Integrated 3D printed heaters for microfluidic applications: Ammonium analysis within environmental water

Portable IC system enabled with dual LED-based absorbance detectors and 3D-printed post-column heated micro-reactor for the simultaneous determination of ammonium, nitrite and nitrate

BACKGROUND

The on-site and simultaneous determination of anionic nitrite (NO2-) and nitrate (NO3-), and cationic ammonium (NH4+), in industrial and natural waters, presents a significant analytical challenge. Toward this end, herein a 3D-printed micro-reactor with an integrated heater chip was designed and optimised for the post-column colorimetric detection of NH4+ using a modified Berthelot reaction. The system was integrated within a portable and field deployable ion chromatograph (Aquamonitrix) designed to separate and detect NO2- and NO3-, but here enabled with dual LED-based absorbance detectors, with the aim to provide the first system capable of simultaneous determination of both anions and NH4+ in industrial and natural waters.

RESULTS

Incorporating a 0.750 mm I.D. 3D-printed serpentine-based microchannel for sample-reagent mixing and heating, the resultant micro-reactor had a total reactor channel length of 1.26 m, which provided for a reaction time of 1.42 min based upon a total flow rate of 0.27 mL min-1, within a 40 mm2 printed area. The colorimetric reaction was performed within the micro-reactor, which was then coupled to a dedicated 660 nm LED-based absorbance detector. By rapidly delivering a reactor temperature of 70 °C in just 40 s, the optimal conditions to improve reaction kinetics were achieved to provide for limits of detection of 0.1 mg L-1 for NH4+, based upon an injection volume of just 10 μL. Linearity for NH4+ was observed over the range 0-50 mg L-1, n = 3, R2 = 0.9987. The reactor was found to deliver excellent reproducibility when included as a post-column reactor within the Aquamonitrix analyser, with an overall relative standard deviation below 1.2 % for peak height and 0.3 % for peak residence time, based upon 6 repeat injections.

SIGNIFICANCE

The printed post-column reactor assembly was integrated into a commercial portable ion chromatograph developed for the separation and detection of NO2- and NO3-, thus providing a fully automated system for the remote and simultaneous analysis of NO2-, NO3-, and NH4+ in natural and industrial waters. The fully automated system was deployed externally within a greenhouse facility to demonstrate this capability.

Continuous Flow with Reagent Injection on an Inlaid Microfluidic Platform Applied to Nitrite Determination

A continuous flow with reagent injection method on a novel inlaid microfluidic platform for nitrite determination has been successfully developed. The significance of the high-frequency monitoring of nutrient fluctuations in marine environments is crucial for understanding our impacts on the ecosystem. Many in-situ systems face limitations in high-frequency data collection and have restricted deployment times due to high reagent consumption. The proposed microfluidic device employs automatic colorimetric absorbance spectrophotometry, using the Griess assay for nitrite determination, with minimal reagent usage. The sensor incorporates 10 solenoid valves, four syringes, two LEDs, four photodiodes, and an inlaid microfluidic technique to facilitate optical measurements of fluid volumes. In this flow system, Taylor-Aris dispersion was simulated for different injection volumes at a constant flow rate, and the results have been experimentally confirmed using red food dye injection into a carrier stream. A series of tests were conducted to determine a suitable injection frequency for the reagent. Following the initial system characterization, seven different standard concentrations ranging from 0.125 to 10 µM nitrite were run through the microfluidic device to acquire a calibration curve. Three different calibrations were performed to optimize plug length, with reagent injection volumes of 4, 20, and 50 µL. A straightforward signal processing method was implemented to mitigate the Schlieren effect caused by differences in refractive indexes between the reagent and standards. The results demonstrate that a sampling frequency of at least 10 samples per hour is achievable using this system. The obtained attenuation coefficients exhibited good agreement with the literature, while the reagent consumption was significantly reduced. The limit of detection for a 20 µL injection volume was determined to be 94 nM from the sample intake, and the limit of quantification was 312 nM. Going forward, the demonstrated system will be packaged in a submersible enclosure to facilitate in-situ colorimetric measurements in marine environments.

