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TEXT OF DESCRIPTION

Technical field

The description relates to methods of manufacturing flexible electronic devices, such as flexible electroanalytical devices.

One or more embodiments may be used for electrochemical sensing of analytes in various fields such as, e.g., food industry, environmental and biological analysis.

Background

Screen-printed electrodes (SPEs) are electroanalytical devices (also referred to as electrochemical measurement cells) that are manufactured by screen-printing different types of ink including dispersed conductive particles on plastic or ceramic substrates. In this context, screen-printing involves the deposition of conductive inks by means of masks containing the design of the circuit to be manufactured.

SPEs facilitate to operate on small volumes, reducing the production of chemical waste and the contact with chemicals by operators, so that they are particularly suitable to be used for analysis in the field and outside the analysis laboratory.

SPEs may present the drawbacks of using volatile solvents in the formulations of conductive inks, and of inherent waste of material during the deposition of the various layers.

Improved processes to obtain cheap and readily available electroanalytical devices are thus desirable.

Object and summary

An object of one or more embodiments is to contribute in providing such improved solutions.

According to one or more embodiments, that object can be achieved by means of a method having the features set forth in the claims that follow.

One or more embodiments may relate to a corresponding thermoplastic material having electrically conductive particles dispersed therein.

The claims are an integral part of the technical teaching provided herein with reference to the embodiments.

One or more embodiments present an improved homogeneity in the electrical conductivity of the conductive materials, improving repeatability of electroanalytical measurements.

One or more embodiments are exempt from the use solvents (e.g., alphatic and aromatic hydrocarbons, ketones and alcohols) or binders (e.g., phenolic and acrylic resins), facilitating a safe handling during their assembly.

One or more embodiments facilitate reducing waste.

One or more embodiments facilitate adapting the design of electroanalytical devices in a flexible manner without having to resort to the use of masks, reducing waste and costs.

One or more embodiments facilitate obtaining an improved integration between a support of the electroanalytical device and the conductive electrodes, avoiding the formation of imperfections due to the air that can be trapped between the conductive material and the support, for instance by ensuring a high pressure in the incorporation phase of the two parts.

In one or more embodiments, applying sonication facilitates to improve the electrical properties without the use of solvents or abrasive pastes.

One or more embodiments may facilitate reducing manufacturing costs and environmental wase.

One or more embodiments involve an eco-compatible activation procedure, sparing the use of organic solvents or other toxic chemicals and suitable to be carried out at room temperature.

One or more embodiments provide a uniform distribution of material in the array of devices, facilitating to reduce risks linked to anisotropy which may be found in 3D printed three dimensional conductive elements.

One or more embodiments provide a way to manufacture devices without using a dual-material printer, therefore reducing complexity of manufacturing.

Brief description of the several views of the drawings

One or more embodiments will now be described, by way of non-limiting example only, with reference to the annexed Figures, wherein:

Figures 1 to 3 are exemplary of acts of a method of manufacturing as per the present disclosure,

Figures 4 and 5 are top views of assemblies as per the present disclosure,

Figure 4A is a side view of a portion of Figure 4 exemplary of the flexible properties thereof,

Figure 6 is a diagram exemplary of a method of manufacturing as per the present disclosure,

Figure 7 is a diagram exemplary of a first activation process as per the present disclosure,

Figure 8 is a diagram exemplary of a method of activating a device for electrochemical sensing as per the present description,

Figure 9 is a diagram of cyclic voltammetric measurements exemplary of effects of different types of treatments on electrochemical response of the device,

Figure 10 is a diagram exemplary of possible application times of a first activation process of the method as per the present disclosure,

Figure 11 is a diagram of cyclic voltammetric measurements of one or more devices as per the present disclosure,

Figure 12 is a diagram indicative of acts of the method as per the present disclosure. Detailed description

In the ensuing description, one or more specific details are illustrated, aimed at providing an in-depth understanding of examples of embodiments of this description. The embodiments may be obtained without one or more of the specific details, or with other methods, components, materials, etc. In other cases, known structures, materials, or operations are not illustrated or described in detail so that certain aspects of embodiments will not be obscured.

