug, polymer(s), and solvent systems need to be addressed to guarantee successful manufacturing. Therefore, this review summarizes the recent progress in electrospun nanofibers for their use as a nanotechnological tool for dissolution optimization and drug delivery systems for poorly water-soluble drugs.

Ultra-thin carbon nanofibers based on graphitization of near-field electrospun polyacrylonitrile

A novel manufacturing means for arrays of carbon fibers with diameters less than 10 nm has been developed. The method improves dramatically upon the state of the art of making carbon fibers by pyrolysis of near field electrospun (NFES) polyacrylonitrile (PAN) fibers. The conductive nature of the PAN ink, touch and retract mode of the droplet at the ejector needle tip and a rotating drum for jet initiation as well as a tight control of the ink flow and droplet shape with a porous paper enable continuous near field electrospinning at an ultra-low voltage of 35 V - far below current low-voltage NFES practice. By pyrolyzing the thus obtained thinner PAN nanofibers on carbon scaffolds, a dramatic further shrinkage of the diameter leads to ultrathin carbon nanofibers e.g. from an ∼245 nm polymer fiber to an ∼5 nm carbon fiber i.e. a 4900% reduction in fiber diameter. To increase and survive the thinning during the pyrolysis process, PAN stabilization at a relatively low temperature (115 °C) and carbon support scaffolds are implemented to provide just the right amount of tension of the suspended polymer nanofibers. A small inter-fiber spacing (<8 μm) of the ultrathin carbon fibers in an array is achieved by simultaneously controlling the linear speed of the spinneret and the rotational speed of the collector. In one application, we demonstrate aligned ultra-thin carbon fibers freely suspended and in good ohmic contact with carbon scaffolds on a silicon substrate.

A Novel Profiled Multi-Pin Electrospinning System for Nanofiber Production and Encapsulation of Nanoparticles into Nanofibers

Electrospinning with various machine configurations is being used to produce polymer nanofibers with different rates of output. The use of polymers with high viscosity and the encapsulation of nanoparticles for achieving functionalities are some of the limitations of the existing methods. A profiled multi-pin electrospinning (PMES) setup is demonstrated in this work that overcomes the limitations in the needle and needleless electrospinning like needle clogging, particle settling, and uncontrolled/uneven Taylor cone formation, the requirement of very high voltage and uncontrolled distribution of nanoparticles in nanofibers. The key feature of the current setup is the use of profiled pin arrangement that aids in the formation of spherical shape polymer droplet and hence ensures uniform Taylor cone formation throughout the fiber production process. With a 10 wt% of Polyvinyl Alcohol (PVA) polymer solution and at an applied voltage of 30 kV, the production rate was observed as 1.690 g/h and average fiber diameter obtained was 160.5 ± 48.9 nm for PVA and 124.9 ± 49.8 nm for Cellulose acetate (CA) respectively. Moreover, the setup also provides the added advantage of using high viscosity polymer solutions in electrospinning. This approach is expected to increase the range of multifunctional electrospun nanofiber applications.

Large-Area Triboelectric Nanogenerator Mass Spectrometry: Expanded Coverage, Double-Bond Pinpointing, and Supercharging

Efficient ionization is a necessary condition for mass spectrometric analysis, but many compounds fail to ionize well enough to yield sufficient detection limits. Triboelectric nanogenerators (TENG) coupled to nanoelectrospray ionization (nanoESI) mass spectrometry (MS) are a highly effective approach to high sensitivity MS analysis. Here, we report on new, large-area TENG that constructively leverage the relationship between electrode size, created charges, and open-circuit voltage, leading to wider chemical coverage. Large-area TENG were found to also promote electrospray gas-phase oxidation reactions that enabled double bond position pinpointing for unsaturated lipids and species-specific lipid quantitation. Furthermore, large-area TENG MS of proteins was observed to yield higher charge state distributions (i.e., supercharging) without the need for high surface tension additives.

Behavior of charged and uncharged drops in high alternating tangential electric fields

The interaction of drops and electric fields occurs in many applications like electrowetting, electrospinning, atomization, but also causes unwanted effects like the aging of high-voltage composite insulators. Water drops are influenced by electric fields due to the polar properties of the water molecules. The behavior of the drops depends on several parameters like the orientation and strength of the electric field, drop volume, and frequency of the applied field. In addition, electric charges can influence the behavior of drops significantly. However, the impact of electric charges, including the interaction with the drop as well as the electric field strength, is far from being well understood. In this work, the impact of electric charges on the behavior of single sessile drops is investigated experimentally under well-defined conditions. The effects of the drop volume, electric field strength, field frequency, and electric charge of the drop are studied. The necessary amount of charge to change the behavior of drops, depending on the applied electric field and drop volume, is determined and different drop behavior regimes are identified. Depending on the boundary conditions, the drop oscillates with the same or double the frequency of the applied voltage. The different regimes are investigated for the first three oscillation modes. The obtained results will help to improve the understanding and to manipulate the behavior of uncharged and charged drops in strong electric fields.

