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Special Issue "Droplet Microfluidics: A Tool for Biology, Chemistry and Materials Engineering"

A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: 30 April 2021.

Special Issue Editors

Dr. Goran T. Vladisavljević
Website
Guest Editor
Department of Chemical Engineering, Loughborough University, Loughborough, UK
Interests: microfluidics; emulsions; membranes; colloid and interface science; nanoprecipitation; microencapsulation; microparticles; carbon capture; healthcare engineering
Dr. Guido Bolognesi
Website
Guest Editor
Department of Chemical Engineering, Loughborough University, Loughborough, UK
Interests: microfluidics; colloid and interface science; soft matter; synthetic biology; emulsions; lipid membranes; particle manipulation; optical tweezers; optical microscopy; microfabrication

Special Issue Information

Dear Colleagues,

Droplet microfluidics is a branch of fluid mechanics, soft condensed matter physics, and microtechnology dealing with droplet generation and manipulation in micrometre-sized structures. Droplets can be generated in microfluidic systems using a variety of different geometries and methods, such as on-demand droplet dispensing, electrowetting processes, microfluidic junctions, flow focusing channels, terrace and edge-based structures, air nozzles, and membrane emulsification. Applications of droplet microfluidics benefit from the ability of microfluidic systems to generate and manipulate droplets in a highly controllable fashion and to incorporate, integrate and synchronise numerous operations and processes within a single microfabricated entity, including droplet generation, indexing, splitting, merging, reagent dosing, encapsulating, incubating, analysing, sorting and manipulating under various fields (electric, acoustic, magnetic, optical, temperature, etc.) either in closed or open systems. Further, droplets can serve as microreactors for chemical and biochemical synthesis, analysis and diagnostics or templates for the synthesis of advanced and functional materials and bio-materials.  

The main aims of the Special Issue “Droplet Microfluidics: A Tool for Biology, Chemistry and Materials Engineering” is to be an open forum where researchers may share their investigations and findings in this promising field and, thanks to the open access platform, increase their visibility and the chances to interact with industries and academics. Contributions to this issue, both in the form of original research or review articles, may cover all aspects of droplet generation and manipulation in microfluidic systems ranging from fundamental aspects and modelling of droplet generation and manipulation to various applications in chemistry, biology and physics such as (but not limited to) chemical synthesis and micromixing within droplets, imaging, high-throughput screening, in vitro compartmentalisation and digestion, single-cell encapsulation, production of nanoparticles and microparticles, synthesis of cell and tissue mimics and drug delivery systems. Contributions may also deal with droplet microfluidic methods and microfabrication of droplet microfluidic systems. Multidisciplinary studies offering new methodologies or insights and emerging applications such as digital microfluidics and synthetic biology applications are particularly welcome.

Dr. Goran T. Vladisavljević
Dr. Guido Bolognesi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Microfluidics
  • Microengineering
  • Microfabricated channels
  • Lab on a chip
  • Droplet generation
  • Droplet manipulation
  • Particle synthesis
  • Micromixing
  • High-throughput screening
  • Drug synthesis and discovery
  • Drug delivery
  • Small-molecule detection
  • Single-cell encapsulation
  • Lipid membranes
  • Surfactants

Published Papers (4 papers)

