Apparatus for propelling and steering microstructures

Abstract

This device (1) a propulsion element (2) comprising at least one part (20) capable of expanding / contracting deformation along a main axis (X2) connecting a front part (21) and a rear part (23); - at least two guide elements (3, 5, 7) adapted to generate a rotation of the propulsion element (2) around a first and a second rotation axis, respectively, transverse to each other and to the main axis (X2) of the propulsion element, under the influence of an energy supply; a control unit (9) configured to actuate the rotation of the propulsion element (2) about at least one axis transverse to the main axis (X2) in coordination with the deformation of the deformable element (20) of the propulsion element (2) extending / retracting along the main axis (X2); Equipped with.

Description

[Technical Field]

[0001] The present invention relates to a device for propelling and steering microstructures, e.g., movable flexible tubes such as stents or catheters, or even microrobots, intended to move through fluids, in particular in the blood vessels of a subject, such as arteries or veins, or in organs of a subject, such as the brain, heart, liver, pancreas, etc. The movable flexible tubes or microrobots can be used to perform various biomedical operations, in particular related to minimally invasive surgery or targeted therapy. [Background technology]

[0002] The ability to reach deep and functional structures without causing damage is a major challenge in minimally invasive surgery, especially neurosurgery. Microtechnology has made it possible to deliver fully autonomous micromedical devices inside a subject's blood vessels or organs. However, such micromedical devices require systems that enable their navigation and steering in three dimensions with an accuracy at least equal to the device's size, even in heterogeneous and sensitive environments.

[0003] In this regard, the present invention aims to provide an apparatus for propelling and steering microstructures, such as flexible tubes or microrobots, that allows for effective and reliable propulsion and steering of the microstructure, including in low Reynolds number fluid environments, with an accuracy at least equal to the size of the microstructure, while preserving as much as possible the integrity of the environment in which the microstructure moves. Summary of the Invention

[0004] To this end, the present invention provides a propulsion element including at least one portion capable of expanding / contracting deformation along a main axis connecting the front and rear of the propulsion element; at least two guide elements adapted to generate a rotation of the propulsion element about a first axis of rotation and a second axis of rotation, respectively, transverse to each other and to the main axis of the propulsion element, under the influence of an energy supply by a respective connection to an energy source; a control unit configured to actuate a rotation of the propulsion element about at least one axis transverse to the main axis in coordination with a deformation of the deformable part of the propulsion element that extends / contracts along the main axis by selectively controlling one or more of the connections to the energy source, the guide element further comprising at least two guide segments based on an active material that is reversibly deformable under the influence of an energy supply by respective connections to the energy source, each guide segment being adapted to generate, by its deformation under the influence of an energy supply, a rotation of the propulsion element about an axis of rotation transverse to the main axis of the propulsion element; and The present invention relates to an apparatus for propelling and steering a microstructure, such as a flexible tube or a microrobot, comprising:

[0005] The propulsion and steering device according to the present invention allows steering of the microstructure in three dimensions by the ability to actuate the rotation of the propulsion elements about at least two rotational axes that are transverse to each other and to the main axis, in coordination with the propulsion of the microstructure obtained by deformation of the deformable parts of the propulsion elements. In the context of the present invention, two axes are transverse to each other if they are not parallel, which includes, but is not limited to, when the two axes are perpendicular to each other.

[0006] In the context of the present invention, the rotational actuation is performed in coordination, in particular simultaneously or sequentially, with the deformation of the deformable parts of the propulsion elements in order to obtain a desired motion and trajectory of the microstructure in a moving environment, in particular in a low Reynolds number fluid environment. More specifically, the rotational actuation can be performed simultaneously with the deformation of the deformable parts of the propulsion elements or sequentially with the deformation of the deformable parts of the propulsion elements, i.e., such that the rotation and deformation occur one after the other, in particular repeatedly.

[0007] In the context of the present invention, the microstructure comprising the propulsion and steering device according to the invention typically has an outer diameter of 5 mm or less, in particular 2 mm or 1 mm or less.

[0008] According to one feature, the propulsion element comprises at least a first guide segment and a second guide segment, such that deformation of the first guide segment causes rotation of the propulsion element about a first axis of rotation perpendicular to a main axis of the propulsion element, and deformation of the second guide segment causes rotation of the propulsion element about a second axis of rotation perpendicular to both the main axis of the propulsion element and the first axis of rotation.

[0009] According to an embodiment of the guide segment, the segment is a region of the deformable part of the propulsion element coated with active material. According to another embodiment of the guide segment, the segment is a segment comprising a support provided with active material and attached to the deformable part of the propulsion element.

[0010] According to one embodiment, the deformable portion of the thrust element is made of a material having a Young's modulus in the range of 0.1 to 10 GPa, preferably 0.5 to 2 GPa. In one embodiment, the front, rear, and deformable portions of the thrust element are all made of the same material. In one embodiment, the materials constituting the front, rear, and deformable portions are biocompatible polymers. An example of a suitable material for the front, rear, and / or deformable portions is a UV-curable inorganic-organic hybrid polymer, such as the product ORMOCLEAR from MICRO RESIST TECHNOLOGY GmbH.

[0011] In one embodiment, at least one guide segment includes an electroactive material or a bimetallic element, and the propulsion and steering device includes an electrical energy source connected to the guide segment for activating its deformation. Specifically, the energy source is a power source connected by wires or cables to the electroactive material or bimetallic element of the guide segment.

