Structured micro/nano materials synthesized via electrospray: a review

Interfacial electrostatic charges promoted chemistry: Reactions and mechanisms

Interfacial electrostatic charges are a universal phenomenon in nature. In recent years, interest in the chemical reactivity of electrostatic charges has grown. Interfacial electrostatic charge-driven chemical synthesis reduces the reliance on redox reagents, catalysts, and hazardous solvents, which promotes environmental sustainability and cost-effectiveness in the chemical industry. Electrostatic charges can be generated at the interfaces between solids, liquids, and gases. The chemical properties of electrostatic charges have been observed at interfaces between solids and liquids, and between liquids and gases. This review summarized the chemical reactivity of interfacial electrostatic charges and its mechanisms. Electrostatic charges play a fundamental role in providing electrons and creating electric fields, which in turn induce charge transfer, radical formation, and molecular orientation. We classified the role of interfacial charges in chemical reactions and provided new perspectives. Interfacial electrostatic charges can be generated with mechanical energy input, a power supply and interface transition from solid-liquid to liquid-gas. Redox and catalytic reactions involving inorganic, organic compounds and biomolecules are driven by interfacial electrostatic charges. Electrostatic chemistry mechanisms are currently a subject of debate because there is insufficient experimental evidence. Challenges and opportunities associated with interfacial electrostatic chemistry are discussed. Knowledge of the reactivity of interfacial electrostatic charges could be used to understand electrostatic phenomena in nature, advance green chemistry, and even study the origins of life. We expect this emerging topic will appeal to scientists in disciplines including interfacial chemistry and electrostatics.

High-Impulse, Modular, 3D-Printed CubeSat Electrospray Thrusters Throttleable via Pressure and Voltage Control

This study reports the proof-of-concept demonstration of novel, additively manufactured, droplet-emitting electrospray emitter arrays for CubeSat thruster applications. The modular thruster design incorporates multiscale features by employing two different vat photopolymerization technologies, i.e., digital light processing for defining mesoscale features, and two-photon polymerization for creating microscale features. The thruster design includes optimized, 50 µm-diameter microfluidic channels to attain uniform emitter array operation. Devices with up to 8 modules of 4 emitters were tested in a vacuum to assess their performance. Stable and uniform electrospray emission was achieved across all emitters, with a near 100% transmission across the extractor. Both pressure (flow rate) and voltage modulation are investigated as methods for controlling the emitted current and, by extension, the thrust generated by the devices. The per-emitter current followed a well-known square root relationship with flow rate; in addition, a linear relationship between per-emitter current and extractor voltage is observed. Compared to pressure control, modulating thrust via voltage control simplifies system design, eliminating the need for complex valves and enabling a wider throttle range. Estimated thrust and specific impulse are comparable to, or better than reported droplet-emitting electrospray thrusters. These findings demonstrate the potential of additive manufacturing to implement electrospray propulsion hardware.

The pursuit of linear dosage in pharmacy: reservoir-based drug delivery systems from macro to micro scale

INTRODUCTION

The pursuit of linear dosage in pharmacy is essential for achieving consistent therapeutic release and enhancing patient compliance. This review provides a comprehensive summary of zero-order drug delivery systems, with a particular focus on reservoir-based systems emanated from different microfabrication technologies.

AREAS COVERED

The consideration of recent advances in drug delivery systems is given to encompass the key areas including the importance of achieving a constant drug release rate for therapeutic applications. Detailed examination of reservoir-based systems, their design, mechanisms of action and materials used are highlighted. By addressing these areas, the discussion aims to provide a thorough understanding of most recent zero-order drug delivery systems, their performance advantages and methods of their manufacturing. To ensure the complete coverage of the explored research area, modern AI-assistant tools were used to find not only the most relevant, but also connected and similar articles.

EXPERT OPINION

Future developments in reservoir-based drug delivery systems are expected to significantly enhance therapeutic effectiveness and patient outcomes through the integration of innovative materials and technologies. The fabrication of intelligent drug delivery systems that utilize sensors and feedback mechanisms can enable real-time monitoring of drug release and patient reactions.

