Navigation guide that can be deformed at a low voltage

Abstract

The present description relates to a navigation guide for a fluid circuit successively comprising a distal part (1), a central part (2) and a proximal part (3). The distal part (1) comprises a substrate covered by an active block comprising at least two organic electroactive layers, first electrodes and second electrodes, each organic electroactive layer being disposed between a first electrode and a second electrode, the substrate having a length / width ratio of between 2 and 150, the distal part (1) forming an angle α of between 20 and 360° relative to the proximal part (3), when no voltage is applied to the active block.

Description

B23048PCT ‐ DD23477 YG DESCRIPTION TITLE: Low voltage deformable navigation guide This application is based on, and claims priority from, French patent application number FR 23 / 12868 filed on November 22, 2023, entitled “Universal navigation device”, which is considered an integral part of this description to the extent permitted by law. Technical field

[0001] This disclosure relates generally to devices for navigating in a fluid, for example devices for arterial navigation (endovascular surgery), or for navigating in branched systems such as plumbing ducts or air conditioning circuits. Prior art

[0002] In endovascular surgery, in order to reach a target blood vessel (such as an artery), surgeons use guides to navigate the arterial circuit.

[0003] A guide connects the target artery with the outside: it allows, for example, the delivery of a balloon catheter and a stent in the case of stenosis.

[0004] However, as they are not steerable, they must be introduced using preformed selective angiography catheters. The catheters are chosen according to the shape of the artery: curved, S-shaped, etc. For illustration purposes, the catheters may be catheters referenced under the names 'Head Hunter 1', 'Cobra 1', 'Simmons Sidewinder 2', 'Vertebral', 'Berenstein', 'Multipurpose A'. B23048PCT ‐ DD23477 YG There is no universal navigation guide: one catheter fits one shape.

[0005] To overcome this drawback, devices comprising an active block based on electroactive polymer have been modeled. For example, the article by Q. Jacquemin et al. (“Design of a new electroactive polymer based continuum actuator for endoscopic surgical robots” 2020, IEEE / RSJ International Conference on Intelligent Robots and Systems (IROS)), the active block of the actuator is positioned on a 25µm thick PEN substrate, the electrodes are made of PEDOT:PSS and the 6µm electroactive polymer layer is made of P(VDF-TrFE-CTFE). By applying voltages higher than 50V / µm, it is possible to bend the device. The length of the device is 5 cm and its width is 4 mm.

[0006] Thus, it would be possible to manufacture a navigation guide comprising a substrate covered by an active block. When a voltage is applied to the active block, it mechanically deforms and causes the substrate to bend.

[0007] However, such devices are still too bulky for arterial navigation. In addition, the device can be either straight or curved in one direction, which is not favorable for navigation in canals with complex geometry (including passages where the device must be oriented in one direction and then the other).

[0008] Finally, the tensions applied to modify the shape of the tip still remain too high. Summary of the invention

[0009] There is a need for a device whose shape can be changed at low voltage, and the device must be miniaturizable to be able to navigate blood vessels. B23048PCT ‐ DD23477 YG

[0010] This aim is achieved by a fluid circuit successively comprising a distal part, a central part and a proximal part. The distal part comprises a substrate covered by at least one active block comprising at least two organic electroactive layers, first electrodes and second electrodes, each organic electroactive layer being arranged between a first electrode and a second electrode. The substrate has a length / width ratio of between 2 and 150, preferably between 5 and 100, and even more preferably 50 and 100. The distal part forms an angle α of between 20 and 360°, preferably between 20° and 250°, relative to the proximal part, in the absence of voltage applied to the active block.

[0011] Advantageously, the active block comprises at least 5 organic electroactive layers, preferably between 7 and 15 organic electroactive layers.

[0012] Advantageously, the substrate has a thickness of between 15 and 75 µm, preferably between 20 and 50 µm.

[0013] Advantageously, the substrate is made of polyimide.

[0014] Advantageously, each electroactive layer is made of PVDF or one of its copolymers, such as P(VDF-TrFE).

[0015] Advantageously, the first electrodes and the second electrodes are made of an electrically conductive polymer, preferably PEDOT-PSS.

[0016] Advantageously, the organic electroactive layers have a thickness of between 2 and 15 µm, preferably between 3 and 15 µm, and even more preferably between 3 and 6 µm, and even more preferably between 3 and 4 µm.