A Novel Bubble-based Microreactor for Enhanced Mass Transfer Dynamics toward Efficient Electrocatalytic Nitrogen Reduction

Electrocatalytic nitrogen reduction reaction (eNRR) is a promising method for sustainable ammonia production. Although the majority of studies on the eNRR are devoted to developing efficient electrocatalysts, it is critical to study the influence of mass transfer because of the poor N2 transfer efficiency. Herein, a novel bubble-based microreactor (BBMR) is proposed that efficiently promotes the mass transfer behavior during the eNRR using microfluidic strategies. The BBMR possesses abundant triphasic interfaces and provides spatial confinement and accurate potential control, ensuring rapid mass transfer dynamics and improved eNRR performance, as confirmed by experimental and simulation studies. The ammonia yield of the reaction over Ag nanoparticles can be enhanced to 31.35 µg h-1 mgcat. -1, which is twice that of the H-cell. Excellent improvements are also achieved using Ru/C and Fe/g-CN catalysts, with 5.0 and 8.5 times increase in ammonia yield, respectively. This work further demonstrates the significant effect of mass transfer on the eNRR performance and provides an effective strategy for process enhancement through electrode design.

Customizable Nichrome Wire Heaters for Molecular Diagnostic Applications

Accurate sample heating is vital for nucleic acid extraction and amplification, requiring a sophisticated thermal cycling process in nucleic acid detection. Traditional molecular detection systems with heating capability are bulky, expensive, and primarily designed for lab settings. Consequently, their use is limited where lab systems are unavailable. This study introduces a technique for performing the heating process required in molecular diagnostics applicable for point-of-care testing (POCT), by presenting a method for crafting customized heaters using freely patterned nichrome (NiCr) wire. This technique, fabricating heaters by arranging protrusions on a carbon black-polydimethylsiloxane (PDMS) cast and patterning NiCr wire, utilizes cost-effective materials and is not constrained by shape, thereby enabling customized fabrication in both two-dimensional (2D) and three-dimensional (3D). To illustrate its versatility and practicality, a 2D heater with three temperature zones was developed for a portable device capable of automatic thermocycling for polymerase chain reaction (PCR) to detect Escherichia coli (E. coli) O157:H7 pathogen DNA. Furthermore, the detection of the same pathogen was demonstrated using a customized 3D heater surrounding a microtube for loop-mediated isothermal amplification (LAMP). Successful DNA amplification using the proposed heater suggests that the heating technique introduced in this study can be effectively applied to POCT.

High-performance microchip electrophoresis separations of preterm birth biomarkers using 3D printed microfluidic devices

We employed digital light processing-stereolithography 3D printing to create microfluidic devices with different designs for microchip electrophoresis (µCE). Short or long straight channel, and two- or four-turn serpentine channel microfluidic devices with separation channel lengths of 1.3, 3.1, 3.0, and 4.7 cm, respectively, all with a cross injector design, were fabricated. We measured current as a function of time and voltage to determine a separation time window and conditions for the onset of Joule heating in these designs. Separations in these devices were evaluated by performing µCE and measuring theoretical plate counts for electric field strengths near and above the onset of Joule heating, with fluorescently labeled glycine and phenylalanine as model analytes. We further demonstrated µCE of peptides and proteins related to preterm birth risk, showing increased peak capacity and resolution compared to previous results with 3D printed microdevices. These results mark an important step forward in the use of 3D printed microfluidic devices for rapid bioanalysis by µCE.

Tailoring diamondised nanocarbon-loaded poly(lactic acid) composites for highly electroactive surfaces: extrusion and characterisation of filaments for improved 3D-printed surfaces

A new 3D-printable composite has been developed dedicated to electroanalytical applications. Two types of diamondised nanocarbons - detonation nanodiamonds (DNDs) and boron-doped carbon nanowalls (BCNWs) - were added as fillers in poly(lactic acid) (PLA)-based composites to extrude 3D filaments. Carbon black served as a primary filler to reach high composite conductivity at low diamondised nanocarbon concentrations (0.01 to 0.2 S/cm, depending on the type and amount of filler). The aim was to thoroughly describe and understand the interactions between the composite components and how they affect the rheological, mechanical and thermal properties, and electrochemical characteristics of filaments and material extrusion printouts. The electrocatalytic properties of composite-based electrodes, fabricated with a simple 3D pen, were evaluated using multiple electrochemical techniques (cyclic and differential pulse voltammetry and electrochemical impedance spectroscopy). The results showed that the addition of 5 wt% of any of the diamond-rich nanocarbons fillers significantly enhanced the redox process kinetics, leading to lower redox activation overpotentials compared with carbon black-loaded PLA. The detection of dopamine was successfully achieved through fabricated composite electrodes, exhibiting lower limits of detection (0.12 μM for DND and 0.18 μM for BCNW) compared with the reference CB-PLA electrodes (0.48 μM). The thermogravimetric results demonstrated that both DND and BCNW powders can accelerate thermal degradation. The presence of diamondised nanocarbons, regardless of their type, resulted in a decrease in the decomposition temperature of the composite. The study provides insight into the interactions between composite components and their impact on the electrochemical properties of 3D-printed surfaces, suggesting electroanalytic potential.