Controlled release of doxorubicin from Poly-(D,L-lactide-co-glycolide) (PLGA) nanoparticles prepared by coaxial electrospraying

Enhancing the efficacy and reducing the toxicity of chemotherapeutic agents like doxorubicin (DOX) is crucial in cancer treatment. Core-shell nanoparticles (NPs) fabricated by coaxial electrospraying offer controlled release of anticancer agents with the polymer shell protecting drug molecules from rapid degradation, prolonging therapeutic effect. This study developed DOX-loaded poly(lactic-co-glycolic acid) (PLGA) NPs. NPs were fabricated with matrix or core-shell structure via single needle or coaxial electrospraying, respectively. Core-shell NPs exhibited high encapsulation efficiency (>80 %) with controlled DOX distribution. Compared to matrix NPs, core-shell NPs demonstrated slower sustained release (69 % in 144 h) after reduced initial burst (22 % in 8 h). Release kinetics followed a diffusion mechanism when compared to free drug and matrix DOX-loaded NPs. In vitro assays showed core-shell NPs' enhanced cytotoxicity against breast cancer cells MCF-7, with higher uptake observed by fluorescence microscopy and flow cytometry. The IC50 for core-shell NPs displayed a significant drop (0.115 μg/mL) compared to matrix NPs (0.235 μg/mL) and free DOX (1.482 μg/mL) after 72 h. Coaxial electrospraying enables the production of therapeutically advantageous core-shell NPs, offering controlled drug release with high encapsulation efficiency, potentially improving clinical anticancer chemotherapy.

Polyhedral Vinyl Polymer Particles Synthesized Via Solvent-Free Radical Polymerization

Liquid marbles (LMs) with a cubic shape are created by using various vinyl monomers as an inner liquid and polymer plates with mm size as a stabilizer. The relationship between the surface tension of the vinyl monomers and formability of the LMs is investigated. LMs can be fabricated using vinyl monomers with surface tensions of 42.7-40.3 mN m-1. The cubic polymer particles are successively synthesized via free-radical polymerizations by irradiation of the cubic LMs with UV light in a solvent-free manner. In addition, controlling the number of polymer plates per one LM, the shape of the plate or the coalescence of the LMs can lead to production of polymer particles with desired forms (e.g., Platonic and rectangular solids) that correspond to the shapes of the original LMs.

Non-Aqueous Polyhedral Liquid Marbles Stabilized with Polymer Plates Having Surface Roughness

Hydrophobic polymer plates with smooth and rough surfaces are used as a stabilizer for cubic liquid marbles (LMs) to study the effect of surface roughness on their formation. The smooth and rough polymer plates can stabilize LMs using liquids with surface tensions of 72.8-26.6 and 72.8-22.9 mN m-1, respectively. It is clarified that the higher the surface roughness, the lower the surface tension of the liquids are stabilized to form the LMs. These results indicated that the introduction of surface roughness improves the hydrophobicity of the polymer plates and the rough polymer plates can stabilize LMs using liquids with a wider surface tension range. Electron microscopy studies and numerical analyses confirmed that the LMs can be formed, when the Cassie-Baxter wetting state, where θY>90° (θY: the contact angle on smooth surfaces) and θR>90° (θR: the contact angle on rough surfaces), and the metastable Cassie-Baxter wetting state, where θY<90° and θR>90°, are realized. Finally, the synthesis of cubic polymer particles are succeeded by free radical polymerization of the cubic LMs containing a hydrophobic vinyl monomer (dodecyl acrylate) in a solvent-free manner.

Aerodynamically Levitated Droplets as Small-Scale Chemical Reactors and Liquid Microprinters

A thin liquid film spread over the inner surface of a rapidly rotating vial creates an aerodynamic cushion on which one or multiple droplets of various liquids can levitate stably for days or even weeks. These levitating droplets can serve as wall-less ("airware") chemical reactors that can be merged without touching-by remote impulses-to initiate reactions or sequences of reactions at scales down to hundreds of nanomoles. Moreover, under external electric fields, the droplets can act as the world's smallest chemical printers, shedding regular trains of pL or even fL microdrops. In one modality, the levitating droplets operate as completely wireless aliquoting/titrating systems delivering pg quantities of reagents into the liquid in the rotating vial; in another modality, they print microdroplet arrays onto target surfaces. The "airware", levitated reactors are inexpensive to set up, remarkably stable to external disturbances and, for printing applications, require operating voltages much lower than in electrospray, electrowetting, or ink jet systems.

Effects of structural variation in electrospray systems on spray characteristics

Electrospraying is a method of atomizing fluids using a high voltage potential difference. Since the atomization of electrostatic atomization does not directly charge the nozzle but only uses the potential difference, various equipment structures are possible. In the case of this study, 12 different equipment structures of nozzle, ring electrode, and substrate were configured, and data on atomization characteristics of electrospray, such as spray modes applied voltage, coating area, coating current, spray velocity, and factors used in industrial processes, were verified. Data are provided for the generation process using uniform and continuous electrospray.

