3D-printed Carbon Research Articles

Integrating 3D printing of polymer matrix composites and metal additive layer manufacturing: surface metallization of 3D printed composite panels through cold spray deposition of aluminium particles

The integration of metals and polymers in the same component to couple the best properties and advantages of both these classes of materials can be useful for engineering applications. In this scenario, the aim of this paper is to integrate additive manufacturing of composites with cold spray deposition of metal particles: in particular, 3D-printed carbon fibre-reinforced plastics (CFRP) panels were coated with aluminium particles to couple the lightweight and high mechanical properties of CFRP with high wear resistance and hardness of metals. CFRP panels have been produced by using the Fused Filament Fabrication (FFF) technology, then the panels have been coated with aluminium particles by using a low pressure cold spray facility. Panels with various stratification sequences have been produced to investigate the feasibility of the process and to highlight the influence of the lay-up strategy on the whole process; the parameters of the cold spray process have been also optimized to ensure an effective deposition. Adhesion tests, distortion measurements, cross-section observations and surface coverage measurements have been chosen as response outputs to evaluate the effectiveness of the process and to assess the influence of the process parameters. The integration between FFF of CFRPs and cold spray deposition of aluminium particles has been proved, values of surface coverage close to 100% and good values of adhesion strength (close to 4 MPa) have been achieved; moreover, the presence of the fibres, giving a higher stiffness to the substrate, avoids the occurrence of distortion phenomena during the deposition. It was also proved that the printing parameters influence the deposition: an increase in the infill density from 30% to 50% leads to an increase in the adhesion strength up to 40%. In summary, the results obtained proved the feasibility of the process and allowed to enucleate directions of future research.

Experimental Characterization and Analysis of the In-Plane Elastic Properties and Interlaminar Fracture Toughness of a 3D-Printed Continuous Carbon Fiber-Reinforced Composite.

The use of continuous fiber as reinforcement in polymer additive manufacturing technologies enhances the mechanical performance of the manufactured parts. This is the case of the Carbon-Fiber reinforced PolyAmide (CF/PA) used by the MarkForged MarkTwo® 3D printer. However, the information available on the mechanical properties of this material is limited and with large variability. In this work, the in-plane mechanical properties and the interlaminar fracture toughness in modes I and II of Markforged’s CF/PA are experimentally investigated. Two different standard specimens and end-tabs are considered for the in-plane properties. Monolithic CF/PA specimens without any additional reinforcement are used for the interlaminar fracture toughness characterization. Two different mode I specimen configurations are compared, and two different test types are considered for mode II. The results show that prismatic specimens with paper end-tabs are more appropriate for the characterization of the in-plane material properties. The use of thick specimens for mode I fracture toughness tests complicates the characterization and can lead to erroneous results. Contrary to what has been reported in the literature for the same material, fracture toughness in mode I is lower than for mode II, which agrees with the normal tendency of traditional composite materials.

Quasi-Static Multifunctional Characterization of 3D-Printed Carbon Fiber Composites for Compressive-Electrical Properties.

Multifunctional carbon fiber composites provide promising results such as high strength-to-weight ratio, thermal and electrical conductivity, high-intensity radiated field, etc. for aerospace applications. Tailoring the electrical and structural properties of 3D-printed composites is the critical step for multifunctional performance. This paper presents a novel method for evaluating the effects of the coating material system on the continuous carbon fiber strand on the multifunctional properties of 3D-printed composites and the material’s microstructure. A new method was proposed for the quasi-static characterization of the Compressive-Electrical properties on the additively manufactured continuous carbon fiber solid laminate composites. In this paper, compressive and electrical conductivity tests were simultaneously conducted on the 3D-printed test coupons at ambient temperature. This new method modified the existing method of addressing monofunctional carbon fiber composites by combining the monofunctionality of two or more material systems to achieve the multifunctional performance on the same component, thereby reducing the significant weight. The quasi-static multifunctional properties reported a maximum compressive load of 4370 N, ultimate compressive strength of 136 MPa, and 61.2 G Ohms of electrical resistance. The presented method will significantly reduce weight and potentially replace the bulky electrical wires in spacecraft, unmanned aircraft systems (UAS), and aircraft.

