Microfluidics systems with societal impact in Analytical Methods

We are delighted to introduce this themed collection on microfluidic systems with societal impact in Analytical Methods. The multi-disciplinary field of microfluidics has seen consistent growth due to its increasing accessibility and applicability to a range of areas, from environmental monitoring to biological assays. The goal of this collection is to highlight the development and use of microfluidic systems throughout science with applications that have strong potential for societal impact. This collection also serves to celebrate the 60th birthdays of two pioneers in analytical chemistry and microfluidic development, Professors Susan M. Lunte and James P. Landers. A special editorial is also provided that highlights the important contributions of these two scientists (DOI: 10.1039/c8ay90079e).

In this themed collection, readers will find a compilation of reviews and original research papers covering a variety of microfluidic methods that are used for tackling an assortment of biomedical and environmental applications. These include paper-based microfluidic systems for a range of applications; 3D-printed systems for bioanalytical applications; microscale electrophoresis systems for clinical applications; other microfluidic approaches with unique detection modes for clinical applications; new materials or analytical modes for droplet-based and integrated analyses; and microfluidic systems for environmental monitoring.

Paper-based developments in this collection include a report by Vincent Remcho and colleagues on new methods of fabricating paper-based microfluidic systems which were used for the analysis of serum proteins and small molecules (DOI: 10.1039/c8ay00981c). Also included is work by Bastian Rapp and colleagues on a method for photolithographic structuring of hydrophobic barriers in paper for the creation of flexible paper-based analytical devices (μPADs) (DOI: 10.1039/c8ay01010b). Christopher Baker and colleagues reported development in adsorption filter membrane materials for effective electrophoresis and electrokinetic gating in μPADs (DOI: 10.1039/c8ay01237g). Woo-Jin Chang and colleagues illustrated rapid fabrication of versatile three-dimensional flow paper-fluidic analytical devices for biomedical applications using a cut-and-insert method (DOI: 10.1039/c8ay01318g). Carlos Garcia and colleagues describe carbon tape as a convenient electrode material for electrochemistry in μPADs in their contribution to the collection (DOI: 10.1039/c8ay00778k). Finally, Chaoyang Yang and colleagues contributed a minireview to this collection highlighting the developments, accomplishments, and challenges of each facet of integrated μPADs, including sample pre-treatment, signal transduction/amplification, and signal output (DOI: 10.1039/c8ay00864g).

Scott Martin and colleagues report the use of 3D printing and modular microfluidics to quantitate nitric oxide release from endothelial cells (DOI: 10.1039/c8ay00829a). Along similar lines, Dana Spence and Tiffany Janes also used a 3D printed system to enable studies on the effect of steroid medicines on nitric oxide production from endothelial cells (DOI: 10.1039/c8ay00870a). James Rusling and colleagues published a technical note demonstrating automated 4-sample immunoassays using a 3D printed microfluidic system (DOI: 10.1039/c8ay01271g). Finally, Wendell Coltro and colleagues published a critical review aiming to describe recent fabrication-based advances of toner-based microfluidic devices for bioanalytical applications (DOI: 10.1039/c8ay01095a).

Naveen Maddukuri and colleagues introduce flow-gated capillary electrophoresis and its usefulness for rapid and efficient chemical separation in their tutorial review (DOI: 10.1039/c8ay00979a). Susan Lunte and Shamal M. Gunawardhana demonstrate continuous adenosine monitoring using microdialysis coupled to a microchip electrophoresis system (DOI: 10.1039/c8ay01041b). Finally, Scott Martin and Benjamin Mehl illustrated enhanced electrophoresis separations combined with electrochemical detection using a polystyrene-PDMA device (DOI: 10.1039/c7ay02505j).

A variety of studies utilise microfluidic systems for clinical applications. Anthony Cass and colleagues demonstrate a pilot study in humans of a microneedle sensor array for continuous glucose monitoring (DOI: 10.1039/c8ay00264a). Sumita Pennathur and colleagues report on microfluidic detection with acoustic spectroscopy (MIDAS) for the analysis of insulin formulation stability (DOI: 10.1039/c7ay01846k). In their work, Eva Lai and colleagues demonstrate label-free enrichment of mesenchymal stem cells from bone marrow using inertial microfluidics (DOI: 10.1039/c7ay02500a). Finally, Anthony Killard and Leanne Harris highlight recent and ongoing advances in microfluidic systems in the areas of haemostasis and coagulation biology in their minireview (DOI: 10.1039/c8ay01230j).

Other studies report device material and analytical advances such as integrated analysis or droplet fluidics. In their paper, Jörg P. Kutter and colleagues describe fabrication of a thiol–ene microfluidic chip containing an integrated solid phase extraction channel and electrospray ionization emitter (DOI: 10.1039/c8ay00646f). Christopher Easley and colleagues demonstrate a multichannel droplet-based microfluidic sample chopper (μChopper) which allows a variety of analytical modes to be employed on-chip (DOI: 10.1039/c8ay00947c). Ryan Bailey and colleagues developed droplet microfluidic devices in thermoplastics for droplet generation and content manipulation using electrical and magnetic fields (DOI: 10.1039/c8ay01474d).

Fiona Regan, Jens Ducrée, and colleagues have written a critical review of centrifugal microfluidics in environmental monitoring. The authors describe the current gap in the use of centrifugal microfluidics for environmental sensing and provide theoretical perspectives from applications in other domains, and recommend adaptations for environmental sensing (DOI: 10.1039/c8ay00361k).

Overall, this collection emphasizes the central role that the journal plays in reporting early and impactful applications of newly developed microfluidic systems. As Professors Lunte and Landers continue to lead the field forward, the authors in this collection are making significant contributions to analytical science and to society, whether fluid is advanced through enclosed channels or within paper, separation and detection are accomplished through time-tested or novel approaches, or applications are environmental or biological. We welcome future submissions with similar diversity in fluid handling, analytical readout, and end-point applications. Such work is certainly at home in Analytical Methods.

Michael Roper

Christopher Easley

Fiona Regan

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