Reference to “an embodiment” or “one embodiment” in the framework of the present description is intended to indicate that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as “in an embodiment” or “in one embodiment” that may be present in one or more points of the present description do not necessarily refer to one and the same embodiment.

Moreover, particular conformations, structures, or characteristics may be combined in any adequate way in one or more embodiments.

The drawings are in simplified form and are not to precise scale.

Throughout the figures annexed herein, like parts or elements are indicated with like references/numerals and a corresponding description will not be repeated for brevity.

The references used herein are provided merely for convenience and hence do not define the extent of protection or the scope of the embodiments.

As exemplified in Figure 1 , a method as per the present disclosure comprises: providing an additive manufacturing machine 10, preferably configured to perform fused deposition modelling (FDM), in a manner per se known; providing a conductive material for the additive manufacturing machine 10, such as a plurality of electrically conductive particles (e.g., carbon-based conductive particles) at least partially embedded in filaments of a thermoplastic elastomer 14, such as conductive polylactic acid (PLA) that is PLA comprising a mixture of carbon-based particles such as carbon black nanoparticles, graphene, graphite and/or carbon nanotubes, for instance; the material is fed through a movable heated (printer) extruder head 12 of the additive manufacturing machine, which deposits it on a layer of a planar bed surface (e.g., a glass screen 16) which may be heated and which delimits the working area for the additive manufacturing process; the additive manufacturing machine 10 comprises control circuitry (e.g., a microcontroller or other electronic processing devices) coupled to the heated head 12 to control the position of the head with respect to the working area as well as other process parameters of the additive manufacturing process, in a manner per se known; for instance, the position may be controlled based on a CAD file provided to the control circuitry of the machine 10, e.g. via a computer readable medium or other digital interfaces, in a manner per se known; performing extrusion and deposition (via the heated head 12) of the conductive material 14 for additive manufacturing onto the rigid structure 16 according to a pattern (which may be provided via the CAD file provided to the additive manufacturing machine, in a manner per se known) to define an array of conductive traces 20 defining a number of conductors PRE, WE, CE and conductive contact areas for the contacts of an array of electrochemical planar electrodes 20.

For instance, an additive manufacturing machine known by the commercial name of FLSUN Cube 3D printer provided by a company named FLSUN at Zhengzhou, Henan, China may be suitable for use in one or more embodiments.

For instance, the conductive structure obtained via additive manufacturing can be both mechanically and electrically tuned by varying the concentration and type(s) of electrically conductive particles. As exemplified in Figure 1 , the additive manufacturing process 10 involves providing a glass sheet 16 placed on top of the heated bed in order to obtain printed parts with a smooth side, substantially exempt from imperfections due to movement of the nozzle head 12.

For instance, the additive manufacturing machine 10 may be equipped with a removable (e.g., 3 mm) glass bed 16 placed above the heating bed.

As exemplified in Figure 1 , the geometry of an array of electrochemical sensing devices 20 obtained via additive manufacturing each comprise a set of electrodes WE, CE, PRE, for instance comprising a working electrode WE, a counter electrode CE, and a pseudo-reference PRE electrode.

For the sake of simplicity, the array of electrochemical sensing devices 20 exemplified in Figure 1 comprises devices whose shape resembles that of known screen-printed electrode devices.

It is noted that the shape and the arrangement and the shape of the set of electrodes WE, CE, PRE is purely exemplary and in no way limiting, as notionally any kind of electrodes in any shape may be produced via a method as per the present disclosure.

Solid electrical conductor comprising good conductors such as conductive particles (e.g., in an electrochemical cell) are known as electrodes.

As appreciable to those skilled in the art, the electrochemical sensing device/circuit 200 in the array 20 may be used to perform electrochemical analysis of an analyte by recording its electrochemical properties via a potetionstat, in a manner per se known.

The current that passes to or from the working electrode WE is recorded by the potentiostat. The counter (or auxiliary) electrode CE balance the reaction occurring at the working electrode and close the electric circuit. As its name suggests, the pseudo-reference electrode PRE is the electrode to which the potential of the working electrode WE is referenced.