3D-printed thermoplastic composite fasteners for single lap joint reinforcement

This study presents findings for the strength and failure mechanism of a 3D-printed Continuous Carbon Fibre reinforced Onyx (CCF/Onyx) Thermo-Plastic Composite Fastener (TPCF) and a single lap-joint (SLJ) made of fibre/polymer composite reinforced by the TPCF. The study was carried out by numerical analysis and experiment methods including test sample design, manufacturing process and mechanical test. The 3D-printed fasteners were manufactured and tested in shear mode for two types of joining arrangement: fastened and hybrid bonded/fastened joints. Firstly, experiment was carried out for the TPCF fastened SLJ and the results show that addition of CCF in the Onyx matrix and post heat-treatment process could significant enhance the TPCF strength. The results was then benchmarked against a SLJ with steel fastening. The shear failure load of the SLJ reinforced by heat-treated CCF/Onyx TPCF of 8 mm diameter was 36% lower than a SLJ reinforced by a steel bolt of the same size. Numerical model for progressive damage simulation was also created based on the failure theory from Puck and Schürmann achieving good correlation with the experimental data. Secondly, the TPCF fasteners were manufactured with two types of heat-treated countersunk head and pan head forming and used to reinforce bonded SLJ. The test results show that the bonded SLJ reinforced by the TPCF fastener of countersunk head is of 11.7% higher strength and an increase in ultimate deformation by 9.1% compared to a bonded SLJ reinforced by steel fastener of 5 mm diameter. From the numerical and experimental study, it was noted that this was attributed to countersunk configuration to reduce out-out-plane bending and provide better crack arresting for the joint bonding.

Effects of Heat-Treatment on Tensile Behavior and Dimension Stability of 3D Printed Carbon Fiber Reinforced Composites.

This work investigated the effects of heat treatment on the tensile behavior of 3D-printed high modules carbon fiber-reinforced composites. The manufacturing of samples with different material combinations using polylactic acid (PLA) reinforced with 9% carbon fiber (PLACF), acrylonitrile butadiene styrene (ABS) reinforced with 9% carbon fiber (ABSCF) were made. This paper addresses the tensile behavior of different structured arrangements at different% of densities between two kinds of filaments. The comparison of the tensile behavior between heat treated and untreated samples. The results showed that heat treatment improves the tensile properties of samples by enhancing the bonding of filament layers and by reducing the porosity content. At all structure specifications, the rectilinear pattern gives higher strength of up to 33% compared with the Archimedean chords pattern. Moreover, there is a limited improvement in the tensile strength and modulus of elasticity values for the samples treated at low heat-treatment temperature. The suggested methodology to evaluate the tensile behavior of the pairs of materials selected is innovative and could be used to examine sandwich designs as an alternative to producing multi-material components using inexpensive materials.

A multimodal optical approach for investigating 3D-printed carbon PEEK composites

In the industrial field, it is of great interest to identify fast and low-cost manufacturing procedures to guarantee reliable and functional products. In this frame, 3D printing is a fast and low-cost innovative technique and its capability to produce fibre-reinforced polymer matrix composites widely opens the application possibilities. 3D printing technology can form also composite materials made by short fibres that can be exploited for manufacturing parts and structures in high-tech sectors such as aerospace, automotive or naval, to cite some. Here we show how a multimodal approach can furnish a whole characterisation of reinforced composites produced with a 3D printing technology during and after tensile and flexural tests. In the multimodal strategy, we employed a couple of full-field and non-contact optical techniques, i.e. 2D-Digital-Image-Correlation (2D-DIC) and Electronic Speckle Pattern Interferometry (ESPI) in combination with SEM and optical microscope for analysing the sample at the micro and macroscale. The result of the work allows us to achieve a complete characterisation of the components realized by 3D printing.