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Research

Open AccessArticle
Compressed Air-Driven Continuous-Flow Thermocycled Digital PCR for HBV Diagnosis in Clinical-Level Serum Sample Based on Single Hot Plate
Molecules 2020, 25(23), 5646; https://doi.org/10.3390/molecules25235646 - 30 Nov 2020
Abstract
We report a novel compressed air-driven continuous-flow digital PCR (dPCR) system based on a 3D microfluidic chip and self-developed software system to realize real-time monitoring. The system can ensure the steady transmission of droplets in long tubing without an external power source and [...] Read more.
We report a novel compressed air-driven continuous-flow digital PCR (dPCR) system based on a 3D microfluidic chip and self-developed software system to realize real-time monitoring. The system can ensure the steady transmission of droplets in long tubing without an external power source and generate stable droplets of suitable size for dPCR by two needles and a narrowed Teflon tube. The stable thermal cycle required by dPCR can be achieved by using only one constant temperature heater. In addition, our system has realized the real-time detection of droplet fluorescence in each thermal cycle, which makes up for the drawbacks of the end-point detection method used in traditional continuous-flow dPCR. This continuous-flow digital PCR by the compressed air-driven method can meet the requirements of droplet thermal cycle and diagnosis in a clinical-level serum sample. Comparing the detection results of clinical samples (hepatitis B virus serum) with commercial instruments (CFX Connect; Bio Rad, Hercules, CA, USA), the linear correlation reached 0.9995. Because the system greatly simplified the traditional dPCR process, this system is stable and user-friendly. Full article
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Open AccessArticle
Protein-Stabilized Palm-Oil-in-Water Emulsification Using Microchannel Array Devices under Controlled Temperature
Molecules 2020, 25(20), 4805; https://doi.org/10.3390/molecules25204805 - 19 Oct 2020
Abstract
Microchannel (MC) emulsification for the preparation of monodisperse oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions containing palm oil as the oil phase was investigated for application as basic material solid/semi-solid lipid microspheres for delivery carriers of nutrients and drugs. Emulsification was characterized by direct [...] Read more.
Microchannel (MC) emulsification for the preparation of monodisperse oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions containing palm oil as the oil phase was investigated for application as basic material solid/semi-solid lipid microspheres for delivery carriers of nutrients and drugs. Emulsification was characterized by direct observation of droplet generation under various operation conditions, as such, the effects of type and concentration of emulsifiers, emulsification temperature, MC structure, and flow rate of to-be-dispersed phase on droplet generation via MC were investigated. Sodium caseinate (SC) was confirmed as the most suitable emulsifier among the examined emulsifiers, and monodisperse O/W and W/O/W emulsions stabilized by it were successfully obtained with 20 to 40 µm mean diameter (dm) using different types of MCs. Full article
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Open AccessArticle
A High-Throughput Screening System Based on Droplet Microfluidics for Glucose Oxidase Gene Libraries
Molecules 2020, 25(10), 2418; https://doi.org/10.3390/molecules25102418 - 22 May 2020
Abstract
Glucose oxidase (GOx) is an important industrial enzyme that can be optimized for specific applications by mutagenesis and activity-based screening. To increase the efficiency of this approach, we have developed a new ultrahigh-throughput screening platform based on a microfluidic lab-on-chip device that allows [...] Read more.
Glucose oxidase (GOx) is an important industrial enzyme that can be optimized for specific applications by mutagenesis and activity-based screening. To increase the efficiency of this approach, we have developed a new ultrahigh-throughput screening platform based on a microfluidic lab-on-chip device that allows the sorting of GOx mutants from a saturation mutagenesis library expressed on the surface of yeast cells. GOx activity was measured by monitoring the fluorescence of water microdroplets dispersed in perfluorinated oil. The signal was generated via a series of coupled enzyme reactions leading to the formation of fluorescein. Using this new method, we were able to enrich the yeast cell population by more than 35-fold for GOx mutants with higher than wild-type activity after two rounds of sorting, almost double the efficiency of our previously described flow cytometry platform. We identified and characterized novel GOx mutants, the most promising of which (M6) contained a combination of six point mutations that increased the catalytic constant kcat by 2.1-fold compared to wild-type GOx and by 1.4-fold compared to a parental GOx variant. The new microfluidic platform for GOx was therefore more sensitive than flow cytometry and supports comprehensive screens of gene libraries containing multiple mutations per gene. Full article
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Open AccessCommunication
Versatile Tool for Droplet Generation in Standard Reaction Tubes by Centrifugal Step Emulsification
Molecules 2020, 25(8), 1914; https://doi.org/10.3390/molecules25081914 - 21 Apr 2020
Cited by 2
Abstract
We present a versatile tool for the generation of monodisperse water-in-fluorinated-oil droplets in standard reaction tubes by centrifugal step emulsification. The microfluidic cartridge is designed as an insert into a standard 2 mL reaction tube and can be processed in standard laboratory centrifuges. [...] Read more.
We present a versatile tool for the generation of monodisperse water-in-fluorinated-oil droplets in standard reaction tubes by centrifugal step emulsification. The microfluidic cartridge is designed as an insert into a standard 2 mL reaction tube and can be processed in standard laboratory centrifuges. It allows for droplet generation and subsequent transfer for any downstream analysis or further use, does not need any specialized device, and manufacturing is simple because it consists of two parts only: A structured substrate and a sealing foil. The design of the structured substrate is compatible to injection molding to allow manufacturing at large scale. Droplets are generated in fluorinated oil and collected in the reaction tube for subsequent analysis. For sample sizes up to 100 µL with a viscosity range of 1 mPa·s–4 mPa·s, we demonstrate stable droplet generation and transfer of more than 6 × 105 monodisperse droplets (droplet diameter 66 µm ± 3 µm, CV ≤ 4%) in less than 10 min. With two application examples, a digital droplet polymerase chain reaction (ddPCR) and digital droplet loop mediated isothermal amplification (ddLAMP), we demonstrate the compatibility of the droplet production for two main amplification techniques. Both applications show a high degree of linearity (ddPCR: R2 ≥ 0.994; ddLAMP: R2 ≥ 0.998), which demonstrates that the cartridge and the droplet generation method do not compromise assay performance. Full article
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