Explore the vast range of titles available.

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.

A rapid and simple method for the amperometric determination of glucose using a nanocomposite film of nickel oxyhydroxide and multi-walled carbon nanotube (MWCNTs) was evaluated. The NiHCF)/MWCNT electrode film was fabricated using the liquid–liquid interface method, and it was used as a precursor for the electrochemical synthesis of nickel oxy-hydroxy (Ni(OH)2/NiOOH/MWCNT). The interaction between nickel oxy-hydroxy and the MWCNTs provided a film that is stable over the electrode surface, with high surface area and excellent conductivity. The nanocomposite presented an excellent electrocatalytic activity for the oxidation of glucose in an alkaline medium. The sensitivity of the sensor was found to be 0.0561 μA μmol L−1, and a linear range from 0.1 to 150 μmol L−1 was obtained, with a good limit of detection (0.030 μmol L−1). The electrode exhibits a fast response (150 injections h−1) and a sensitive catalytic performance, which may be due to the high conductivity of MWCNT and the increased active surface area of the electrode. Additionally, a minimal difference in the slopes for ascending (0.0561 µA µmol L−1) and descending (0.0531 µA µmol L−1) was observed. Moreover, the sensor was applied to the detection of glucose in artificial plasma blood samples, achieving values of 89 to 98% of recovery.

Silver materials are known to present excellent properties, such as high electrical and thermal conductivity as well as chemical stability. Silver-based inks have drawn a lot of attention for being compatible with various substrates, which can be used in the production uniform and stable pseudo-reference electrodes with low curing temperatures. Furthermore, the interest in the use of disposable electrodes has been increasing due to the low cost and the possibility of their use in point-of-care and point-of-need situations. Thus, in this work, two new inks were developed using Ag as conductive material and colorless polymers (nail polish (NP) and shellac (SL)), and applied to different substrates (screen-printed electrodes, acetate sheets, and 3D-printed electrodes) to verify the performance of the proposed inks. Measurements attained with open circuit potential (OCP) attested to the stability of the potential of the pseudo-reference proposed for 1 h. Analytical curves for β-estradiol were also obtained using the devices prepared with the proposed inks as pseudo-references electrodes, which presented satisfactory results concerning the potential stability (RSD < 2.6%). These inks are simple to prepare and present great alternatives for the development of pseudo-reference electrodes useful in the construction of disposable electrochemical systems.

We show that fused deposition modelling (FDM) 3D-printed electrodes can be used for quality control of fuel bioethanol. 3D-printing using carbon black/polylactic acid (CB-PLA) filaments resulted in conductive and biodegradable electrodes for biofuel analysis. As a proof-of-concept, copper determination in fuel bioethanol was performed, as such ions catalyse oxidation processes during storage and transport. Square-wave anodic-stripping voltammetry (SWASV) of copper was achieved after sample dilution in 0.1 mol L−1 HCl as supporting electrolyte (resulting in 30:70% v/v ethanol:water). The linear responses were in the range between 10 and 300 μg L−1 (R = 0.999), inter-day precision was lower than 8% (n = 10, for 20 μg L−1) and limits of detection (LOD) and quantification (LOQ) using 180 s as deposition time were 0.097 μg L−1 and 0.323 μg L−1, respectively. Recovery values between 95 and 103% for the analysis of bioethanol spiked with known amounts of copper were obtained. These results show great promise of the application of 3D-printed sensors for the quality control of biofuels.

