3D-printed and CNC milled flow-cells for chemiluminescence detection

3D-printed chemiluminescence flow cells with customized cross-section geometry for enhanced analytical performance

Low force stereolithography is exploited for the first time for one-step facile fabrication of chemiluminescence (CL) flow-through cells that bear unrivalled features as compared to those available through milling or blowing procedures or alternative 3D printing technologies. A variety of bespoke cross-section geometries with polyhedral features (namely, triangular, square, and five-side polygon) as well as semicircular cross-section are herein critically evaluated in terms of analytical performance against the standardcircular cross-section in a flat spirally-shape format. The idea behind is to maximize capture of elicited light by the new designs while leveraging 3D printing further for fabrication of (i) customized gaskets that enable reliable attaching of the active mixing zone of the CL cell to the detection window, (ii) in-line 3D-printed serpentine reactors, and (iii) flow confluences with tailorable shapes for enhancing mixing of samples with CL reagents. Up to twenty transparent functional cells were simultaneously fabricated without inner supports following post-curing and surface treatment protocols lasting less than 5 h. In fact, previous attempts to print spirally-shaped cells in one-step by resorting to less cost effective photopolymer inkjet printing technologies were unsuccessful because of the requirement of lengthy procedures (>15 days) for quantitative removal of the support material. By exploiting the phthalazinedione-hydrogen peroxide chemistry as a model reaction, the five-side irregular pentagon cell exhibited superior analytical figures of merit in terms of LOD, dynamic range and intermediate precision as compared to alternative designs. Computational fluid dynamic simulations for mapping velocities at the entry region of the spiral cell corroborated the fact that the 5-side polygon cross-section flow-cell with Y-type confluence permitted the most efficient mixing of reagents and sample while enabling larger flow velocities near the inlet that contribute to a more efficient capture of the photons from the flash-type reaction. The applicability of the 3D-printed 5-side polygon CL cell for automatic determination of hydrogen peroxide using a computerized hybrid flow system was demonstrated for the analysis of high matrix samples, viz., seawater and saliva, with relative recoveries ranging from 83 to 103%.

Transparent Cross-Flow Platform as Chemiluminescence Detection Cell in Cross Injection Analysis

This work presents the use of a transparent 'Cross Injection Analysis' (CIA) platform as a flow system for chemiluminescence (CL) measurements. The CL-CIA flow device incorporates introduction channels for samples and reagents, and the reaction and detection channels are in one acrylic unit. A photomultiplier tube placed above the reaction channel detects the emitted luminescence. The system was applied to the analysis of (i) Co(II) via the Co(II)-catalyzed H₂O₂-luminol reaction and (ii) paracetamol via its inhibitory effect on the catalytic activity of Fe(CN)₆^3- on the H₂O₂-luminol reaction. A linear calibration was obtained for Co(II) in the range of 0.002 to 0.025 mg L^-1 Co(II) (r² = 0.9977) for the determination of Co(II) in water samples. The linear calibration obtained for the paracetamol was 10 to 200 mg L^-1 (r² = 0.9906) for the determination of pharmaceutical products. The sample throughput was 60 samples h^-1. The precision was ≤4.2% RSD. The consumption of the samples and reagents was ca. 170 µL per analysis cycle.

PolyJet printed high aspect ratio three-dimensional bifurcating microfluidic flow distributor and its application in solid-phase extraction