As exemplified in Figure 1 , the electrode may further comprise connection lines in order to provide an electrical signal, e.g., to a potentiostat coupled thereto.

It is noted that, while discussed mainly with reference to the production of electroanalytical devices/circuits, one or more embodiments as discussed herein may be adapted to provide any kind of flexible printed electronic device/circuit, for instance flexible printed circuit boards for a variety of applications.

As exemplified in Figure 1 , an advantage of using additive manufacturing is the possibility to print a plurality of devices 20 for electrochemical sensing arranged in a planar array in order to reduce the time and waste due the filament change involved for printing the electroanalytical devices 20.

For instance, the conductive tracks PRE, WE, CE exemplified in Figure 1 may have a layer height in a range of about 0.05-0.4 mm to be used as working WE, counter CE, and pseudo-reference PRE electrodes are printed on a glass bed 16 using carbon-based polymer filaments 14 (such as PLA filaments doped with carbon-based composites, for instance doped with graphene) by using extrusion temperature in a range about 190- 230°C for the filaments provided via the heated head 12 and setting a temperature about 60-70 °C for the heated bed 16 of the additive manufacturing machine 10.

For instance, the array of devices 20 exemplified in Figure 1 comprises an array of twenty-four electroanalytical three- electrode devices, such a number being purely exemplary and in no way limiting.

As exemplified in Figure 2, the method further comprises providing a flexible (e.g., polymeric) substrate made of a material different from the one made conductive by the introduction of the conductive particles, such as polycaprolactone (PCL), for instance.

It is noted that PLA conductive filaments comprising and carbon-based particles are just examples which are in no way limiting of the possible materials that may be used.

For instance, one or more embodiments may employ other thermoplastic materials such as TPU, ABS mixed with carbon-based particles or other conductive particles (e.g., copper, noble metals such as palladium, iridium, or silver, gold or platinum).

As exemplified herein, the electrically conductive particles may comprise at least one conductive material selected from the group consisting of gold, silver, carbon, nickel, copper, platinum, palladium, aluminum, and other conductive metals and/or alloys (e.g., indium or palladium).

For instance, the electrically conductive particles may have a particle size in the range of about 1 nm to about 100 microns, preferably from about 100 nm to about 10 microns.

For screen-printed electrodes, after printing, ways of doping the printed electrode tracks with particles of electrocatalyst materials and/or organic (surface) modifiers are known, which may enhance the functionality of the SPEs.

As appreciable to those of skill in the art, an electrocatalyst is a catalyst that participates in electrochemical reactions. Electrocatalysts comprise catalyst materials that may be applied to/embedded in the surface of electrodes to enhance their performance, e.g., improving sensitivity or selectivity of the electrodes with respect to an investigated phenomenon, thanks to electrocatalysis mechanisms per se known.

For instance, carbon nanotubes and graphene-based materials can be used as electrocatalysts, as well as platinized electrodes.

In addition to electrocatalysts, another kind of enhancers for the performance of the electrodes comprises organic (surface) modifiers, such as for example alizarin or polyaniline, which may be suitable to improve the performance of the electrodes in term of selectivity and sensitivity as well to extend the range of application (e.g., facilitating pH monitoring, enhancing the electrochemical active area). For instance, at least one of the materials in the group of electrocatalyst materials and in the group of organic modifiers may be: dispersed in the thermoplastic material 14 prior to additive manufacturing, and/or applied on the surface of the manufactured electrodes, in a manner per se known.

It is noted that some of the materials in the group of electrocatalyst materials may also belong to the group of conductive particles and/or that of organic modifiers. For instance, indium or palladium may be both used as noble metals to encapsulate as conductive particles in the thermoplastic material as well as electrocatalyst materials which may be applied to/embedded in the thermoplastic material, e.g., postmanufacturing.

In one or more embodiments, particles of electrocatalyst materials may be embedded in the thermoplastic material 14, facilitating to produce in a single manufacturing step a set of electrodes 20 tailored for various applications.