Laser-assisted 3D printing of carbon fibre reinforced plastic parts

Laser-assisted 3D printing process of fabricating carbon fibre reinforced plastic parts by sandwiching fibres between plastic layers was developed to improve the bond strength of the fibres to the plastic layers. Here, bundled carbon fibres are placed on the 3D-printed lower plastic layer, and the upper plastic layer is deposited on the fibres. Next, the two layers sandwiching the fibres are laser-heated using a blue diode laser beam. The plastic colour changed the heating temperature at the interface between the fibres and the plastic layer due to the transmittance and absorption phenomena; the translucent layer having high transmittance was most appropriate. The strength and rigidity of the 3D-printed carbon fibre reinforced plastic parts were improved by laser heating. Carbon fibre reinforced plastic parts having closed cross-sections are manufactured and strengthened by optimising the sandwiched fibre orientation. Besides, a tailored part locally reinforced by the carbon fibres is easily 3D-printed, and the deformation behaviours are observed.

Hierarchical Atomic Layer Deposited V2 O5 on 3D Printed Nanocarbon Electrodes for High-Performance Aqueous Zinc-Ion Batteries.

Aqueous rechargeable zinc-ion batteries (ARZIBs) are promising energy storage systems owing to their ecofriendliness, safety, and cost-efficiency. However, the sluggish Zn2+ diffusion kinetics originated from its inherent large atomic mass and high polarization remains an ongoing challenge. To this end, electrodes with 3D architectures and high porosity are highly desired. This work reports a rational design and fabrication of hierarchical core-shell structured cathodes (3D@V2 O5 ) for ARZIBs by integrating fused deposition modeling (FDM) 3D-printing with atomic layer deposition (ALD). The 3D-printed porous carbon network provides an entangled electron conductive core and interconnected ion diffusion channels, whereas ALD-coated V2 O5 serves as an active shell without sacrificing the porosity for facilitated Zn2+ diffusion. This endows the 3D@V2 O5 cathode with high specific capacity (425 mAh g-1 at 0.3 A g-1 ), competitive energy and power densities (316 Wh Kg-1 at 213 W kg-1 and 163 Wh Kg-1 at 3400 W kg-1 ), and good rate performance (221 mAh g-1 at 4.8 A g-1 ). The developed 3D@V2 O5 cathode provides a promising model for customized and scalable battery electrode engineering technology. As the ALD-coated layer determines the functional properties, the proposed strategy shows a promising prospect of FDM 3D printing using 1D carbon materials for future energy storage.

The role of electrolysis and enzymatic hydrolysis treatment in the enhancement of the electrochemical properties of 3D-printed carbon black/poly(lactic acid) structures

Additive manufacturing, also known as 3D printing, is beginning to play an unprecedented role in developing many applications for industrial or personalized products. The conductive composite structures require additional treatment to achieve an electroactive surface useful for electrochemical devices. In this paper, the surfaces of carbon black/poly(lactic acid) CB-PLA printouts were activated by electrolysis or enzymatic digestion with proteinase K, or a simultaneous combination of both. The proposed modification protocols allow the tailoring of electrochemically active surfaces and electron transfer kinetics determined by electrochemical techniques (CV, EIS) by [Fe(CN)6]4-/3- redox probe. X-ray photon spectroscopy and SEM imaging were applied to determine the delivered surface chemistry. CB-PLA hydrolysis under alkaline conditions and anodic polarization greatly impacted the charge transfer kinetics. The enzymatic hydrolysis of PLA with proteinase K led to highly efficient results, yet requires an unsatisfactory prolonged activation duration of 72 h, which can be efficiently reduced by electrolysis carried out in the presence of the enzyme. Our studies hint that the activation protocol originates from surface electropolymerization rather than a synergistic interaction between the electrolysis and enzymatic hydrolysis. The detailed mechanism of CB-PLA hydrolysis supported by electrolysis is a promising new route to achieve time-efficient and environmentally-friendly activation procedure.

