One-step rapid preparation of CL-20/TNT co-crystal assembly and spheroidized coating based on droplet microfluidic technology

Energetic materials pose challenges in preparation and handling due to their contradictory properties of high-energy and low-sensitivity.The emergence of co-crystal explosives is a new opportunity to change this situation.If the co-crystal explosive is coated into spherical particles with uniform particle size distribution,this contradiction can be further reduced.Therefore,binder-coated hexanitrohexaazaisowurtzitane/2,4,6-trinitrotoluene(CL-20/TNT)co-crystal microspheres were prepared by droplet microfluidic technology in this work.The coating effects of different binder formulations of nitrocellulose(NC)and NC/fluorine rubber(F2604)on the co-crystal spheres were studied.The scanning electron microscopy(SEM)results showed that the use of droplet microfluidic technology with the above binders can provide co-crystal microspheres with regular spherical morphology,uniform particle size distribution and good dispersion.X-ray diffraction(XRD),fourier-transform infrared(FT-IR),differential scanning calorimetry(DSC)and thermo-gravimetric(TG)methods were employed to compare the properties of the co-crystal microspheres,raw material and pure co-crystal.The formation of CL-20/TNT co-crystal in the microspheres was confirmed,and the co-crystal microspheres exhibited better thermal stability than the raw material and pure co-crystal.In addition,the mechanical sensitivity and combustion performance of the co-crystal microspheres were further studied.The results showed that the co-crystal microspheres were more insensitive than CL-20 and pure co-crystal,and displayed excellent self-sustained combustion performance and theoretical detonation performance.This study provides a new method for the fast,simple and one-step preparation of CL-20/TNT co-crystal microspheres,with binder coating,uniform particle size distribution,and excellent performance level.

High-throughput microfluidic production of carbon capture microcapsules:fundamentals,applications,and perspectives

In the last three decades,carbon dioxide(CO_(2)) emissions have shown a significant increase from various sources.To address this pressing issue,the importance of reducing CO_(2) emissions has grown,leading to increased attention toward carbon capture,utilization,and storage strategies.Among these strategies,monodisperse microcapsules,produced by using droplet microfluidics,have emerged as promising tools for carbon capture,offering a potential solution to mitigate CO_(2) emissions.However,the limited yield of microcapsules due to the inherent low flow rate in droplet microfluidics remains a challenge.In this comprehensive review,the high-throughput production of carbon capture microcapsules using droplet microfluidics is focused on.Specifically,the detailed insights into microfluidic chip fabrication technologies,the microfluidic generation of emulsion droplets,along with the associated hydrodynamic considerations,and the generation of carbon capture microcapsules through droplet microfluidics are provided.This review highlights the substantial potential of droplet microfluidics as a promising technique for large-scale carbon capture microcapsule production,which could play a significant role in achieving carbon neutralization and emission reduction goals.

Hydrophilic surface modification of PDMS for droplet microfluidics using a simple,quick,and robust method via PVA deposition

Polydimethylsiloxane(PDMS)is a dominant material in the fabrication of microfluidic devices to generate water-in-oil droplets,particularly lipid-stabilized droplets,because of its highly hydrophobic nature.However,its key property of hydrophobicity has hindered its use in the microfluidic generation of oil-in-water droplets,which requires channels to have hydrophilic surface properties.In this article,we developed,optimized,and characterized a method to produce PDMS with a hydrophilic surface via the deposition of polyvinyl alcohol following plasma treatment and demonstrated its suitability for droplet generation.The proposed method is simple,quick,effective,and low cost and is versatile with respect to surfactants,with droplets being successfully generated using both anionic surfactants and more biologically relevant phospholipids.This method also allows the device to be selectively patterned with both hydrophilic and hydrophobic regions,leading to the generation of double emulsions and inverted double emulsions.