The integration of eco-friendly composites based on polymers and conductive fillers offers exciting opportunities for creating sustainable materials with superior electrical properties, paving the way for innovative advancements in electroanalytical devices. In this study, we explored the potential of biodegradable polylactic acid (PLA), carbon black (CB), and biochar derived from coconut shell waste to develop fused filament fabrication (FFF) filaments without the need for hazardous solvents. To assess the influence of biochar on the electrochemical properties, additional filaments composed exclusively of CB and PLA were also fabricated for comparison. The resulting conductive FFF filaments were used to fabricate additively manufactured electrodes. The biochar-CB/PLA electrode presented superior electrochemical activity, as indicated by cyclic voltammetry (CV) scans for both outer-sphere ([Ru(NH 3 ) 6 ] 2+/3+ ) and inner-sphere ([Fe(CN) 6 ] 3-/4- ) redox couples. The biochar-CB/PLA electrodes also exhibited a lower charge transfer resistance ( Rct  = 1.01 ± 0.05 kΩ) than the CB/PLA sensor ( Rct  = 9.11 ± 0.03 kΩ), highlighting the improved performance of the conductive biochar-CB/PLA filament in the production of working electrodes. The biochar, acting as an adsorbent, enhances electrochemical performance by pre-concentrating analytes at the electrode surface. Furthermore, the biochar-CB/PLA electrodes were successfully employed to detect carbendazim (CBZ), a widely used fungicide, in environmental (lake and tap water) and food (lemon juice and drinking water) samples, using differential pulse voltammetry (DPV). A linear range of 0.1 to 5.0 µmol L −1 and a limit of detection (LOD) of 0.01 µmol L −1 were achieved for CBZ determination. Recovery values (~ 90–115%) were achieved for the analysis of samples, indicating the potential of biochar-CB/PLA-based electrodes for reliable and sustainable electrochemical sensing applications. Graphical Abstract

Babassu ( Atallea sp. ), a native palm tree from South America’s Amazon produces bio-oil and biochar with significant potential for industrial applications. Babassu oil as a bio-based plasticizer is reported here for the first time to replace petrochemical alternatives in the production of conductive filaments for additive manufacturing purposes. The newly developed filament, consisting of 30 wt.% carbon black (CB), 60 wt.% polylactic acid (PLA), and 10 wt.% Babassu oil, demonstrates enhanced thermal stability, improved printability, and superior electrochemical performance. 3D-printed electrodes made from this Babassu-CB/PLA filament outperform those made from commercial CB/PLA filaments, exhibiting better voltammetric responses (e.g., lower peak-to-peak separation and higher current intensity) for inner-sphere redox probes. As a proof-of-concept, these bio-based electrodes were successfully used to detect cocaine in real-world street samples, with a limit of detection (LOD) of 1.2 µmol L −1 . The Babassu-CB/PLA electrodes provided reliable cocaine quantification without interference from common adulterants such as caffeine, paracetamol, and phenacetin and showed no matrix effects, as confirmed by recovery values ranging from 88 to 102%. Notably, the use of Babassu oil eliminates the need for laborious post-treatment protocols to achieve optimal electrochemical performance. In this study, only mechanical polishing on the electrode surface is required. This study highlights the potential of Babassu oil as a sustainable alternative in the fabrication of conductive filaments for electrochemical applications, advancing the field of environmentally friendly and efficient 3D-printed sensors. Graphical Abstract

The use of 3D-printed electrodes is reported fabricated from in-house conductive filament composed of a mixture of recycled poly (lactic acid) (rPLA), graphite (Gpt), and carbon black (CB) for fast detection of the abused drug ketamine. Firstly, the performance of these electrodes was evaluated in comparison to 3D-printed electrodes produced employing a commercially available conductive filament. After a simple pretreatment step (mechanical polishing), the new 3D-printed electrodes presented better performance than the electrodes produced from commercial filament in relation to peak-to-peak separation of the redox probe [Fe(CN) 6 ] 3- / 4- (130 mV and 759 mV, respectively), charge transfer resistance (R ct  = 1.04 ± 0.05 kΩ and 9.62 ± 0.03 kΩ, respectively), and heterogeneous rate constant (k 0  = 7.16 ± 0.05 × 10 –3  cm s −1 and 3.57 ± 0.03 × 10 –3  cm s -1 , respectively). Excellent analytical characteristics for the detection of ketamine were achieved, including wide linear range (10 to 250 μmol L -1 ), excellent sensitivity (0.024 ± 0.001 μA μmol L -1 ), low limit of detection (LOD = 0.7 μmol L -1 ), and recovery values from 82 to 115% for beverage samples (white and red wines, beer, water, and vodka) spiked with the abused drug ketamine. Graphical Abstract

