Drift cell

Abstract

The present invention relates to a drift cell comprising a monobloc body comprising a first resistive and electrically conductive material (1) and a second electrically insulating material (2). The monobloc body is formed by N helices of the first material (1) alternating with N helices of the second material (2). The means for preparing the cell consist of a 3D printer, such that the helices of the body are formed by a plurality of stacked printed layers (3) and wherein, p being the perimeter of the cell outline and ec and ea the thickness of the layer (3) of the first and second material (1, 2), respectively, for a value of p / [N·(ec+ea)] substantially greater than 1 and a value of p substantially greater than the printing nozzle width (w), it follows that the resistance (R) of the electrode is (Formula), where L is the drift length and ρ is the resistivity of the first material (1).

Description

DESCRIPTION Drift cell Technical field of the invention

[0001] The present invention pertains to the technical field of scientific instrumentation, specifically to a drift cell used in various measuring instruments such as radiation detectors and ion mobility spectrometers. Background of the Invention

[0002] Drift cells are regions in which a charged particle, an electron or an ion, drifts under the effects of an electric field and are applied in at least two very different types of measuring instruments, radiation detectors and ion mobility spectrometers (IMS).

[0003] In radiation detectors, the passage of a charged particle ionizes a gas. The free electrons produced by this interaction are drawn by the electric field to an anode where they are detected, and the drift time can be correlated with the distance between the point of interaction and the anode. These instruments have applications in basic research in particle physics, radiation protection, medical physics, inspection of potentially hazardous goods, and muon radiography in geology, volcanology, and archaeology.

[0004] In ion mobility spectrometers, a pulsed release of gases to be characterized, previously ionized, occurs. These gases are separated as they pass through the drift cell due to their different drift speeds and are detected when they reach the cathode located at the end of the drift chamber, thus allowing the distinction between the different components through the temporal separation of their output.

[0005] These devices are widely used for the chemical analysis of ionized gas molecules. Their use is widespread and they are common equipment for detecting explosives, drugs, and chemical weapons at airports.

[0006] Drift cells have been used as particle detectors for over 50 years. They consist of a closed structure in which an electric field is induced to cause charged particles to drift at a constant speed, allowing information to be obtained from the arrival time of these particles. The drift time inside the cell depends on the length and drift velocity, and these two variables must be controlled to increase the accuracy of the measurement.

[0007] The drift length depends primarily on the geometry of the drift cell and the possible existence of multiple drift paths with varying lengths from the point of charge particle generation to the collection electrode (cathode or anode, depending on the type of drift cell). This path dispersion can be improved by increasing the cell's aspect ratio (longitudinal dimension parallel to the drift path versus transverse dimension). As for the drift velocity, it depends on the chosen gas, pressure, temperature, and the uniformity of the electric field; therefore, accuracy increases with greater uniformity of the electric field in the drift region.

[0008] In the basic configuration of a drift cell, only two electrodes (cathode and anode) are needed to define a drift electric field region. This configuration has the advantage of its simplicity of construction, but it produces a heterogeneous electric field distribution that depends strongly on the geometric arrangement of the electrodes and the other elements of the system.

[0009] In the most common drift cell design, a series of electrodes are arranged to create the electric field. The smaller the separation between these electrodes, the greater the uniformity of the electric field, and therefore the better the drift cell's resolution. In IMS devices, these electrodes are usually conductive rings, typically metallic.

[0010] In this configuration, each electrode is connected to a different voltage, typically through a resistor chain that acts as a voltage divider. This design uses a large number of discrete components, increasing the system's complexity and cost, while also making it more difficult to maintain the chamber's airtight seal.

[0011] As an alternative to the scheme of multiple discrete electrodes connected to a voltage divider, proposals have emerged based on a continuous resistive electrode, which acts as both a voltage divider and an electric field-forming electrode. These types of designs can achieve highly homogeneous electric fields due to the greater continuity of electrical voltage around the drift chamber. Another advantage is that they can be monolithic or single-body, which is beneficial for manufacturing and sealing.

[0012] However, it is necessary to choose the geometry and materials appropriately, so that the material resistance is neither too large nor too small, to achieve an ideal balance between electrical consumption (and therefore energy dissipation) and the quality and homogeneity of the resulting electric field.

[0013] If the total resistance is too low, the electrical consumption, and therefore the heat dissipation, when connected to the high-voltage source, becomes excessive. However, if the resistance is too high, it loses immunity to external fields (for example, the grounding electrodes of the equipment casing) and loses its ability to dissipate charge deposited on the electrodes during operation, resulting in irregularity and degradation of measurement accuracy.