Nanomaterials Reinforced Polymer Filament for Fused Deposition Modeling: A State-of-the-Art Review

For the past years, fused deposition modeling (FDM) technology has received increased attention in the applications of industrial manufacturing fields, particularly for rapid prototyping, small batch production and highly customized products, owing to the merits of low-cost, user-friendliness and high design freedom. To further expand the application potential and promote the performance of the as-manufactured products, many efforts have been spent on the development of suitable materials for FDM applications. In recent years, the involvement of nanomaterials in the FDM-based polymer matrix, which has been demonstrated with great opportunities to enhance the performance and versatility of FDM printed objects, has attracted more and more research interest and the trend is expected to be more pronounced in the next few years. This paper attempts to provide a timely review regarding the current research advances in the use of nanomaterials to reinforce polymer filaments for the FDM technique. Polymer composite filaments based on nanomaterials such as carbon nanotubes, nanoclay, carbon fibers, graphene, metal nanoparticles and oxides are discussed in detail regarding their properties and applications. We also summarized the current research challenges and outlooked the future research trends in this field. This paper aims at providing a useful reference and guidance for skilled researchers and also beginners in related fields. Hopefully, more research advances can be stimulated in the coming years.

Characterization of Conductive 3D Printed Fingertips Manufactured by Fused Filament Fabrication

This study purposed to develop conductivity 3D printed (3DP) fingertips and confirm their potential for use in a pressure sensor. Index fingertips were 3D printed using thermoplastic polyurethane filament with three types of infill patterns (Zigzag (ZG), Triangles (TR), Honeycomb (HN)) and densities (20%, 50%, 80%). Hence, the 3DP index fingertip was dip-coated with 8 wt% graphene/waterborne polyurethane composite solution. The coated 3DP index fingertips were analyzed by appearance property, weight changes, compressive property, and electrical property. As results, the weight increased from 1.8 g to 2.9 g as infill density increased. By infill pattern, ZG was the largest, and the pick-up rate decreased from 18.9% for 20% infill density to 4.5% for 80% infill density. Compressive properties were confirmed. Compressive strength increased as infill density increased. In addition, the compressive strength after coating was improved more than 1000 times. Especially, TR had excellent compressive toughness as 13.9 J for 20%, 17.2 J for 50%, and 27.9 J for 80%. In the case of electrical properties, the current become excellent at 20% infill density. By infill patterns at 20% infill density, TR has 0.22 mA as the best conductivity. Therefore, we confirmed the conductivity of 3DP fingertips, and the infill pattern of TR at 20% was most suitable.

Fused Deposition Modelling of Polymer Composite: A Progress

Additive manufacturing (AM) highlights developing complex and efficient parts for various uses. Fused deposition modelling (FDM) is the most frequent fabrication procedure used to make polymer products. Although it is widely used, due to its low characteristics, such as weak mechanical properties and poor surface, the types of polymer material that may be produced are limited, affecting the structural applications of FDM. Therefore, the FDM process utilises the polymer composition to produce a better physical product. The review's objective is to systematically document all critical information on FDMed-polymer composite processing, specifically for part fabrication. The review covers the published works on the FDMed-polymer composite from 2011 to 2021 based on our systematic literature review of more than 150 high-impact related research articles. The base and filler material used, and the process parameters including layer height, nozzle temperature, bed temperature, and screw type are also discussed in this review. FDM is utilised in various biomedical, automotive, and other manufacturing industries. This study is expected to be one of the essential pit-stops for future related works in the FDMed-polymeric composite study.

