Centrifugal Microfluidic Synthesis of Nickel Sesquioxide Nanoparticles

Nickel sesquioxide (Ni2O3) nanoparticles were synthesized using centrifugal microfluidics in the present study. The obtained nanoparticles were characterized using SEM to investigate their morphology and microstructure, and XRD was employed to analyze their purity. The nanoparticle size data were measured and analyzed using ImageJ (v1.8.0) software. The flow process and mixing procedure were monitored through computational fluid dynamics simulation. Among the synthesized Ni2O3 nanoparticles, those obtained at the rotation speed of 1000 rpm for 10 min with angular acceleration of 4.2 rad/s2 showed the best performance in terms of high purity, complete shape and microstructure, small diameter, and narrow diameter distribution. The experimental results demonstrate that the rotation speed of the microfluidic chip and reaction time contribute to a decrease in particle diameter and a narrower diameter distribution range. In contrast, an increase in acceleration of the rotation speed leads to an expanded nanoparticle size range and, thus, a wider distribution. These findings contribute to a comprehensive understanding of the effects exerted by various factors in centrifugal microfluidics and will provide new insights into nanoparticle synthesis using centrifugal microfluidic technology.

Recent Progress of Droplet Microfluidic Emulsification Based Synthesis of Functional Microparticles

The remarkable control function over the functional material formation process enabled by droplet microfluidic emulsification approaches can lead to the efficient and one-step encapsulation of active substances in microparticles, with the microparticle characteristics well regulated. In comparison to the conventional fabrication methods, droplet microfluidic technology can not only construct microparticles with various shapes, but also provide excellent templates, which enrich and expand the application fields of microparticles. For instance, intersection with disciplines in pharmacy, life sciences, and others, modifying the structure of microspheres and appending functional materials can be completed in the preparation of microparticles. The as-prepared polymer particles have great potential in a wide range of applications for chemical analysis, heavy metal adsorption, and detection. This review systematically introduces the devices and basic principles of particle preparation using droplet microfluidic technology and discusses the research of functional microparticle formation with high monodispersity, involving a plethora of types including spherical, nonspherical, and Janus type, as well as core-shell, hole-shell, and controllable multicompartment particles. Moreover, this review paper also exhibits a critical analysis of the current status and existing challenges, and outlook of the future development in the emerging fields has been discussed.

Scalable Production of Biomedical Microparticles via High-Throughput Microfluidic Step Emulsification

Drug microcarriers are widely used in disease treatment, and microfluidics is well established in the preparation of microcarrier particles. A proper design of the microfluidic platform toward scalable production of drug microcarriers can extend its application values in wound healing, where large numbers of microcarriers are required. Here, a microfluidic step emulsification method for the preparation of monodisperse droplets is presented. The droplet size depends primarily on the microchannel depth rather than flow rate, making the system robust for high-throughput production of droplets and hydrogel microparticles. Based on this platform, basic fibroblast growth factor (bFGF) is uniformly encapsulated in the microparticles, and black phosphorus (BP) is incorporated for controllable release via near-infrared (NIR) stimulation. The microparticles serve as drug carriers to be applied to the wound site, inducing angiogenesis and collagen deposition, thereby accelerating wound repair. These results indicate that the step emulsification technique provides a promising solution to scalable production of drug microcarriers for wound healing as well as tissue regeneration.

Design of functional nanoparticles by microfluidic platforms as advanced drug delivery systems for cancer therapy

Nanoparticle systems are functional carriers that can be used in the cancer therapy field for the delivery of a variety of hydrophobic and/or hydrophilic drugs. Recently, the advent of microfluidic platforms represents an advanced approach to the development of new nanoparticle-based drug delivery systems. Particularly, microfluidics can simplify the design of new nanoparticle-based systems with tunable physicochemical properties such as size, size distribution and morphology, ensuring high batch-to-batch reproducibility and consequently, an enhanced therapeutic effect in vitro and in vivo. In this perspective, we present accurate state-of-the-art microfluidic platforms focusing on the fabrication of polymer-based, lipid-based, lipid/polymer-based, inorganic-based and metal-based nanoparticles for biomedical applications.