[0012] In the context of the present invention, an electroactive material is a material that transforms, particularly by changing its shape or its size, under the influence of an electrical energy supply. Examples of suitable electroactive materials in the context of the present invention include shape memory alloys such as Nitinol, or electroactive polymers (EAPs), particularly dielectric electroactive polymers and ionic electroactive polymers. As a non-limiting example, an ionic electroactive polymer that can be used in connection with the present invention is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0013] In the context of the present invention, a bimetallic element is an element comprising two materials that, when electrically conductive, undergo elastic deformation according to different mechanical properties under the influence of heat, which can be provided by an electric current, and whose intimate contact results in a significant deformation of the bimetallic element. Such bimetallic elements can be formed, in particular, by co-rolling two metal strips. Examples of suitable bimetallic elements in the context of the present invention are copper-steel or iron-nickel bimetallic elements, since these are bimetallic combinations of metals with completely different thermal expansion coefficients.

[0014] In one embodiment, at least one guide segment includes a photoactive material, and the propulsion and steering device includes a radiation source that emits radiation toward the guide segment to activate its deformation. Specifically, the radiation source is a laser light source or an LED (light emitting diode), and the radiation is transmitted to the photoactive material of the guide segment using an optical fiber having a distal end positioned toward the photoactive material of the guide segment.

[0015] In the context of the present invention, a photoactive material is a material that deforms under the influence of radiation, in particular under the influence of a light energy supply. An example of a suitable photoactive material in the context of the present invention includes a network of liquid crystals containing azobenzene molecules. The radiation source can be a white light source containing all wavelengths in the visible spectrum. As a non-limiting example, a photoactive material that can be used in connection with the present invention is an actuator based on a dual photosensitive liquid crystal, in particular containing an azomerocyanine dye that is locally converted into a hydroxyazopyridinium form by acid treatment.

[0016] According to one feature, at least two of the aforementioned guide segments are configured such that, when they deform simultaneously, they actuate deformation of the deformable part of the propulsion element to extend / contract along the main axis, and when they deform selectively, they actuate rotation of the propulsion element about a rotation axis transverse to the main axis. By selectively supplying energy to the guide segments, it is possible to actuate rotation and extension / contraction deformation of the propulsion element, which allows reliable steering and propulsion of the microstructure.

[0017] According to one feature, the guide segments are distributed isotropically around the main axis of the propulsion element, which results in improved control of the directional steering of the propulsion element.

[0018] According to one embodiment, the deformable part of the propulsion element comprises a single flexible leg arranged helically around the main axis between the front and rear parts of the propulsion element, the flexible leg including at least two guide segments distributed along the flexible leg and configured to generate, by their deformation, a rotation of the propulsion element about a first and a second axis of rotation, respectively, transverse to each other and to the main axis of the propulsion element.

[0019] According to another embodiment, the deformable part of the propulsion element comprises at least two flexible legs arranged helically around the main axis between the front and rear of the propulsion element, and the propulsion and steering device comprises at least one pair of guide segments in each of the first and second flexible legs configured to generate, by deformation thereof, a rotation of the propulsion element about a first and second axis of rotation, respectively, transverse to each other and to the main axis of the propulsion element.

[0020] According to an aspect of the invention, the guide element comprises at least two electromagnetic guide coils each provided with a respective connection to a source of electrical energy, which together with a magnet fixed to the propulsion element form an electromagnetic transducer, the magnet being substantially parallel to the main axis of the propulsion element in a rest position, and each guide coil is adapted to generate, under the influence of an electrical energy supply, a rotation of the magnet relative to its rest position, causing rotation of the propulsion element about an axis of rotation transverse to the main axis of the propulsion element.

[0021] According to one feature, for each electromagnetic transducer, a magnet is attached to the guide coil and the propulsion element, the magnet being inserted inside the guide coil for actuation of the rotation of the propulsion element. Such a configuration ensures an electromagnetic conversion efficiency that allows reliable and precise control of the rotation of the propulsion element by acting on the electrical connections of each guide coil. Of course, the polarity of the magnet and the power supply of each guide coil are adapted to obtain the desired rotation of the propulsion element.

[0022] According to one embodiment, the propulsion and steering device further comprises a linear actuation electromagnetic coil provided with a respective connection to a source of electrical energy, which also forms an electromagnetic transducer together with the magnet fixed to the propulsion element, the linear actuation coil being adapted to generate a movement of the magnet parallel to the main axis under the influence of an electrical energy supply, causing a deformation of the deformable part of the propulsion element extending / retracting along the main axis. By selectively powering the guide coil and the linear actuation coil, it is possible to actuate the rotation and extension / contraction deformation of the propulsion element, which makes it possible to reliably steer and propel the microstructure.

[0023] According to another embodiment, at least two of the aforementioned electromagnetic guide coils are configured to, when simultaneously supplied with electrical energy, actuate deformation of the deformable portion of the propulsion element to extend / contract along the main axis, and, when selectively powered, generate rotation of the magnet relative to its rest position, causing rotation of the propulsion element about an axis of rotation transverse to the main axis. For example, by selectively powering the guide coils simultaneously or sequentially, it is possible to actuate rotation and extension / contraction deformation of the propulsion element, which allows reliable steering and propulsion of the microstructure.