Mechanical behavior and microstructure of 3D-printed carbon nanotubes-reinforced Cu composite

This paper addresses the current limitations of three-dimensional (3D)-printed materials by developing a novel ink formulation using carbon nanotubes (CNTs)-reinforced Cu matrix composites. The fabricated inks consisted of CNTs/Cu powders with a binder (polyethylene glycol/polyvinyl butyral) and a solvent mixture (anhydrous ethanol/triethyl phosphate). 3D CNTs/Cu composites were fabricated by a process that included molecular-level mixing (MLM), micro-extrusion-based 3D printing (MED-3D), and pressureless sintering. The 3D-printed CNTs/Cu composite was prepared via an MED-3D process and exhibited structural stability and dimensional accuracy. The porosity and mechanical strength of the 3D-printed CNTs/Cu composite were controlled by optimizing the sintering temperature. The 3D-printed CNTs/Cu composites (surface porosity: 6.01%; internal porosity: 4.45%; sintering temperature: 1173 K) exhibited outstanding mechanical strength, reaching a maximum compressive strength of 10.65 ± 0.9 MPa, which is 104.9% higher than that of pure Cu. It is expected that CNT-reinforced metal matrix composites with structural and functional integration can be prepared by introducing CNTs into 3D metal-based scaffolds using MED-3D.

3D-printed carbon fiber/polyamide-based flexible honeycomb structural absorber for multifunctional broadband microwave absorption

The growing demand of wearable device and the irreplaceable roles in stealth technique have boosted the exploration of high-performance flexible microwave absorbers. Herein, a novel flexible honeycomb structural absorber (FHSA) of carbon fiber (CF)/polyamide (PA)/carbonyl iron (CIP) composite was successfully fabricated via selective laser sintering (SLS) 3D-printing. The CFs arrangement and unit-structure were rationally controlled during the SLS 3D printing process for acquiring enhanced microwave absorption (MA) property, especially for the high bending angles. Therefore, under the high bending angle of 150°, the minimum reflection loss of the designed FHSA can reach −47 dB at 16.2 GHz with a broadband absorption of 13.2 GHz, covering the whole C2, X, and Ku bands, which breaks the traditional restraints that the flexible absorbers can only have the high MA property in tiling or minor bending status. In addition, the FHSA also showed the advantages of highly flexible deformation, self-recovery and no-crease damage in repeated bending, which could largely improve the environment applicability. This work provides a controllable strategy for the design of flexible microwave absorber, showing potential applications in wearable functional devices and military stealth protection.

Impact Toughness of Hybrid Carbon Fiber-PLA/ABS Laminar Composite Produced through Fused Filament Fabrication.

Nowadays, the components of carbon fiber-reinforced polymer composites (an important material) are directly produced with 3D printing technology, especially Fused Filament Fabrication (FFF). However, such components suffer from poor toughness. The main aim of this research is to overcome this drawback by introducing an idea of laying down a high toughness material on the 3D-printed carbon fiber-reinforced polymer composite sheet, thereby making a hybrid composite of laminar structure. To ascertain this idea, in the present study, a carbon-reinforced Polylactic Acid (C-PLA) composite sheet was initially 3D printed through FFF technology, which was then laid upon with the Acrylonitrile Butadiene Styrene (ABS), named as C-PLA/ABS hybrid laminar composite, in an attempt to increase its impact toughness. The hybrid composite was fabricated by varying different 3D printing parameters and was then subjected to impact testing. The results revealed that toughness increased by employing higher layer thickness and clad ratio, while it decreased by increasing the fill density, but remained unaffected due to any change in the raster angle. The highest impact toughness (23,465.6 kJ/m2) was achieved when fabrication was performed employing layer thickness of 0.5 mm, clad ratio of 1, fill density of 40%. As a result of laying up ABS sheet on C-PLA sheet, the toughness of resulting structure increased greatly (280 to 365%) as compared to the equivalent C-PLA structure, as expected. Two different types of distinct failures were observed during impact testing. In type A, both laminates fractured simultaneously without any delamination as a hammer hit the sample. In type B, the failure initiated with fracturing of C-PLA sheet followed by interfacial delamination at the boundary walls. The SEM analysis of fractured surfaces revealed two types of pores in the C-PLA lamina, while only one type in the ABS lamina. Further, there was no interlayer cracking in the C-PLA lamina contrary to the ABS lamina, thereby indicating greater interlayer adhesion in the C-PLA lamina.