[0014] There are proposals for single resistive electrodes, such as reference document JP2019109254, which uses an insulating substrate onto which an electrode with the desired pattern (helical or other) is deposited using techniques like photolithography or inkjet printing. This implies that manufacturing the cells requires the prior fabrication of a complex, custom-made system to deposit the patterns inside the insulating tube.

[0015] Furthermore, its application to an IMS system requires the separate manufacturing of each component, including the cell itself, followed by their assembly. This increases manufacturing complexity, lengthens lead times, and results in higher manufacturing costs.

[0016] Another drawback of these drift cells is that they only allow for a circular cross-section. This isn't a problem for their application to IMS, but they are not suitable for radiation detectors, since in this case rectangular cross-section cells are used or, if cylindrical, the drift direction does not coincide with the axis of the cylinder.

[0017] There are other drift cells, such as those made using 3D printing, as shown, for example, in the publication "The Use of 3D Printing in the Development of Gaseous Radiation Detectors", Sam Fargher, Chris Steer, Lee Thompson. EPJ Web Conf. 170 01016 (2018).

[0018] In this case, drift cells have only an anode and a cathode and do not have field-forming electrodes. The field that forms inside them is inherently non-uniform and they do not provide the same type of spatial information as a drift cell with a uniform drift region.

[0019] Other examples of drift cells made using 3D printing can be found in reference document CN 115064431, and the publications:

[0020] “Accurate and on-demand chemical sensors: A print-in-place ion mobility spectrometer”, Brian C. Hauck, Bradley R. Ruprecht, Patrick C. Riley, Sensors and Actuators B: Chemical, Volume 362, 2022, 131791, ISSN 0925-4005;

[0021] “3D-printing of a complete modular ion mobility spectrometer” Carolin Drees, Simon Hoving, Wolfgang Vautz, Joachim Franzke, Sebastian Brandt, Materials Today, Volume 44, 2021, Pages 58-68, ISSN 1369-7021;

[0022] “Leveraging 3D printing to enhance mass spectrometry: A review” M. Grajewski, M. Hermann, RD Oleschuk, E. Verpoorte, G.IJ. Salentijn, Analytica Chimica Acta (2021).

[0023] All of these documents propose 3D printing for drift cells applied to IMS and all of them implement configurations with separate electrodes in which the voltage gradient is produced by a voltage divider formed by discrete resistors.

[0024] The problem that arises in these cases is that the use of multiple discrete electrodes does not allow for uniformity of the generated electric field, which results in a lower resolution of the final system measurement.

[0025] Furthermore, since it has to include a resistive voltage divider, the number of parts for building the device is very high and requires assembly after the 3D printing of the cell.

[0026] It is therefore necessary to find a way to obtain a drift cell that allows for perfect uniformity of the electric field created and that reduces the number of parts needed for its construction. Description of the invention

[0027] The drift cell presented here comprises a monoblock body composed of at least a first resistive and electrically conductive material and a second electrically insulating material.

[0028] This body has a helical structure and is configured by an N number of helices of the first material that form an electrode and are alternated with an equal number N of helices of the second material. The helices are formed by a curved line or a polygonal line.

[0029] The cell fabrication means consist of a 3D printer with a first print head configured for printing the first material and a second print head configured for printing the second material, such that the body helices are formed by a plurality of overlapping print layers, where at least from the second layer onwards each print layer consists of one or more first sections of the first material and one or more second sections of the second material, where the first and second sections (4.1, 4.2) are alternated with each other and each first and second section of said layers overlaps with the first and second section respectively of the consecutive upper layer.

[0030] In this cell, where p is the perimeter of the cell's outline, e c the thickness of the first material layer y a the thickness of the layer of the second material, for a value of the expression p / [N (e c+e a )] eminently greater than 1 and a value of p eminently greater than the value of the nozzle width (w), it follows that the value of the resistance (R) between the ends of the electrode, composed of all the N helices is

[0031] where L is the drift length, and p is the resistivity of the first material.

[0032] The drift cell proposed here represents a significant improvement over the state of the art. This is because it creates a highly uniform electric field thanks to its monoblock construction. Furthermore, since the electrode is formed by the helical structure of the cell body itself, the body is completely sealed, resulting in very high linearity and very high resolution of the electric field, all without the need for additional components.