[0024] According to one embodiment, each guide coil has its central axis substantially parallel to the main axis of the propulsion element. According to another embodiment, each guide coil has its central axis substantially perpendicular to the main axis of the propulsion element.

[0025] The number of guide coils may be any number equal to or greater than two. Specifically, the following arrangements may be considered in connection with the present invention, but are not limited to them: two guide coils arranged longitudinally along the direction of the main axis of the propulsion element, with their central axes not coinciding with and substantially parallel to the main axis of the propulsion element; two guide coils arranged transversely, with their central axes substantially parallel to the main axis of the propulsion element; at least three guide coils, specifically three, four, five, or six guide coils, arranged longitudinally along the direction of the main axis of the propulsion element, with their central axes not coinciding with and substantially parallel to the main axis of the propulsion element; at least three guide coils, specifically three, four, five, or six guide coils, distributed around the main axis of the propulsion element, with their central axes substantially parallel to the main axis of the propulsion element; at least three guide coils, specifically three, four, five, or six guide coils, distributed around the main axis of the propulsion element, with their central axes substantially perpendicular to the main axis of the propulsion element.

[0026] According to one feature, the control unit is further configured to actuate the deformation of the deformable part of the propulsion element by extension / contraction along the main axis, thus allowing optimal coordination between actuation of the rotation of the propulsion element and actuation of the extension / contraction deformation of the propulsion element.

[0027] According to one feature, the propulsion and steering device comprises a linear actuator configured to actuate deformation of a deformable portion of a propulsion element that extends / contracts along a main axis. According to one embodiment, the linear actuator comprises an electromagnetic transducer including a combination of an electromagnetic coil fixed to one end of the deformable portion and a permanent magnet fixed to the other end of the deformable portion. According to one embodiment, the linear actuator comprises a pump. This embodiment is suitable when the deformable portion of the propulsion element can contain a fluid in its internal volume, particularly when the deformable portion has an outer casing that forms a continuous circumferential wall. In one embodiment, the deformable portion of the propulsion element comprises a bellows, and the actuator comprises a pump.

[0028] In one embodiment, the propulsion and steering device comprises at least one propulsion cilium fixed to the front of the propulsion element, one end of the propulsion cilium being fixed to the front while the other end of the propulsion cilium is fixed to the front, in particular to the 10 -5 ~10 -1 The free end is configured to move freely to generate non-reciprocating motion of the microstructure in a fluid having a low Reynolds number comprised between . The presence of such cilia provides propulsive motion of the microstructure in viscous or viscoelastic materials, particularly in organs of a subject, such as the brain. Continuous extension / contraction cycles of the deformable portion of the propulsion element cause movement of the propulsion cilia in the viscous or viscoelastic material, thus providing a net propulsive force due to the interaction of the propulsion cilia with the viscous or viscoelastic material.

[0029] According to one feature, for each extension / contraction deformation cycle of the deformable part of the propulsion element along its main axis, 10 -5 ~10 -1 The path of the free end of the or each propulsion cilium during the contraction phase of the propulsion element in a fluid having a low Reynolds number comprised between is different from the path of the free end of the or each propulsion cilium during the extension phase of the propulsion element in said fluid. Such implementation of the propulsion cilium for the extension and contraction phases of the deformable part makes it possible to obtain a non-reciprocating motion of the microstructure, which allows for efficient movement in a flowable material with a low Reynolds number.

[0030] Specifically, in a non-limiting embodiment, the path of the free end of the propulsion cilia(s) in the viscous or viscoelastic material is topologically equivalent to an elliptical or circular path for each extension / contraction cycle of the deformable portion. It should be noted that a free end path topologically equivalent to a straight line segment is not suitable for obtaining non-reciprocating motion of a microstructure, even if different dynamics are applied along the path.

[0031] According to one embodiment, the rear portion of the propulsion element comprises at least one propulsion cilium. It should be understood that, in the context of the present invention, it is sufficient for propulsion cilium to be present only at the front portion of the propulsion element. However, a configuration in which propulsion cilium is also provided at the rear portion may contribute to the propulsion of microstructures through viscous or viscoelastic substances. According to one embodiment, if the rear portion of the propulsion element comprises at least one propulsion cilium on its surface, the or each propulsion cilium at the rear portion may be identical to or different from the propulsion cilium(s) at the front portion of the propulsion element.

[0032] According to one embodiment, the or each propulsion cilium at the front and / or rear of the propulsion element is made of a material having a Young's modulus comprised between 0.1 and 10 GPa, preferably between 0.5 and 2 GPa. According to one embodiment, the or each propulsion cilium is made of the same material as the deformable part of the propulsion element. In one embodiment, the material of the propulsion cilium is a biocompatible polymer. Examples of suitable materials for the propulsion cilium(s) include polydimethylsiloxane (PDMS), silicone, or UV-curable inorganic-organic hybrid polymers such as ORMOCLEAR.

[0033] According to one embodiment, the at least two guide elements are positioned radially outside the deformable part.

[0034] According to one embodiment, the deformable part comprises a oscillating disc arranged between a front part and a rear part, and at least two guide elements are arranged between the rear part and the oscillating disc.

[0035] According to one embodiment, the propulsion and steering device comprises at least two propulsion elements arranged in tandem, and the control unit is in particular -5 ~10 -1The present invention is configured to cycle the deformation of the propulsion elements to extend and contract along their major axes according to a predetermined temporal sequence to generate non-reciprocating motion of the microstructure in a fluid having a low Reynolds number comprised between 0.01 and 0.05. Such a configuration is another method for obtaining non-reciprocating motion of the microstructure that allows efficient movement in a low Reynolds number fluid. This configuration can be used alone or in combination with at least one propulsion cilia to generate non-reciprocating motion as described above.

