Additive manufacturing or three-dimensional (3D)-printing is an emerging technology that has been applied in the development of novel materials and devices for a wide range of applications, including ...Electrochemistry and Analytical Chemistry areas. This review article focuses on the contributions of 3D-printing technology to the development of electrochemical sensors and complete electrochemical sensing devices. Due to the recent contributions of 3D-printing within this scenario, the aim of this review is to present a guide for new users of 3D-printing technology considering the required features for improved electrochemical sensing using 3D-printed sensors. At the same time, this is a comprehensive review that includes most 3D-printed electrochemical sensors and devices already reported using selective laser melting (SLM) and fused deposition modeling (FDM) 3D-printers. The latter is the most affordable 3D-printing technique and for this reason has been more often applied for the fabrication of electrochemical sensors, also due to commercially-available conductive and non-conductive filaments. Special attention is given to critically discuss the need for the surface treatment of FDM 3D-printed platforms to improve their electrochemical performance. The insertion of biochemical and chemical catalysts on the 3D-printed surfaces are highlighted as well as novel strategies to fabricate filaments containing chemical modifiers within the polymeric matrix. Some examples of complete electrochemical sensing systems obtained by 3D-printing have successfully demonstrated the enormous potential to develop portable devices for on-site applications. The freedom of design enabled by 3D-printing opens many possibilities of forthcoming investigations in the area of analytical electrochemistry.
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•We review the contributions of 3D-printing to fabricate electrochemical sensors.•Different 3D-printing methods are compared highlighting fused deposition modeling (FDM).•Surface treatment and modification with (bio)chemical mediators for improved performance.•Strategies for fabrication of conductive filaments are presented for future applications.•3D-printing of all-in-one electrochemical devices in different designs are assessed.
Herein, we report a complete additively manufactured (AM) electrochemical sensing platform. In this approach, a fully AM/3D-printed electrochemical system, using a conventional low-cost 3D printer ...(fused deposition modeling) fabricating both the conductive electrodes and the nonconductive/chemically inert electrochemical cell is reported. The electrodes (working, counter, and pseudo-reference) are AM using a conductive fused-filament comprised of a mixture of carbon black nanoparticles and polylactic acid (CB/PLA). AM components partially coated with silver ink presented a similar behavior to a conventional Ag/AgCl reference electrode. The performance of the AM working electrode was evaluated after a simple and fast polishing procedure on sandpaper and electrochemical activation in a NaOH solution (0.5 mol L–1). Following the electrochemical activation step, a considerable improvement in the electrochemical behavior (current intensity and voltammetric profile) was obtained for model analytes, such as dopamine, hexaammineruthenium(III) chloride, ferricyanide/ferrocyanide, uric acid, and ascorbic acid. Excellent repeatability (RSD = 0.4%, N = 10) and limit of detection (0.1 μmol L–1) were obtained with the all complete AM electrochemical system for dopamine analysis. The electrochemical performance of the developed system (after simple electrochemical activation of the working electrode) was similar or better than those obtained using commercial glassy carbon and screen-printed carbon electrodes. The results shown here represents a significant advance in AM (3D printing) technology for analytical chemistry.
•Fused deposition modeling 3D-printed electrode for (bio)sensors applied to real samples.•Enzymatic glucose biosensing on 3D-printed graphene-PLA electrode in plasma.•Oxygenated groups from PLA ...matrix favored enzyme immobilization by crosslinking.•Graphene-PLA 3D-printed electrochemical response improves after surface treatment.•Rapid and precise analysis of urine and saliva by pulsed amperometry using flow system.