[0017] Advantageously, the substrate has a thickness between 20 and 50µm, the active block comprises between 8 and 12 layers B23048PCT ‐ DD23477 YG electroactive layers, each electroactive layer having a thickness between 3 and 4 µm.

[0018] Advantageously, the guide comprises between 2 and 5 active blocks arranged on the same face of the substrate, the active blocks being able to be identical or different.

[0019] Advantageously, the guide comprises between 2 and 5 active blocks, a portion of the active blocks being arranged on a first face of the substrate and another portion of the active blocks being arranged on a second face of the substrate, the active blocks being able to be identical or different.

[0020] Advantageously, the active blocks are covered by an encapsulation layer made of a polymer material, for example, PDMS, PMMA, PVDF or one of its derivatives.

[0021] This object is also achieved by a method of using a navigation guide comprising the following steps: - providing a navigation guide successively comprising a distal portion, a central portion and a proximal portion, the distal portion comprising a substrate covered by at least one active block comprising at least two organic electroactive layers, first electrodes and second electrodes, each organic electroactive layer being arranged between a first electrode and a second electrode, the substrate having a length / width ratio of between 2 and 150, preferably between 5 and 100, and even more preferably 50 and 100, the distal portion forming an angle α of between 20 and 360°, preferably between 20° and 250°, with respect to the proximal portion, in the absence of voltage applied to the active block, - applying a voltage, preferably between 50 and 500 V, even more preferably between 100 V and 150 V, to the B23048PCT ‐ DD23477 YG organic electroactive layers 103, whereby the angle α between the distal portion and the proximal portion decreases to a value between 0 and 50°, or even to a negative value. Brief description of the drawings

[0022] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which:

[0023] Figure 1 shows, schematically and in section, a navigation guide according to a particular embodiment of the invention - the different parts are not to scale;

[0024] Figure 2A shows, schematically and in section, a substrate covered by an active block, according to another particular embodiment of the invention;

[0025] Figure 2B represents, schematically and in section, a substrate covered by several active blocks, according to another particular embodiment of the invention;

[0026] Figure 3 shows, schematically and in section, the distal end of a navigation guide, curved in the absence of applied tension, according to another particular embodiment of the invention;

[0027] Figure 4A, Figure 4B, Figure 4C, Figure 4D, Figure 4E and Figure 4F are photographic images showing the mechanical deformation of a substrate (25 mm x 2.5 mm), in the absence of applied voltage (0V) and as a function of different applied voltages (from 100V to 500V), in reverse control, according to other particular embodiments of the invention;

[0028] Figure 5A, Figure 5B, Figure 5C and Figure 5D are photographic images showing the deformation B23048PCT ‐ DD23477 Mechanical YG of a substrate (20 mm x 0.25 mm) in the absence of applied voltage (0V) and as a function of different applied voltages (from 50V to 150V), in reverse control, according to other particular embodiments of the invention;

[0029] Figure 6 is a graph showing the displacement of the end of a substrate as a function of the applied voltage for several substrate widths (from 0.25 mm to 1.5 mm), in conventional control, for comparison; the displacement is measured relative to the position of the substrate in the absence of applied voltage ('delta rel'). Description of the embodiments

[0030] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0031] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed.

[0032] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

[0033] In the following description, when referring to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to B23048PCT ‐ DD23477 YG orientation qualifiers, such as the terms "horizontal", "vertical", etc., are referred to unless otherwise specified in the orientation of the figures.

[0034] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0035] Subsequently, we will more specifically describe the devices for arterial navigation, the device can nevertheless be used for any type of navigation in a fluid, for example for navigation in various branched systems (plumbing pipe or air conditioning circuit for example) or even as a remotely controllable switch.

[0036] We will now describe the navigation guide in more detail with reference to the attached figures.

[0037] As shown in Figure 1, the navigation guide consists of 3 main parts: the distal part 1 (also called the tip), the transition zone 2 (also called the central part or central core) and the proximal part 3 (also called the body).

[0038] The guide allows navigation in the vessels thanks to the distal end 1 which can be oriented under the action of an electric field.

[0039] The distal end 1 comprises a substrate 10 covered by at least one active block (Figures 2A and 2B).