Novel erythrocyte-shaped electrosprayed nanoparticles for co-delivery of paclitaxel and osimertinib: Preparation, characterization, and evaluation

In this work, novel erythrocyte-shaped electrosprayed nanoparticles (EENPs) were designed and constructed by tri-axial electrospraying technique with PEG as the outer layer, PLGA as the middle drugs (paclitaxel [PTX] and osimertinib [OSI]) carrier layer and air as the inner layer. The prepared EENP were characterized and evaluated based on their spectral and morphological attributes. After the PTX/OSI ratio and process optimization, the EENP has inspiring features, including nanoscale size, erythrocyte morphology with a concave disk shape, and satisfactory drug loading (DL) and encapsulation efficiency (EE). In vitro drug release showed that PTX and OSI in the formulation were released in the same ratio, and the cumulative release percentage at 24 h was close to 80 %. Furthermore, the TGIR in the EENP formulation group exceeded 90 %, approximately 3.8-fold higher than that in the free drug group. In summary, we developed an erythrocyte three-core-shell nanoparticle for the co-delivery of PTX and OSI, providing a potential chemotherapeutic delivery system for the treatment of breast cancer.

Peptide-Driven Proton Sponge Nano-Assembly for Imaging and Triggering Lysosome-Regulated Immunogenic Cancer Cell Death

Triggering lysosome-regulated immunogenic cell death (ICD, e.g., pyroptosis and necroptosis) with nanomedicines is an emerging approach for turning an "immune-cold" tumor "hot"-a key challenge faced by cancer immunotherapies. Proton sponge such as high-molecular-weight branched polyethylenimine (PEI) is excellent at rupturing lysosomes, but its therapeutic application is hindered by uncontrollable toxicity due to fixed charge density and poor understanding of resulted cell death mechanism. Here, a series of proton sponge nano-assemblies (PSNAs) with self-assembly controllable surface charge density and cell cytotoxicity are created. Such PSNAs are constructed via low-molecular-weight branched PEI covalently bound to self-assembling peptides carrying tetraphenylethene pyridinium (PyTPE, an aggregation-induced emission-based luminogen). Assembly of PEI assisted by the self-assembling peptide-PyTPE leads to enhanced surface positive charges and cell cytotoxicity of PSNA. The self-assembly tendency of PSNAs is further optimized by tuning hydrophilic and hydrophobic components within the peptide, thus resulting in the PSNA with the highest fluorescence, positive surface charge density, cell uptake, and cancer cell cytotoxicity. Systematic cell death mechanistic studies reveal that the lysosome rupturing-regulated pyroptosis and necroptosis are at least two causes of cell death. Tumor cells undergoing PSNA-triggered ICD activate immune cells, suggesting the great potential of PSNAs to trigger anticancer immunity.

Multivariate Analysis of Cellular Uptake Characteristics for a (Co)polymer Particle Library

Controlling cellular responses to nanoparticles so far is predominantly empirical, typically requiring multiple rounds of optimization of particulate carriers. In this study, a systematic model-assisted approach should lead to the identification of key parameters that account for particle properties and their cellular recognition. A copolymer particle library was synthesized by a combinatorial approach in soap free emulsion copolymerization of styrene and methyl methacrylate, leading to a broad compositional as well as constitutional spectrum. The proposed structure-property relationships could be elucidated by multivariate analysis of the obtained experimental data, including physicochemical characteristics such as molar composition, molecular weight, particle diameter, and particle charge as well as the cellular uptake pattern of nanoparticles. It was found that the main contributors for particle size were the polymers' molecular weight and the zeta potential, while particle uptake is mainly directed by the particles' composition. This knowledge and the reported model-assisted procedure to identify relevant parameters affecting particle engulfment of particulate carriers by nonphagocytic and phagocytic cells can be of high relevance for the rational design of pharmaceutical nanocarriers and assessment of biodistribution and nanotoxicity, respectively.

