Another experiment on calcium(II) extraction was carried out using ionic liquids as the extraction reagent, named 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM NTf2) and 1-butyl-3-methylimidazolium azolium bis(trifluoromethylsulfonyl)imide (BMIM NTf2) in a Y-type droplet microfluidic device. Muto and co-workers investigated the extraction process of lithium using D2EHPA in a droplet microfluidic device.
Precious metals
From the preliminary study of lithium extraction using the monoacetic acid derivative of calix[4]arene (shown in Figure 4 as 1 Ac) on the individual metal extraction, it was found that 100% of lithium ions were quantitatively extracted just within 2.00 s. the extraction time. Using 1.00 M HCl, as much as 99.5% of lithium ions were successfully stripped from the ligand, which is remarkable.
Rare-earth metals
Even though only 54.8% silver(I) ions were stripped from the first cycle with 2.0 M ammonium thiocyanate, as much as 94.4% silver(I) ions were recovered in the second cycle. On the other hand, 27.4 and 37.2% platinum(IV) ions were extracted in the first and second cycles of extraction process using a tetrapyridyl derivative of calix[4].
Heavy metals
This phenomenon was caused by the shorter diffusion distance and larger specific surface area of the T-type droplet microfluidic device than the Y-type [ 60 ]. In addition, lead(II) ions were easily removed to 98% using distilled water as the removal reagent, which is a convenient and inexpensive procedure.
Conclusions
Liquid-liquid extraction of lithium ions using a slug flow microreactor: Effect of extraction reagent and microtube material. Microfluidic solvent extraction of Ce(III) and Pr(III) from a chloride solution using EHEHPA (P507) in a serpentine microreactor.
TOP 1%
Introduction
Gañán-Calvo first introduced the use of micron-scale capillaries, later established by Thorsen et al. This opened a whole new wave of interest in microfluidic systems in a wide range of fields, such as biochemical, engineering and pharmaceutical benefits from the advantages of small and precise. Droplet-based microfluidics, a subcategory of microfluidics, focuses on the discrete volume creation using immiscible fluids and allows the handling of fluids under limited spatial and temporal control.
The proverbial use of lab-on-a-chip (LOC) in various biochemical assays is driven by the time and cost efficiency of performing low-volume, high-throughput automated assays. This allows the synthesis of functional droplets such as microcapsules for drug delivery and encapsulation of cells, microparticles and various types of Janus particles. Likewise, there has also been an increase in the design and fabrication of new and innovative devices in droplet microfluidics, which are supposed to enable easier and more cost-effective approaches to droplet generation, such as using devices available in market.
Different applications where microfluidic approach is used have different prerequisites for commercialization, for example for material synthesis such as catalyst preparation or drug formulations, high throughput is expected to generate sufficient material, while throughput for chemical/biological assays may not be a focus criterion, instead the development of chip-to-world interfaces for stable connection with analytical units will be crucial.
Summary of existing droplet-based microfluidic technology
Soft lithography, an extension from conventional photolithography, allows the lithographic master to be used for rapid prototyping of elastomeric material such as polydimethylsiloxane (PDMS). Its internal properties, such as high gas permeability and optical transparency have even greatly expanded its use in biomedical research such as cell culture and tissue analysis [16]. With the wide choices available, researchers often make their choices for the development of microfluidic systems based on applications, material compatibility, ease of fabrication, as well as the initial cost incurred; many methods/techniques remain undeveloped or have ceased to be developed apparently due to high start-up cost.
While glass and PDMS have been widely used in the initiation of many microfluidic research and applications, the well-known disadvantages associated with the fabrication and use of these materials have often been deliberately overlooked by the microfluidic community. There has been a growing interest in the development of materials such as polymethymethacrylate (PMMA), polycarbonate and cyclic olefin (co)polymers through microfabrication techniques such as hot stamping, injection molding, microfabrication and stereolithography [20, 21]. Hot stamping and injection molding are both repetitive techniques similar to soft lithography, using thermoplastic materials.
In hot stamping, thermoplastic film is patterned against a die, and the casting is formed as molds.
Some novel and innovative designs of droplet generators 1 Off-the-shelf devices
According to Benson et al., the device can produce both oil-in-water (O/W) and water-in-oil (W/O) emulsions by just rinsing with ethanol before forming the other, and the device is also reusable and can be disassembled for cleaning. The device is mainly composed of dosing needles of different sizes (60–1550 μm) and assembled with mini T- and cross-connections as shown in Figure 4. The stainless steel dosing needles are arranged and aligned to form microchannels for the flow of immiscible phases. Assembly of the device is done with the help of plastic pipes and UV curable glue.
The droplet size can be controlled by varying the needle used as well as the flow rate of each stage. To the best of the author's knowledge, there is no work reported yet on parallelizing off-the-shelf devices. Additive manufacturing (3D printing) has been widely adopted in the fabrication of microfluidic devices as the technology advances in generating structures with ever higher precision.
The shape of the droplet is distorted due to the electro-hydrodynamic flow patterns inside and outside the droplet.