[0040] The substrate 10 comprises a first main face 10a and a second main face 10b.

[0041] The active block 11 is a multi-layer active block: it comprises several active layers. The active block 11 comprises at least two electroactive layers 103, first electrodes 101 and second electrodes 102. The first electrodes 101 and the second electrodes 102 are B23048PCT ‐ DD23477 YG positioned on either side of each electroactive layer 103. The active block 11 is formed from an electroactive stack.

[0042] In the case where the multilayer active block ends with an electroactive layer, this acts as an encapsulation layer and protects the upper electrode.

[0043] Thus, the navigation guide is fundamentally distinguished from the prior art by the presence of at least one multi-layer active block, electrically activatable, on one of the faces of the substrate 10.

[0044] The distal part 1 thus obtained is curved when no tension is applied (figure 3). In other words, the distal portion 1 forms an angle α of between 20 and 360°, preferably between 20 and 250°, even more preferably between 20° and 200° and even more preferably between 50° and 200°, with the body of the guide 3. When a voltage is applied to the active block 11 (i.e. to the organic electroactive layers 103), the latter is mechanically deformed, creating tension and compression zones on the faces 10a, 10b of the substrate 10, which leads to a reduction in the angle α between the distal portion 1 and the body of the guide 3. The angle α can decrease to a zero or even negative value (i.e. the sample bends in the other direction) for certain voltages and for certain dimensions of the substrate 10 of the distal portion 1.

[0045] This type of reverse control is particularly advantageous since the voltages applied to rectify the distal part 1 are relatively low (typically between 50V and 200V).

[0046] The voltages involved are lower than those used in conventional devices where the application of a voltage allows the end to be bent B23048PCT ‐ DD23477 YG distal, that is, to change the distal end from a straight position to a curved position.

[0047] The substrate 10 is a flexible substrate, i.e. it can deform when the piezoelectric stack is subjected to a voltage. The material is chosen so as to allow reversible deformation.

[0048] The substrate 10 is, for example, made of a polymer such as polyimide (PI) or poly(ethylene naphthalate) (PEN). It can also be made of polyarylate (PAR).

[0049] The substrate 10 has a small thickness, typically between 15 and 75 µm, preferably between 20 and 50 µm, for example 25 µm. With such thicknesses, the substrate can be easily deformed while still allowing the electroactive stack(s) to be supported and / or navigation in the target fluidic circuit.

[0050] For arterial navigation, the substrate 10 has a length for example between 10 and 30 mm, preferably between 15 and 25 mm, in particular for a device having a single electroactive block. For navigation in plumbing or air conditioning circuits, the dimensions will be adapted to those of the pipes / circuits.

[0051] The substrate 10 has a width, for example, between 0.1 mm and 5 mm, preferably between 0.2 and 3 mm.

[0052] The length / width ratio is preferably between 2 and 150, even more preferably between 5 and 100, for example between 50 and 100. The higher the ratio, the lower the tension required to deform the substrate 10 of the distal part 1 will be.

[0053] The distal part 1 comprises two ends: a first end is in contact with the central part and B23048PCT ‐ DD23477 YG a second end is free. In other words, it is not connected to other elements.

[0054] According to an alternative embodiment, shown in FIG. 2B, the substrate 10 is covered by several portions of active PN blocks (at least two), each portion of active PN blocks comprising at least one active block 11. The active blocks 11 can be actuated independently of each other.

[0055] The guide may include between 2 and 5 active block sections. By between X and Y, we mean here and hereafter that the terminals are included.

[0056] According to one embodiment, a portion of PN active blocks may comprise a single active block.

[0057] The active blocks 11 of the different PN portions can be arranged on the same side of the substrate 10. This makes it possible to increase the angle between the distal part and the central part.

[0058] The active blocks 11 of the different PN portions can be arranged, randomly or regularly, on the two faces 10a, 10b of the substrate 10.

[0059] According to another embodiment, a portion of active blocks PN may comprise two active blocks 11. The active blocks 11 are arranged on either side of the substrate 10, on each of the faces 10a and 10b. A portion PN then comprises two active blocks 11 arranged opposite each other (figure 2B).