Bioinspired Hierarchical Multi-Protective Membrane for Extreme Environments via Co-Electrospinning-Electrospray Strategy

Extreme environments can cause severe harm to human health, and even threaten life safety. Lightweight, breathable clothing with multi-protective functions would be of great application value. However, integrating multi-protective functions into nanofibers in a facile way remains a great challenge. Here, a one-step co-electrospinning-electrospray strategy is developed to fabricate a superhydrophobic multi-protective membrane (S-MPM). The water contact angle of S-MPM can reach up to 164.3°. More importantly, S-MPM can resist the skin temperature drop (11.2 °C) or increase (17.2 °C) caused by 0 °C cold or 70 °C hot compared with pure electrospun membrane. In the cold climate (-5 °C), the anti-icing time of the S-MPM is extended by 2.52 times, while the deicing time is only 1.45 s due to the great photothermal effect. In a fire disaster situation, the total heat release and peak heat release rate values of flame retarded S-MPM drop sharply by 24.2% and 69.3%, respectively. The S-MPM will serve as the last line of defense for the human body and has the potential to trigger a revolution in the practical application of next-generation functional clothing.

Nanofibrous Dressing with Nanocomposite Monoporous Microspheres for Chemodynamic Antibacterial Therapy and Wound Healing

The excessive use of antibiotics and consequent bacterial resistance have emerged as crucial public safety challenges for humanity. As a promising antibacterial treatment, using reactive oxygen species (ROS) can effectively address this problem and has the advantages of being highly efficient and having low toxicity. Herein, electrospinning and electrospraying were employed to fabricate magnesium oxide (MgO)-based nanoparticle composited polycaprolactone (PCL) nanofibrous dressings for the chemodynamic treatment of bacteria-infected wounds. By utilizing electrospraying, erythrocyte-like monoporous PCL microspheres incorporating silver (Ag)- and copper (Cu)-doped MgO nanoparticles were generated, and the unique microsphere-filament structure enabled efficient anchoring on nanofibers. The composite dressings produced high levels of ROS, as confirmed by the 2,7-dichloriflurescin fluorescent probe. The sustained generation of ROS resulted in efficient glutathione oxidation and a remarkable bacterial killing rate of approximately 99% against Staphylococcus aureus (S. aureus). These dressings were found to be effective at treating externally infected wounds. The unique properties of these composite nanofibrous dressings suggest great potential for their use in the medical treatment of bacteria-infected injuries.

Nonspherical Epoxy Resin Polymer Particles Synthesized via Solvent-Free Polyaddition Reactions

Cubic liquid marbles (LMs) were fabricated by using various epoxy monomers as internal liquids and millimeter-sized polymer plates as stabilizers. Successively, cubic polymer particles were synthesized via solvent-free polyaddition reactions by exposing the cubic LMs to NH₃ vapor used as a curing agent. The effect of the solubility parameters (SPs) for the epoxy monomers on the formation of the cubic polymer particles was investigated. As a result, we succeeded in fabricating cubic polymer particles reflecting the shapes of the original LMs by using epoxy monomers with SP values of 23.70-21.66 (MPa)^1/2. Furthermore, the shapes of the LMs could be controlled on demand (e.g., pentahedral and rectangular) by control of the number of polymer plates per LM and/or coalescence of the LMs, resulting in fabrication of polymer particles with shapes reflecting those of the LMs.

Application of Biomedical Microspheres in Wound Healing

Tissue injury, one of the most common traumatic injuries in daily life, easily leads to secondary wound infections. To promote wound healing and reduce scarring, various kinds of wound dressings, such as gauze, bandages, sponges, patches, and microspheres, have been developed for wound healing. Among them, microsphere-based tissue dressings have attracted increasing attention due to the advantage of easy to fabricate, excellent physicochemical performance and superior drug release ability. In this review, we first introduced the common methods for microspheres preparation, such as emulsification-solvent method, electrospray method, microfluidic technology as well as phase separation methods. Next, we summarized the common biomaterials for the fabrication of the microspheres including natural polymers and synthetic polymers. Then, we presented the application of the various microspheres from different processing methods in wound healing and other applications. Finally, we analyzed the limitations and discussed the future development direction of microspheres in the future.

Core-Shell Particles: From Fabrication Methods to Diverse Manipulation Techniques

Core-shell particles are micro- or nanoparticles with solid, liquid, or gas cores encapsulated by protective solid shells. The unique composition of core and shell materials imparts smart properties on the particles. Core-shell particles are gaining increasing attention as tuneable and versatile carriers for pharmaceutical and biomedical applications including targeted drug delivery, controlled drug release, and biosensing. This review provides an overview of fabrication methods for core-shell particles followed by a brief discussion of their application and a detailed analysis of their manipulation including assembly, sorting, and triggered release. We compile current methodologies employed for manipulation of core-shell particles and demonstrate how existing methods of assembly and sorting micro/nanospheres can be adopted or modified for core-shell particles. Various triggered release approaches for diagnostics and drug delivery are also discussed in detail.