High-throughput droplet microfluidic synthesis of hierarchical metal-organic framework nanosheet microcapsules

Using two-dimensional(2D)metal-organic framework(MOF)nanosheets as new building blocks to create more complex architectures at the mesoscopic/macroscopic scale has attracted extensive interest in recent years.Nevertheless,it remains a great challenge to assemble MOF nanosheets into hierarchical hollow structures so far.In this paper,we describe a successful example of hierarchical MOF nanosheet microcapsules,with precisely controlled sizes,produced on large scale within minutes with a continuous droplet microfluidic strategy.Following a reaction/diffusion growth mechanism,the microcapsule shells feature a continuous smooth inner layer and a porous outer layer.Such hierarchical structure enables the encapsulation of magnetite nanoparticles inside and loading of dense gold nanoparticles outside the microcapsules,which exhibit highly efficient heterogeneous catalytic activity and easy recyclability.The present microfluidic assembly method offers a new pathway for preparing hierarchical MOF nanosheet structures,with the potential for extension to the formation of other 2D nanosheets in general.

Integration of Droplet Microfluidic Tools for Single-cell Functional Metagenomics:An Engineering Head Start

Droplet microfluidic techniques have shown promising outcome to study single cells at high throughput.However,their adoption in laboratories studying“-omics”sciences is still irrelevant due to the complex and multidisciplinary nature of the field.To facilitate their use,here we provide engineering details and organized protocols for integrating three droplet-based microfluidic technologies into the metagenomic pipeline to enable functional screening of bioproducts at high throughput.First,a device encapsulating single cells in droplets at a rate of~250 Hz is described considering droplet size and cell growth.Then,we expand on previously reported fluorescence-activated droplet sorting systems to integrate the use of 4 independent fluorescence-exciting lasers(i.e.,405,488,561,and 637 nm)in a single platform to make it compatible with different fluorescence-emitting biosensors.For this sorter,both hardware and software are provided and optimized for effortlessly sorting droplets at 60 Hz.Then,a passive droplet merger is also integrated into our pipeline to enable adding new reagents to already-made droplets at a rate of 200 Hz.Finally,we provide an optimized recipe for manufacturing these chips using silicon dry-etching tools.Because of the overall integration and the technical details presented here,our approach allows biologists to quickly use microfluidic technologies and achieve both single-cell resolution and high-throughput capability(>50,000 cells/day)for mining and bioprospecting metagenomic data.

Recent advances in droplet microfluidics for microbiology

Advances in microbiology rely on innovations in technology. Droplet microfluidics, as a versatile and powerful technique that allows high-throughput generation and manipulation of subnanoliter volume droplets, has become an indispensable tool shifting experimental paradigms in microbiology. Droplet microfluidics has opened new avenues to various microbiological research, from resolving single-cell heterogeneity to investigating spatiotemporal dynamics of microbial communities, from precise quantitation of microbiota to systematic decipherment of microbial interactions, and from isolating rare and uncultured microbes to improving genetic engineered strains. In this review, we present recent advances of droplet microfluidics in various fields of microbiology: i) microbial cultivation, ii) microorganism detection and characterization, iii) antibiotic susceptibility testing, iv) microbial interactions, v) microbial biotechnology.We also provide our perspectives on the challenges and future directions for droplet microfluidic-based microbiology research.

Effect of injection angle,density ratio,and viscosity on droplet formation in a microfluidic T-junction

The T-junction microchannel device makes available a sharp edge to form micro-droplets from biomaterial solutions. This article investigates the effects of injection angle, flow rate ratio, density ratio,viscosity ratio, contact angle, and slip length in the process of formation of uniform droplets in microfluidic T-junctions. The governing equations were solved by the commercial software. The results show that contact angle, slip length, and injection angles near the perpendicular and parallel conditions have an increasing effect on the diameter of generated droplets, while flow rate, density and viscosity ratios, and other injection angles had a decreasing effect on the diameter.