[0060] The end of the guide can thus be oriented in two directions: the bending can be done indifferently in one direction or the other. Even if a portion of active PN blocks can be activated in both directions, it is possible to connect or activate only one of the two sides depending on the use of the guide. B23048PCT ‐ DD23477 YG

[0061] The presence of several portions of active PN blocks can make it possible, by applying a tension to the active blocks, to straighten the distal part 1 more easily relative to the body of the guide 3 and / or to obtain several deformation configurations of the distal part 1. The actuated length is modular. This can be particularly advantageous when it is necessary to navigate in a complex fluidic system having curved zones and straight zones.

[0062] The voltage applied to each active block 11 is preferably between 50 V and 1000 V, and preferably between 50 V and 200 V. Such voltages are sufficient to straighten the distal portion. Such voltages correspond to voltages between 10 MV / m and 330 MV / m and preferably between 10 MV / m and 70 MV / m.

[0063] Preferably, the portion of active blocks closest to the second end of the distal portion 1 is at a distance lm of 0 to 2 cm from the end of the distal portion and, even more preferably, at a distance of 0.5 to 1.5 cm from the end of the distal portion. This distance lm is also called dead length.

[0064] The distance li between two consecutive portions of active blocks PN and PN-1 is, for example, between 0.1 and 5 mm, preferably between 0.5 and 2 mm.

[0065] The distal part 1 has a length L preferably between 1 and 7 cm, and preferably between 1 and 4 cm.

[0066] The length L corresponds to the sum of the lengths of the different active blocks, the different inter-active block distances and the extreme length.

[0067] Each active block 11 has a length, for example, between 0.5 and 3 cm, preferably between 1.5 and 2.5 cm. B23048PCT ‐ DD23477 YG

[0068] Each active block 11 has, for example, a width between 0.1 mm and 1 cm, preferably between 0.2 mm and 3 mm. With such widths, it is possible to carry out arterial navigation.

[0069] The different active blocks 11 may have identical or different dimensions, an identical or different number of electroactive layers.

[0070] For example, as shown in Figure 2B, the device comprises three portions of active blocks P1, P2 and P3, each portion of active blocks having an active block 11 arranged on either side of the flexible substrate 10. The first portion of active blocks P1 comprises active blocks 11 having an electroactive layer 103, the second portion P2 of active blocks comprises active blocks 11 having 4 electroactive layers, and the third portion P3 of active blocks comprises active blocks 11 having two electroactive layers. The dimensions (length and thickness in particular) of the active blocks 11 are different here.

[0071] Preferably, the active blocks 11 comprise between 2 and 15 electroactive layers 103, and even more preferably between 5 and 15 layers 103 and even more preferably between 8 and 12 electroactive layers 103. When the active block 11 comprises several electroactive layers 103, the active block 11 is formed from a stack comprising an alternation of electroactive layers 103 and electrodes 101, 102. The stack begins with a first electrode 101 and ends with a second electrode 102, except in the case where a dielectric layer as encapsulation.

[0072] Each electroactive layer 103 has a thickness, for example, between 3 and 15 µm, preferably between 3 and 5 µm. With such thicknesses, the applied voltages can be relatively low. B23048PCT ‐ DD23477 YG

[0073] Electroactive materials are materials that deform under the application of an electric field. In particular, piezoelectric materials (such as PVDF-TrFE) are electroactive materials. There are other classes of electroactive materials, for example, electrostrictive materials (such as PVDF-TrFE-CTFE).

[0074] Preferably, each electroactive layer 103 is an organic electroactive layer. Each electroactive layer preferably comprises a polymer matrix made of PVDF, a PVDF copolymer or a PVDF terpolymer. It may be a copolymer of vinylidene fluoride and at least one other monomer copolymerizable with VDF. Advantageously, the copolymer comprises at least 50 mol%, preferably at least 70 wt%, even more preferably at least 80 mol% of VDF.

[0075] By way of illustration, the copolymerizable monomer(s) are, for example, chosen from chlorotrifluoroethylene (CTFE), chlorofluoroethylene (CFE), hexafluoropropylene (HFP), trifluoroethylene (VF3), methyl methacrylate (MMA), tetrafluoroethylene (TFE), and perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE).

[0076] For example, the copolymer is a poly(vinylidene fluoride-trifluoroethylene) PVDF / TrFe copolymer, also noted P(VDF-TrFe) or PVDF-CTFE.