As exemplified in Figure 2, such a flexible substrate 40 may be provided already made or may be also produced via additive manufacturing, by supplying the additive manufacturing machine 10 with the polymer material, e.g., in the form of a filament 14.

For instance, the working area may have a size 100-120 mm of width, 100-120 mm of depth and 0.4-1 mm of height, produced using commercially available polycaprolactone (PCL) filaments as material for the additive manufacturing process 10.

For instance, the additive manufacturing machine 10 may be set to ensure 100% infill using a flow of 105% in order to counter the risk of trapping bubbles of air.

In an exemplary case, the extrusion temperature was set in a range about 80-140°C when using PCL filaments 14 and the temperature of the heated bed 16 was set in a range about 60- 70°C. For instance, these values facilitate good extrusion of the material, layer adhesion and auto-levelling of the melt surface.

As exemplified herein, the method comprises: displacing the assembly comprising the glass screen 16 with the printed electrodes of devices 20 on top from the heated bed of the additive manufacturing machine and put in a vacuum oven OV (known per se), e.g., preheated at a reference temperature, with the adhering conductive printed tracks facing up, and placing the flexible substrate 40 on top of the assembly, applying a uniform weight 18 on top of the flexible substrate and the assembly of glass screen 16 and the printed array of devices 20; for instance, the weight may comprise a further rigid glass block 18 as a weight (e.g., about 60g),

For instance, an initial reference temperature for the vacuum oven OV may be set in a range about 40-50°C in order to be close to that set for printing bed during the additive manufacturing process in order to avoid detachment of the electrodes CE, WE, PRE from the glass 16 and at the same time lower than melting point of the flexible support, in order to counter its immediate melting.

The method further comprises: preferably, evacuating the air inside the oven chamber (e.g., via a vacuum valve W, as exemplified in Figure 3), in order to facilitate reducing as much as possible imperfections in the final product due to air bubbles trapped between the flexible support 40 and the array of devices 20, and increasing the temperature of the oven OV from the reference temperature value to a final temperature above the melting point of the flexible substrate 40, e.g., in a range about 60°C-85°C in case of a PCL flexible substrate.

For instance, the final temperature may be determined in an interactive way by monitoring the change of optical properties of the flexible substrate 40, e.g., from opaque to transparent during phase transition.

During the melting process, the flexible substrate 40 incorporates the electroanalytical device 20 lying onto the glass surface 16, providing a molten assembly 30, as exemplified in Figure 4.

Inventors have noted that using for the flexible substrate and the thermoplastic material different materials belonging to the class of polyester materials facilitates to obtain good chemical compatibility and adhesion between the layers of the assembly.

The method further comprises: preferably, gradually introducing back the air (again, via the valve VV) in the oven cavity OV, in order to restore ambient pressure, thereby reducing any cavities remained inside the assembly 30 of the flexible substrate 40 and the array of devices 20 integrated therein, taking advantage from the extra pressure provided by atmosphere, gradually cooling back the oven OV from the final temperature back to room temperature, so as to perform solidification of the flexible substrate 40 (e.g., returned opaque), removing the top weight 18 and detaching from the glass bed 16 the resulting assembly 30, obtaining a flexible and smooth platform where conductive tracks WE, PRE, CE are embedded in the flexible support, leaving exposed to the outside the sole surface, as exemplified in Figures 4 and 5.

As exemplified in Figure 5, an alternative embodiment may present a slightly different geometry, e.g., with two working electrodes WE1 , WE2, the counter electrode CE and the pseudoreference electrode PRE.

For instance, the method as exemplified herein facilitates producing assemblies 30 containing an array 20 of twenty-four electroanalytical devices 200 in a relatively short time, e.g., approximatively 3 hours.

It is noted that such a number of devices in the array is purely exemplary and in no way limiting, as the method is notionally suited to produce any number of devices 200 in the array. As exemplified in Figure 4A, a single device 200 may be cut-out from the array of devices 20, for instance via scissors, and may be squeezed slightly to show its flexible properties.

