Multi sensor compatible 3D-printed electrochemical cell for voltammetric drug screening

Research on high sensitivity piezoresistive sensor based on structural design

With the popularity of smart terminals, wearable electronic devices have shown great market prospects, especially high-sensitivity pressure sensors, which can monitor micro-stimuli and high-precision dynamic external stimuli, and will have an important impact on future functional development. Compressible flexible sensors have attracted wide attention due to their simple sensing mechanism and the advantages of light weight and convenience. Sensors with high sensitivity are very sensitive to pressure and can detect resistance/current changes under pressure, which has been widely studied. On this basis, this review focuses on analyzing the performance impact of device structure design strategies on high sensitivity pressure sensors. The design of structures can be divided into interface microstructures and three-dimensional framework structures. The preparation methods of various structures are introduced in detail, and the current research status and future development challenges are summarized.

Merging 3D-printing technology and disposable materials for electrochemical purposes: A sustainable alternative to ensure greener electroanalysis

3D-printing technology has revolutionized electrochemical applications by enabling rapid prototyping of various devices with high precision, even in highly complex structures. However, a significant challenge remains in developing less costly and more sustainable analytical approaches and methods aimed at mitigating the negative environmental impacts of chemical analysis procedures. In this study, we propose a solution to these challenges by creating a simple and versatile electrochemical system that combines 3D-printing technology with recyclable disposable materials, such as graphite from an exhausted battery and a stainless-steel screw. Our results demonstrate a novel strategy for developing electrodes and other laboratory-made devices that align with the principles of sustainability and green chemistry. Furthermore, we provide evidence of the effectiveness of the proposed system in an analytical application involving the simultaneous determination of tert-butylhydroquinone, acetaminophen, and levofloxacin using the voltammetric technique in lake and groundwater samples. The results indicate sufficient accuracy, with recovery values ranging from 91 to 110%. Additionally, we utilized the Analytical GREEnness calculator as a metric system to evaluate the environmental friendliness of the proposed electroanalytical protocol. The final score confirms a favorable level of sustainability, reaffirming the eco-friendly nature of our approach.

Novel disposable and portable 3D-printed electrochemical apparatus for fast and selective screening of 25E-NBOH in forensic samples

The advent of new psychoactive substances (NPS) has caused enormous difficulty for legal control since they are rapidly commercialized, and their chemical structures are routinely altered. In this aspect, derivatives phenethylamines, such as 25E-NBOH, have received great attention in the forensic scenario. Hence, we propose portable and cost-effective (U$ 5.00) 3D-printed devices for the electrochemical screening of 25E-NBOH for the first time. The cell and all electrodes were printed using acrylonitrile butadiene styrene filament (insulating material) and conductive filament (graphite embedded in a polylactic acid matrix), respectively, both by the fused deposition modeling (FDM) 3D printing technique. The electrochemical apparatus enables micro-volume analysis (50-2000 μL), especially important for low sample volumes. A mechanistic route for the electrochemical oxidation of 25E-NBOH is proposed based on cyclic voltammetric data, which showed two oxidation processes around +0.75 V and +1.00 V and a redox pair between +0.2 and -0.2 V (vs. graphite ink pseudo-reference). A fast and sensitive square-wave voltammetry method was developed, which exhibited a linear working range from 0.85 to 5.1 μmoL-1, detection limit of 0.2 μmol L-1, and good intra-electrode precision (n = 10, RSD <5.3 %). Inter-electrode measurements (n = 3, RSD <9.8 %) also attested that the electrode production process is reproducible. Interference tests in the presence of other drugs frequently found in blotting paper indicated high selectivity of the electrochemical method for screening of 25E-NBOH. Screening analysis of blotting paper confirmed the presence of 25E-NBOH in the seized samples. Moreover, a recovery percentage close to 100 % was found for a spiked saliva sample, suggesting the method's usefulness for quantitative purposes aimed at information on recent drug use.

Core-Shell Nanocables Decorated with Carbon Spherical Shells and Silver Nanoparticles for Sensing Ethinylestradiol Hormone in Water Sources and Pills

The selective, rapid detection of low levels of hormones in drinking water and foodstuffs requires materials suitable for inexpensive sensing platforms. We report on core-shell Ag@C nanocables (NCs) decorated with carbon spherical shells (CSSs) and silver nanoparticles (AgNPs) by using a hydrothermal green approach. Sensors were fabricated with homogeneous, porous films on screen-printed electrodes, which comprised a 115 nm silver core covered by a 122 nm thick carbon layer and CSSs with 168 nm in diameter. NCs and CSSs were also decorated with 10-25 nm AgNPs. The NC/CSS/AgNP sensor was used to detect ethinylestradiol using square wave voltammetry in 0.1 M phosphate buffer (pH 7.0) over the 1.0-10.0 μM linear range with a detection limit of 0.76 μM. The sensor was then applied to detect ethinylestradiol in tap water samples and a contraceptive pill with recovery percentages between 93 and 101%. The high performance in terms of sensitivity and selectivity for hormones is attributed to the synergy between the carbon nanomaterials and AgNPs, which not only increased the sensor surface area and provided sites for electron exchange but also imparted an increased surface area.