Reactive oxygen plasma treatment of 3D-printed carbon electrodes towards high-performance electrochemical sensors

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)6]3-/[Fe(CN)6]4- 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.

Mechanism based failure of 3D-printed continuous carbon fiber reinforced thermoplastic composites

The present work describes a computational mechanism based failure analysis conducted for 3D-printed continuous carbon fiber reinforced thermoplastic composites (CFRTPCs), which could not be seen in the available literature. The material failure is investigated based on intraply failure evaluation and adopts different failure criteria for the material constituents. The micromechanical modeling employs the Asymptotic Homogenization technique and comprises the selection of a representative volume element statistically equivalent to the microstructure of the material, which is identified from cross-section micrographs. In contrast to recent work, it is demonstrated that an additional relation is required for the macroscopic deviatoric stresses acting over the matrix. This avoids an overestimation of the matrix failure when the reinforced lamina is subjected to longitudinal and shear loads. The resulting failure envelopes are presented and compared to those provided by analytical failure theories available in the literature. The results obtained by the micromechanical approach showed its ability to predict failure of 3D-printed CFRTPCs, in addition to bring different elements for the discussion that could not be captured with analytical models. In this context, it is believed that the characteristics inherent to the microstructure reproduced in the RVE, particularly contributed to obtaining more realistic failure envelopes.

Compression behaviours of 3D-printed CF/PA metamaterials: Experiment and modelling

This study characterises the compressive behaviours of 3D-printed carbon fibre (CF) reinforced polyamide (PA) composite metamaterials with negative Poisson's ratio (NPR) or enhanced effective elastic modulus (EEEM), which were designed via a multidisciplinary approach and additively manufactured with fused filament fabrication. The continuous carbon reinforced PA (CCF/PA) metamaterials are compared to those made of short carbon fibre reinforced PA (SCF/PA) when subjected to in-plane compression. A numerical model based on continuum damage mechanics is developed to describe the response and failure of the 3D-printed CCF/PA composites while another one based an elastic-plastic model is developed for the 3D-printed SCF/PA parts. For metamaterials with NPR, the stiffness, peak force, energy absorption (EA) and specific energy absorption (SEA) of CCF/PA metamaterials are respectively 152.1%, 90%, 107.6% and 86%, respectively, larger than those of SCF/PA, while the SCF/PA metamaterials can reach a greater NPR (about −0.3) than CCF/PA (−0.2 ~ −0.1). For composites with EEEM, the stiffness, peak force, EA and SEA of CCF/PA are significantly improved by 433.3%, 183.3%, 228.7% and 208.2%, respectively, in comparison to those of SCF/PA. Based on experimental observation and numerical simulation, matrix failure is found to be predominant for CCF/PA NPR and EEEM composites.

Effect of build-up orientations and process parameters on the tensile strength of 3D printed short carbon fiber/PA-6 composites

3D printers using fused filament fabrication (FFF) with thermoplastic filaments have been employed for rapid prototyping applications. The present research focuses on 3D-printed short carbon fiber/PA-6 composites. Specimens with four types of build-up orientations (0°, 90°, ±45°, and layup) were fabricated using two types of 3D printer: Mark Two, produced by Markforged, and X-Plus produced by Qidi Tech. Tensile tests were performed on these specimens. X-ray CT and SEM observations were conducted to investigate the defects and gaps between the print paths. The effect of the bed temperature and extrusion rate were experimentally investigated. For the ±45° specimens fabricated using Mark Two, a large gap between the print paths was confirmed. An increase in the extrusion rate of 5% (1.05) and a minor increase in the nozzle temperature of 3.6% (from 275 °C to 285 °C) yielded a smaller gap between the print paths, 20 % higher tensile strength of the ±45° specimen, 10 % higher tensile strength of the 0° specimen, and 4% higher strength of the lay-up direction specimen with X-Plus. The bed temperature had a minor effect on tensile strength.