[0077] It can also be a terpolymer. For example, a PVDF / TRFE / CTFE or PVDF / TRFE / CFE terpolymer would be chosen. Such materials are called electrostrictive materials.

[0078] According to another embodiment, the polymer is not a ferroelectric polymer: it can be PVDF-HFP. B23048PCT ‐ DD23477 YG

[0079] Each organic electroactive layer 103 may be a composite material. For example, the layer may comprise, in addition to the polymer matrix, ferroelectric particles and, optionally, PEDOT:PSS particles in order to increase the relative permittivity of the material and thus improve its electrical behavior.

[0080] For example, ferroelectric particles are made of BaTiO3 (BTO), PZT (lead zirconate titanate), AlN, ZnO, or SBN (Sr-Ba-Nb oxide) or SBT (Sr-Ba-Ti oxide). Such particles are, for example, used with a crosslinkable epoxy matrix. Thus, the layer has a certain stiffness, which allows the electrical impulse to be efficiently transformed into mechanical displacement.

[0081] The electrodes 101, 102 have, for example, a thickness of between 0.1 and 3 µm, preferably between 1.5 and 2.5 µm.

[0082] Preferably, the electrodes 101, 102 are made of an electrically conductive polymer, preferably PEDOT-PSS (poly(3,4-ethylenedioxythiophene).

[0083] The materials forming the different active blocks 11 may be identical or different. Preferably, they are identical. Even more preferably, each active block 11 comprises electrodes 101, 102 made of PEDOT-PSS and an electroactive layer made of P(VDF-TrFe), the assembly being optionally covered by an encapsulation layer.

[0084] When using the navigation guide, depending on the desired shape, it is possible to apply no voltage, or to apply one or more different voltages to the active blocks 11. With such a device, it is possible to have one end curved in one direction or B23048PCT ‐ DD23477 YG in the other, a straight shape or an S-shaped end.

[0085] According to one embodiment, each of the parts of the navigation guide comprises a substrate making it possible to support different elements (electrical tracks, electrical wires, active blocks).

[0086] Preferably, the guide body may be composed of wires, optionally coated in a polymer material.

[0087] In the case where electrical tracks are used, the proximal part 3 (also called body) and the transition zone 2 (also called central core) each comprise a substrate. The substrate of the proximal part 3 and the substrate of the transition zone 2 may be identical or different. These substrates are preferably made of a polymer such as PEN or PI. The thickness of these substrates is, for example, between 25 and 250 µm.

[0088] The substrate 10 of the distal part 1 is thinner than those of the central 2 and proximal 3 parts so that it can be deformed more easily. According to another embodiment, the substrate 10 of the distal part 1 may have the same thickness as those of the central 2 and proximal 3 parts.

[0089] Electrical connection means are arranged to route the signal to the active blocks 11 positioned at the distal part 1.

[0090] Several solutions can be considered for routing the electrical signal in the body 3 of the navigation guide and / or in the core 2 of the navigation guide.

[0091] According to a first embodiment, the connection is made by means of electrical wires (i.e. electrically conductive wires). The wires are, for example, B23048PCT ‐ DD23477 YG in an electrically insulating sheath. The wires may be braided or positioned concentrically.

[0092] According to another embodiment, the connection is made by means of electrical tracks (i.e. electrically conductive tracks). The tracks can be printed on the substrate. The tracks can be arranged on one side of the substrate or on both sides of the substrate.

[0093] The tracks can be made of a metal (gold or silver for example) or an electrically conductive polymer material. For example, the electrically conductive polymer material is PEDOT:PSS. It can also be a polymer in which electrically conductive particles are dispersed, for example carbon or gold particles. The particles advantageously have a largest dimension less than 300 nm to avoid increasing the roughness.

[0094] Several configurations are possible, in order to connect the electrical tracks and / or the electrical wires.

[0095] For example, it is possible to cover part of the lower electrode (the one in contact with the substrate) with one of the electrical tracks.

[0096] Electrical tracks and / or wires can be connected to the lower electrode of an active block by means of an electrically conductive glue (e.g. charged epoxy) or by means of soldering.