Controlled generation of droplets using an electric field in a flow-focusing paper-based device

Droplet-based microfluidics is a modular platform in high-throughput single-cell and small sample analyses. However, this droplet microfluidic system was widely fabricated using soft lithography or glass capillaries, which is expensive and technically demanding for various applications, limiting use in resource-poor settings. Besides, the variation in droplet size is also restricted due to the limitations on the operating forces that the paper-based platform is able to withstand. Herein, we develop a fully integrated paper-based droplet microfluidic platform for conducting droplet generation and cell encapsulation in independent aqueous droplets dispersed in a carrier oil by incorporating electric fields. Through imposing an electric field, the droplet size would decrease with increasing the electric field and smaller droplets can be produced at high applied voltage. The droplet diameter can be adjusted by the ratio of inner and outer flow velocities as well as the applied electric field. We also demonstrated the proof of concept encapsulation application of our paper device by encapsulating yeast cells under an electric field. Using a simple wax printing method, carbon electrodes can be integrated on the paper. The integrated paper-based microfluidic platform can be fabricated easily and conducted outside of centralized laboratories. This microfluidic system shows great potential in drug and cell investigations by encapsulating cells in resource-limited environments.

Polymer based nanoparticles for biomedical applications by microfluidic techniques: from design to biological evaluation

The development of microfluidic technologies represents a new strategy to produce and test drug delivery systems.

Microfluidics for core-shell drug carrier particles - a review

Core-shell drug-carrier particles are known for their unique features. Due to the combination of superior properties not exhibited by the individual components, core-shell particles have gained a lot of interest. The structures could integrate core and shell characteristics and properties. These particles were designed for controlled drug release in the desired location. Therefore, the side effects would be minimized. So, these particles' advantages have led to the introduction of new methods and ideas for their fabrication. In the past few years, the generation of drug carrier core-shell particles in microfluidic chips has attracted much attention. This method makes it possible to produce particles at nanometer and micrometer levels of the same shape and size; it usually costs less than other methods. The other advantages of using microfluidic techniques compared to conventional bulk methods are integration capability, reproducibility, and higher efficiency. These advantages have created a positive outlook on this approach. This review gives an overview of the various fluidic concepts that are used to generate microparticles or nanoparticles. Also, an overview of traditional and more recent microfluidic devices and their design and structure for the generation of core-shell particles is given. The unique benefits of the microfluidic technique for core-shell drug carrier particle generation are demonstrated.

Modular off-chip emulsion generator enabled by a revolving needle

Microfluidic chips have demonstrated unparalleled abilities in droplet generation, including precise control over droplet size and monodispersity. And yet, their rather complicated microfabrication process and operation can be a barrier for inexperienced researchers, which hinders microdroplets from unleashing their potential in broader fields of research. Here, we attempt to remove this barrier by developing an integrated and modular revolving needle emulsion generator (RNEG) to achieve high-throughput production of uniformly sized droplets in an off-chip manner. The RNEG works by driving a revolving needle to pinch the dispersed phase in a minicentrifuge tube. The system is constructed using modular components without involving any microfabrication, thereby enabling user-friendly operation. The RNEG is capable of producing microdroplets of various liquids with diameters ranging from tens to hundreds of micrometres. We further examine the principle of operation using numerical simulations and establish a simple model to predict the droplet size. Moreover, by integrating curing and centrifugation processes, the RNEG can produce hydrogel microparticles and transfer them from an oil phase into a water phase. Using this ability, we demonstrate the encapsulation and culture of single yeast cells within hydrogel microparticles. We envisage that the RNEG can become a versatile and powerful tool for high-throughput production of emulsions to facilitate diverse biological and chemical research.