Investigation of manufacturing defects in 3D-printed CFRP using laser ultrasonic testing and x-ray micro-computed tomography

3D-printed carbon fiber reinforced plastic (CFRP) composites have attracted significant attention due to their design flexibility and low manufacturing cost. However, 3D-printed CFRP contains inherent defects that occur during the manufacturing process. As the manufacturing defects are likely to degrade the mechanical performance of the 3D-printed CFRP, these defects require extensive investigation. Typically, x-ray micro-computed tomography (micro-CT) is used to detect manufacturing defects, but as micro-CT cannot be applied to large structures, the laser ultrasonic testing (LUT) method has been proposed. In this study, two specimens with different stacking sequences were manufactured using a continuous fiber 3D printer. The two specimens were then inspected using LUT and micro-CT. The manufacturing defects were successfully visualized using LUT, and similar defects were detected in the micro-CT inspection results. The size, location, and shape of the detected defects were evaluated by comparing the LUT and micro-CT inspection results. Consequently, the LUT method showed a performance comparable to that of micro-CT for detecting the manufacturing defects of 3D-printed CFRP. Since the LUT is capable of inspecting large scale 3D-printed composites, it will be absolutely advantageous in real world applications.

Interlayer Adhesion Analysis of 3D-Printed Continuous Carbon Fibre-Reinforced Composites

Carbon fibre-reinforced materials are becoming more and more popular in various fields of industries because of their lightweight and perfect mechanical properties. Additive manufacturing technologies can be used for the production of complex parts from various materials including composites. Fused deposition modelling (FDM) is an excellent technology for the production of composite structures reinforced with short or continuous carbon fibre. In this study, modified FDM technology was used for the production of composites reinforced with continuous carbon fibre. The main aim of this study is to evaluate the shear strength of 3D-printed composite structures. The influence of printing layer height and line width on shear strength was analysed. Results showed that layer height has a significant influence on shear strength, while the influence of printing line width on shear strength is slightly smaller. Reduction of layer height from 0.4 mm to 0.3 mm allows increasing shear strength by about 40 percent. Moreover, the influence of the shear area and overlap length on shear force showed linear dependency, in which the shear area is increasing the shear force increasing proportionally. Finally, the results obtained can be used for the design and development of new 3D-printed composite structures.

Topological design for 3D-printing of carbon fibre reinforced composite structural parts

This study develops a novel procedure combining topological design and fibre placement paths based on average load transmission trajectories for high load-bearing capacity of 3D-printed carbon fibre reinforced composite parts. First, a two-stage topological design procedure is established to acquire the optimal topology for confining maximum stress and minimising structural compliance. Second, based on calculations for the average load transmission trajectories within the optimal topology, continuous carbon fibre placement paths are defined for 3D-printing with fused filament fabrication (FFF). Experimental studies are performed for topologically designed short cantilever and three-point-bending specimens to characterise the reinforcement effect of short carbon fibre (SCF, vol% = 15%) and continuous carbon fibre (CCF, vol% = 35%) on specimens printed with pure polyamide (PA). The CCF increases the stiffness and the magnitude of peak load of the cantilever specimens by 1198% and 1633%, respectively, while the increments are 569% and 293%, respectively, for three-point-bending specimens, showing the significant impact of the procedure. The SCF also increases the stiffness and peak load of the both structural configurations but to a much lesser degree.

How normalisation factors influence the interpretations of 3D-printed sensors for electroanalysis

Abstract The ability to produce electrodes through 3D-printing techniques for use in sensing applications has significant potential. This is mainly due to the mass production of electrodes at any desired geometry. However, comparing different 3D-printed carbon electrodes for electroanalytical performance can be challenging due to the significant variation in each conductive printed material. This study investigates different normalisations that could be applied to compare between different 3D-printed electrodes. We compared 3D-printed carbon black and graphene electrodes for the monitoring of three important biological analytes (dopamine, ascorbic acid and hydrogen peroxide). These 3D printed electrodes have different conductive loads and surface profiles, and therefore we utilised eight different approaches for normalising the current response. There was no perfect normalisation technique and therefore using a combination of approaches to survey the best performing electrode would be a better approach. This study showcases the different possible normalisation methods and highlights the impact these can have on the interpretation of electrodes for electroanalytical measurement.