[0036] Another object of the present invention is a microstructure equipped with a propulsion and steering device as described above. According to an embodiment of the present invention, the microstructure is adapted to flow in a low Reynolds number flowable material, in particular in a 10 -5 ~10 -1 and configured to move through a flowable material having a Reynolds number Re between u and u. As is well known, the Reynolds number Re is a dimensionless quantity that quantifies the relative magnitudes of inertial and viscous forces for given flow conditions. The Reynolds number Re can be expressed as the ratio of inertial forces to viscous forces in a fluid: Re=uL / ν, where u is the average velocity of the fluid relative to the object, L is the characteristic length dimension, and ν is the kinematic viscosity of the fluid.

[0037] Another object of the invention is a method for propelling and steering a microstructure, such as a flexible tube or a microrobot, comprising a propulsion and steering device as described above, the method comprising: -Microstructures with propulsion and steering devices, in particular 10 -5 ~10 -1 and introducing the fluid into the fluid having a low Reynolds number comprised between - actuating rotation of the propulsion element about at least one axis transverse to the main axis of the propulsion element in coordination with deformation of the deformable portion of the propulsion element to extend / contract along the main axis by selectively controlling, using a control unit, one or more of the connections to the energy source; Includes.

[0038] Features and advantages of the present invention will become apparent in the following description of some embodiments of the apparatus and method for propelling and steering microstructures according to the present invention, given by way of example only, and made with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0039] [Figure 1] 1 is a schematic cross-sectional view of a microrobot with a propulsion and steering device according to a first embodiment of the invention, comprising a propulsion element in the form of a helical spring including three flexible legs, each of which comprises a guide segment based on electroactive material provided with a respective electrical connection; [Figure 2] 2 is a cross-sectional view similar to FIG. 1 illustrating activation of the rotational movement of the microrobot. [Figure 3] FIG. 3 is an enlarged, partial perspective view of a propulsion element of the microrobot of FIGS. 1 and 2. [Figure 4] 3 is a cross-sectional view similar to FIG. 2 of a microrobot with a propulsion and steering device according to a second embodiment of the invention, comprising a propulsion element in the form of a helical spring including three flexible legs, each flexible leg comprising a guide segment based on a photoactive material associated with an optical fiber that transmits the respective emitted light; [Figure 5] 3 is a cross-sectional view similar to FIG. 2 of a microrobot with a propulsion and steering device according to a third embodiment of the present invention, comprising a propulsion element in the form of a helical spring including two flexible legs, each flexible leg comprising a plurality of guide segments based on electroactive material, each guide segment of each flexible leg being provided with a respective electrical connection so that they can be powered independently by a power source; [Figure 6] 3 is a cross-sectional view similar to FIG. 2 of a microrobot with a propulsion and steering device according to a fourth embodiment of the present invention, comprising a propulsion element in the form of a helical spring including a single flexible leg with a plurality of guide segments based on electroactive material, each guide segment of the flexible leg being provided with a respective electrical connection so that they can be powered independently by a power source. [Figure 7]2 for a microrobot with a propulsion and steering device according to a fifth embodiment of the present invention, the microrobot having two propulsion elements arranged in tandem, the control unit configured to activate cycles of deformation of the propulsion elements extending / retracting along their major axes according to a predetermined temporal sequence to generate non-reciprocating motion of the microstructure. [Figure 8] 1 for a microrobot with a propulsion and steering device according to a sixth embodiment of the present invention, the microrobot comprising a propulsion element in the form of a helical spring including three flexible legs, and an electromagnetic transducer having three coils including a linear actuation coil and two rotary guide coils, each provided with a respective electrical connection; [Figure 9] 9 is a cross-sectional view similar to FIG. 8, illustrating activation of the rotational movement of the microrobot. [Figure 10] FIG. 10 is an enlarged perspective view of a portion of the propulsion element of the microrobot of FIGS. 8 and 9. [Figure 11] 11 is a perspective view similar to FIG. 10 of a portion of a propulsion element of a microrobot equipped with a propulsion and steering device according to a seventh embodiment of the present invention. [Figure 12] 11 is a perspective view similar to FIG. 10 of a portion of a propulsion element of a microrobot equipped with a propulsion and steering device according to an eighth embodiment of the present invention. [Figure 13] 10 is a partial perspective view similar to FIG. 3 of a propulsion element of a microrobot with a propulsion and steering device according to a ninth embodiment of the present invention. [Figure 14] 13, but of a partial perspective view similar to FIG. 13 of a propulsion element of a microrobot with a propulsion and steering device according to a tenth embodiment of the present invention. [Figure 15] 13, but of a partial perspective view similar to FIG. 13 of a propulsion element of a microrobot with a propulsion and steering device according to an eleventh embodiment of the present invention. [Figure 16] FIG. 16 is a partial perspective view similar to FIG. 15 of the same embodiment of the present invention, but in operation. DETAILED DESCRIPTION OF THE INVENTION

[0040] In a first embodiment shown in Figures 1-3, the microrobot 10 is configured to move in a viscous or viscoelastic substance, such as cerebrospinal fluid or the extracellular matrix of a subject's brain, which are flowable substances with low Reynolds numbers for microrobots.