Electrochemical platform produced by 3D printing for analysis of small volumes using different electrode materials

Fused deposition modeling (FDM) 3D printing is a promising additive manufacturing technique to produce low-cost disposable electrochemical devices. However, the print of devices like well-known screen-printed electrodes (all electrodes on the same device) is difficult using the available technology (few materials available for production of working electrodes). In this paper we present a procedure to produce disposable and robust electrochemical devices by FDM 3D printing that allows reproducible analysis of small volumes (50-2000 μL). The device consists of just two printed parts that allow easy coupling of different conductive materials for using as disposable or non-disposable working electrodes with reproducible geometric area. Printed counter and pseudo-reference electrodes can also be easily fitted into the microcell. Moreover, conventional counter (platinum wire) and mini reference electrodes can also be used. As a proof of concept, paracetamol, cocaine and uric acid were used as model analytes using different materials as working electrodes. Linear calibration curves (r > 0.99) with similar slopes (0.29 ± 0.01 μA μmol L-1; RSD = 3.4%) were obtained by square wave voltammetry (SWV) using a complete printed system and different volumes of standard solutions of paracetamol (50, 100, and 200 μL). For uric acid, a linear range of 10-125 μmol L-1 (r > 0.99), was obtained using differential pulse voltammetry as the electrochemical technique and a disposable laser-induced graphene base as the working electrode. With the coupling of boron-doped diamond working electrode, screening tests were successfully performed in seized cocaine samples with selective detection of cocaine in the presence of its most common adulterants. The production cost per unit of a complete electrochemical system is around US 5.00. In large-scale production, only the working electrode needs to be replaced while the microcell and counter/pseudo reference electrodes do not need to be discarded.

Improving the performance and versatility of microfluidic thread electroanalytical devices by automated injection with electronic pipettes: a new and powerful 3D-printed analytical platform

Microfluidic cotton thread-based electroanalytical devices (μTEDs) are analytical systems with attractive features such as spontaneous passive flow, low cost, minimal waste production, and good sensitivity. Currently, sample injection in µTEDs is performed by hand using manual micropipettes, which have drawbacks such as inconstant speed and position, dependence of skilled analysts, and need of physical effort of operator during prolonged times, leading to poor reproducibility and risk of strain injury. As an alternative to these inconveniences, we propose, for the first time, the use of electronic micropipettes to carry out automated injections in µTEDs. This new approach avoids all disadvantages of manual injections, while also improving the performance, experience, and versatility of µTEDs. The platform developed here is composed by three 3D-printed electrodes (detector) attached to a 3D-printed platform containing an adjustable holder that keeps the electronic pipette in the same x/y/z position. As a proof-of-concept, both injection modes (manual and electronic) were compared using three model analytes (nitrite, paracetamol, and 5-hydroxytryptophan) on µTED with amperometric detection. As result, improved analytical performance (limits of detection between 2.5- and 5-fold lower) was obtained when using electronic injections, as well as better repeatability/reproducibility and higher analytical frequencies. In addition, the determination of paracetamol in urine samples suggested better precision and accuracy for automated injection. Thus, electronic injection is a great advance and changes the state-of-art of µTEDs, mainly considering the use of more modern and versatile electronic pipettes (wider range of pre-programmed modes), which can lead to the development of even more automated systems.

Electrochemical sensor based on 3D-printed substrate by masked stereolithography (MSLA): a new, cheap, robust and sustainable approach for simple production of analytical platforms

