One step multi-material 3D printing for the fabrication of a photometric detector flow cell

Compact photometric detector integrated with separation microchip for potential portable liquid chromatography system

In recent years, miniaturized analytical instruments have been developing to meet the needs of portable and rapid analysis. The key of miniaturized analytical equipment is the miniaturization and integration of functional modules. This paper aims to develop a miniaturized photometric detector and separation microfluidic chip for a liquid chromatography (LC) system. The detector uses a light-emitting diode to emit ultraviolet light, which is collimated by an internal double lens. A Z-shaped flow cell with a long optical path is designed and fabricated in the separation microfluidic chip with a three-layer structure, which provides a tubing-free connection between the separation and detection unit. Detector performance is evaluated using hemoglobin (Hb) samples, with an upper limit of detection linearity (95 %) of 0.345 AU and stray light level as low as 0.08 %. Additionally, the microchip channel can be filled with cation exchange resin and C18 particles. Finally, an ion LC system and a reversed-phase LC system were constructed based on the miniaturized photometric detector and two microchips with different packed columns, respectively, and were successfully used in the separation and detection of two metabolic markers (glycated hemoglobin or bilirubin). The results of this study are expected to facilitate the development of a portable LC system and their application in community health services and family health management of chronic diseases.

A microchip based Z-cell absorbance detector integrating micro-lenses and slits for portable liquid chromatography

A miniaturized microchip-based absorbance detector was developed for portable high-performance liquid chromatography (HPLC) to test glycated hemoglobin (HbA1c). The microchip integrating a Z-shaped cell, two collimating micro-lenses and two ink-filled optical slits is small in size (30 mm × 15 mm × 7 mm). The Z-shaped cell has a cross-sectional size of 500 μm × 500 μm and a physical optical path length of 2 mm. Two collimating micro-lenses were inserted in empty grooves on both sides of the cell, one micro-lens for collimating the initial light and the other for focusing the transmitted light. Optical slits on each end of the cell were used to block the stray light. Therefore, this detector indicated a low stray light level (0.011 %) and noise level (2.5 × 10-4 AU). This detector was applied for the commercial HPLC system to detect HbA1c level, and showed a low limit of detection (0.5 μg/mL) and excellent repeatability (≤ 2.03 %). The sensitivity was enhanced by 3.4 times when the optical path length was increased from 0.5 mm to 2 mm and the stray light was blocked by optical slits. The miniaturized microchip-based absorbance detector developed shows a great potential for application in portable and compact HPLC.

A low-cost spectroscopic nutrient management system for Microscale Smart Hydroponic system

Hydroponics offers a promising approach to help alleviate pressure on food security for urban residents. It requires minimal space and uses less resources, but management can be complex. Microscale Smart Hydroponics (MSH) systems leverage IoT systems to simplify hydroponics management for home users. Previous work in nutrient management has produced systems that use expensive sensing methods or utilized lower cost methods at the expense of accuracy. This study presents a novel inexpensive nutrient management system for MSH applications that utilises a novel waterproofed, IoT spectroscopy sensor (AS7265x) in a transflective application. The sensor is submerged in a hydroponic solution to monitor the nutrients and MSH system predicts the of nutrients in the hydroponic solution and recommends an adjustment quantity in mL. A three-phase model building process was carried out resulting in significant MLR models for predicting the mL, with an R2 of 0.997. An experiment evaluated the system's performance using the trained models with a 30-day grow of lettuce in a real-world setting, comparing the results of the management system to a control group. The sensor system successfully adjusted and maintained nutrient levels, resulting in plant growth that outperformed the control group. The results of the models in actual deployment showed a strong, significant correlation of 0.77 with the traditional method of measuring the electrical conductivity of nutrients. This novel nutrient management system has the potential to transform the way nutrients are monitored in hydroponics. By simplifying nutrient management, this system can encourage the adoption of hydroponics, contributing to food security and environmental sustainability.

Light-oriented 3D printing of liquid crystal/photocurable resins and in-situ enhancement of mechanical performance

Additive manufacturing technology has significantly impacted contemporary industries due to its ability to generate intricate computer-designed geometries. However, 3D-printed polymer parts often possess limited application potential, primarily because of their weak mechanical attributes. To overcome this drawback, this study formulates liquid crystal/photocurable resins suitable for the stereolithography technique by integrating 4'-pentyl-4-cyanobiphenyl with a photosensitive acrylic resin. This study demonstrates that stereolithography facilitates the precise modulation of the existing liquid crystal morphology within the resin. Furthermore, the orientation of the liquid crystal governs the oriented polymerization of monomers or prepolymers bearing acrylate groups. The products of this 3D printing approach manifest anisotropic behavior. Remarkably, when utilizing liquid crystal/photocurable resins, the resulting 3D-printed objects are approximately twice as robust as those created using commercial resins in terms of their tensile, flexural, and impact properties. This pioneering approach holds promise for realizing autonomously designed structures that remain elusive with present additive manufacturing techniques.

