Low voltage deformable navigation guide

Abstract

Low voltage deformable navigation guide 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) comprising a substrate covered by an 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, the distal part (1) forming an angle α of between 20 and 360° with respect to the proximal part (3), in the absence of voltage applied to the active block. Figure for abstract: Fig. 3

Description

Title of the invention: Low voltage deformable navigation guide Technical field

[0001] The present description relates generally to devices for navigation in a fluid, for example devices for arterial navigation (endovascular surgery), or for navigation in branched systems such as plumbing conduits or air conditioning circuits. Prior art

[0002] In endovascular surgery, in order to reach a target blood vessel (such as an artery for example), 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 'HeadHunter 1', 'Cobra 1', 'Simmons Sidewinder 2', 'Vertebral', 'Berenstein', 'Multipurpose A'. There is no universal navigation guide: one catheter corresponds to one shape.

[0005] In order 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 25pm thick PEN substrate, the electrodes are made of PEDOT:PSS and the 6pm electroactive polymer layer is made of P(VDF-TrFE-CTFE). By applying voltages greater than 50V / pm, 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, the latter 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 an element in canals with complex geometry (including passages where the device must be oriented in one direction then in the other).

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

[0009] There is a need for a device whose shape can be changed at low voltage, the device needing to be miniaturizable to be able to navigate blood vessels.

[0010] This object is achieved by a fluid circuit successively comprising a distal portion, a central portion and a proximal portion. The distal portion 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 portion forms an angle α of between 20 and 360°, preferably between 20° and 250°, relative to the proximal portion, 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 of between 20 and 50 pm, the active block comprises between 8 and 12 electroactive layers, each electroactive layer having a thickness of between 3 and 4 pm.

[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 possibly being 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 aim is also achieved by a method of using a navigation guide comprising the following steps: - provide a navigation guide comprising successively a distal part, a central part and a proximal part, 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 part forming an angle a 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, - applying a voltage, preferably between 50 and 500 V, even more preferably between 100 V and 150 V, to the organic electroactive layers 103, whereby the angle α between the distal part and the proximal part decreases to a value between 0 and 50°, or even to a negative value. Brief description of the drawings

[0022] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0023] [Fig.l] represents, schematically and in section, a navigation guide according to a particular embodiment of the invention - the different parts are not to scale;

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

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

[0026] [Fig. 3] represents, 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] [Fig.4A], [Fig.4B], [Fig.4C], [Fig.4D], [Fig.4E] and [Fig.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 depending on different voltages ap replicated (from 100V to 500V), in reverse control, according to other particular embodiments of the invention;

[0028] [Fig.5A], [Fig.5B], [Fig.5C] and [Fig.5D] are photographic images showing the mechanical deformation 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] [Fig.6] is a graph representing 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 described embodiments have been shown and are detailed.

[0032] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, 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 reference is made 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 orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to 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 particularly 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 conduit 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 [Fig. 1], the navigation guide comprises 3 parts 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 (FIGS. 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 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, the latter 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 activable, on one of the faces of the substrate 10.

[0044] The distal part 1 thus obtained is curved when no tension is applied ([Fig.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 tensions involved are lower than those used in conventional devices for which the application of a tension makes it possible to bend the distal end, in other words to make the distal end pass from a straight position to a curved position.

[0047] The substrate 10 is a flexible substrate, that is to say that it can deform when the piezoelectric stack is subjected to a voltage. The material is chosen from way 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 allowing 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-to-width ratio is preferably between 2 and 150, more preferably between 5 and 100, for example between 50 and 100. The higher the ratio, the lower the voltage required to deform the substrate 10 of the distal part 1 will be.

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

[0054] According to an embodiment variant, shown in [Fig.2B], the substrate 10 is covered by several portions of PN active blocks (at least two), each portion of PN active blocks including 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 portions of active blocks. By between X and Y, it is meant here and hereinafter that the bounds 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 ([Fig.2B]).

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

[0061] The presence of several portions of active PN blocks can make it possible, by applying a voltage 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 adjustable. 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 part 1 is at a distance 1m of 0 to 2 cm from the end of the distal part and, even more preferably, at a distance of 0.5 to 1.5 cm from the end of the distal part. This distance 1m 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, of the different inter-active block distances and of the extreme length.

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

[0068] Each active block 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 perform 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 [Fig.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.

[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 weight%, 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 copolymer of poly(vinylidene fluoride-trifluoroethylene) PVDF / TrFe, 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 will be chosen. Such materials are so-called electrostrictive materials.

[0078] According to another embodiment variant, the polymer is not a ferroelectric polymer: it may be PVDF-HFP.

[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, the ferroelectric particles are made of BaTiO3 (BTO), PZT (lead zirconate titanoate), AIN, ZnO, or SBN (Sr-Ba-Nb oxide) or SBT (Sr-Ba-Ti oxide). Such particles are used, for example, 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 not apply any 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 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 body of the guide 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 in order to be able to be deformed more easily. According to another variant 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 so as to route the signal to the active blocks 11 positioned at the distal part 1.