[0033] It is used as an electrode or prime material, a material suitable for 3D printing, whose resistivity is between 5 and 10' 5 and 5 10' 1 Q m, and has an intermediate resistivity value between that of a metallic element and an insulating element, so that it can function simultaneously as an electrode and as a voltage divider, therefore it is not necessary to implement discrete electrodes with terminals and independent high voltage connections or an external resistance ladder.

[0034] It is sufficient to connect both ends of the resistive electrode of the drift cell thus constructed to the desired upper and lower voltages, which may or may not coincide with the voltages of the anode and / or cathode of the charge collection system, so that the electric potential or voltage gradually varies between said ends of the electrode, forming a highly uniform electric field inside the drift cell.

[0035] Furthermore, given the resistance characteristics of each propeller, it is possible to achieve sufficiently low resistance values ​​without the use of external discrete components to keep power consumption at acceptable levels. This is all possible solely through the resistivity of the conductive material used.

[0036] This drift cell is very easy to make using a 3D printer with two extrusion heads and low-cost conductive filaments. The cell can be manufactured in an integrated manner using 3D printing, along with other elements of the system, reducing the total cost of the whole.

[0037] Furthermore, this cell can be created with any section, not just a circular section, making it equally valid for IMS and radiation detectors.

[0038] This results in a highly efficient drift cell, achieving a highly uniform field and great simplicity in its manufacture, using a single-piece body made of two materials, without the need for additional components. Thus, construction is carried out in a single step, thereby accelerating the process and reducing time and costs. Brief description of the drawings

[0039] In order to aid a better understanding of the characteristics of the invention, according to a preferred embodiment thereof, a series of drawings are provided as an integral part of this description, where, for illustrative and non-limiting purposes, the following has been represented:

[0040] Figure 1 shows a schematic view of the body of a drift cell with N = 1, for a first preferred embodiment of the invention.

[0041] Figure 2 shows a perspective view of the electrode from inside one end of the cell, for a value N = 1, for a first preferred embodiment of the invention.

[0042] Figure 3 shows a perspective view of the electrode from inside one end of the cell, for a value of N = 2, for a second preferred embodiment of the invention.

[0043] Figure 4 shows a perspective view of the electrode from inside one end of the cell, for a value of N = 3, for a third preferred embodiment of the invention.

[0044] Figure 5 shows a side view of a first overlapping option of the body-forming layers of a drift cell, for a first preferred embodiment of the invention.

[0045] Figure 6 shows a side view of a second overlapping option of the body-forming layers of a drift cell, for a first preferred embodiment of the invention.

[0046] Figure 7 shows a side view of a third overlapping option of the body-forming layers of a drift cell, for a first preferred embodiment of the invention.

[0047] Figure 8 shows a perspective view of a sequence of layer depositions with the different sections of body formation of a drift cell for the first overlap option, for a first preferred embodiment of the invention.

[0048] Figure 9 shows a perspective view of a sequence of layer depositions with the different sections of formation of the body of a drift cell, for the third overlap option, for a first preferred embodiment of the invention. Detailed description of a preferred embodiment of the invention

[0049] In view of the figures provided, it can be observed how in a first preferred embodiment of the invention, the drift cell proposed herein comprises a monoblock body composed of at least a first resistive and electrically conductive material (1) and a second electrically insulating material (2), and has a helical structure, configured by means of a number N of helices of the first material that form an electrode, alternating with the same number N of helices of the second material.

[0050] Optionally, other materials can be used for purposes other than acting as an electrode and insulating material respectively, such as a material to adapt the cell body to an external support or to be used as a printing support for cantilevered printed layers.

[0051] The helices of this drift cell are formed by a curved line or a polygonal line; specifically, in this first embodiment, helices with a curved line are considered, so that the body has a circular section as shown in Figures 1 and 2. In Figure 1, the helices of each material have been represented schematically as a line without thickness, but both helices have a thickness such that together they form a hermetic monoblock body.

[0052] In this first embodiment, a single helix of each material has been considered, i.e., N = 1, as shown in Figure 2, but in other embodiments, a greater number of helices can be used, such as a second embodiment shown in Figure 3, in which N = 2, or a third embodiment with N = 3, which can be seen in Figure 4, in which the cell formed by 3 helices of each material is represented.

[0053] In other embodiments, the helices may be formed by a polygonal line, in which case the body has a rectangular / elongated, square, semicircular or any other similar shape.

[0054] According to another aspect, the cell's manufacturing means consist of a 3D printer with a first print head configured for printing the first material (1) and a second print head configured for printing the second material (2), so that the body's helices are formed by a plurality of overlapping printed layers (3).