[0041] The microrobot 10 comprises a propulsion and steering device 1 according to the invention, to which an active part 11 of the microrobot is fixed, which may be, for example, a sensor, an actuator, a reservoir adapted to release a drug, etc.

[0042] 1 and 2, the propulsion and steering device 1 comprises a propulsion element 2 including a front part 21, a rear part 23, and a deformable part 20 connecting the front part 21 and the rear part 23. In this first embodiment, the deformable part 20 is a helical spring that is expandable / contractible along a main axis X2 of the propulsion element 2. The main axis X2 of the propulsion element 2 is defined herein as the central axis of the deformable part 20, which is substantially perpendicular to the plane of the distal plate 230 of the rear part 23, to which the deformable part 20 is fixed.

[0043] The helical spring forming the deformable part 20 comprises three flexible legs 22, 24, 26 arranged in a spiral around the main axis X2 between the front part 21 and the rear part 23 of the propulsion element. Each flexible leg 22, 24, 26 is provided with a respective guide segment 3, 5, 7 based on an electroactive material, for example the ionic electroactive polymer PEDOT. Each of the three guide segments 3, 5, 7 is reversibly deformable under the influence of an electrical energy supply and is connected to a power source 8 by a respective electrical cable 83, 85, 87.

[0044] Each guide segment 3, 5, 7 is adapted to, upon the supply of electrical energy, cause deformation of the corresponding flexible leg and rotation of the propulsion element 2. For each guide segment 3, 5, 7, the axis of rotation caused by the deformation of the guide segment intersects the main axis X2 of the propulsion element and the axis of rotation caused by the deformation of each of the other two guide segments. As clearly shown in the enlarged view of FIG. 3, the guide segments 3, 5, 7 are distributed isotropically around the main axis X2 of the propulsion element 2, which allows for optimization of the directional steering of the propulsion element. Thus, in the present invention, the guide segments 3, 5, 7, together with the flexible legs 22, 24, 26, form a single multifunctional group ensuring both rotation and propulsion. The present invention does not feature any combination of different elements, each ensuring a separate function.

[0045] The propulsion and steering device 1 also comprises a linear actuator 4 configured to continuously actuate the extension / retraction cycle of the deformable part 20 of the propulsion element 2. The actuator 4 is an electromagnetic transducer comprising a permanent magnet 41 and an electromagnetic coil 42. The magnet 41 is fixed to the front part 21 of the propulsion element 2 at the front end of the deformable part 20, while the coil 42 is attached to the rear part 23 and thus fixed to the rear end of the deformable part 20. Depending on the current applied to the coil 42, the magnet 41 moves towards or away from the coil 42, which causes the deformable part 20 to retract or extend.

[0046] 1 and 2, the front portion 21 of the propulsion element 2 comprises a plurality of propulsion cilia 28 on its surface configured to interact with a material along which the microrobot 10 moves. Successive extension / contraction cycles of the deformable portion 20 actuated by the electromagnetic transducer 4 cause movement of the propulsion cilia 28 through the material, generating a propulsive force and causing movement of the microrobot 10.

[0047] For each extension / contraction cycle of the deformable portion 20 actuated by the electromagnetic transducer 4, each propulsion cilium 28 is configured such that the path of the free end 29 of the propulsion cilium 28 in the viscous or viscoelastic material during the contraction phase of the deformable portion 20 is different from the path of the free end 29 in the viscous or viscoelastic material during the extension phase of the deformable portion 20. Advantageously, the path of the free end 29 of the propulsion cilium 28 in the viscous or viscoelastic material is topologically equivalent to an elliptical or circular path for each extension / contraction cycle. In this way, non-reciprocating motion of the microrobot 10 is obtained, enabling efficient locomotion of the microrobot 10 in fluid materials with low Reynolds numbers, such as cerebrospinal fluid or the extracellular matrix of the brain.

[0048] The propulsion and steering device 1 also includes a control unit 9 configured to actuate the rotation of the propulsion element 2 about at least one axis transverse to the main axis X2 by selectively controlling one or more of the electrical connections 83, 85, 87. The control unit 9 is also configured to actuate the deformation of the deformable portion 20 to extend / contract along the main axis X2. Thus, it is possible to optimally coordinate the actuation of the rotation of the propulsion element 2 with the actuation of the extension / contraction deformation of the deformable portion 20 along the main axis X2 to obtain a desired motion and trajectory of the microrobot 10 in a moving material. Thus, the control unit 9 can actuate the single element, the propulsion element 2, which generates the propulsion and rotation of the device 1.

[0049] Especially 10 -5 ~10 -1 The method for propelling and steering the microrobot 10 in a fluid having a low Reynolds number comprise selectively controlling one or more of the electrical connections 83, 85, 87 using a control unit 9 to actuate rotation of the propulsion element 2 about at least one axis transverse to the major axis X2 in coordination with, whether simultaneously or sequentially, deformation of the deformable portion 20 to extend / contract along the major axis X2.

[0050] By way of non-limiting example, a microrobot 10 having the following characteristics will have good propulsion and guidance performance in flowable materials with low Reynolds numbers: -Total length of microrobot 10: 2mm, - Microrobot 10 diameter: 2mm, the length of the deformable part 20 of the propulsion element 2: 0.5 mm, -Linear actuator coil 42 length: 0.5mm, -Length of magnet 41: 0.8mm, - Cross section of each propulsive cilium 28: 2,500 μm 2 .