[0090] Several solutions can be envisaged 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, in an electrically insulating sheath. The wires can 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 a single face of the substrate or on both faces of the substrate.

[0093] The tracks may be made of a metal (gold or silver for example) or of an electrically conductive polymer material. For example, the electrically conductive polymer material is PEDOT:PSS. It may also be a polymer in which electrically conductive particles are dispersed, for example carbon or gold particles. The particles advantageously have a largest dimension of 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 a part of the lower electrode (the one in contact with the substrate) with one of the electrical tracks.

[0096] The electrical tracks and / or electrical wires can be connected to the lower electrode of an active block by means of an electrically conductive glue (of the charged epoxy type for example) 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 welded to the lower electrode and, on the other hand, glued or welded to the electric wire or to the electric track.

[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 may be covered with a cover. In particular, it is possible to use an electrically conductive cover. For example, the cover may comprise nanoparticles. The cover makes it possible to plug any holes and / or to avoid 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, it may be a polymer layer. The polymer may be identical or different from the polymer of the substrate. 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 example printed by screen printing. It can also be a metal sheet. The sheet can have a thickness between 10 and 1000 μm, preferably between 10 and 1000 μm. The sheet can 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 polymer material, for example, an epoxy, polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA), polyvinylidene fluoride (PVDF) or one of its derivatives.

[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 may be carried out 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 may be added to the device, for example, on the flexible substrate or on the encapsulation layer, between the portions of active blocks, 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 which can be, for example, up to 180 cm or even 300 cm.

[0107] The distal part 1 can be produced in the following way:

[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] During step b), the layer of electroactive material can be deposited by spin coating. Other types of localized deposition can be used such as screen printing, spraying, dispensing or even inkjet deposition. 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 final thickness desired for the electroactive layer 103.

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

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

[0114] The method also comprises 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 ps 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 of between approximately 200 nm and 380 nm. The number of flashes, or pulses, of UV light produced during this irradiation varies according to the thickness over which the material must be crystallized. For example, for a thickness of P(VDF-TrFe) equal to approximately 2 pm, 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 the total crystallization of the material. The annealing can be carried out 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 step of polarizing 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 carried out at room temperature or hot (up to approximately 100°C). When the polarization is carried out at room temperature, it is possible to apply a direct voltage up to approximately 150V / pm or even 200V / pm of layer thickness for a duration, for example, between a few seconds and a few minutes. For example, a voltage of 120V / pm 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 / pm and 80 V / pm 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 reaching the tem . room temperature, then the electric field applied to the material, via the applied DC voltage, is stopped. Such polarizations allow PVDF to reach remanent polarization values ​​of 8 pC / cm2.

[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 to the terminals of the electrodes. A thickness of piezoelectric material between 3 and 4 μm will preferably be chosen in order to promote the polarization of the piezoelectric material of this capacity, and the level of the electric 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. The 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 mbar. The duration of annealing, for Imbar, can be at least 1 minute, preferably 3 minutes.

[0121] At the end of the method, 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 embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

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

[0125] In a first step, 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 pm. The stack comprises 10 layers of P(VDF-TrFE) each 3.3 pm thick. The electrodes are made of PEDOT:PSS. They have a thickness of 1.5 pm.

[0126] The first device comprises a substrate with dimensions 25 x 2.5mm2. In the absence of applied voltage, it is curved ([Fig.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 flat 10 (ie it is no longer curved) when the applied voltage is 500V ([Fig.4F]).

[0127] The second device comprises a substrate with dimensions 20 x 0.25mm2. In the absence of applied voltage, it is curved ([Fig.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 ([Fig.5D]).

[0128] The geometry of the substrate 10 has an influence on the distribution of the stresses. When the device is very slender (i.e. the length / width ratio is high), the stresses are preferentially concentrated in the length direction, and less tension is necessary 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 curved, the wider the device (the lower the length / width ratio) and the lower the voltage required to bend it ([Fig.6]). The substrate used in this comparative example is covered by a 3cm long active block.

Claims

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) 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 pm, preferably between 20 and 50 pm.

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 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) are made of an electrically conductive polymer, preferably 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 pm, preferably between 3 and 15 pm, and even more preferably between 3 and 6 pm, and even more preferably between 3 and 4 pm.

8. A guide according to any preceding claim, ca- characterized in that the substrate (10) has a thickness of between 20 and 50 pm, the active block (11) comprises between 8 and 12 electroactive layers (103), each electroactive layer (103) having a thickness of between 3 and 4 pm.

9. Navigation guide according to any one of 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. Navigation guide according to any one of claims 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.

11. Navigation guide according to any one of the 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. A method of using a navigation guide comprising the following steps: - providing a navigation guide successively comprising a distal portion (1), a central portion (2) and a proximal portion (3), the distal portion (1) comprising a substrate (10) 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 proximal portion (3), in the absence of voltage applied to the active block (11).- Applying a voltage, preferably between 50 and 500 V, even more preferably between 100 V and 150 V, to the organic electroactive layers (103), whereby the angle a. between the distal part (1) and the proximal part (3) decreases to a value between 0 and 50°, or even to a negative value.

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