[0055] Furthermore, at least from the second body layer onwards, each of the print layers (3) is formed by one or more first sections (4.1) of a first material (1) and one or more second sections (4.2) of a second material (2), wherein the first and second sections (4.1, 4.2) are arranged alternately with each other and each first and second section (4.1, 4.2) of said layers (3) has an overlap with a first and second section (4.1, 4.2) respectively of the same material of the consecutive upper layer.

[0056] Furthermore, given the perimeter (p) of the cell outline, the thickness of the resistive material layer (e) c ) and the thickness of the insulating material layer (e a ), for a value of the expression p / [N (e c +e a )] eminently greater than 1 and a value of p eminently greater than the value of the nozzle width (w), it follows that the value of the resistance (R) of the electrode is

[0057] where L is the drift length, and p is the resistivity of the conducting material.

[0058] For a first embodiment presented here, in which the drift cell has a single helix for the first material (1) and a single helix for the second material (2), i.e., N = 1, the resistance for each of the helices is expressed in the form:

[0059] Both in the case of drift cells applied to radiation detectors and those applied to ion mobility spectrometry, a total potential difference on the order of kilovolts is usually introduced and, consequently, it is necessary to have resistive dividers on the order of megaohms to keep the electrical consumption at acceptable values.

[0060] With this drift cell thus obtained, these resistive values ​​are achieved without the use of external discrete components, but only through the resistivity of the conductive material used, arranged in the proposed geometry.

[0061] In this drift cell, the first material (1) acts as both a resistive and electrically conductive material. This offers significant advantages because this material has a resistance value intermediate between that of metallic and insulating elements, and it can function simultaneously as an electrode and a voltage divider. Therefore, it is not necessary to implement discrete electrodes with separate high-voltage terminals and connections and an external resistance ladder. In this case, it is sufficient to interconnect the electrode at one end to the conductive filament and arrange it on a continuous surface that runs the entire length of the cell to the anode element (or the desired upper voltage).

[0062] However, in this first embodiment where N = 1 and therefore there is only one helix of conducting material or first material, a problem may arise In its application to radiation detectors where drift cells acquire large dimensions, it is difficult to keep the total resistance of the field-forming electrode sufficiently low, since the electrode resistance grows linearly with the product of drift length and the perimeter of the cell section, i.e., with the product L p.

[0063] In these cases, one can opt for implementations in which a number of helices N > 1 is considered, so that, for example, for a second case in which N = 2, as shown in Figure 3, when two helices are connected in parallel, the resistance of the assembly that forms the electrode is divided by the number of helices, that is, by 2. In addition, the total length of each of the helices is divided by the total number of helices, so in this case it is also divided by 2.

[0064] Thus, the resistance of the electrode is inversely proportional to the square of the number of helices, that is, the greater the number of helices, the more the resistance value is reduced.

[0065] This factor provides flexibility in the design because for any geometry it is possible to find a design that adapts to the needs of the drift cell, using one of the commercially available resistive materials.

[0066] In this way, and given that the anode filament can be made with a very narrow pitch (<50 µm), a highly precise drift cell can be built whose body is composed of a single element, manufactured in a single process, providing performance equivalent to other cells composed of hundreds of discrete components.

[0067] In this first embodiment, it is desired to obtain an electrode resistance on the order of 10 7Q in a cell with a drift length of 10 cm and a diameter slightly less than 2 cm. This can be achieved with 500 turns of a helix made with a layer thickness of 100 microns, a nozzle of 0.6 mm diameter and a conductive filament with a resistivity of 0.02 Q m.

[0068] The thickness of the insulating material layer would also be, for example, 100 pm.

[0069] The total length of the resistive circuit, assuming a single strand, is 30 m, so for a resistivity of the first material (1) of 0.02 Q m, the total resistance of the resistive circuit obtained is approximately 1 ■ 10 7 Q, that is, 10 MQ. (0.0001 - 0.0001) • 0.0001 ' 0 S 0006 "

[0070] According to another aspect, in this first preferred embodiment of the invention, the overlap between two first sections (4.1) arranged in a layer (3.1) and the consecutive upper layer (3.2) is formed by a first segment (5.1) of the first section (4.1) located in the lower layer (3.1) coinciding with a second segment (5.2) of the corresponding first section (4.1) of the upper layer (3.2), where said upper layer (3.2) has a rotation with respect to the lower layer (3.1), as shown in Figures 5 and 8.