The development of miniaturized, sustainable and eco-friendly analytical sensors with low production cost is a current trend worldwide. Within this idea, this work presents  the innovative use of masked stereolithography (MSLA) 3D-printed substrates for the easy fabrication of pencil-drawn electrochemical sensors (MSLA-3D-PDE). The use of a non-toxic material such as pencil (electrodes) together with a biodegradable 3D printing resin (substrate) allowed the production of devices that are quite cheap (ca. US$ 0.11 per sensor) and with low environmental impact. Compared to paper, which is the most used substrate for manufacturing pencil-drawn electrodes, the MSLA-3D-printed substrate has the advantages of not absorbing water (hydrophobicity) or becoming crinkled and weakened when in contact with solutions. These features provide more reproducible, reliable, stable, and long-lasting sensors. The MSLA-3D-PDE, in conjunction with the custom cell developed, showed excellent robustness and electrochemical performance similar to that observed of the glassy carbon electrode, without the need of any activation procedure. The analytical applicability of this platform was explored through the quantification of omeprazole in pharmaceuticals. A limit of detection (LOD) of 0.72 µmol L^-1 was achieved, with a linear range of 10 to 200 µmol L^-1. Analysis of real samples provided results that were highly concordant with those obtained by UV-Vis spectrophotometry (relative error ≤ 1.50%). In addition, the greenness of this approach was evaluated and confirmed by a quantitative methodology (Eco-Scale index). Thus, the MSLA-3D-PDE appears as a new and sustainable tool with great potential of use in analytical electrochemistry.

Adjusting the Connection Length of Additively Manufactured Electrodes Changes the Electrochemical and Electroanalytical Performance

Changing the connection length of an additively manufactured electrode (AME) has a significant impact on the electrochemical and electroanalytical response of the system. In the literature, many electrochemical platforms have been produced using additive manufacturing with great variations in how the AME itself is described. It is seen that when measuring the near-ideal outer-sphere redox probe hexaamineruthenium (III) chloride (RuHex), decreasing the AME connection length enhances the heterogeneous electrochemical transfer (HET) rate constant (k0) for the system. At slow scan rates, there is a clear change in the peak-to-peak separation (ΔEp) observed in the RuHex voltammograms, with the ΔEp shifting from 118 ± 5 mV to 291 ± 27 mV for the 10 and 100 mm electrodes, respectively. For the electroanalytical determination of dopamine, no significant difference is noticed at low concentrations between 10- and 100-mm connection length AMEs. However, at concentrations of 1 mM dopamine, the peak oxidation is shifted to significantly higher potentials as the AME connection length is increased, with a shift of 150 mV measured. It is recommended that in future work, all AME dimensions, not just the working electrode head size, is reported along with the resistance measured through electrochemical impedance spectroscopy to allow for appropriate comparisons with other reports in the literature. To produce the best additively manufactured electrochemical systems in the future, researchers should endeavor to use the shortest AME connection lengths that are viable for their designs.

Using nanostructured carbon black-based electrochemical (bio)sensors for pharmaceutical and biomedical analyses: A comprehensive review

The outstanding electronic properties of carbon black (CB) and its economic advantages have fueled its application as nanostructured electrode material for the development of new electrochemical sensors and biosensors. CB-based electrochemical sensing devices have been found to exhibit high surface area, fast charge transfer kinetics, and excellent functionalization. In the present work, we set forth a comprehensive review of the recent advances made in the development and application of CB-based electrochemical devices for pharmaceutical and biomedical analyses - from quantitative monitoring of drug formulations to clinical diagnoses - and the underlying challenges and constraints that need to be overcome. We also present a thorough discussion about the strategies and techniques employed in the development of new electrochemical sensing platforms and in the enhancement of their analytical properties and biocompatibility for anchoring active biomolecules, as well as the combination of these sensing devices with other materials aiming at boosting the performance and efficiency of the sensors.

Exploring the coating of 3D-printed insulating substrates with conductive composites: a simple, cheap and versatile strategy to prepare customized high-performance electrochemical sensors

The development of 3D-printed electrochemical sensors by fused deposition modeling (FDM) has been increasing exponentially in the last five years. In this context, commercial conductive filaments composed of a blend of carbon particles (e.g., graphene or carbon black (CB)) and insulating thermoplastic polymers (e.g., polylactic acid (PLA) or acrylonitrile butadiene styrene (ABS)) have been widely used for electrode fabrication. However, such materials may be expensive and the electrodes when used "as-printed" exhibit poor electrochemical performance as a function of the low content of conductive particles in the composition (∼10 to 20 wt%), which requires one or more post-treatment steps (e.g. polishing, chemical, electrochemical, and photochemical) to reach good electrochemical performance. In this technical note a less used approach to produce "ready-to-use" electrochemical platforms based on 3D printing is explored, which consists of the coating of 3D-printed insulating substrates with homemade conductive composites. To demonstrate the potentiality of this alternative protocol, 3D-printed ABS insulating substrates at two geometries were coated in a highly loaded graphite (55 wt%) homemade composite (G-ABS) and evaluated for the detection of the ferri/ferrocyanide redox probe and model analytes in stationary and hydrodynamic 3D-printed systems (nitrite in micro-flow injection analysis/μFIA and paracetamol in batch injection analysis/BIA, respectively). The analytical parameters acquired with the coated electrodes were comparable to those obtained using conventional electrodes (glassy carbon, boron-doped diamond and carbon screen-printed) and 3D-printed sensors fabricated with commercial filaments. Moreover, the inclusion of carbon black in the fluid conductive composite was demonstrated as a perspective to obtain modified coated 3D-printed surfaces easily for the first time. This alternative "do it yourself" strategy is promising for the large-scale production of very cheap (US$ 0.08) and high-performance electrodes based on FDM 3D printing. Moreover, this approach dispenses the acquisition of commercial conductive filaments and the laborious development of homemade filaments.