As exemplified in Figure 6, a method as exemplified herein comprises: block 100: providing conductive thermoplastic material 14 comprising thermoplastic material with a plurality of electrically conductive particles dispersed therein, block 102: providing a rigid support surface 16, preferably a glass sheet, block 104: depositing, via additive manufacturing 10, a layer of conductive traces 20 of the conductive thermoplastic material 14 onto the rigid support surface 16, said conductive traces 20 defining a number of planar electrodes WE, CE, PRE of an array of devices 20 for electrochemical sensing of analytes, block 106: providing a flexible substrate film 40 comprising film material having a film melting point lower than a melting point of the conductive thermoplastic material 14, block 108: pressing 18 the flexible substrate film 40 in contact with a top surface of the layer of conductive traces 20 deposited onto the rigid support surface 16, block 110: gradually heating (preferably, under vacuum conditions, e.g. about 0.01 atm, where 1 atm = 101325 Pa and 1 Pa = 1 Pascal = 10" ⁵ bar) the flexible substrate film 40 pressed in contact with the top surface of the layer of conductive traces 20 deposited onto the rigid support surface 16 until reaching the film melting point, melting the flexible substrate film 40 without melting the layer of conductive traces 20 as a result so that the layer of conductive traces 20 is encapsulated in the flexible substrate film 40, forming an assembly 30 as a result, and block 112: cooling down the assembly 30 (preferably while restoring ambient pressure at 1 atm) of the molten flexible substrate film 40 and the layer of conductive traces 20 encapsulated therein, obtaining a solid flexible film 30 encapsulating the layer of conductive traces 20 as a result. For instance, the PCL filament known by the commercial name of Facilan Ortho Natural Elogiam may be suitable for use in one or more embodiments.

For instance, a commercially available conductive graphene/PLA composite material for FDM may be suitable for use in one or more embodiments.

As exemplified herein, electrochemical measurements can be performed by an electrochemical analyser. For instance, an electrochemical analyser known by the commercial name of 730E CHI and provided by CH Instruments at Austin, Texas, United States of America.

As exemplified herein, the method further comprises: washing the obtained assembly in water, e.g., for about 10-20 minutes, drying the surface at room temperature, attaching thin strips of adhesive tape on top of the manufactured devices in the array of devices, for instance in order to delimitate the active working surface and to protect electrical connections from contact with liquid samples.

In general, prior to their use for electrochemical sensing, an activation step is applied to the device 200 to improve the exposure of electroactive surface and to eliminate as much as possible the insulating thermoplastic component.

As exemplified in Figure 7, such an activation may be based on the use of ultrasound waves generated by an ultrasound source S, e.g., in a sonication processing machine 60.

Sonication 60 is a technique per se known which allows to mechanically agitate particles/systems in a sample by applying sound energy produced by a source S, e.g., a ultrasonic cleaner.

As exemplified herein, a method comprises a first activation process comprising: immersing the assembly 30 in an aqueous bath 50 comprising a first solution (e.g., 0.5-2 M NaOH solution), and applying sonication processing 60 to the assembly in the aqueous bath 50, e.g., for a time interval about 15-90 minutes. For instance, such a first activation processing SA comprising sonication in basic environment facilitates etching of a very thin layer of material at the surface of electrodes WE, CE, PRE as it promotes hydrolysis of external bond layer of the assembly 30 comprising both the flexible surface 40 and the plastic material 14 incorporating the conductive particles, helping to expose the active surface of the conductive particles embedded in the non-conductive filaments used for manufacturing, increasing the availability of exposed conductive particles (e.g., graphene).

As exemplified herein, the method comprises a second activation process known per se. For instance, the process discussed in document Richter, E. M. et al. Complete Additively Manufactured (3D-Printed) Electrochemical Sensing Platform. Anal. Chem. 91 , 12844-12851 (2019) is suitable for use as the second activation process and comprises: immersing the sonicated assembly in the first solution (e.g., 0.5M NaOH solution) and applying to the working electrode WE an anodic potential of +1 .4 V vs Ag/AgCI(Kci, 3M). for 200s followed by applying a cathodic potential of -1 .0 V vs Ag/AgCI(Kci, 3M). for 200s.

For instance, the aqueous solutions can be prepared with deionized water.