[0097] Optionally, an electrically conductive plate (for example made of metal, in particular copper) can be positioned on the substrate, on the one hand glued or soldered to the lower electrode and, on the other hand, glued or soldered to the electric wire or to the electric track. B23048PCT ‐ DD23477 YG

[0098] According to another embodiment, mechanical systems such as staples or rivets can be used to connect the electrode of the active block to the wire or track.

[0099] The various connections can be covered with a cover. In particular, it is possible to use an electrically conductive cover. For example, the cover can include nanoparticles. The cover can be used to plug any holes and / or prevent breakdown phenomena.

[0100] It is also possible to increase the stiffness of the central core 2 by locally adding an additional layer on the substrate. For example, this may be a polymer layer. The polymer may be the same or different from the substrate polymer. It may also be a metallized polymer layer. The polymer layers may be deposited by bonding. Welding may also be implemented. Alternatively, the additional layer is a dielectric layer, for example printed by screen printing. It may also be a metal foil. The foil may have a thickness of between 10 and 1000 µm, preferably between 10 and 100 µm. The foil may be made of zinc or aluminum.

[0101] The connection of the electrodes 101 to each other and of the electrodes 102 to each other can be shared in order to divide the number of electrical tracks / electrical wires. This makes it possible to reduce the size due to the connections, and thus reduce the width of the substrate.

[0102] Preferably, the distal end 1 is covered by an encapsulation layer. The encapsulation layer coats the different portions of active blocks. The encapsulation layer may be made of a polymeric material, for example, epoxy, polydimethylsiloxane (PDMS), B23048PCT ‐ DD23477 YG poly(methyl methacrylate) (PMMA), polyvinylidene fluoride (PVDF) or a derivative thereof.

[0103] Even more preferably, the distal end 1, the central core 2 and at least part of the body 3 are covered by the encapsulation layer.

[0104] Encapsulation can be achieved by dipping, thermal evaporation or spraying a solution. The encapsulation step is advantageously carried out once the electrical connections have been made.

[0105] Radiopaque elements can be added to the device, for example, on the flexible substrate or on the encapsulation layer, between the active block portions, in order to be able to ensure visual tracking of navigation in the target system. The elements are, for example, in the form of crosses, squares or dots.

[0106] The navigation guide has a length that can go, for example, up to 180 cm or even 300 cm.

[0107] The distal part 1 can be made as follows:

[0108] a) depositing at least one electrically conductive zone on a substrate 10, to form a first electrode 101,

[0109] b) forming an electroactive layer 103 on the electrically conductive area,

[0110] c) forming a second electrode 102 on the electroactive layer 103.

[0111] In step b), the electroactive material layer can be deposited by spin coating. Other types of localized deposition can be used such as screen printing, spraying, dispensing or even deposition B23048PCT ‐ DD23477 YG by inkjet. Preferably, the electroactive layer is deposited by screen printing. In one pass, the deposited thickness is between 1 and 20 µm. It is possible to superimpose several layers by screen printing until the desired final thickness for the electroactive layer 103.

[0112] For the active blocks 11, between 1 and 10 layers, preferably at least five layers and, preferably, ten layers of composites intercalated between two electrodes 101, 102, will be deposited, according to the following sequence: N x (electrode 101 / composite 103 / electrode 102). The number of layers deposited depends on the thickness of the dielectric.

[0113] Steps a), b) and c) are repeated to form the stack, with step a) being repeated, not on the substrate, but on the underlying electroactive layer.

[0114] The method also includes a step of crystallizing the electroactive layer, to improve its performance. This irradiation is for example carried out with UV flash light, with a flash duration, or pulse, of between approximately 500 µs and 2 ms, a fluence (energy delivered per unit area) of between approximately 15 J / cm² and 25 J / cm², and with light of wavelength between approximately 200 nm and 380 nm. The number of flashes, or pulses, of UV light produced during this irradiation varies depending on the thickness over which the material is to be crystallized. For example, for a thickness of P(VDF-TrFe) equal to approximately 2 µm, the irradiation can be carried out with a fluence equal to approximately 17 J / cm², a pulse duration equal to approximately 2 ms and a number of pulses equal to 5.

[0115] The material, possibly having undergone previous crystallization, is then subjected to annealing, for example, carried out at approximately 130°C for approximately 60 min, to finalize B23048PCT ‐ DD23477 YG the complete crystallization of the material. Annealing can be done at ambient pressure or at low pressure.