Additive manufacturing, also known as 3D-printing, is receiving great interest by chemists due to the easy design of novel materials, fast prototyping and reducing waste, which enables large-scale fabrication of electrochemical devices. Herein we demonstrate the development of (bio)sensors for the analysis of biological fluids using 3D-printing. Fused deposition modelling was used to fabricate (bio)sensing platforms from commercially-available filaments made of polylactic acid containing graphene (G-PLA). An enzymatic glucose biosensor fabricated on the G-PLA surface was developed and applied for glucose sensing in blood plasma using chronoamperometry. Oxygenated groups from the polymeric matrix provides suitable condition to enzyme immobilization by crosslinking with glutaraldehyde. The biosensor presented a limit of detection (LOD) of 15 μmol L−1, inter-day and intra-day precision lower than 5 %, and adequate recovery values (90–105 %) for the analysis of plasma. We also show that the surface treatment of the 3D-printed sensor (mechanical polishing followed solvent immersion) provides improved electrochemical properties for the direct detection of nitrite and uric acid. Differential-pulse voltammetry and multiple-pulse amperometry under flow conditions were evaluated and compared for the determination of both species in saliva and urine. Highlights are presented for the amperometric detection within a linear range from 0.5–250 μmol L−1 for both analytes, LODs of 0.02 and 0.03 μmol L−1 for uric acid and nitrite, respectively, and high precision (RSD < 2.1 %). This report shows the first application of 3D-printed sensors and biosensors for the analysis of real biological samples with analytical features comparable to conventional modified electrodes.
This work shows that the electrochemical activity of a 3D-printed electrode fabricated using a conductive composite of polylactic acid (PLA) containing carbon black (CB) can be substantially improved ...through a simple and fast chemical/electrochemical pretreatment in 0.5 mol L−1 NaOH. Scanning electron microscopy and infrared spectroscopy data showed that the pretreatment process promotes the removal of the non-conductive PLA material, providing greater exposure of the conductive particles. Cyclic voltammetry of the redox probe ferricyanide/ferrocyanide indicated faster electron transfer on the treated 3D-printed surface and increase in electroactive area. Moreover, electrochemical impedance spectroscopic results also confirmed faster electron transfer after surface pretreatment. As a proof-of-concept, a low-cost and sensitive method for the determination of cadmium and lead in real urine and saliva samples by square-wave anodic stripping voltammetry was developed. The chemical/electrochemical treatment provided an impressive 30-fold current increase in the detection of both metals. Acceptable limits of detection (2.9 μg L−1 for Cd2+ and 2.6 μg L−1 for Pb2+), wide linear ranges for both metals (30 μg L−1 to 270 μg L−1; R = 0.997), high stability (RSD lower than 4.5%; n = 10), and adequate recovery values (between 93% and 112%) for the analysis of spiked samples were achieved. Additionally, interday (n = 3), intra-day (n = 3), inter-electrode (n = 2) and inter-treatment (n = 2) experiments revealed RSD values lower than 6.5%, which indicates high reproducibility of the proposed treated 3D-printed electrode. The strategy here proposed opens up new applications for 3D-printed electrode in analytical electrochemistry with improved electrochemical sensing properties in comparison to screen-printed electrodes.
The fabrication of carbon black/polylactic acid (PLA) electrodes using a 3D printing pen is presented and compared with electrodes obtained by a desktop fused deposition modelling (FDM) 3D printer. ...The 3D pen was used for the fast production of electrodes in two designs using customized 3D printed parts to act as template and guide the reproducible application of the 3D pen: (i) a single working electrode at the bottom of a 3D-printed cylindrical body and (ii) a three-electrode system on a 3D-printed planar substrate. Both devices were electrochemically characterized using the redox probe Fe(CN)63−/4- via cyclic voltammetry, which presented similar performance to an FDM 3D-printed electrode or a commercial screen-printed carbon electrode (SPE) regarding peak-to-peak separation (ΔEp) and current density. The surface treatment of the carbon black/PLA electrodes fabricated by both 3D pen and FDM 3D-printing procedures provided substantial improvement of the electrochemical activity by removing excess of PLA, which was confirmed by scanning electron microscopic images for electrodes fabricated by both procedures. Structural defects were not inserted after the electrochemical treatment as shown by Raman spectra (iD/iG), which indicates that the use of 3D pen can replace desktop 3D printers for electrode fabrication. Inter-electrode precision for the best device fabricated using the 3D pen (three-electrode system) was 4% (n = 5) considering current density and anodic peak potential for the redox probe. This device was applied for the detection of 2,4,6-trinitrotoluene (TNT) via square-wave voltammetry of a single-drop of 100 μL placed upon the thee-electrode system, resulting in three reduction peaks commonly verified for TNT on carbon electrodes. Limit of detection of 1.5 μmol L−1, linear range from 5 to 500 μmol L−1 and RSD lower than 4% for 10 repetitive measurements of 100 μmol L−1 TNT were obtained. The proposed devices can be reused after polishing on sandpaper generating new electrode surfaces, which is an extra advantage over chemically-modified electrochemical sensors applied for TNT detection.