For instance, sonication 60 and/or further electrochemical activation steps may be applied to the whole array of devices 20 (or a portion thereof) in the assembly 30 or to single devices 200 cut-out from the assembly 30.

For instance, the mechanical action of ultrasound S, such as streaming, microjets and shockwave combined with its capacity to accelerate the hydrolysis reaction has been also profitably adopted to clean and regenerate the surface of the electrodes PRE, WE, CE in case of passivation, that cause a reduction of their functionality.

As exemplified herein, the sonication processing 60 facilitates exposing the conductive particles to the surface of the electrodes WE, PRE, CE of devices 200 in the array 20, providing a uniform contact surface and therefore reducing errors in measurement.

For instance, the sonication 60 may facilitate restoring electrochemical activity of the devices 200 in the array 20, facilitating devices reuse and reducing environmental waste.

As exemplified herein, the materials used may be biodegradable, facilitating environmental sustainability of the manufactured products.

As exemplified in Figure 8, a method of activating at least one device 200; 20 for electrochemical sensing of analytes comprises: block 140: providing the at least one device for electrochemical sensing, block 150: immersing the at least one device 200; 20 in an aqueous bath 50 comprising sodium hydroxide NaOH, block 160: applying ultrasound waves to the at least one device 200; 20 immersed in said aqueous bath, providing a sonicated device SA, and block 170: applying further electrochemical activation processing, in a manner per se known, providing an electroactivated device SA+EA.

In one or more embodiments, the array 20 were intended for performing measurements on controlled small volume of samples (e.g., about 80-100 pL, where 1 pL = 1 microLiter = 10’ ⁶ L) directly applied to the cell which was placed in horizontal position onto a planar surface (currently referred to as “drop mode”). The electrochemical behaviour of the electrodes was studied using a 1 mM solution of potassium hexacyanoferrate(ll) K4Fe(CN)e dissolved in 0.1 M of potassium chloride (KCI). This analyte was chosen as redox prototype in view of its known reversible electrochemical behaviour. Cyclic voltammetric experiments were run in the potential window from -0.2 V to + 0.7 V vs Ag/AgCI(Kci, 3M) at different scan rates.

Firstly, experiments were run by means of an external Ag/AgCI(Kci, 3M). reference electrode in order to have a stable reference potential.

Cyclic voltammetric experiments were firstly performed on electrodes as printed (labelled AP) and electro-activated (labelled EA) using the measurement procedure discussed in the foregoing. Then a sonication treatment in sodium hydroxide (NaOH) aqueous bath for 1 hour was carried out and electrodes only sonicated (labelled SA) or electro-activated after sonication (labelled SA+EA) were tested.

Figure 9 shows cyclic voltammograms recorded for a device 200 in the printed arrays 20 in various stages of the manufacturing process used to analyse 1 mM K4Fe(CN)e redox probe.

As exemplified in Figure 9, the performance of the device 200 as-printed (labelled AP) is compared with the performance of the device after the first activation processing (sonication in aqueous bath only, labelled SA), after the second activation processing only (labelled EA), and electro-activated after sonication (sonication in NaOH aqueous bath followed by the second activation processing, labelled SA+EA).

As exemplified in Figure 9, sonication 60 in NaOH acqueous bath 50 and electrochemical activation improve the performance in signal detection of the electrochemical device. In particular, when sonication SA and electrochemical activation EA are applied in sequence, the measured electrochemical signal is increased in current amplitude and improved in shape.

Because of the good results obtained applying a combination of sonication and electro-activation, the effect of different sonication times on electrochemical performance of the device 200 is explored.

Figure 10 shows the electrochemical signal detected using devices 200 to which sonication processing 60 in the same NaOH aqueous bath 50 has been applied, by varying the time interval of the sonication processing 60, and followed by the application of the second electro-activation processing. As exemplified in Figure 10, different time intervals for sonication were explored in a range from 15 minutes up to 90 minutes (e.g., for 0.5 M NaOH aqueous solution). Again, the signals are detected using the K4Fe(CN)e redox probe (1 mM) and figure 8 shows the resulting cyclic voltammograms recorded at devices. Electrochemical anodic and cathodic activation took place at 1.4 V (200 s) and -1.0 V (200 s) in 0.5 M of sodium hydroxide (NaOH) solution. Electrochemical measurements were performed at a scan rate of 50 mV s ^-1 , using as background electrolyte 0.1 M potassium chloride (KCI) and as reference electrode Ag/AgCI(Kci, 3M).