[0116] The crystallization of the material can therefore be carried out in two stages: firstly, irradiation by UV light pulse to properly crystallize the second face of the material layer in order to increase its thermal conductivity, then thermal annealing completing the crystallization for the rest of the material not crystallized by the previous irradiation.

[0117] When the material is a P(VDF-TrFe) based copolymer, a polarization step of the material is carried out before its use. This step can be carried out, for example, by applying a direct electrical voltage to its terminals, via the electrodes, in order to improve the coefficient of this material. This polarization is carried out only once for the entire lifetime of the material. This polarization by direct current can be done at room temperature or hot (up to about 100°C). When the polarization is carried out at room temperature, it is possible to apply a direct voltage up to about 150V / µm or even 200V / µm of layer thickness for a duration, for example, between a few seconds and a few minutes. For example, a voltage of 120V / µm will be applied for 20s.When the polarization is carried out hot, for example at a temperature of about 90°C, a direct voltage for example between about 50 V / µm and 80 V / µm can be applied to the dielectric layer for a duration for example between about 1 min and 5 min. The temperature is then lowered until it reaches room temperature, then the electric field applied to the material, via the applied direct voltage, is stopped. Such polarizations allow PVDF to achieve remanent polarization values ​​of 8 µC / cm. 2 . B23048PCT ‐ DD23477 YG

[0118] The molecules inside the layer remain oriented in this way, even when the material is no longer subjected to this electric field. The material can be polarized in this way by applying an initial polarization voltage across the electrodes. A piezoelectric material thickness of between 3 and 4 µm is preferably chosen to promote the polarization of the piezoelectric material of this capacity, and the level of the electrical voltage applied between the electrodes to achieve the initial polarization of the piezoelectric material (when the piezoelectric material must be initially polarized).

[0119] Annealing is advantageously carried out at the end of the process, or between the different stages. Annealing is, for example, at a temperature between 100°C and 150°C, preferably around 100°C to remove residual traces of solvent and / or finalize the crystallization of the piezoelectric material.

[0120] Annealing can be carried out under vacuum. For example, it is a vacuum of the order of 1 mbar. The annealing time, for 1 mbar, can be at least 1 minute, preferably 3 minutes.

[0121] At the end of the process, contact is advantageously made so as to connect the active blocks 11 of the distal part 1 to the core 2 and to the proximal part 3 of the navigation guide.

[0122] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0123] Finally, the practical implementation of the described embodiments and variants is within the reach of the B23048PCT ‐ DD23477 YG person skilled in the art from the functional indications given above.

[0124] Illustrative and non-limiting examples of different embodiments

[0125] Initially, two devices were fabricated. Each device comprises a substrate covered by an active block-type stack. The substrate is made of polyimide. It has a thickness of 25 µm. The stack comprises 10 layers of P(VDF-TrFE) each 3.3 µm thick. The electrodes are made of PEDOT:PSS. They have a thickness of 1.5 µm.

[0126] The first device comprises a substrate with dimensions of 25 x 2.5mm². In the absence of applied voltage, it is curved (Figure 4A). When a voltage is applied, the substrate is mechanically deformed: the curvature is reduced. The higher the applied voltage, the more the substrate flattens (Figures 4B, 4C, 4D, 4E and 4F). The substrate is planar (i.e. it is no longer curved) when the applied voltage is 500V (Figure 4F).

[0127] The second device comprises a substrate with dimensions of 20 x 0.25mm². In the absence of applied voltage, it is curved (Figure 5A). When a voltage is applied, the substrate is mechanically deformed: the curvature is reduced. The higher the applied voltage, the more the substrate flattens (Figures 5B, 5C, 5D). The substrate is almost flat (i.e. it is no longer curved) when the applied voltage is 150V (Figure 5D).

[0128] The geometry of the substrate 10 has an influence on the distribution of stresses. When the device is very slender (i.e. the length / width ratio is high), the stresses are preferentially concentrated in the direction of B23048PCT ‐ DD23477 YG length, and less tension is required to lay the device flat.