Crystal phase control and ignition properties of HNS/CL-20 composite microspheres prepared by microfluidics combined with emulsification techniques

Improved controllability and energy density of ignition agents are of great significance for the devel-opment of energetic composite materials.In this study,droplet microfluidics and emulsification tech-niques were combined to prepare HNS/CL-20 composite microspheres with polyglycidyl azide polymer(GAP)as the binder.The influence of binder content on the morphology of microspheres was investi-gated,and the microspheres were characterized and tested for particle size,crystal structure,thermal decomposition,dispersibility,mechanical sensitivity,combustion behavior and detonation performance.The results showed that microspheres prepared with a binder content of 3%had higher sphericity and particle size uniformity.The microspheres retained the crystal structure of both HNS and CL-20(ε-type).Compared with raw HNS,the microspheres had higher apparent activation energy,better safety per-formance,and good dispersibility.The ignition experiments and detonation performance tests show that HNS/CL-20 composite microspheres have excellent ignition performance,obvious combustion flame,and significant energy release effects,which are expected to achieve high energy and high-speed response of the igniter,thus improving the ignition reliability in special environments or systems.

Automated and miniaturized screening of antibiotic combinations via robotic-printed combinatorial droplet platform

Antimicrobial resistance(AMR)has become a global health crisis in need of novel solutions.To this end,antibiotic combination therapies,which combine multiple antibiotics for treatment,have at-tracted significant attention as a potential approach for combating AMR.To facilitate advances in anti-biotic combination therapies,most notably in investigating antibiotic interactions and identifying synergistic antibiotic combinations however,there remains a need for automated high-throughput plat-forms that can create and examine antibiotic combinations on-demand,at scale,and with minimal reagent consumption.To address these challenges,we have developed a Robotic-Printed Combinatorial Droplet(RoboDrop)platform by integrating a programmable droplet microfuidic device that generates antibiotic combinations in nanoliter droplets in automation,a robotic arm that arranges the droplets in an array,and a camera that images the array of thousands of droplets in parallel.We further implement a resazurin-based bacterial viability assay to accelerate our antibiotic combination testing.As a demonstration,we use RoboDrop to corroborate two pairs of antibiotics with known interactions and subsequently identify a new synergistic combination of cefsulodin,penicillin,and oxacillin against a model E.coli strain.We therefore envision RoboDrop becoming a useful tool to efficiently identify new synergistic antibiotic combinations toward combating AMR.

Functional Surfactants for Molecular Fishing,Capsule Creation,and Single-Cell Gene Expression

Creating a single surfactant that is open to manipulation,while maintaining its surface activity,robustness,and compatibility,to expand the landscape of surfactant-dependent assays is extremely challenging.We report an oxidation-responsive precursor with thioethers and multiple 1,2-diols for creating a variety of functional surfactants from one parent surfactant.Using these multifunctional surfactants,we stabilize microfluidics-generated aqueous droplets.The droplets encapsulate different components and immerse in a bioinert oil with distinct interfaces where an azide-bearing surfactant allow fishing of biomolecules from the droplets,aldehyde-bearing surfactant allow fabrication of microcapsules,and hydroxyl-bearing surfactants,with/without oxidized thioethers,allow monitoring of single-cell gene expression.Creating multifunctional surfactants poses opportunities for broad applications,including adsorption,bioanalytics,catalysis,formulations,coatings,and programmable subset of emulsions.

Recent developments of droplets-based microfluidics for bacterial analysis

Droplet-based microfluidics enables the generation of uniform microdroplets at picoliter or nanoliter scale with high frequency(∼kHz)under precise control.The droplets can function as bioreactors for versatile chemical/biological study and analysis.Taking advantage of the discrete compartment with a confined volume,(1)isolation and manipulation of a single cell,(2)improvement of in-droplet effective concen-trations,(3)elimination of heterogeneous population effects,(4)diminution of contamination risks can be achieved,making it a powerful tool for rapid,sensitive,and high-throughput detection and analysis of bacteria,even for rare or unculturable strains in conventional methods.This mini-review will focus on the generation and manipulation of micro-droplets and bacteria detection and analysis carried out by droplet-based microfluidics.Finally,applications with high potential of droplet-based bacteria analysis are briefly introduced.Due to the advantages of rapid,sensitive,high throughput,and compatibility with rare and unculturable bacteria in conventional methods,droplet-based microfluidics has tremendous potential of providing novel solutions for biological medicine,microbiological engineering,environmental ecology,etc.