A new electrochemical device fabricated by the combination of 3D printing manufacturing and laser-generated graphene sensors is presented. Cell and electrodes were 3D printed by the fused deposition modeling (FDM) technique employing acrylonitrile butadiene styrene filament (insulating material that composes the cell) and conductive filament (lab-made filament based on graphite dispersed into polylactic acid matrix) to obtain reference and auxiliary electrodes. Infrared-laser engraved graphene, also reported as laser-induced graphene (LIG), was produced by laser conversion of a polyimide substrate, which was assembled in the 3D-printed electrochemical cell that enables the analysis of low volumes (50–2000 μL). XPS analysis revealed the formation of nitrogen-doped graphene multilayers that resulted in excellent electrochemical sensing properties toward the detection of atropine (ATR), a substance that was found in beverages to facilitate sexual assault and other criminal acts. Linear range between 5 and 35 μmol L −1 , detection limit of 1 μmol L −1 , and adequate precision (RSD = 4.7%, n = 10) were achieved using differential-pulse voltammetry. The method was successfully applied to beverage samples with recovery values ranging from 80 to 105%. Interference studies in the presence of species commonly found in beverages confirmed satisfactory selectivity for ATR sensing. The devices proposed are useful portable analytical tools for on-site applications in the forensic scenario. Graphical Abstract

A laser-induced graphene (LIG) surface modified with Prussian blue (iron hexacyanoferrate) is demonstrated as a novel electrochemical sensing platform for the sensitive and selective detection of hydrogen peroxide. Electrochemical Prussian blue (PB) modification on porous graphene films engraved by infrared laser over flexible polyimide was accomplished. Scanning electron microscopy images combined with Raman spectra confirm the formation of porous graphene and homogenous electrodeposition of PB over this porous surface. Electrochemical impedance spectroscopy reveals a substantial decrease in the resistance to charge transfer values (from 395 to 31.4 Ω) after the PB insertion, which confirms the formation of a highly conductive PB-graphene composite. The synergistic properties of PB and porous graphene were investigated for the constant monitoring of hydrogen peroxide at 0.0 V vs . Ag|AgCl|KCl (sat.) , under high-flow injections (166 µL s −1 ) confirming the high stability of the modified surface and fast response within a wide linear range (from 1 to 200 µmol L −1 ). Satisfactory detection limit (0.26 µmol L −1 ) and selectivity verified by the analysis of complex samples confirmed the excellent sensing performance of this platform. We highlight that the outstanding sensing characteristics of the developed sensor were superior in comparison with other PB-based or LIG-based electrochemical sensors reported for hydrogen peroxide detection. Graphical abstract

The development of a tailored filament is reported composed of reduced graphene oxide (rGO) and carbon black (CB) in a polylactic acid (PLA) matrix and its use in the production of electrochemical sensors. The electrodes containing rGO showed superior performance when compared with  those prepared in the absence of this material. Physicochemical and electrochemical characterizations of the electrodes showed the successful incorporation of both rGO and CB and an improved conductivity in the presence of rGO (lower resistance to charge transfer). As a proof-of-concept, the developed electrodes were applied to the detection of the forensic analytes TNT and cocaine. The electrodes containing rGO presented a superior analytical performance for both TNT and cocaine detection, showing the lower limit of detection values (0.22 and 2.1 µmol L −1 , respectively) in comparison with pure CB-PLA electrodes (0.93 and 11.3 µmol L −1 , respectively). Besides, better-defined redox peaks were observed, especially for TNT, as well as increased sensitivity for both molecules. Graphical abstract