Device Processing Challenges for Miniaturized Sensing Systems Targeting Biological Fluids

This article presents a review of device processing technologies used in the fabrication of biomedical systems, and highlights the requirements of advanced manufacturing technology. We focus on biomedical systems that perform diagnostics of fluidic specimens, with analytes that are in the liquid phase. In the introduction, we define biomedical systems as well as their versatile applications and the essential current trends. The paper gives an overview of the most important biomolecules that typically must be detected or analyzed in several applications. The paper is structured as follows. First, the conventional architecture and construction of a biosensing system is introduced. We provide an overview of the most common biosensing methods that are currently used for the detection of biomolecules and its analysis. We present an overview of reported biochips, and explain the technology of biofunctionalization and detection principles, including their corresponding advantages and disadvantages. Next, we introduce microfluidics as a method for delivery of the specimen to the biochip sensing area. A special focus lies on material requirements and on manufacturing technology for fabricating microfluidic systems, both for niche and mass-scale production segments. We formulate requirements and constraints for integrating the biochips and microfluidic systems. The possible impacts of the conventional microassembly techniques and processing methods on the entire biomedical system and its specific parts are also described. On that basis, we explain the need for alternative microassembly technologies to enable the integration of biochips and microfluidic systems into fully functional systems.

Photothermal Localization in an Optofluidic Microreactor for Rapid Pretreatment toward Online Pollutant Analysis

The realization of high-efficient digestion in a microfluidic reactor is considered to be advantageous for pretreatment toward online pollutant detection. However, it is difficult to achieve satisfactory device performance due to the gap between the low digestion reaction efficiency and the demand for rapid pretreatment for online detection. Herein, we design and manufacture an optofluidic microreactor combined with a MnO₂ nanofilm localizing the heat inside the reaction chamber under solar irradiation, which contributes a lot to the on-chip nutrient digestion efficiency enhancement. The overall temperature of the water sample in the reactor chamber can be dramatically increased in a fleeting time of less than 1 s and maintained at 78 °C. The digestion rate constant of the microreactor is improved by about 100 times compared with that obtained by the traditional method in the national standard, which is attributed to temperature enhancement and various oxidation reactions in the heated reaction chamber. Notably, when pretreating the actual total phosphorus water samples, the digestion efficiency is demonstrated to be higher than 95% within 12 s under solar light irradiation. The optofluidic platform brings many benefits to accelerate the various photochemically enhanced reactions using solar light and is extremely adapted for rapid pretreatment of biochemical samples to further develop their online analysis.

Analytical Chemistry: Tasks, Resolutions and Future Standpoints of the Quantitative Analyses of Environmental Complex Sample Matrices

Currently, the challenges that analytical chemistry has to face are ever greater and more complex both from the point of view of the selectivity of analytical methods and their sensitivity. This is especially true in quantitative analysis, where various methods must include the development and validation of new materials, strategies, and procedures to meet the growing need for rapid, sensitive, selective, and green methods. In this context, given the International Guidelines, which over time, are updated and which set up increasingly stringent “limits”, constant innovation is required both in the pre-treatment procedures and in the instrumental configurations to obtain reliable, accurate, and reproducible information. In addition, the environmental field certainly represents the greatest challenge, as analytes are often present at trace and ultra-trace levels. These samples containing analytes at ultra-low concentration levels, therefore, require very labor-intensive sample preparation procedures and involve the high consumption of organic solvents that may not be considered “green”. In the literature, in recent years, there has been a strong development of increasingly high-performing sample preparation techniques, often “solvent-free”, as well as the development of hyphenated instrumental configurations that allow for reaching previously unimaginable levels of sensitivity. This review aims to provide an update of the most recent developments currently in use in sample pre-treatment and instrument configurations in the environmental field, also evaluating the role and future developments of analytical chemistry in light of upcoming challenges and new goals yet to be achieved.