[0051] Manufacturing Process The front section 21, rear section 23, and deformable section 20 were fabricated integrally by 3D laser lithography using ORMOCLEAR, a UV-curable inorganic-organic hybrid polymer, as a photoresist. The photoresist was applied to a glass substrate, and a point laser selectively cured the photoresist according to a 3D CAD plan. The propulsion cilia 28 were fabricated integrally with the front section 21, i.e., made of the same material as the front section 21. The guide segments 3, 5, and 7 were obtained by depositing a layer of PEDOT, an ionic electroactive polymer, on each of the flexible legs 22, 24, and 26 of the deformable section 20. The linear actuation coil 42 was obtained by winding copper wire around the rear section 23. The magnet 41 was a neodymium permanent magnet attached to the front section 21 with acrylic adhesive.

[0052] In the second embodiment shown in FIG. 4, elements similar to those in the first embodiment bear the same reference numerals. The microrobot 10 of the second embodiment differs from the first embodiment in that the guide segments 3, 5, and 7 contain photoactive material instead of electroactive material. The propulsion and steering device 1 includes a dedicated radiation source for each guide segment 3, 5, and 7 based on a photoactive material, the radiation source being directed toward the guide segment to activate its deformation. By way of example, in this second embodiment, the photoactive material of each guide segment 3, 5, and 7 is a network of liquid crystals containing azobenzene molecules, and the radiation source for each guide segment 3, 5, and 7 is a white light source, with the different sources housed in the same case 8'.

[0053] In this second embodiment, all guide segments 3, 5, 7 are based on the same photoactive material, and to avoid radiation interactions that could activate deformations of the guide segments other than those associated with the dedicated radiation source, the radiation is transmitted to the photoactive material of each guide segment 3, 5, 7 using a respective optical fiber 83′, 85′, 87′, having a distal end positioned opposite the photoactive material of the guide segment 3, 5, 7. According to a variant, the guide segments 3, 5, 7 may be based on different photoactive materials adapted to be activated by radiation of different wavelengths. In this case, each guide segment 3, 5, 7 is associated with a radiation source that emits in its own wavelength range. Here again, the radiation can be transmitted to the photoactive material of the guide segment 3, 5, 7 using an optical fiber having a distal end positioned opposite the photoactive material of the guide segment.

[0054] In the third embodiment shown in FIG. 5 , elements similar to those in the first embodiment bear the same reference numerals. The microrobot 10 of the third embodiment differs from the first embodiment in that the deformable part 20 of the propulsion element 2 is a helical spring with two flexible legs 22, 24 instead of three flexible legs as in the first embodiment. The two flexible legs 22, 24 are arranged spirally around the main axis X2 between the front part 21 and the rear part 23 of the propulsion element, and each is provided with three guide segments based on electroactive material: 31, 32, 33 and 51, 52, 53, respectively. For each of the two flexible legs 22, 24, the guide segments 31, 32, 33 or 51, 52, 53 are distributed along the flexible leg and connected to the power supply 8 by respective electrical wires. All electrical wires of the different guide segments of the flexible leg 22 or 24 run through a cable 83 or 85.

[0055] In the fourth embodiment shown in FIG. 6, elements similar to those of the first embodiment bear the same reference numerals. The microrobot 10 of the fourth embodiment differs from the first embodiment in that the deformable part 20 of the propulsion element 2 is a helical spring with a single flexible leg 22 spirally arranged around the main axis X2 between the front part 21 and the rear part 23 of the propulsion element. The flexible leg 22 includes four guide segments 31, 32, 33, 34 based on an electroactive material, which are distributed along the flexible leg 22 and each connected to the power supply 8 by a respective electric wire, and all the electric wires of the different guide segments of the flexible leg 22 pass through a cable 83. The guide segments 31, 32, 33, 34 are configured to generate, by their deformation, a rotation of the propulsion element 2 about a first and a second rotation axis, respectively, which intersect with each other and the main axis X2 of the propulsion element.

[0056] In the fifth embodiment shown in Figure 7, elements similar to those in the first embodiment have the same reference numerals. The microrobot 10 of the fifth embodiment differs from the first embodiment in that the propulsion and steering device 1 includes two propulsion elements 21 and 22 arranged in tandem, and the control unit 9 is configured to actuate the extension / contraction deformation cycles of the deformable portions 201 and 202 of the two propulsion elements according to a predetermined temporal sequence to generate non-reciprocating motion of the microrobot 10. Such a configuration is a means, other than propulsion cilia, for achieving non-reciprocating motion of the microrobot 10, enabling efficient locomotion in low Reynolds number fluids.

[0057] In this fifth embodiment, for each of the two propulsion elements 21 and 22, the deformable part 201 or 202 is identical to the deformable part 20 of the first embodiment, i.e. the main axis X of the propulsion element 21 or X 22 and three flexible legs 221, 241, 261 or 222, 242, 262 arranged in a spiral around the flexible leg 221. Each flexible leg 221, 241, 261 or 222, 242, 262 is provided with a respective guide segment 31, 51, 71 or 32, 52, 72 based on an electroactive material, which is reversibly deformable under the influence of an electrical energy supply and which is connected to a power source 81 or 82 by a respective electrical cable 831, 851, 871 or 832, 852, 872.