Droplet-based microfluidics: now and then
- Microfluidic emulsification: toward parallelization
- From “proof of concept” to commercialization
The demonstration of plug-and-play modular devices is believed to be able to partially solve the world's long-standing chip connectivity problems. particles for commercial applications; however, there is no other information on the status of the parallelized device, if the technology is commercialized. Inkjet printing is a classic example of a microfluidic application commercialized to date, having been developed in the 1950s and commercialized and largely manufactured in the 1970s for printing digital images, via push dots on paper. After the debut of inkjet printing, a particularly limited number of microfluidic applications successfully came to market in the following years, mainly in the fields of microfluidic genotyping and POC diagnostics.
Alas, the overwhelming achievements in microfluidic research and development are not reflected in the slow market uptake of microfluidic technology. The industrial realization of microfluidic innovations is mostly held back by the inflexibility of microfluidic components for integration, economic non-viability and the lack of standardization. Automatic and assembly-free prototyping of simple devices is considered a goal that cannot be achieved in the near future.
The extensive lateral development of microfluidic studies and the lack of standardization of methods and materials instead become the stumbling block for a standard microfluidic solution to reach mainstream applications, delaying the commercial adoption of the technology [5, 44].
Conclusion
Microfluidic devices generally have two of three geometric length scales on the order of microns. Recent developments and innovations could make microfluidic technology ubiquitous and create microfluidic devices that are more functional, efficient and cost-effective than conventional techniques. The development of microfluidic systems that enable microdroplet formation in microfluidic devices has received significant attention over the past 20 years.
The increase in interest is due to the use of microfluidic devices in a wide range of biological and biomedical applications, including disease diagnosis, cell therapy, drug screening, single cell analysis, and drug delivery. In terms of practicality and high capacity, microfluidic platforms generally suffer from the high cost and limited capacity for high capacity production of microfluidic synthesized particles. Moreover, the basic microfluidic research is still in high demand to bridge the gap between the functional material synthesis and the industrial perspective of exploring the possibilities and potential benefits of microfluidic processes [2, 13].
Finally, this chapter provides an impression of what the consolidated areas of microfluidic formulation in functional materials synthesis will look like in about a decade from now.
Microfluidic technology for water remediation and resource recovery Due to excessive discharges of harmful wastes and by-products to the environ-
- Droplet microfluidic system
- Microfluidic reactors
The development and application of several AOP mechanisms will be discussed in the next sub-section. Then, a brief example of the application of different types of microreactors in water treatment and resource recovery is listed in Table 2. The application of microfluidic technology offers a large number of advantages in photocatalytic water treatment.
Moreover, microfluidic layer has short diffusion length, typically 10–100 μm to facilitate the diffusion of organic pollutants to the reaction surface [31]. The microreactor has a self-refreshing effect, as the flowing liquid can refresh the reaction surface naturally. The Electro-Fenton process is extremely effective for water treatment of the wastewater that cannot be effectively treated using biological technologies [39-41].
The application of microfluidic technology in PWT provides the advantages of large surface-area-to-volume ratio and flow control in inexpensive and portable devices [27].
Droplet microfluidics for the production of micro- or nanofunctional sorbents
- Emulsion template: single, double or multiple
Droplet microfluidics for the production of micro or nanofunctional sorbents. produced as single, double and multiple emulsion [17, 47]. These five modes have their own characteristics, for example, the structure and composition of the droplets can be changed to produce inorganic nanoparticles, metal particles and polymer particles [49]. Non-spherical particles have unique properties and they are usually fabricated by many strategies such as seed emulsion polymerization [50], template formation [51] and self-assembly [52].
However, non-spherical, monodisperse, high-quality particles with tailored geometries and shapes are still difficult to produce using these methods. Droplets of different sizes and shapes in microfluidic channels are confined with microfluidic technology for the fabrication of non-spherical particles. There are various types of spherical particles, such as polymer microspheres, inorganic microspheres, noble metal nanospheres, and semiconductor nanospheres [48].
Nanospheres of precious metals such as gold, silver and platinum have properties that depend on their shape and size.
Sorption performance of different functional micro-sorbents for pollutants removal
- Application and sorption performance of chitosan-based microsorbents Chitosan is a natural polymer material that is found in abundance. It is made
- Application and sorption performance of non-chitosan-based microsorbents Aside from chitosan, other microfluidic synthesized materials such as graphene
In this subsection, the sorption performance of different functional microsorbents will be discussed, as well as the kinetic model and adsorption isotherm. 2] both reported that the sorption performance of chitosan microspheres in the absorption of the common textile azo dyes. Apart from synthetic dyes, chitosan microspheres were also synthesized to remove copper(II) ions, the sorption performance was about 38.52 mg/g [29].
65] synthetic sized anisotropic Janus microparticles loaded with Fe3O4 and MnO2 nanoparticles for the adsorption of basic dyes in wastewater. The suction performance of ink pick-up using Janus micromotors can range from 47 to 94%. Ion-embedded chitosan microspheres Adsorption of heavy metal copper (II) ions qmax: 81.97 mg/g (Ce < 400 ppm).
Chitosan/silica hybrid microspheres Adsorption of heavy metal copper (II) ions qmax: 53 mg/g (100 ppm) Not available Not available [60].
