The Use of a 3D-Printed Microfluidic Device and Pressure Mobilization for Integrating Capillary Electrophoresis with Electrochemical Detection

Compact 3D-Printed Unit for Separation of Simple Gas Mixtures Combined with Chemiresistive Sensors

Inexpensive chemiresistive sensors are often insufficiently selective as they are sensitive to multiple components of the gas mixture at the same time. One solution would be to insert a device in front of the sensor that separates the measured gas mixture and possibly isolates the unwanted components. This study focused on the fabrication and characterization of a compact unit, which was fabricated by 3D printing, for the separation and detection of simple gas mixtures. The capillary, the basic part of the compact unit, was 4.689 m long and had a diameter of 0.7 mm. The compact unit also contained a mixing chamber on the inlet side and a measuring chamber with a MiCS-6814 sensor on the outlet side. Mixtures of ethanol and water at different concentrations were chosen for characterization. The measured calibration curve was found to have a reliability of R2 = 0.9941. The study further addressed the elements of environmental friendliness of the materials used and their sustainability.

Past, current, and future roles of 3D printing in the development of capillary electrophoresis systems

3D printing, an additive manufacturing technology, has made significant inroads into improving systems for bioanalysis in recent years. This approach is particularly powerful due to the ease and flexibility in rapidly creating novel and complex designs for analytical applications. As such, 3D printing offers an emerging technology for creating systems for electrophoretic analysis. Here, we review 3D printing work on improving and miniaturizing capillary electrophoresis (CE), emphasizing publications from 2019‒2022. We describe enabling uses of 3D printing in interfacing upstream sample preparation or downstream detection with CE. Recent developments in miniaturized CE enabled by 3D printing are also elaborated, including key areas where 3D printing could further improve over the current state-of-the-art. Lastly, we highlight promising future trends for using 3D printing in miniaturizing CE and the significant potential for innovative advancements. 3D printing is poised to play a key role in moving forward miniaturized CE in the coming years.

Microfluidics for Electrochemical Energy Conversion

Electrochemical energy conversion is an important supplement for storage and on-demand use of renewable energy. In this regard, microfluidics offers prospects to raise the efficiency and rate of electrochemical energy conversion through enhanced mass transport, flexible cell design, and ability to eliminate the physical ion-exchange membrane, an essential yet costly element in conventional electrochemical cells. Since the 2002 invention of the microfluidic fuel cell, the research field of microfluidics for electrochemical energy conversion has expanded into a great variety of cell designs, fabrication techniques, and device functions with a wide range of utility and applications. The present review aims to comprehensively synthesize the best practices in this field over the past 20 years. The underlying fundamentals and research methods are first summarized, followed by a complete assessment of all research contributions wherein microfluidics was proactively utilized to facilitate energy conversion in conjunction with electrochemical cells, such as fuel cells, flow batteries, electrolysis cells, hybrid cells, and photoelectrochemical cells. Moreover, emerging technologies and analytical tools enabled by microfluidics are also discussed. Lastly, opportunities for future research directions and technology advances are proposed.

Overview of in-capillary enzymatic reactions using capillary electrophoresis

This review summarizes the research that has recently been performed on in-capillary enzymatic reactions integrated with capillary electrophoresis. The manuscript is subdivided in homogeneous and heterogeneous approaches. The main homogeneous techniques are Electrophoretically Mediated Microanalysis, At-inlet and Transverse Diffusion of Laminar Flow Profiles. The main heterogeneous ones are Immobilized MicroEnzyme Reactors with enzymes grafted on either non-magnetic or magnetic particles. The overview covers the period from 2018 to early 2021. The applications range from drug discovery over natural products to food, beverage and pesticide analysis.

Recent (2018-2020) development in capillary electrophoresis

Development of new capillary electrophoresis (CE) methodology and instrumentation, as well as application of CE to solve new problems, remains an active research area because of the attractive features of CE compared to other separation techniques. In this review, we focus on the representative works about sample preconcentration, separation media or capillary coating development, detector construction, and multidimensional separation in CE, which are judiciously selected from the papers published in 2018–2020.

3D-printed fluidic electrochemical microcell for sequential injection/stripping analysis of heavy metals

In this paper, a 3D-printed microfluidic device is described which is suitable for sequential injection/anodic stripping voltammetric (SIA-ASV) determination of Pb(II) and Cd(II). The fluidic device is manufactured by 3D-printing in a single-step using a dual extruder 3D printer. The device is composed of a microfluidic cell (printed from a non-conductive polylactic acid (PLA) filament) and of 3 electrodes (printed from a conductive carbon-loaded PLA filament) which are integrated within the fluidic cell. During the preconcentration step, a zone of the sample (containing the target cations) and a zone of Bi(III) solution are mixed on-line and the cations are reduced on the working electrode forming a bismuth alloy. The detection step involves a voltametric scan in static solution, in which the accumulated metals are oxidized while the oxidation current is monitored. After the optimization of the relevant parameters, the limit of detection is 0.38 μg L^-1 for Pb(II) and 0.57 μg L^-1 for Cd(II), while the within-device repeatability and the between-device reproducibility are lower than 4.5% (n = 8) and 9% (n = 6), respectively, for both cations at the 30 μg L^-1 level. The device was successfully applied to the simultaneous determination of Pb(II) and Cd(II) in a honey sample.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Poly(alkyl glycidyl ether) hydrogels for harnessing the bioactivity of engineered microbes

Herein, we describe a method to produce yeast-laden hydrogel inks for the direct-write 3D printing of cuboidal lattices for immobilized whole-cell catalysis.