As exemplified in Figure 10, increasing the sonication time from fifteen to sixty (and up to ninety) minutes may improve the intensity of signal.

For instance, the time of the sonication may vary as a function of the quantity of sodium hydroxide NaOH used in the acqueous bath, e.g., the time may be reduced by increasing the amount of sodium hydroxide NaOH in the acqueous bath.

Figure 11 shows cyclic voltammetric measurements recorded at the electrode of the devices electro-activated after sonication (SA+EA) for increasing concentrations of analyte potassium hexacyanoferrate(ll) K4Fe(CN)e in a range 0.1 mM to 5 mM at scan rate of 50 mV s ^-1 .

As exemplified in Figure 11 , there is a substantially linear increase of the peak current as a function of the concentration of the analyte.

As exemplified herein, a method comprises: providing 100 a thermoplastic material 14 with a plurality of electrically conductive particles encapsulated therein, the conductive thermoplastic material having a first melting point, providing 102 a rigid support 16 having a top surface, preferably a glass sheet, depositing 104, via additive manufacturing 10, at least one layer of conductive traces 20 of the conductive thermoplastic material onto the top surface of the rigid support, said conductive traces defining a set of electrodes WE, CE, PRE, providing 106 a flexible substrate film 40 comprising film material having a second melting point lower than the first melting point of the conductive thermoplastic material, pressing 108 the flexible substrate film in contact with the top surface of the rigid support having the at least one layer of conductive traces deposited thereon, heating 110 the flexible substrate film pressed in contact with the top surface of the of the rigid support having the at least one layer of conductive traces deposited thereon until reaching a temperature equal or higher than the second melting point and lower than the first melting point, melting the flexible substrate film without melting the at least one layer of conductive traces as a result, thereby forming an assembly 30 comprising the at least one layer of conductive traces encapsulated in the molten flexible substrate film, and cooling down 112 the assembly of the molten flexible substrate film 40 and the at least one layer of conductive traces encapsulated therein, obtaining a solid flexible film encapsulating the at least one layer of conductive traces therein as a result.

As exemplified herein, a thermoplastic material for additive manufacturing comprises a plurality of electrically conductive particles dispersed therein.

As exemplified herein, the thermoplastic material 14 comprises biodegradable thermoplastic material.

As exemplified herein, the thermoplastic material 14 comprises at least one thermoplastic material selected in the group consisting of polylactic acid, PLA, thermoplastic polyurethanes, TPU, and acrylonitrile butadiene styrene, ABS.

As exemplified herein, the plurality of electrically conductive particles dispersed in the thermoplastic material 14 comprises at least one conductive material selected from the group consisting of: carbon, copper, gold, silver, nickel, chromium, noble metals and other conductive metals and/or alloys (such as indium or palladium, for instance). As exemplified herein, the thermoplastic material 14 further comprises particles of at least one electrocatalyst material (for instance, dispersed therein or applied to the surface), preferably the electrocatalyst material being selected from the group consisting of: nickel oxide, ruthenium oxide, bismuth oxide, manganese oxide, cobalt phthalocyanine and iron(ll)- phthalocyanine and others (such as potassium ferrocyanide, iridium or palladium, for instance).

As exemplified herein, the thermoplastic material 14 further may comprise at least one organic modifier material, for instance the organic modifier material being selected from the group consisting of polyaniline and alizarin.