[0058] The propulsion and steering device 1 of this fifth embodiment does not comprise a linear actuator, similar to the electromagnetic transducer 4 of the previous embodiment, which successively activates the extension / contraction cycle of the deformable part 201 or 202 of the propulsion element. In fact, in this fifth embodiment, for each of the two propulsion elements 21 and 22, the guide segments 31, 51, 71 or 32, 52, 72 based on electroactive material, when they simultaneously deform, move in the direction of the main axis X 21 or X 22 activating the deformation of the deformable parts 201 or 202 to expand / contract along the main axis X when they selectively deform 21 or X22 By selectively supplying electrical energy to the guide segments 31, 51, 71, 32, 52, 72, it is possible to actuate the rotation and / or extension / contraction deformation of each of the propulsion elements 21, 22, which allows for reliable both steering and propulsion of the microrobot 10.

[0059] In the sixth embodiment shown in Figures 8-10, elements similar to those of the first embodiment bear the same reference numerals. The microrobot 10 of the sixth embodiment differs from the first embodiment in that the guide element comprises two electromagnetic guide coils 43 and 45 instead of guide segments based on an active material. Each of the guide coils 43 and 45 is provided with a respective connection 63, 65 to an electrical energy source 6 and forms an electromagnetic transducer together with a permanent magnet 41 fixed to the front part 21 of the propulsion element 2. In the rest position, the magnet 41 is substantially parallel to the main axis X2 of the propulsion element. Each of the two guide coils 43, 45 is adapted to generate a rotation of the magnet 41 relative to its rest position under the influence of an electrical energy supply, which causes rotation of the propulsion element 2 around a rotation axis transverse to the main axis X2.

[0060] The propulsion and steering device 1 of this sixth embodiment also comprises a linear actuation electromagnetic coil 42, similar to the coil 42 of the previous embodiment, provided with a respective connection 62 to an electric energy source 6 and forming, together with the magnet 41, an electromagnetic transducer. The linear actuation coil 42 is adapted to generate, under the influence of an electric energy supply, a movement of the magnet 41 parallel to the main axis X2, which causes a deformation of the deformable part 20 extending / retracting along the main axis X2. By selectively powering the guide coils 43, 45 and the linear actuation coil 42, it is possible to actuate the rotational and extension / contraction deformation of the propulsion element 2, which makes it possible to ensure directional steering and propulsion of the microrobot 10.

[0061] The relative arrangement of the linear actuation coil 42 and the guide coils 43, 45 is shown in the enlarged view of Figure 10. This view shows the respective grooves 232, 233, 235 for receiving the coils 42, 43, 45. The central axis of the linear actuation coil 42 received in groove 232 is aligned with the major axis X2 of the propulsion element 2. The central axis of the guide coil 43 received in groove 233 is offset from the major axis X2 of the propulsion element 2 in an upward direction and along a direction extending into the plane of the sheet of Figure 10. Finally, the central axis of the guide coil 45 received in groove 235 is offset from the major axis X2 of the propulsion element 2 in a downward direction and along a direction extending out of the plane of the sheet of Figure 10.

[0062] In the seventh embodiment shown in Fig. 11, elements similar to those of the sixth embodiment have the same reference numerals. In this seventh embodiment, the propulsion and steering device 1 comprises three guide coils 43, 45, 47 (not shown), each provided with a respective connection to a source of electrical energy and configured to form an electromagnetic transducer together with a permanent magnet 41 fixed to the front of the propulsion element 2. Respective grooves 233, 235, 237 for receiving the guide coils 43, 45, 47 are shown in Fig. 11. The three guide coils 43, 45, 47 are arranged vertically along the direction of the main axis X2 of the propulsion element 2, with their central axes not coinciding with but substantially parallel to the main axis X2.

[0063] 11 , the central axis of the guide coil 43 received in the groove 233 is offset downward and into the plane of the sheet in FIG. 11 with respect to the major axis X2 of the propulsion element 2. The central axis of the guide coil 45 received in the groove 235 is offset upward and into the plane of the sheet in FIG. 11 with respect to the major axis X2 of the propulsion element 2. Finally, the central axis of the guide coil 47 received in the groove 237 is offset downward and out of the plane of the sheet in FIG. 11 with respect to the major axis X2 of the propulsion element 2. The three guide coils 43, 45, 47 are configured to actuate deformation of the deformable portion 20 of the propulsion element 2 to expand / contract along the major axis X2 when they are simultaneously supplied with electrical energy, and to generate rotation of the magnet 41 relative to its rest position when they are selectively powered, causing rotation of the propulsion element 2 about an axis of rotation transverse to the major axis X2.

[0064] In the eighth embodiment shown in Figure 12, elements similar to those of the sixth embodiment have the same reference numerals. In this eighth embodiment, the propulsion and steering device 1 comprises a linear actuation coil 42 and three guide coils 43, 45, 47 (not shown), each provided with a respective connection to a source of electrical energy and configured to form an electromagnetic transducer together with a permanent magnet 41 fixed to the front of the propulsion element 2. Respective grooves 232, 233, 235, 237 for receiving the coils 42, 43, 45, 47 are shown in Figure 12. The linear actuation coil 42 is arranged at the rear of the propulsion element 2, with its central axis substantially parallel to the main axis X2 of the propulsion element 2, while the three guide coils 43, 45, 47 are distributed around the linear actuation coil 42 and are equidistant from each other, with their central axes substantially perpendicular to the main axis X2.