Ultrasensitive detection of DNA and protein markers in cancer cells

Cancer cells differ from normal cells in various parameters, and these differences are caused by genomic mutations and consequential altered gene expression. The genetic and functional heterogeneity of tumor cells is a major challenge in cancer research, detection, and effective treatment. As such, the use of diagnostic methods is important to reveal this heterogeneity at the single-cell level. Droplet microfluidic devices are effective tools that provide exceptional sensitivity for analyzing single cells and molecules. In this review, we highlight two novel methods that employ droplet microfluidics for ultrasensitive detection of nucleic acids and protein markers in cancer cells. We also discuss the future practical applications of these methods.

Role of binders in reactive composites: A case study with spherical B/Pb_(3)O_(4) particles

The strategic selection of appropriate preparation methods and binder strategies is crucial for enhancing the particle and combustion performance of pyrotechnic delay compositions(PDCs).This study,utilizing droplet microfluidics technology(DMT)and micron-scale raw materials,prepared spherical B/Pb_(3)O_(4) composite particles with varying concentrations of fluorine rubber(F_(2604)).The morphology,specific surface area,bulk density,flowability,friction sensitivity,thermal decomposition,and combustion performance of these microspheres were characterized.The results indicate that as the binder content increases,the particle size of the microspheres first decreases and then increases,the specific surface area decreases,and the bulk density increases,correlating with tighter binding of the reactant powders by the binder.Furthermore,tighter powder-to-powder binding results in a progressive decrease in the thermal decomposition peak temperature of the samples(from 404.2℃ to 346.4℃).Additionally,increased binder content reduces the friction sensitivity and combustion rate of the samples,which is attributed to the energy absorption properties of the binder.Compared to the control group,the microsphere samples exhibit significantly enhanced bulk density,flowability,friction safety,and combustion delay precision,potentially improving the reliability of PDCs in ignition sequences.

Measurement of copy number variation in single cancer cells using rapid-emulsification digital droplet MDA

Uniform amplification of low-input DNA is important for applications across biology,including single-cell genomics,forensic science,and microbial and viral sequencing.However,the requisite biochemical amplification methods are prone to bias,skewing sequence proportions and obscuring signals relating to copy number.Digital droplet multiple displacement amplification enables uniform amplification but requires expert knowledge of microfluidics to generate monodisperse emulsions.In addition,existing microfluidic methods are tedious and labor intensive for preparing many samples.Here,we introduce rapid-emulsification multiple displacement amplification,a method to generate monodisperse droplets with a hand-held syringe and hierarchical droplet splitter.Although conventional microfluidic devices require >10 min to emulsify a sample,our system requires tens of seconds and yields data of equivalent quality.We demonstrate the approach by using it to accurately measure copy number variation(CNV)in single cancer cells.

Function of hepatocyte spheroids in bioactive microcapsules is enhanced by endogenous and exogenous hepatocyte growth factor

The ability to maintain functional hepatocytes has important implications for bioartificial liver development,cell-based therapies,drug screening,and tissue engineering.Several approaches can be used to restore hepatocyte function in vitro,including coating a culture substrate with extracellular matrix(ECM),encapsulating cells within biomimetic gels(Collagen-or Matrigel-based),or co-cultivation with other cells.This paper describes the use of bioactive heparin-based core-shell microcapsules to form and cultivate hepatocyte spheroids.These microcapsules are comprised of an aqueous core that facilitates hepatocyte aggregation into spheroids and a heparin hydrogel shell that binds and releases growth factors.We demonstrate that bioactive microcapsules retain and release endogenous signals thus enhancing the function of encapsulated hepatocytes.We also demonstrate that hepatic function may be further enhanced by loading exogenous hepatocyte growth factor(HGF)into microcapsules and inhibiting transforming growth factor(TGF)-β1 signaling.Overall,bioactive microcapsules described here represent a promising new strategy for the encapsulation and maintenance of primary hepatocytes and will be beneficial for liver tissue engineering,regenerative medicine,and drug testing applications.