4D Printing of Extrudable and Degradable Poly(Ethylene Glycol) Microgel Scaffolds for Multidimensional Cell Culture

Granular synthetic hydrogels are useful bioinks for their compatibility with a variety of chemistries, affording printable, stimuli-responsive scaffolds with programmable structure and function. Additive manufacturing of microscale hydrogels, or microgels, allows for the fabrication of large cellularized constructs with percolating interstitial space, providing a platform for tissue engineering at length scales that are inaccessible by bulk encapsulation where transport of media and other biological factors are limited by scaffold density. Herein, synthetic microgels with varying degrees of degradability are prepared with diameters on the order of hundreds of microns by submerged electrospray and UV photopolymerization. Porous microgel scaffolds are assembled by particle jamming and extrusion printing, and semi-orthogonal chemical cues are utilized to tune the void fraction in printed scaffolds in a logic-gated manner. Scaffolds with different void fractions are easily cellularized post printing and microgels can be directly annealed into cell-laden structures. Finally, high-throughput direct encapsulation of cells within printable microgels is demonstrated, enabling large-scale 3D culture in a macroporous biomaterial. This approach provides unprecedented spatiotemporal control over the properties of printed microporous annealed particle scaffolds for 2.5D and 3D tissue culture.

Candle Soot-Based Electrosprayed Superhydrophobic Coatings for Self-Cleaning, Anti-Corrosion and Oil/Water Separation

The interest in candle soot (CS)-based superhydrophobic coatings has grown rapidly in recent years. Here, a simple and low-cost process has been developed for the fabrication of CS-based superhydrophobic coatings through electrospraying of the composite cocktail solution of CS and polyvinylidene fluoride (PVDF). Results show that the superhydrophobicity of the coating closely relates to the loading amount of CS which results in coatings with different roughnesses. Specifically, increasing the CS amount (not more than 0.4 g) normally enhances the superhydrophobicity of the coating due to higher roughness being presented in the produced microspheres. Further experiments demonstrate that the superhydrophobicity induced in the electrosprayed coating results from the synergistic effect of the cocktail solution and electrospray process, indicating the importance of the coating technique and the solution used. Versatile applications of CS-based superhydrophobic coatings including self-cleaning, anti-corrosion and oil/water separation are demonstrated. The present work provides a convenient method for the fabrication of CS-based superhydrophobic coatings, which is believed to gain great interest in the future.

Impact of Deacetylation Degree on Properties of Chitosan for Formation of Electrosprayed Nanoparticles

Biopolymer of natural origin as chitosan has been studied and applied widely in practice. In the pharmaceutical field, especially, chitosan nanoparticles have been researched for a variety of drug delivery systems. There are many factors influencing the success of the chitosan nanoparticle delivery system. Therein, the specific parameters to the physicochemical nature of chitosan greatly determine the efficiency of its drugs carrier. The degree of deacetylation (DD) of chitosan is one of those parameters. In this study, the influence of DD on chitosan properties was clarified to facilitate the preparation of nanoparticles by the electrospraying method. DD can affect the solubility, crystallinity, and surface tension of chitosan, but it cannot strongly impact the viscosity of chitosan solution as much as the molecular weight (Mv). From these results, M3 chitosan, owning a high DD of 86.70%, and crystalline index of 44%, was dissolved in acetic acid for the collection of electrosprayed nanoparticles. The M3 solution having low viscosity of under 50 mm2/s displayed the easy adjustment of the stable Taylor-cone droplet at the nozzle tip. Particularly, the M3 chitosan solution with a concentration of 1.5 wt.% in acetic acid of 90 wt.% concentration operated at the working condition of 12 kV voltage, a distance between the two electrodes of 10 cm created spherical particles with an average diameter of 338 nm, narrow size distribution. These chitosan nanoparticles can obtain the initial requirement for application as injectable drugs carrier.