Microfluidic assisted recognition of miRNAs towards point-of-care diagnosis: Technical and analytical overview towards biosensing of short stranded single non-coding oligonucleotides

MiRNAs are short stranded single non-coding oligonucleotides that play an important role in regulating gene expression. MiRNAs are stable in RNase enriched environments such as human body fluids and their dysregulation or abnormal abundance in human body fluids as a diagnostic biomarker has been associated with several diseases. Due to the low concentration of miRNAs, it is difficult to detect using interactive methods (ideal detection limit is femtomolar range). However, clinicians lack sensitive and reliable methods for quantifying miRNA. Microfluidic devices integrated with electrochemical, optical (fluorometric, SERs, FRET, colorimetric), electrochemiluminescence and photoelectrochemical signal readout led to development innovative diagnostic device test, can probably overcome the limitations of the traditional methods. In the present review, microfluid methods for the sensitive and selective recognition of miRNA in various biological matrices are surveyed. Also, advantages and limitation of recognition methods on the performance and efficiency of microfluidic based biosensing of miRNAs are critically investigated. Finally, the future perspectives on the diagnosis of disease based on microfluidic analysis of miRNAs are provided.

Making waves: Time for chemical surface water quality monitoring to catch up with its technical potential

A comprehensive real-time evaluation of the chemical status of surface water bodies is still utopian, but in our opinion, it is time to use the momentum delivered by recent advanced technical, infrastructural, and societal developments to get significantly closer. Procedures like inline and online analysis (in situ or in a bypass) with close to real-time analysis and data provision are already available in several industrial sectors. In contrast, atline and offline analysis involving manual sampling and time-decoupled analysis in the laboratory is still common practice in aqueous environmental monitoring. Automated tools for data analysis, verification, and evaluation are changing significantly, becoming more powerful with increasing degrees of automation and the introduction of self-learning systems. In addition, the amount of available data will most likely in near future be increased by societal awareness for water quality and by citizen science. In this analysis, we highlight the significant potential of surface water monitoring techniques, showcase "lighthouse" projects from different sectors, and pin-point gaps we must overcome to strike a path to the future of chemical monitoring of inland surface waters.

Time-efficient fabrication method for 3D-printed microfluidic devices

Recent developments in 3D-printing technology have provided a time-efficient and inexpensive alternative to the fabrication of microfluidic devices. At present, 3D-printed microfluidic systems face the challenges of post-processing, non-transparency, and being time consuming, limiting their practical application. In this study, a time-efficient and inexpensive fabrication method was developed for 3D-printed microfluidic devices. The material for 3D-printed microfluidic chips is Dowsil 732, which is used as a sealant or encapsulant in various industries. The curing time and surface hydrophobicity of the materials were evaluated. The results indicated that the surface of Dowsil 732 is hydrophilic. An optimization model of the direct ink writing method is proposed to establish a time-efficient and accurate fabrication method for microfluidic devices. The results indicate that the optimization model can effectively describe the change trend between printing speed, printing pressure, and channel wall accuracy, and the model accuracy rate exceeds 95%. Three examples-a micromixer, concentration gradient generator, and droplet generator-were printed to demonstrate the functionality and feasibility of the fabrication method.

Modelling of Anisotropic Electrical Conduction in Layered Structures 3D-Printed with Fused Deposition Modelling

3D-printing conductive structures have recently been receiving increased attention, especially in the field of 3D-printed sensors. However, the printing processes introduce anisotropic electrical properties due to the infill and bonding conditions. Insights into the electrical conduction that results from the anisotropic electrical properties are currently limited. Therefore, this research focuses on analytically modeling the electrical conduction. The electrical properties are described as an electrical network with bulk and contact properties in and between neighbouring printed track elements or traxels. The model studies both meandering and open-ended traxels through the application of the corresponding boundary conditions. The model equations are solved as an eigenvalue problem, yielding the voltage, current density, and power dissipation density for every position in every traxel. A simplified analytical example and Finite Element Method simulations verify the model, which depict good correspondence. The main errors found are due to the limitations of the model with regards to 2D-conduction in traxels and neglecting the resistance of meandering ends. Three dimensionless numbers are introduced for the verification and analysis: the anisotropy ratio, the aspect ratio, and the number of traxels. Conductive behavior between completely isotropic and completely anisotropic can be modeled, depending on the dimensionless properties. Furthermore, this model can be used to explain the properties of certain 3D-printed sensor structures, like constriction-resistive strain sensors.