Spectroelectrochemical sensing of reaction intermediates and products in an affordable fully 3D printed device

Recent advances in fused deposition modelling 3D printing (FDM 3DP) and synthesis of printable electrically conductive materials enabled the manufacture of customized electrodes and electrochemical devices by this technique. The past couple of years have seen a boom in applying approaches of FDM 3DP in the realm of spectroelectrochemistry (SEC). Despite significant progress, reported designs of SEC devices still rely on conventionally manufactured optical components such as quartz windows and cuvettes. To bridge this technological gap, in this work we apply bi-material FDM 3DP combining electrically conductive and optically translucent filaments to manufacture working electrodes and cells, constituting a fully integrated microfluidic platform for transmission absorption UV-Vis SEC measurements. The cell design enables de-aeration of samples and their convenient handling and analysis. Employing cyclic voltammetric measurements with ruthenium(III) acetylacetonate, ethylviologen dibromide and ferrocenemethanol redox-active probes as model analytes, we demonstrate that the presented platform allows SEC sensing of reactants, intermediates and products of charge transfer reactions, including the inspection of their long-term stability. Approaches developed and presented in this work pave the way for manufacturing customized SEC devices with dramatically reduced costs compared to currently available commercial platforms.

Material Extrusion of Multi-Polymer Structures Utilizing Design and Shrinkage Behaviors: A Design of Experiment Study

Material extrusion (ME) is an additive manufacturing technique capable of producing functional parts, and its use in multi-material fabrication requires further exploration and expansion. The effectiveness of material bonding is one of the main challenges in multi-material fabrication using ME due to its processing capabilities. Various procedures for improving the adherence of multi-material ME parts have been explored, such as the use of adhesives or the post-processing of parts. In this study, different processing conditions and designs were investigated with the aim of optimizing polylactic acid (PLA) and acrylonitrile-butadiene-styrene (ABS) composite parts without the need for pre- or post-processing procedures. The PLA-ABS composite parts were characterized based on their mechanical properties (bonding modulus, compression modulus, and strength), surface roughness (Ra, Rku, Rsk, and Rz), and normalized shrinkage. All process parameters were statistically significant except for the layer composition parameter in terms of Rsk. The results show that it is possible to create a composite structure with good mechanical properties and acceptable surface roughness values without the need for costly post-processing procedures. Furthermore, the normalized shrinkage and the bonding modulus were correlated, indicating the ability to utilize shrinkage in 3D printing to improve material bonding.

3D printed opto-microfluidic autonomous analyzer for photometric applications

3D printed opto-microfluidic autonomous analyzer for photometric applications performs the automation of analytical micro-processes. The proposed device was designed under restrictions of small size and low energy consumption, which allow its portability for in-situ, on line and real time analysis. The autonomous process and auto-calibration consists of four functions: control and data acquisition; hydrodynamic: fluid pumping and flow injection; optical detection and wireless communication. All electronics systems where controlled with a virtual instrument interface. In the experiments carried out to measure fluorides, the results obtained were very close to those obtained with laboratory equipment. The consumption of reagents was 50% less and waste was reduced by 80%. The cost of the portable and autonomous microanalyzer is 75% less than large and robust laboratory equipment.

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%.

Emerging 3D printing technologies and methodologies for microfluidic development

This review paper examines recent (mostly 2018 or later) advancements in 3D printed microfluidics. Microfluidic devices are widely applied in various fields such as drug delivery, point-of-care diagnosis, and bioanalytical research. In addition to soft lithography, 3D printing has become an appealing technology to develop microfluidics recently. In this work, three main 3D printing technologies, stereolithography, fused filament deposition, and polyjet, which are commonly used to fabricate microfluidic devices, are thoroughly discussed. The advantages, limitations, and recent microfluidic applications are analyzed. New technical advancements within these technology frameworks are also summarized, which are especially suitable for microfluidic development. Next, new emerging 3D-printing technologies are introduced, including the direct printing of polydimethylsiloxane (PDMS), glass, and biopolymers. Although limited microfluidic applications based on these technologies can be found in the literature, they show high potential to revolutionize the next generation of 3D-printed microfluidic apparatus.