[0071] Similarly, the second sections (4.2) are overlapped, so there is an overlap between first sections (4.1) of consecutive layers of the first material (1) and an overlap between second sections (4.2) of consecutive layers of the second material (2).

[0072] With this overlap, each layer (3) is printed at a constant height and in this case consists of a part printed with the first material (1) and a part printed with the second material (2). In cases with more than one helix, there would be two or more first and second sections (4.1, 4.2) of each material in each layer (3), depending on the number of helices.

[0073] The overlap creates a stepped profile that ensures continuity of each of the materials between the layers (3).

[0074] As can be seen in Figure 5, in each of the deposited layers (3), the first and second sections (4.1, 4.2) of each material must partially overlap, i.e., coincide vertically in a segment at the end, with the first or second section (4.1, 4.2) of the same material deposited in the lower layer (3.1), thus ensuring a continuous helix of the first material (1) or conductive material and a continuous helix of the second material (2) or insulating material, both without breaks.

[0075] The length of the first overlap segment (5.1) at the end of the first section (4.1) of a first material (1) of a lower layer (3.1) and the corresponding second segment (5.2) at the end of the first section (4.1) of the upper layer (3.2) responds to criteria for optimizing the resistance between different conductive layers, according to the conductivity or resistivity values ​​in the XY plane and in the Z direction measured or provided by the material manufacturer.

[0076] In this first preferred embodiment, a first layer (3.0) is considered to be formed exclusively of the first material (1), and from that layer (3.0) onwards, layers (3) are composed of the first material (1) and the second material (2). Each new layer is rotated 157.5° with respect to the previous one, so that an overlap of 22.5° (1 / 16 of a turn) is ensured between consecutive layers (3) of the first material (1) or conductive material to guarantee electrical continuity between them.

[0077] In a second overlapping option, shown in Figure 6, a particular case of the first option is proposed in which, given two first sections (4.1) of a first material (1), for example, arranged in a layer (3.1) and in the consecutive upper layer (3.2), the first segment (5.1) of the first section (4.1) and the second segment (5.2) of the first section (4.1) of the corresponding upper layer (3.2) in an overlap, exhibit a progressive variation of thickness, the variation of the second segment (5.2) being inverse to the variation of the first segment (5.1), so that the total thickness of the material of the first section (4.1) in the overlapping zone, composed of a first segment (5.1) and a second segment (5.2) in the consecutive upper (3.2) and lower (3.1) layers remains constant and equal to that of the rest of the first section (4.1) of both layers (3.1, 3.2).

[0078] The same procedure is followed for the second sections of each layer.

[0079] Another possible arrangement of the layers and overlapping regions can be seen in Figures 7 and 9, where, for example, in the case of the overlap between two first sections (4.1) of a first material (the same occurs with the second material) arranged in a layer (3.1) and the consecutive upper layer (3.2), this overlap is formed by a progressive variation of the thickness of the first material (1) combined with a progressive variation in the opposite direction of the second material (2), so that the thickness of each layer (3) in each section of it is the result of the sum of the thickness of the first section (4.1) and the second section (4.2) coinciding in that section.

[0080] Thus, the thickness of the first section (4.1) is linearly increasing in a lower layer (3.1) and exhibits a linearly opposite variation in the first section (4.1) of the upper layer (3.2) coinciding with it, therefore, in this case, in the upper layer (3.2) that first section (4.1) is linearly decreasing.

[0081] Thus, the thickness of each helix remains constant, with the particularity that the first material (1) has a thickness (e c ) of layer that may be equal to or different from the thickness (e a ) of the second material layer (2).

[0082] In Figure 7, the boundaries of each layer have been represented by dashed lines.

[0083] This manufacturing method facilitates obtaining a drift cell in which the thicknesses (e c ) of the layers of a first material (1) and the thicknesses (e aThe layers of a second material (2) may not be equal, allowing an additional degree of freedom in the design of the drift cell, which can provide greater freedom when choosing the conductive material or other design parameters. This is not possible to achieve with the other overlap modes.

[0084] Depending on the resistance characteristics in the XY plane and in the Z printing direction, it may be advisable to increase the layer overlap (3) to compensate for the additional resistance introduced by the contact between different first and second sections (4.1, 4.2). In this case, a thickness asymmetry could be introduced in that region between the conductive and insulating filaments by making the latter thinner (by reducing the speed of the material push motor) to compensate for the increased thickness caused by the overlap of the conductive filament.

[0085] However, in this first preferred embodiment of the invention, the helices of both materials have the same thickness.