[0129] It should be noted that this trend is only valid in reverse control (in other words when the application of a voltage allows the substrate to be straightened). In so-called conventional control, when the applied voltage allows the substrate to be bent, the wider the device (the lower the length / width ratio) and the lower the voltage required to bend it (figure 6). The substrate used in this comparative example is covered by a 3cm long active block.

Claims

B23048PCT ‐ DD23477 YG CLAIMS 1.Navigation guide for a fluid circuit successively comprising a distal part (1), a central part (2) and a proximal part (3), The distal part (1) comprising a substrate (10) having a first main face (10a) and a second main face (10b), one of the main faces (10a, 10b) being covered by at least one active block (11) comprising at least two organic electroactive layers (103), first electrodes (101) and second electrodes (102), each organic electroactive layer (103) being arranged between a first electrode (101) and a second electrode (102), the substrate (10) having a length / width ratio of between 2 and 150, preferably between 5 and 100, and even more preferably 50 and 100, the distal part (1) forming an angle α of between 20 and 360°, preferably between 20° and 250°, relative to the proximal part (3), in the absence of voltage applied to the active block (11). 2.Navigation guide according to claim 1, characterized in that the active block (11) comprises at least 5 organic electroactive layers (103), preferably between 7 and 15 organic electroactive layers (103).

3. Navigation guide according to one of claims 1 and 2, characterized in that the substrate (10) has a thickness of between 15 and 75 µm, preferably between 20 and 50 µm.

4. Navigation guide according to one of claims 1 to 3, characterized in that the substrate (10) is made of polyimide.

5. Navigation guide according to any one of the preceding claims, characterized in that each. B23048PCT ‐ DD23477 YG electroactive layer (103) is made of PVDF or one of its copolymers, such as P(VDF-TrFE).

6. Navigation guide according to any one of the preceding claims, characterized in that the first electrodes (101) and the second electrodes ( 102) sont en un polymère électriquement conducteur, depreferably PEDOT-PSS.

7. Navigation guide according to any one of the preceding claims, characterized in that the organic electroactive layers (103) have a thickness of between 2 and 15 µm, preferably between 3 and 15 µm, and even more preferably between 3 and 6 µm, and even more preferably between 3 and 4 µm.

8. Guide selon l’une quelconque des revendications précédentes, characterized in that the substrate (10) has a thickness of between 20 and 50 µm, the active block (11) comprises between 8 and 12 electroactive layers (103), each electroactive layer (103) having a thickness of between 3 and 4 µm.

9. Guide de navigation selon l’une quelconque des Claims 1 to 8, characterized in that the guide comprises between 2 and 5 active blocks (11) arranged on the same face of the substrate (10), the active blocks (11) being able to be identical or different.

10. Guide de navigation selon l’une quelconque desClaims 1 to 8, characterized in that the guide comprises between 2 and 5 active blocks (11), a part of the active blocks being arranged on a first face (10a) of the substrate (10) and another part of the active blocks being arranged on a second face (10b) of the substrate (10), the active blocks (11) being able to be identical or different. B23048PCT ‐ DD23477 YG 11. Guide de navigation selon l’une quelconque des preceding claims, characterized in that the active blocks (11) are covered by an encapsulation layer made of a polymer material, for example, PDMS, PMMA, PVDF or one of its derivatives.

12. Procédé d’utilisation d’un guide de navigation including the following steps: – fournir un guide de navigation comprenant successivementa distal portion (1), a central portion (2) and a proximal portion (3), the distal portion (1) comprising a substrate (10) having a first main face (10a) and a second main face (10b), one of the main faces (10a, 10b) being covered by at least one active block (11) comprising at least two organic electroactive layers (103), first electrodes (101) and second electrodes (102), each organic electroactive layer (103) being arranged between a first electrode (101) and a second electrode (102), the substrate (10) having a length / width ratio of between 2 and 150, preferably between 5 and 100, and even more preferably 50 and 100, the distal portion (1) forming an angle α of between 20 and 360°, preferably between 20° and 250°, relative to the distal portion (1) proximal (3), in the absence of voltage applied to the active block (11). - Appliquer une tension, de préférence entre 50 et 500V, even more preferably between 100 V and 150 V, to the organic electroactive layers (103), whereby the angle α between the distal part (1) and the proximal part B23048PCT ‐ DD23477 YG (3) decreases to a value between 0 and 50°, or even to a negative value.

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