Application of Electrospray in Preparing Solid Lipid Nanoparticles and Optimization of Nanoparticles Using Artificial Neural Networks

BACKGROUND

Electrospray (Electrohydrodynamic atomization) has been introduced as a novel approach to prepare nanoparticles. This work aimed to prepare SLNs through electrospray and evaluate factors affecting particle size of prepared Solid Lipid Nanoparticles (SLNs).

METHODS

SLNs were prepared by electrospray method. To study the factors affecting particle size of SLNs, Artificial Neural Networks (ANNs) were employed. Four input variables, namely, Tween 80 concentration, lipid concentration, flow rate, and polymer to lipid ratio were analyzed through ANNs and particle size was the output.

RESULTS

The analyzed model presented concentration of Tween 80 (surfactant) and lipid as effective parameters on particle size. By increasing surfactant and decreasing lipid concentration, minimum size could be obtained, while flow rate and polymer to lipid ratio appeared not to be effective.

CONCLUSION

Concentration of surfactant/lipid plays the most important role in determining the size.

A comparative study on droplet characteristics and specific charge of ethanol in two small-scale electrospray systems

An investigation on the droplet characteristics of ethanol in small-scale combustors with two different systems was conducted experimentally and theoretically. The classical capillary-mesh electrode arrangement was applied in Type A electrospray system, and for Type B, an additional ring electrode is included. The droplet size and velocity were measured by a Phase Doppler Anemometer. The electric filed intensity was theoretically calculated in the two electrospray systems. Compared with Type A, Type B system has smaller droplet size and velocity in the same spraying mode. Meanwhile the electrospray process in Type B system is more stable than that in Type A with its smaller root mean square velocity. By measuring the spraying current, the average specific charge of the droplets for the two systems was obtained in different spraying modes. And it was found that the addition of the ring electrode can help to increase the droplet charge, which is the fundamental reason for Type B electrospray system to perform better. The corona charge of the droplets was theoretically calculated for the two electrospray systems. It was found that the calculated specific charge generated by corona charging was in good agreement with the experimental results.

Bioinspired Tip-Guidance Liquid Jetting and Droplet Emission at a Rotary Disk via a Surface Energy Gradient

Effective droplet emission is of fundamental importance for practical application, such as agricultural sprays to painting, atomization, emulsification, and catalytic action. Highly viscous liquids are commonly used, such as printing inks, which hinder the ejection at the nozzle. A big challenge faced by people is how to obtain stable and controllable liquid droplets in a wide range of viscosities. Inspired by the rotation shaking of droplets on fiber clusters and the rotary spraying disk technique, here, we demonstrate uniform microdroplet (1-2000 mPa·s) generation in a tip-guided way that replaces the commonly confined nozzle by a double-layer spinning "sandwich" multitip disk (SSMD). A surface energy gradient induced by the margin structure of the alternating gas wedge and solid tip guides liquid to move along the solid tip, which is ejected at the end of the tip, forming a ring of droplet clusters. SSMD improves the effective droplet-jet process to 7/10 of the whole drainage process and enhances the efficiency with a production drop volume of ∼3.19 × 10⁷ μL/h and production droplet numbers of ∼3.3 × 10⁴ per second. Droplets can be fine-tuned between 0.1 and 1.0 mm via the tip structure, liquid property, and spinning angular velocity with a narrow size distribution. This facile tip-guided design could inspire the possibility of energy-efficient droplet production techniques in various fluid applications, such as spraying and printing. It may further improve other fluid systems that serve as a crucial component for high-speed droplet manipulation, liquid transport, and water vapor capturing.

Optimization of polycaprolactone fibrous scaffold for heart valve tissue engineering

Pore size is generally small in nanofibrous scaffolds prepared by electrospinning polymeric solutions. Increase of scaffold thickness leads to decrease in pore size, causing impediment to cell infiltration into the scaffolds during tissue engineering. In contrast, comparatively larger pore size can be realized in microfibrous scaffolds prepared from polymeric solutions at higher concentrations. Further, microfibrous scaffolds are conducive to infiltration of reparative M2 phenotype macrophages during in vivo/in situ tissue engineering. However, rise of mechanical properties of a fibrous scaffold with the increase of polymer concentration may limit the functionality of a scaffold-based, tissue-engineered heart valve. In this study, we developed microfibrous scaffolds from 14%, 16% and 18% (wt/v) polycaprolactone (PCL) polymer solutions prepared with chloroform solvent. Porcine valvular interstitial cells were cultured in the scaffolds for 14 d to investigate the effect of microfibers prepared with different PCL concentrations on the seeded cells. Further, fresh microfibrous scaffolds were implanted subcutaneously in a rat model for two months to investigate the effect of microfibers on infiltrated cells. Cell proliferation, and its morphologies, gene expression and deposition of different extracellular matrix proteins in the in vitro study were characterized. During the in vivo study, we characterized cell infiltration, and myofibroblast and M1/M2 phenotypes expression of the infiltrated cells. Among different PCL concentrations, microfibrous scaffolds from 14% solution were suitable for heart valve tissue engineering for their sufficient pore size and low but adequate tensile properties, which promoted cell adhesion to and proliferation in the scaffolds, and effective gene expression and extracellular matrix deposition by the cells in vitro. They also encouraged the cells in vivo for their infiltration and effective gene expression, including M2 phenotype expression.