Compositionally Anisotropic Colloidal Surfactant Decorated with Dual Metallic Nanoparticles as a Pickering Emulsion Stabilizer and Their Application in Catalysis

We aim to introduce compositionally anisotropic Janus particles, hemispheres of which was modified by hydrophilic poly(2-dimethyl amino ethyl methacrylate) [poly(DMAEMA)] brushes to display amphiphilic surfactant-type characteristics. Acquired by the electrohydrodynamic co-jetting technique, these colloidal surfactants were employed to stabilize octanol/water-based Pickering emulsion, which shows prolonged stability for more than 4 months. To explore their potential as the interfacial catalyst, iron(0) nanoparticles were incorporated in one hemisphere during electrojetting, whereas gold nanoparticles (GNPs) were patched onto the surface of the other hemisphere, which was previously modified by the poly(DMAEMA) brush. Ultimately, simultaneous rapid reduction (100% conversion in 1 min) of p-nitrophenol or methyl orange (MO) by GNPs in the aqueous phase and dechlorination of trichloroethylene (a hazardous chlorinated solvent waste) present in the octanol phase were accomplished at the organic-water interface stabilized by the Janus particles decorated by dual metallic nanoparticles. In addition, facile recovery and recyclability of the catalyst were also achieved. The novel colloidal surfactant demonstrated in this study may open up a new avenue to accomplish catalysis of several organic reactions occurring at the water-oil interface.

Core-Shell Microcapsules: Biofabrication and Potential Applications in Tissue Engineering and Regenerative Medicine

The construction of biomaterial scaffolds that accurately recreate the architecture of living tissues in vitro is a major challenge in the field of tissue engineering and regenerative medicine. Core-shell microcapsules...

Core-shell microparticles: From rational engineering to diverse applications

Core-shell microparticles, composed of solid, liquid, or gas bubbles surrounded by a protective shell, are gaining considerable attention as intelligent and versatile carriers that show great potential in biomedical fields. In this review, an overview is given of recent developments in design and applications of biodegradable core-shell systems. Several emerging methodologies including self-assembly, gas-shearing, and coaxial electrospray are discussed and microfluidics technology is emphasized in detail. Furthermore, the characteristics of core-shell microparticles in artificial cells, drug release and cell culture applications are discussed and the superiority of these advanced multi-core microparticles for the generation of artificial cells is highlighted. Finally, the respective developing orientations and limitations inherent to these systems are addressed. It is hoped that this review can inspire researchers to propel the development of this field with new ideas.

Water stable colloidal lignin-PVP particles prepared by electrospray

In this study, electrospray deposition has been used as a method to prepare lignin submicron spherical particles. Regularities of electrospraying of lignin solutions in DMSO were revealed. The influence of voltage, distance between electrodes, feed rate, temperature and concentration of lignin solution on the morphology, size and polydispersity of the obtained particles was determined. SEM, IR, TG-DSC, elemental analysis, dynamic light scattering, Zeta potential and nitrogen sorption were used to characterize the particles and to determine their properties. The aqueous colloidal solutions of the submicron particles of lignins from various plant sources were stabilized by preparing the lignin/polyvinylpyrrolidone polymeric complexes.

Hyaluronic acid hydrogels, as a biological macromolecule-based platform for stem cells delivery and their fate control: A review

Stem cell-based therapies offer numerous potentials to repair damaged or defective organs. The therapeutic outcomes of human studies, however, fall far short from what is expected. Enhancing stem cells local density and longevity would possibly maximize their healing potential. One promising strategy is to administer stem cells via injectable hydrogels. However, stem cells differentiation process is a delicate matter which is easily affected by various factors such as their interaction with their surrounding materials. Among various biomaterial options for hydrogels' production, hyaluronic acid (HA) has shown great promise. HA is a naturally occurring biological macromolecule, a polysaccharide of large molecular weight which is involved in cell proliferation, cell migration, angiogenesis, fetal development, and tissue function. In the current study we will discuss the applications, prospects, and challenges of HA-based hydrogels in stem cell delivery and fate control.

From shaping to functionalization of micro-droplets and particles

The structure of microdroplet and microparticle is a critical factor in their functionality, which determines the distribution and sequence of physicochemical reactions. Therefore, the technology of precisely tailoring their shape is requisite for implementing the user demand functions in various applications. This review highlights various methodologies for droplet shaping, classified into passive and active approaches based on whether additional body forces are applied to droplets to manipulate their functions and fabricate them into microparticles. The passive approaches cover batch emulsification, solvent evaporation and diffusion, micromolding, and microfluidic methods. In active approaches, the external forces, such as electrical and magnetic fields or optical lithography, are applied to microdroplets. Special attention is also given to latest technologies using microdroplets and microparticles, especially in the fields of biological, optical, robotic, and environmental applications. Finally, this review aims to address the advantages and disadvantages of the introduced approaches and suggests the direction for further development in this field.