A novel 3D printed device with conductive elements for electromembrane extraction combined with HPLC and UV detector

This paper is focused on proposing for a new design and setup for electromembrane extraction. A new cap was designed and conductive vials of different shape were fabricated using three-dimensional printing. The new cap holds three fibers to enhance electromembrane extraction recovery. Conductive vials can simultaneously perform as electrodes therefore, there is no need to include an electrode in sample solutions. Phenobarbital and phenytoin were used as model compounds to assess the setup performance. Under optimal conditions, these analytes were extracted from the sample solution at pH = 9 to the acceptor solution at pH = 13 with a voltage of 40 V for 20 min, while 1-octanol was employed as the supported-liquid-membrane. The influence of conductive vials geometry on the recovery was examined and effects of different shapes were studied by performing numerical simulation to establish electric potential distribution. Of the vials tested with circular, triangular and floral-like cross-sections the latter exhibited the best voltage distribution. The circular vial had the highest recovery attributed to its better hydrodynamic shape, which allows rapid fluid sample transport and therefore enhanced system recovery. The extraction recovery and RSD of circular vial with three fibers was 33.0 and 7.6 for phenobarbital and 42.2 and 10.4 for phenytoin. This article is protected by copyright. All rights reserved.

3D printed miniature atomic emission detector coupling with gas chromatography: A sensitive and cost-effective strategy for the determination of volatile methylsiloxanes in municipal sewage

The determination of volatile methylsiloxanes (VMSs) in municipal sewage has attracted great attention. Gas chromatography-mass spectrometry (GC-MS) is the most mature detection technique for VMSs, however, its instrumentation and operation cost are unfavorable in low- and middle-income countries. Herein, a novel and cost-effective strategy by using a 3D printed miniature microplasma optical emission detector (μAED) as an alternative to MS detector, was developed to detect VMSs in municipal sewage by GC after preconcentration by a laboratory-built automatic purge and trap (P&T) system. Two types of μAEDs have been fabricated and their analytical performances were compared. The one using two tungsten rods as electrodes shows better performance and was thus selected as the detecting system for real sample analysis. Under the optimized conditions, the P&T-GC-μAED system provided limits of detection of 3.6 ng L^-1 to 15.5 ng L^-1 of Si for tested VMSs. Relative standard deviations were better than 3.0% and good recoveries ranging from 82.4% to 102.8% were obtained for all analytes. The applicability of this system was demonstrated via the measurement of VMSs in the influents and effluents from 10 wastewater treatment plants (WWTPs) in Chengdu, China.

Extraction of small molecule from human plasma by prototyping 3D printed sorbent through extruded filament for LC-MS/MS analysis

Analytical sample preparation techniques are regarded as crucial steps for analyzing compounds from different biological matrices. The development of new extraction techniques is a modern trend in the bioanalytical sciences. 3D printed techniques have emerged as a valuable technology for prototyping devices in customized shapes for a cost-effective way to advance analytical sample preparation techniques. The present study aims to fabricate customized filaments through the hot-melt extrusion (HME) technique followed by fused deposition modeling mediated 3D printing process for rapid prototyping of 3D printed sorbents to extract a sample from human plasma. Thus, we fabricated our own indigenous filament using poly (vinyl alcohol), Eudragit® RSPO, and tri-ethyl citrate through HME to prototype the fabricated filament into a 3D printed sorbent for the extraction of small molecules. The 3D sorbent was applied to extract hydrocortisone from human plasma and analyzed using a validated LC-MS/MS method. The extraction procedure was optimized, and the parameters influencing the sorbent extraction were systematically investigated. The extraction recovery of hydrocortisone was found to be >82% at low, medium, and high quality control samples, with a relative standard deviation of <2%. The intra-and inter-day precisions for hydrocortisone ranged from 1.0% to 12% and 2.0%-10.0%, respectively, whereas the intra-and inter-day accuracy for hydrocortisone ranged from 93.0% to 111.0% and 92.0% to 110.0%, respectively. The newly customizable size and shape of the 3D printed sorbent opens new possibilities for extracting small molecules from human plasma.