Electrochemical (Bio)Sensors Enabled by Fused Deposition Modeling-Based 3D Printing: A Guide to Selecting Designs, Printing Parameters, and Post-Treatment Protocols

The 3D printing (or additive manufacturing, AM) technology is capable to provide a quick and easy production of objects with freedom of design, reducing waste generation. Among the AM techniques, fused deposition modeling (FDM) has been highlighted due to its affordability, scalability, and possibility of processing an extensive range of materials (thermoplastics, composites, biobased materials, etc.). The possibility of obtaining electrochemical cells, arrays, pieces, and more recently, electrodes, exactly according to the demand, in varied shapes and sizes, and employing the desired materials has made from 3D printing technology an indispensable tool in electroanalysis. In this regard, the obtention of an FDM 3D printer has great advantages for electroanalytical laboratories, and its use is relatively simple. Some care has to be taken to aid the user to take advantage of the great potential of this technology, avoiding problems such as solution leakages, very common in 3D printed cells, providing well-sealed objects, with high quality. In this sense, herein, we present a complete protocol regarding the use of FDM 3D printers for the fabrication of complete electrochemical systems, including (bio)sensors, and how to improve the quality of the obtained systems. A guide from the initial printing stages, regarding the design and structure obtention, to the final application, including the improvement of obtained 3D printed electrodes for different purposes, is provided here. Thus, this protocol can provide great perspectives and alternatives for 3D printing in electroanalysis and aid the user to understand and solve several problems with the use of this technology in this field.

A novel miniaturized electroanalytical device integrated with gas extraction for the voltammetric determination of sulfite in beverages

Voltammetry and amperometry are inexpensive and high-performance analytical techniques. However, their lack of selectivity limits their use in complex matrices such as biological, environmental, and food samples. Therefore, voltammetric and amperometric analyses of these samples usually require time-consuming and laborious sample pretreatments. In this study, we present a simple and cost-effective approach to fabricate a miniaturized electrochemical cell that can be easily coupled to a head space-like gas extraction procedure in such a way the sample pretreatment and voltammetric detection are performed in a single step. As a proof of concept, we have used the proposed system to quantify sulfite in beverage samples after its conversion to SO_2(g). Despite the simplicity and low cost of the proposed system, it provided good analytical performance and a limit of detection of 4.0 μmol L^-1 was achieved after only 10 min of extraction. The proposed system is quite versatile since it can be applied to quantify any volatile electroactive species. Also, the proposed system provides a unique way to assess real-time extraction curves, which are essential to study and optimize new gas extraction procedures. Therefore, the approach described in this study could contribute to both applied and fundamental Analytical Chemistry.

Fully Integrated 3D-Printed Electronic Device for the On-Field Determination of Antipsychotic Drug Quetiapine

In this work, we developed a novel all-3D-printed device for the simple determination of quetiapine fumarate (QF) via voltammetric mode. The device was printed through a one-step process by a dual-extruder 3D printer and it features three thermoplastic electrodes (printed from a carbon black-loaded polylactic acid (PLA)) and an electrode holder printed from a non-conductive PLA filament. The integrated 3D-printed device can be printed on-field and it qualifies as a ready-to-use sensor, since it does not require any post-treatment (i.e., modification or activation) before use. The electrochemical parameters, which affect the performance of the sensor in QF determination, were optimized and, under the selected conditions, the quantification of QF was carried out in the concentration range of 5 × 10⁻⁷–80 × 10⁻⁷ mol × L⁻¹. The limit of detection was 2 × 10⁻⁹ mol × L⁻¹, which is lower than that of existing electrochemical QF sensors. The within-device and between-device reproducibility was 4.3% and 6.2% (at 50 × 10⁻⁷ mol × L⁻¹ QF level), respectively, demonstrating the satisfactory operational and fabrication reproducibility of the device. Finally, the device was successfully applied for the determination of QF in pharmaceutical tablets and in human urine, justifying its suitability for routine and on-site analysis.

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.