Bioactive hydrogel microcapsules for guiding stem cell fate decisions by release and reloading of growth factors

Human pluripotent stem cells(hPSC)hold considerable promise as a source of adult cells for treatment of diseases ranging from diabetes to liver failure.Some of the challenges that limit the clinical/translational impact of hPSCs are high cost and difficulty in scaling-up of existing differentiation protocols.In this paper,we sought to address these challenges through the development of bioactive microcapsules.A co-axial flow focusing microfluidic device was used to encapsulate hPSCs in microcapsules comprised of an aqueous core and a hydrogel shell.Importantly,the shell contained heparin moieties for growth factor(GF)binding and release.The aqueous core enabled rapid aggregation of hPSCs into 3D spheroids while the bioactive hydrogel shell was used to load inductive cues driving pluripotency maintenance and endodermal differentiation.Specifically,we demonstrated that one-time,1 h long loading of pluripotency signals,fibroblast growth factor(FGF)-2 and transforming growth factor(TGF)-β1,into bioactive microcapsules was sufficient to induce and maintain pluripotency of hPSCs over the course of 5 days at levels similar to or better than a standard protocol with soluble GFs.Furthermore,stem cell-carrying microcapsules that previously contained pluripotency signals could be reloaded with an endodermal cue,Nodal,resulting in higher levels of endodermal markers compared to stem cells differentiated in a standard protocol.Overall,bioactive heparin-containing core-shell microcapsules decreased GF usage five-fold while improving stem cell phenotype and are well suited for 3D cultivation of hPSCs.

Recent advances in the production of controllable multiple emulsions using microfabricated devices

This review focuses on recent developments in the fabrication of multiple emulsions in micro-scale systems such as membranes, microchannel array, and microfluidic emulsification devices. Membrane and microchannel emulsification offer great potential to manufacture multiple emulsions with uniform drop sizes and high encapsulation efficiency of encapsulated active materials. Meanwhile, microfluidic devices enable an unprecedented level of control over the number, size, and type of internal droplets at each hierarchical level but suffer from low production scale. Microfluidic methods can be used to generate high-order multiple emulsions （triple, quadruple, and quintuple）, non-spherical （discoidal and rod-like） drops, and asymmetric drops such as Janus and ternary drops with two or three distinct surface regions. Multiple emulsion droplets generated in microfabricated devices can be used as templates for vesicles like polymersomes, liposomes, and colloidosomes with multiple inner compartments for simultaneous encaosulation and release of incomoatible active materials or reactants.

Crosstalk-free colloidosomes for high throughput single-molecule protein analysis

Droplet microfluidics is a powerful platform for high-throughput single-molecule protein analysis.However,the issues of coalescence and crosstalk of droplets compromise the accuracy of detection and hinder its wide application.To address these limitations,a novel colloidosome-based method was presented by combining a Pickering emulsion with droplet microfluidics for single-molecule protein analysis.Utilizing the self-assembly of easily synthesized colloidal surfactant F-SiO2 NPs at the water/oil interface,the colloidosomes are rigidly stabilized and can effectively avoid the leakage of fluorescent molecules.The crosstalk-free colloidosomes enable high-throughput single-molecule protein analysis,including heterogenous dynamic studies and digital detection.As a robust and accurate method,colloidosome-based microfluidics is promising as a powerful tool for a wide variety of applications,such as directed enzyme evolution,digital enzyme-linked immunosorbent assay(ELISA),and screening of antibiotics.