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•3D pen fabricated carbon black/polylactic acid electrodes compared with 3D-printed electrodes.•Morphological analysis shows no difference, except to electrochemical surface treatment.•Highly reproducible planar three-electrode devices were fabricated (RSD = 4%, n = 5).•Similar results to those obtained on 3D-printed or screen-printed electrodes.•Application to TNT detection in a single drop (100 μL placed upon the device).
This mini‐review presents an overview of recent trends for 3D printed sensors and biosensors (with a focus on Fused Deposition Modeling (FDM) based technology), along with their posttreatment ...surfaces to improve electrochemical applications. The protocols described in the literature and advances in this field were covered, bringing a critical discussion about the achievements and limitations to improve the electrical properties of conducting filaments, as well as their electroanalytical performance. In addition, the pros and cons of the processes used in surface posttreatment to improve the performance of electrodes constructed by FDM are presented, comparing the time consumed during chemical and electrochemical treatments or combining the two to improve the characteristics of the sensors. Finally, the discussion about the real necessity of surface treatments of electrodes constructed by FDM technology, the techniques used for this, and some ecological protocols are discussed (surface posttreatments with and without reagents) or whether the simple optimization of printing parameters could also significantly improve the electrochemical performance of sensors built with such technologies.
This work presents a novel procedure involving the sequential chemical treatment to generate reduced graphene oxide (rGO) within 3D-printed polylactic acid (PLA) electrodes and their potential ...applications for sensing and biosensing. A new configuration of a compact all-3D-printed electrochemical device containing the three electrodes is presented, in which the working electrode was treated to generate rGO within PLA (rGO-PLA) after treatment within NaBH4. The rGO-PLA electrodes presented a notable current increase for the redox probe ferrocene-methanol in comparison with the same surface treated by dimethylformamide immersion. Also, the electrochemical impedance spectroscopic data that presented the lowest resistance to electron transfer for the proposed electrode. The electrochemical experiments were in accordance with Raman spectra and surface roughness obtained by atomic force microscopy images. As proofs-of-concept, the rGO-PLA electrode was applied for serotonin determination in synthetic urine using differential-pulse voltammetry with a limit of detection of 0.032 μmol L−1. Also, the second application involved the fabrication of a tyrosinase-based biosensor capable of determining catechol in natural water samples with a limit of detection of 0.26 μmol L−1. Based on both applications, the 3D-printed rGO-PLA showed to be an excellent platform for sensing and biosensing purposes.
•A new platform using reduced graphene oxide is proposed.•The electrochemical cell, sensors, and biosensors were produced by 3D-printing.•The proposed electrode could be applied for other electrochemical sensing and biosensing.•The 3D-printed sensor and biosensor were applied for the determination of phenolic compounds.