Microfluidic distributors that can uniformly distribute fluid from a single channel to multiple channels and into, or across, 3D spaces and vice versa has always represented a challenge. Recently, significant interest has been observed in 3D printing three-dimensional flow distributors. However, they either lack their use at low flow rates or in high aspect ratio environments, which are usually encountered in various applications, such as generating organs-on-a-chip, chromatographic columns, solid-phase extractors, etc. Hence, herein, a three-dimensional bifurcating microfluidic distributor that can be used in both low flow rate and high aspect ratio environments has been designed and developed using PolyJet printing. A 1:4 aspect ratio distributor has been developed with 64 exit channels (array of 16 X 4), however, it can be easily customised to modulate both the aspect ratio and the number of exit channels (in the order of 2). Computational fluid dynamic (CFD) simulation of 0.2 and 0.1 mL min^-1 flow through the distributor recorded a maldistribution factor of only 2.29% and 1.72%, respectively. The distributor has resulted in low-dispersion divergence and convergence of flow to and from 64 parallel channels while operating at flow rates ranging from 0.25 mL min^-1 to 2 mL min^-1. It has been further used to develop a high-performance online solid-phase extractor. The extractor was designed with the three-dimensional bifurcating distributor based inlet and outlet and a packed bed of 15 × 20 × 8 mm (length × breadth × height), which resulted in extraction efficiency of 88.8% ± 0.3. In comparison, the extraction efficiency of 81.1% ± 1.1 and 70.4% ± 0.8 was obtained with its two-dimensional distributor and single-channel inlet and outlet based counterparts, respectively.

A 3D Printer Guide for the Development and Application of Electrochemical Cells and Devices

3D printing is a type of additive manufacturing (AM), a technology that is on the rise and works by building parts in three dimensions by the deposit of raw material layer upon layer. In this review, we explore the use of 3D printers to prototype electrochemical cells and devices for various applications within chemistry. Recent publications reporting the use of Fused Deposition Modelling (fused deposition modeling®) technique will be mostly covered, besides papers about the application of other different types of 3D printing, highlighting the advances in the technology for promising applications in the near future. Different from the previous reviews in the area that focused on 3D printing for electrochemical applications, this review also aims to disseminate the benefits of using 3D printers for research at different levels as well as to guide researchers who want to start using this technology in their research laboratories. Moreover, we show the different designs already explored by different research groups illustrating the myriad of possibilities enabled by 3D printing.

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.

Trace multi-class organic explosives analysis in complex matrices enabled using LEGO®-inspired clickable 3D-printed solid phase extraction block arrays

The development of a new, lower cost method for trace explosives recovery from complex samples is presented using miniaturised, click-together and leak-free 3D-printed solid phase extraction (SPE) blocks. For the first time, a large selection of ten commercially available 3D printing materials were comprehensively evaluated for practical, flexible and multiplexed SPE using stereolithography (SLA), PolyJet and fused deposition modelling (FDM) technologies. Miniaturised single-piece, connectable and leak-free block housings inspired by Lego® were 3D-printed in a methacrylate-based resin, which was found to be most stable under different aqueous/organic solvent and pH conditions, using a cost-effective benchtop SLA printer. Using a tapered SPE bed format, frit-free packing of multiple different commercially available sorbent particles was also possible. Coupled SPE blocks were then shown to offer efficient analyte enrichment and a potentially new approach to improve the stability of recovered analytes in the field when stored on the sorbent, rather than in wet swabs. Performance was measured using liquid chromatography-high resolution mass spectrometry and was better, or similar, to commercially available coupled SPE cartridges, with respect to recovery, precision, matrix effects, linearity and range, for a selection of 13 peroxides, nitramines, nitrate esters and nitroaromatics. Mean % recoveries from dried blood, oil residue and soil matrices were 79 ± 24%, 71 ± 16% and 76 ± 24%, respectively. Excellent detection limits between 60 fg for 3,5-dinitroaniline to 154 pg for nitroglycerin were also achieved across all matrices. To our knowledge, this represents the first application of 3D printing to SPE of so many organic compounds in complex samples. Its introduction into this forensic method offered a low-cost, 'on-demand' solution for selective extraction of explosives, enhanced flexibility for multiplexing/design alteration and potential application at-scene.