As exemplified herein, the method comprises: introducing the flexible substrate film 40 pressed in contact with the top surface of the of the rigid support 16 having the at least one layer of conductive traces 20 deposited thereon inside a heating chamber OV comprising at least one valve W to vary the pressure therein, reducing VV the pressure inside the heating chamber, heating 110 the flexible substrate film 40 pressed in contact with the top surface of the of the rigid support 16 having the at least one layer of conductive traces 20 deposited thereon, until reaching a temperature equal or higher than the second melting point and lower than the first melting point, increasing W the pressure inside the heating chamber, and cooling down 112 the assembly of the molten flexible substrate film and the at least one layer of conductive traces encapsulated therein, obtaining a solid flexible film encapsulating the layer of conductive traces as a result.

As exemplified herein, the method comprises: reducing W the pressure inside the heating chamber until reaching a pressure in a range between 0.005 atm and 0.01 atm, and increasing W the pressure inside the heating chamber until restoring the pressure inside the heating chamber at a pressure level about 1 atm.

As exemplified herein, the second melting point is in a range between sixty Celsius degrees and seventy Celsius degrees.

As exemplified herein, the second melting point is lower than said first melting point, e.g., at least by forty Celsius degrees.

As exemplified herein, heating 110 the flexible substrate film pressed in contact with the top surface of the of the rigid support having the at least one layer of conductive traces deposited thereon, until reaching a temperature equal or higher than the second melting point and lower than the first melting point comprises heating until reaching a temperature in a range between sixty Celsius degrees and eighty-five Celsius degrees.

As exemplified herein, the flexible substrate film 40 comprises flexible polymer material. For instance, the method comprises providing the flexible substrate film via additive manufacturing.

As exemplified herein, the flexible polymer material of the flexible substrate film (40) comprises polycaprolactone, PCL.

As exemplified herein, said conductive traces 20 define a set of electrodes of at least one device for electrochemical sensing of one or more analytes, the set of electrodes comprising at least one working electrode WE, WE1 , WE2, a counter electrode CE and a reference electrode PRE.

As exemplified herein, the method comprises: immersing 150 the at least one device 200; 20 for electrochemical sensing of one or more analytes in an aqueous bath 50, the aqueous bath (50) comprising sodium hydroxide, applying ultrasound waves 160 to the at least one device 200; 20 for electrochemical sensing of one or more analytes immersed in said aqueous bath for a time length of at least five minutes.

As exemplified herein, the method comprises applying ultrasound waves to the at least one device for electrochemical sensing of one or more analytes for a time length in a range between fifteen minutes and ninety minutes.

As discussed, the first activation processing step comprising sonication 60 of the devices 20 in an aqueous bath 50 facilitates etching of a very thin layer of material at the surface of electrode WE, PRE, CE, and may therefore be suitable to be applied to used devices 20 that may suffer from passivation.

It is well known that during the electrooxidation of phenolic compounds a noticeable decrease in the current is observed due to the formation of a polymeric film on the electrode surface. For example, 10 cyclic voltammetries, in the potential window from - 0.2 to + 1 .2 V vs Ag/AgCI(3MKci), can be consecutively run in order to polymerize water soluble 4-hydroxybenzioic acid (HBA) onto working electrode surface. For instance, a significant decrease of the peak current may be observed during continuous potential cycling, indicating that the electrode surface becomes deactivated gradually due to formation of the passivating film.

As exemplified herein, in order to restore the functionality of the electrode after passivation, a treatment comprising sonication 60 immersed in 0.5 M NaOH bath 50 for a time length about 5-10 minutes may be applied, followed by electroactivation EA. In the considered example, the HBA passivation procedure may then be repeated.

As appreciable from Figure 12, the oxidation peak corresponding to the first cycle of the ten scans returned to be comparable to that initially recorded with newly printed and treated electrodes. This operation was repeated four times obtaining similar results in terms of peak potential and currents after each cleaning cycles.

As shown in in Figure 12, cyclic voltrammetric profiles recorded indicate that the treatment is effective in restoring activity to electrodes fouled without resort to repolishing and mechanical treatment.

For instance, it removes contamination from electrode surfaces by etching the overlayer, thus making the additive manufactured devices 20 completely cleanable and reusable.

Without prejudice to the underlying principles, the details and embodiments may vary, even significantly, with respect to what has been described by way of example only, without departing from the extent of protection. The extent of protection is defined by the annexed claims.