Metal organic frameworks (MOFs) are hybrid materials built with both organic and inorganic components. The potential of these structures was highlighted in the 1990s and since then, over 90 000 ...articles dealing with MOFs have been published (still growing rapidly), demonstrating a wide variety of applications. However, an improvement in the electrochemical properties of MOFs is still required to enhance the attributes to satisfy the real and strategic applications of MOF-electrode materials in energy conversion and storage (batteries, supercapacitors, and as catalysts for fuel cells and water splitting), especially in the development of electrochemical sensors. In this sense, being the focus of this review, the great potential of MOF-derived structures for the construction of electrochemical sensors is presented, highlighting the recent advances and strategies on MOF-derived materials, such as metals, metal oxide/hydroxide, metal sulfides, metal phosphides, carbons, or their composites and their potential as electrode materials. In fact, MOF-derived materials exhibit exceptional conductivity, electrochemical activity, and stability, which surpass the relative low conductivity and lack chemical/structural robustness of pristine MOFs, inheriting only the essential structural and compositional properties from their MOF precursors.
Considering the demand for highly sensitive and selective electrochemical sensors, MOF-derived materials and their composites have demonstrated relevant advances in electrochemical sensing, as summarized in this review article.
The energy requirement of modern society increases every day. The depletion of the reserves of fossil fuel combined with the deleterious effects of CO2 in the atmosphere is forcing all the world to ...search for alternative ways of generation and storing energy. Many scientists around the world are pursuing different forms to produce and store energy. Solar and wind sources are a reality for production of electricity, but are not continuous and require storage devices. The development of batteries and hybrid supercapacitors of high energy and power density is of great importance to complement this requirement of energy storage. Rechargeable metal–air batteries which utilize oxygen electrocatalysis seem to be an ideal choice, once the source of energy is not intermittent as solar and wind energy and is based on oxygen bifunctional electrocatalysis of both oxygen reduction and O2 evolution reactions. In addition, water splitting allows the conversion and storage of solar/wind energy into chemical energy, generating fuels with high energy content. From this perspective, spinel MnCo2O4-based materials are promising structures for energy storage and conversion of energy. In this review, the use of low cost and abundant multifunctional materials for the development of supercapacitor devices and batteries was summarized. Completely, the design of electrocatalysts for water splitting and their capability to proportionate the tetra-electronic process of the oxygen reduction reaction are reviewed, including the main strategies in the preparation of these materials and considering their key multifunctional role in the way to a more sustainable society.
Conductive 3D-printed platforms have been recognized an emerging class of materials with great potential to electrochemistry. However, such 3D-printed electrodes require a surface treatment to remove ...excess of polymer that hinders the electron transfer. We report a fast (2-min) and chemical-free protocol for the surface treatment of 3D-printed conductive electrodes based on reactive cold oxygen plasma. A dramatic improvement of electrochemical activity of 3D-printed carbon black-polylactic acid (CB-PLA) electrodes was verified by the decrease in the peak-to-peak separation of the voltammetric response for the Fe(CN)63-/Fe(CN)64- couple and in the resistance of change transfer. The O2-plasma treatment increased oxide groups and graphitic groups at the CB-PLA surface (verified by XPS) and provided higher rugosity (SEM images) thus higher exposure of conducting carbon sites and increased electroactive area in comparison with CO2-plasma, which explains the improved electrochemical performance using O2-plasma treated electrodes. This protocol is faster and provided improved electrochemical activity compared with electrochemical, chemical, or biological treatments. As proofs-of concept, the benefits of surface plasma treatment of the 3D-printed electrodes were demonstrated towards the electrochemical sensing of dopamine and nitrite, molecules of biological interest, including the analysis of human saliva. Values of sensitivity and detection limit were greatly improved when using O2-plasma treatment for both molecules (up to 100-fold increase in sensitivity for the voltammetric detection of dopamine), suggesting great promises for the development of highly-sensitive electrochemical sensors.
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•Cold plasma treatment of 3D-printed carbon electrodes provides high electron transfer.•Chemical-free and fast (2 min) protocol using reactive oxygen plasma over the electrode.•Decrease in the ∆E of the voltammetric response for the Fe(CN)63-/Fe(CN)64- couple.•Diminution of the resistance of charge transfer after plasma treatment of the surfaces.•Faster and more efficient than electrochemical, chemical, or biological treatments of 3D printed surfaces.
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