Microfluidic and mathematical modeling of aquatic microbial communities

Aquatic microbial communities contribute fundamentally to biogeochemical transformations in natural ecosystems, and disruption of these communities can lead to ecological disasters such as harmful algal blooms. Microbial communities are highly dynamic, and their composition and function are tightly controlled by the biophysical (e.g., light, fluid flow, and temperature) and biochemical (e.g., chemical gradients and cell concentration) parameters of the surrounding environment. Due to the large number of environmental factors involved, a systematic understanding of the microbial community-environment interactions is lacking. In this article, we show that microfluidic platforms present a unique opportunity to recreate well-defined environmental factors in a laboratory setting in a high throughput way, enabling quantitative studies of microbial communities that are amenable to theoretical modeling. The focus of this article is on aquatic microbial communities, but the microfluidic and mathematical models discussed here can be readily applied to investigate other microbiomes.

Microfluidics in Biotechnology: Quo Vadis

The emerging technique of microfluidics offers new approaches for precisely controlling fluidic conditions on a small scale, while simultaneously facilitating data collection in both high-throughput and quantitative manners. As such, the so-called lab-on-a-chip (LOC) systems have the potential to revolutionize the field of biotechnology. But what needs to happen in order to truly integrate them into routine biotechnological applications? In this chapter, some of the most promising applications of microfluidic technology within the field of biotechnology are surveyed, and a few strategies for overcoming current challenges posed by microfluidic LOC systems are examined. In addition, we also discuss the intensifying trend (across all biotechnology fields) of using point-of-use applications which is being facilitated by new technological achievements.

Novel approaches for colorimetric measurements in analytical chemistry - A review

Colorimetric techniques have been developed and used in routine analyses for over a century and apparently all their potentialities have been exhaustively explored. However, colorimetric techniques have gained high visibility in the last two decades mainly because of the development of the miniaturization concept, for example, paper-based analytical devices that mostly employ colorimetric reactions, and by the advances and popularity of image capture instruments. The impressive increase in the use of these devices was followed by the development and enhancement of different modes of color detection to meet the demands of making qualitative, semi-quantitative, and fully quantitative analyses of multiple analytes. Cameras, scanners, and smartphones are now being used for this purpose and have become suitable alternatives for different approaches to colorimetric analysis; this, in addition to advancements in miniaturized devices. On the other hand, recent developments in optoelectronics technologies have launched more powerful, more stable and cheaper light-emitting diodes (LEDs), which once again have become an interesting tool for the design of portable and miniaturized devices based on colored reactions. Here, we present a critical review of recent developments and challenges of colorimetric detection in modern analytical chemistry in the last five years, and present thoughts and insights towards future perspectives in the area to improve the use of colorimetric detection in different application approaches.

3D printing in analytical chemistry: current state and future

The rapid development of additive technologies in recent years is accompanied by their intensive introduction into various fields of science and related technologies, including analytical chemistry. The use of 3D printing in analytical instrumentation, in particular, for making prototypes of new equipment and manufacturing parts having complex internal spatial configuration, has been proved as exceptionally effective. Additional opportunities for the widespread introduction of 3D printing technologies are associated with the development of new optically transparent, current- and thermo-conductive materials, various composite materials with desired properties, as well as possibilities for printing with the simultaneous combination of several materials in one product. This review will focus on the application of 3D printing for production of new advanced analytical devices, such as compact chromatographic columns for high performance liquid chromatography, flow reactors and flow cells for detectors, devices for passive concentration of toxic compounds and various integrated devices that allow significant improvements in chemical analysis. A special attention is paid to the complexity and functionality of 3D-printed devices.

The rise of continuous flow biocatalysis – fundamentals, very recent developments and future perspectives

Very recent developments in the field of biocatalysis in continuously operated systems. Special attention on the future perspectives in this key emerging technological area ranging from process analytical technologies to digitalization.

Microfluidics for Environmental Applications

Microfluidic and lab-on-a-chip systems have become increasingly important tools across many research fields in recent years. As a result of their small size and precise flow control, as well as their ability to enable in situ process visualization, microfluidic systems are increasingly finding applications in environmental science and engineering. Broadly speaking, their main present applications within these fields include use as sensors for water contaminant analysis (e.g., heavy metals and organic pollutants), as tools for microorganism detection (e.g., virus and bacteria), and as platforms for the investigation of environment-related problems (e.g., bacteria electron transfer and biofilm formation). This chapter aims to review the applications of microfluidics in environmental science and engineering - with a particular focus on the foregoing topics. The advantages and limitations of microfluidics when compared to traditional methods are also surveyed, and several perspectives on the future of research and development into microfluidics for environmental applications are offered.