3D-Printed Microfluidic Nanoelectrospray Ionization Source Based on Hydrodynamic Focusing

Nanoelectrospray ionization (nESI) mass spectrometry (MS) is an ideal detection method for microfluidic chips, and its performances depend on nESI emitters. However, the fabrication of monolithic nESI emitters in chips was difficult. Herein, we propose a three-dimensional (3D) printing method to develop a microfluidic nanoelectrospray ionization source (NIS), composed of a nESI emitter and other components. Firstly, the NIS was compatible with a 50 - 500 nL min^-1 nanoflows by imposing 3D hydrodynamic focusing to compensate for the total flow rate, achieving a 7.2% best relative standard deviation in the total ion current (TIC) profiles. Additionally, it was applied to probe thirteen organic chemicals, insulin, and lysozyme with adequate signal-to-noise ratios and an accuracy of m/z between 9.02 × 10^-1 and 1.48 × 10³ ppm. Finally, the NIS achieved comparable limits of detection compared with its commercial counterpart. Considering the standardized preparation of NIS, it would be a potential option to develop 3D-printed customized Chip-MS platforms.

Use of universal 3D-Printed smartphone spectrophotometer to develop a time-based analysis for hypochlorite

A fully-functional smartphone-based spectrophotometer was designed and built using 3D printing. The major advantage of this approach is its capacity to be interfaced with a variety of smartphones, allowing the use of the smartphone's camera and display, and regardless of the relative position of the camera. The analytical performance of the device was analyzed using a model dye (crystal violet), leading to a proportional response for concentrations in the 0.06-15.0 mg L^-1 range, with a variability of 1.0% (intra-day) and 2.6% (inter-day). To demonstrate the functionality of the device, the degradation process of the dye by sodium hypochlorite was studied. The results obtained were applied to develop a paper-based test for NaClO in sanitation solutions, in which the time required to bleach the dye was used to estimate the concentration of the solution. This device represents a simple and inexpensive tool for everyday laboratory use and could address important analytical challenges in low-income communities and features a versatile arrangement, that is compatible with a wide variety of smartphones and software platforms.

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.

Miniature Multiwavelength Deep UV-LED-Based Absorption Detection System for Capillary LC

A new miniature deep UV absorbance detector has been developed using low-cost and high-performance LEDs, which can be operated in both scanning (230 to 300 nm) and individual wavelength (240, 255, and 275 nm) detection modes. The detector is mostly composed of off-the-shelf components, such as LEDs, trifurcated fiber optic assembly, a capillary Z-type flow cell, and photodiodes. It has been characterized for use with a standard capillary LC system and was benchmarked against a standard variable wavelength capillary LC detector. The detector shows very low levels of stray light (<0.4%), utilization of up to 99.0% of the effective path length of the flow cell, a wide dynamic range (0.5 to 200 μg/mL for sulfamethazine, carbamazepine, and flavone), and low noise levels (at 300 μAU level). The detector was applied within a miniaturized LC system.

Dual-Purpose Photometric-Conductivity Detector for Simultaneous and Sequential Measurements in Flow Analysis

This work presents a new dual-purpose detector for photometric and conductivity measurements in flow-based analysis. The photometric detector is a paired emitter-detector diode (PEDD) device, whilst the conductivity detection employs a capacitively coupled contactless conductivity detector (C4D). The flow-through detection cell is a rectangular acrylic block (ca. 2 × 2 × 1.5 cm) with cylindrical channels in Z-configuration. For the PEDD detector, the LED light source and detector are installed inside the acrylic block. The two electrodes of the C4D are silver conducting ink painted on the PEEK inlet and outlet tubing of the Z-flow cell. The dual-purpose detector is coupled with a sequential injection analysis (SIA) system for simultaneous detection of the absorbance of the orange dye and conductivity of the dissolved oral rehydration salt powder. The detector was also used for sequential measurements of creatinine and the conductivity of human urine samples. The creatinine analysis is based on colorimetric detection of the Jaffé reaction using the PEDD detector, and the conductivity of the urine, as measured by the C4D detector, is expressed in millisiemens (mS cm-1).

3D Printing in analytical sample preparation

In the last 5 years, additive manufacturing (three-dimensional printing) has emerged as a highly valuable technology to advance the field of analytical sample preparation. Three-dimensional printing enabled the cost-effective and rapid fabrication of devices for sample preparation, especially in flow-based mode, opening new possibilities for the development of automated analytical methods. Recent advances involve membrane-based three-dimensional printed separation devices fabricated by print-pause-print and multi-material three-dimensional printing, or improved three-dimensional printed holders for solid-phase extraction containing sorbent bead packings, extraction disks, fibers, and magnetic particles. Other recent developments rely on the direct three-dimensional printing of extraction sorbents, the functionalization of commercial three-dimensional printable resins, or the coating of three-dimensional printed devices with functional micro/nanomaterials. In addition, improved devices for liquid-liquid extraction such as extraction chambers, or phase separators are opening new possibilities for analytical method development combined with high-performance liquid chromatography. The present review outlines the current state-of-the-art of three-dimensional printing in analytical sample preparation.