Flow Chemistry in Contemporary Chemical Sciences: A Real Variety of Its Applications

Flow chemistry is an area of contemporary chemistry exploiting the hydrodynamic conditions of flowing liquids to provide particular environments for chemical reactions. These particular conditions of enhanced and strictly regulated transport of reagents, improved interface contacts, intensification of heat transfer, and safe operation with hazardous chemicals can be utilized in chemical synthesis, both for mechanization and automation of analytical procedures, and for the investigation of the kinetics of ultrafast reactions. Such methods are developed for more than half a century. In the field of chemical synthesis, they are used mostly in pharmaceutical chemistry for efficient syntheses of small amounts of active substances. In analytical chemistry, flow measuring systems are designed for environmental applications and industrial monitoring, as well as medical and pharmaceutical analysis, providing essential enhancement of the yield of analyses and precision of analytical determinations. The main concept of this review is to show the overlapping of development trends in the design of instrumentation and various ways of the utilization of specificity of chemical operations under flow conditions, especially for synthetic and analytical purposes, with a simultaneous presentation of the still rather limited correspondence between these two main areas of flow chemistry.

Flow-through magnetic-stirring assisted system for uranium(VI) extraction: First 3D printed device application

A 3D printed solid-phase extraction (SPE) device for uranium(VI) extraction has been fabricated using stereolithographic 3D printing. The 3D printed device is shaped as a stirred reactor chamber containing a network of small cubes, which were impregnated with TEVA resin for the extraction of U(VI) from water matrices without doing any previous pretreatment. A flow-through system was combined with off-line ICP-MS detection for the accurate and rapid determination of U(VI) at trace levels. The automatic system was satisfactorily optimized using experimental design, obtaining 0.03 and 0.09 ng U(VI) of detection and quantification limits, respectively, and a durability of 11 consecutive extractions. The reliability of the proposed system was confirmed through the analysis of a reference water material (CSN/CIEMAT 2011), and to water samples (tap, mineral and groundwater) by addition/recovery assays obtaining recoveries between 95 and 106%. This study present for the first time the design of a 3D printing SPE device impregnated with TEVA resin for the on-line extraction of U(VI), showing that 3D printing is a powerful tool for simplifying the construction of complex experimental devices and its operation in analytical procedures for pretreatment applications in water matrices.

A new 3D printed radial flow-cell for chemiluminescence detection: Application in ion chromatographic determination of hydrogen peroxide in urine and coffee extracts

A new polymer flow-cell for chemiluminescence detection (CLD) has been designed and developed by diverging multiple linear channels from a common centre port in a radial arrangement. The fabrication of radial flow-cell by 3D PolyJet printing and fused deposition modeling (FDM) has been evaluated, and compared with a similarly prepared spiral flow-cell design commonly used in chemiluminescence detectors. The radial flow-cell required only 10 h of post-PolyJet print processing time as compared to ca. 360 h long post-PolyJet print processing time required for the spiral flow-cell. Using flow injection analysis, the PolyJet 3D printed radial flow-cell provided an increase in both the signal magnitude and duration, with an average increase in the peak height of 63% and 58%, peak area of 89% and 90%, and peak base width of 41% and 42%, as compared to a coiled-tubing spiral flow-cell and the PolyJet 3D printed spiral flow-cell, respectively. Computational fluid dynamic (CFD) simulations were applied to understand the origin of the higher CLD signal obtained with the radial flow-cell design, indicating higher spatial coverage near the inlet and lower linear velocities in the radial flow-cell. The developed PolyJet 3D printed radial flow-cell was applied in a new ion chromatography chemiluminescence based assay for the detection of H₂O₂ in urine and coffee extracts.

3D printed device including disk-based solid-phase extraction for the automated speciation of iron using the multisyringe flow injection analysis technique