[0086] According to another aspect, in this first preferred embodiment, the first material (1) is made of a material suitable for FFF 3D printing or FDM 3D printing, with resistivities between 5 and 10' 5 and 5 10E' 1 Q m.

[0087] This material, used as the first material (1), or resistive and electrically conductive material, forms the electrode and replaces the commonly used metallic electrodes. Using this material as an electrode offers significant advantages because, being a material with a resistance value intermediate between that of a metallic element and an insulating material, it can function simultaneously as an electrode and as a voltage divider. Therefore, it is not necessary to implement discrete electrodes with independent high-voltage terminals and connections and an external resistance ladder.

Claims

CLAIMS 1- Drift cell, characterized in that it comprises a monoblock body which in turn comprises at least a first resistive and electrically conductive material (1) and a second electrically insulating material (2), and has a helical structure, configured by a number N of helices of the first material (1) which form an electrode, alternating with the same number N of helices of the second material (2), the helices being formed by a curved line or by a polygonal line, where the means of making the cell are formed by a 3D printer with a first and a second print head configured for printing the first and second material (1, 2) respectively, such that the helices of the body are formed by a plurality of superimposed printing layers (3) with a certain thickness, where at least from the second layer onwards each of the printing layers (3) is formed by one or more first sections (4).1) of the first material (1) and one or more second sections (4.2) of the second material (2), wherein the first and second sections (4.1, 4.2) are alternated with each other and each first and second section (4.1, 4.2) of said layers (3) has an overlap with a first and second section (4.1, 4.2) respectively of the consecutive upper layer and wherein, p being the perimeter of the cell outline, e. c is the thickness of the layer (3) of the first material (1) and a is the thickness of the layer (3) of the second material (2), for a value of the expression p / [N (e c +e a )] eminently greater than 1 and a value of p eminently greater than the value of the print nozzle width (w), it follows that the value of the resistance (R) of the electrode is where L is the drift length, and p is the resistivity of the first material (1). 2- Drift cell according to claim 1, wherein the overlap between two first or two second sections (4.1, 4.2) arranged in a layer (3.1) and the consecutive upper layer (3.2) is formed by a first segment (5.1) of the first or second section (4.1, 4.2) located in the lower layer (3.1) coinciding with a second segment (5.2) of the corresponding first or second section (4.1, 4.2) of the upper layer (3.2). 3- Drift cell according to claim 2, wherein the thickness of said first and second segment (5.1, 5.2) is eminently constant. 4- Drift cell according to claim 2, wherein the first segment (5.1) of the first or second section (4.1, 4.2) and the second segment (5.2) of the corresponding first or second section (4.1, 4.2) in an overlap, have a progressive variation of thickness, the variation of the second segment (5.2) being inverse to the variation of the first segment (5.1), so that the thickness of each material in the overlap zone remains constant and equal to that of the rest of the first or second section (4.1, 4.2). 5- Drift cell according to claim 1, wherein the overlap between two first or two second sections (4.1, 4.2) of the same material (1, 2) arranged in a layer (3.1) and the consecutive upper layer (3.2) is formed by a progressive variation of the thickness of each material such that the thickness of each layer (3) in each section thereof is the result of the overlap of the thickness of at least one first section (4.1) and at least one second section (4.2) coinciding in said section, wherein the thickness of the first section (4.1) is progressively increasing or decreasing in the lower layer (3.1) and presents an opposite progressive variation in the first section (4.1) of the upper layer (3.2) coinciding with it, and the thickness of the second section (4.2) is progressively increasing or decreasing in the lower layer (3.1) and presents an opposite progressive variation in the second section (4.2) of the upper layer (3.2) coinciding with the same, so that the thickness of each helix remains constant, where the first material (1) has a thickness (e. c ) of the same or different layer thickness (e a ) of the second material layer (2). 6- Drift cell according to any of the preceding claims, wherein the helices of each material have the same thickness. 7- Drift cell according to any of the preceding claims, wherein the propellers are formed by a curved line and the body has a circular section. 8- Drift cell according to any of claims 1 to 5, wherein the propellers are formed by a polygonal line and the body has a rectangular / elongated, or square, or semicircular section. 9- Drift cell according to any of the preceding claims, wherein the first layer (3.0) is formed by the first material (1). 10- Drift cell according to any of the preceding claims, wherein the first material (1) is formed from a material suitable for FFF 3D printing or FDM 3D printing, with resistivities between 5-10 -5 and 5-10' 1 Q m.

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