The development of advanced manufacturing techniques is crucial for the design of novel analytical tools with unprecedented features. Advanced manufacturing, also known as 3D printing, has been explored for the first time to fabricate modular devices with integrated features for disk-based automated solid-phase extraction (SPE). A modular device integrating analyte oxidation, disk-based SPE and analyte complexation has been fabricated using stereolithographic 3D printing. The 3D printed device is directly connected to flow-based analytical instrumentation, replacing typical flow networks based on discrete elements. As proof of concept, the 3D printed device was implemented in a multisyringe flow injection analysis (MSFIA) system, and applied to the fully automated speciation, SPE and spectrophotometric quantification of Fe in water samples. The obtained limit of detection for total Fe determination was 7ng, with a dynamic linear range from 22ng to 2400ng Fe (3mL sample). An intra-day RSD of 4% (n = 12) and an inter-day RSD of 4.3% (n = 5, 3mL sample, different day with a different disk), were obtained. Incorporation of integrated 3D printed devices with automated flow-based techniques showed improved sensitivity (85% increase on the measured peak height for the determination of total Fe) in comparison with analogous flow manifolds built from conventional tubing and connectors. Our work represents a step forward towards the improved reproducibility in the fabrication of manifolds for flow-based automated methods of analysis, which is especially relevant in the implementation of interlaboratory analysis.

Evaluation of coloured materials in microfluidic flow-cells for chemiluminescence detection

Recent advances in the construction of chemiluminescence flow-cells has included high precision milling of channels into a range of different polymer materials, in efforts to maximise the transfer of light from the chemical reaction to the photodetector. However, little is known of the extent that the colour of polymer materials will influence this transfer. This may become increasingly important as chemiluminescence detection zones are integrated with other operations within microfluidic devices or micro total analysis systems (μTAS). Herein, we compare microfluidic flow-cells fabricated from five polymer sheets (clear, white, black, red, blue), using two flow-cell designs (spiral and serpentine), two modes of photodetection, and four chemiluminescence reactions that provide a range of different emission colours. The direct transfer of light from the reaction within the white flow-cell channel to the photodetector made only minor contributions (10%-20%) to the measured intensity, with the majority of the measured light first interacting with the polymer material into which the channels were machined. The extent that the emitted light was absorbed or reflected by the coloured polymer materials was dependent on not only the properties of the polymer, but also the spectral distribution of the chemiluminescence. The changes in chemiluminescence intensities from absorption of light by the flow-cell materials can be accompanied by distortion of the spectral distribution.

Adding Biomolecular Recognition Capability to 3D Printed Objects

Three-dimensional (3D) printing technologies will impact the biosensor community in the near future, at both the sensor prototyping level and the sensing layer organization level. The present study aimed at demonstrating the capacity of one 3D printing technique, digital light processing (DLP), to produce hydrogel sensing layers with 3D shapes that are unattainable using conventional molding procedures. The first model of the sensing layer was composed of a sequential enzymatic reaction (glucose oxidase and peroxidase), which generated a chemiluminescent signal in the presence of glucose and luminol. Highly complex objects with assembly properties (fanciful ball, puzzle pieces, 3D pixels, propellers, fluidic and multicompartments) with mono-, di-, and tricomponents configurations were achieved, and the activity of the entrapped enzymes was demonstrated. The second model was a sandwich immunoassay protocol for the detection of brain natriuretic peptide. Here, highly complex propeller shape sensing layers were produced, and the recognition capability of the antibodies was elucidated. The present study opens then the path to a totally new field of development of multiplex sensing layers, printed separately and assembled on demand to create complex sensing systems.

Fully 3D-Printed Preconcentrator for Selective Extraction of Trace Elements in Seawater

In this study, we used a stereolithographic 3D printing technique and polyacrylate polymers to manufacture a solid phase extraction preconcentrator for the selective extraction of trace elements and the removal of unwanted salt matrices, enabling accurate and rapid analyses of trace elements in seawater samples when combined with a quadrupole-based inductively coupled plasma mass spectrometer. To maximize the extraction efficiency, we evaluated the effect of filling the extraction channel with ordered cuboids to improve liquid mixing. Upon automation of the system and optimization of the method, the device allowed highly sensitive and interference-free determination of Mn, Ni, Zn, Cu, Cd, and Pb, with detection limits comparable with those of most conventional methods. The system's analytical reliability was further confirmed through analyses of reference materials and spike analyses of real seawater samples. This study suggests that 3D printing can be a powerful tool for building multilayer fluidic manipulation devices, simplifying the construction of complex experimental components, and facilitating the operation of sophisticated analytical procedures for most sample pretreatment applications.