[0065] In this eighth embodiment, actuation of the deformation of the deformable part 20 to expand / contract along the main axis X2 is obtained by powering the linear actuation coil 42, while actuation of the rotation of the magnet 41 relative to its rest position, which causes rotation of the propulsion element 2 about a rotation axis transverse to the main axis X2, is obtained by selectively powering the guide coils 43, 45, 47.

[0066] In the ninth and tenth embodiments shown in Figures 13 and 14, respectively, elements similar to those of the sixth embodiment bear the same reference numerals. In these ninth and tenth embodiments, the propulsion element 2 according to the ninth and tenth embodiments includes a front section 21, a rear section 23, and a deformable section 20 connecting the front section 21 and the rear section 23, as in the propulsion element of the embodiment shown in Figure 3. In these ninth and tenth embodiments, the deformable section 20 is a helical spring that can expand / contract along the main axis X2 of the propulsion element 2. As before, the axis X2 is defined as the central axis of the deformable section 20, which is substantially perpendicular to the plane of the distal plate 230 of the rear section 23, to which the deformable section 20 is fixed. The helical spring forming the deformable section 20 includes three flexible legs 22, 24, 26 that are arranged helically around the main axis X2 between the front section 21 and the rear section 23 of the propulsion element 2.

[0067] In these ninth and tenth embodiments, the helical spring forming the deformable portion 20 interfaces with at least one guide element 3, 5, 7, each extending between the front 21 and rear 23 of the propulsion element 2. In embodiments not shown, the guide element extends around the helical spring. In the ninth and tenth embodiments, the helical spring extends around at least one guide element 3, 4, 5. More specifically, in the ninth and tenth embodiments, the device 1 includes three guide elements 3, 5, 7, each forming a deformable leg or segment, arranged helically around the main axis X2 between the front 21 and rear 23 of the propulsion element. In the ninth embodiment shown in FIG. 13, the deformable segments 3, 5, 7 and flexible legs 22, 24, 26 are evenly distributed around the circumference of the propulsion element 2, such that the propulsion element 2 has a circular alternating arrangement of the flexible legs 22, 24, 26 and the deformable segments 3, 5, 7. In the tenth embodiment shown in Figure 14, each deformable segment 3, 5, 7 is radially aligned with a flexible leg 22, 24, 26 of the helical spring. Thus, each flexible leg 22, 24, 26 interfaces with a guide element 3, 5, 7 in each of the embodiments of Figures 13 and 14.

[0068] As in the previous embodiment, each deformable segment 3, 5, 7 comprises an electroactive material, such as the ionic electroactive polymer PEDOT. Thus, each of the three guide elements 3, 5, 7 is reversibly deformable under the influence of electrical energy. Each guide element 3, 5, 7 is adapted to deform its corresponding flexible leg 22, 24, 26 and rotate the propulsion element 2 upon electrical energy application. For each guide segment 3, 5, 7, the axis of rotation caused by the deformation of the guide segment intersects the main axis X2 of the propulsion element 2 and the axes of rotation caused by the deformation of each of the other two guide elements. The isotropic distribution of the guide segments 3, 5, 7 around the main axis X2 of the propulsion element 2 allows for optimized steering of the propulsion element 2, as in the first embodiment. Therefore, regardless of the embodiment, it should be noted that in the present invention, the guide segments 3, 5, 7, together with the flexible legs 22, 24, 26, form a single multifunctional group that ensures both rotation and propulsion. The present invention does not feature any combination of different elements each of which ensures a distinct function.

[0069] In an eleventh embodiment shown in Figures 15 and 16, elements similar to those of the first embodiment have the same reference numerals. In this eleventh embodiment, the device 1 for propelling and steering a microrobot 10, as in the previous embodiments, is configured to move through a viscous or viscoelastic substance, such as cerebrospinal fluid or the extracellular matrix of a subject's brain, which are flowable substances with low Reynolds numbers.

[0070] An alternative embodiment of the propulsion element 2 is shown in Figures 15 and 16. In this eleventh embodiment, the propulsion element 2 includes a front portion 21, a rear portion 23, and a deformable portion 20 connecting the front portion 21 and the rear portion 23. The deformable portion 20 is divided into a front sub-portion 20A and a rear sub-portion 20B, and the two sub-portions 20A, 20B are connected together by a wobbler disk 30. The wobbler disk 30 is located between the front portion 21 and the rear portion 23 and equidistant from each of them. In the example shown in Figures 15 and 16, the wobbler disk 30 has a diameter similar to that of the distal plate 230. However, in embodiments not shown, the diameter of the wobbler disk 30 may be larger than the diameter of the distal plate 230.

[0071] At rest, the oscillating disk 30 is substantially parallel to the distal plate 230. In this embodiment, the oscillating disk 30 of the propulsion element 2 comprises a plurality of propulsion cilia 28 on its surface configured to interact with a material along which the microrobot 10 moves. Successive extension / contraction cycles of the deformable portion 20 cause movement of the propulsion cilia 28 through the material, generating a propulsive force and causing movement of the microrobot 10. Therefore, it may be advantageous for the oscillating disk 30 to have a larger diameter than the distal plate 230 to facilitate attachment of the propulsion cilia 28 thereto.

[0072] In this eleventh embodiment, the front sub-part 20A of the deformable part 20 is a helical spring that is expandable / contractible along the main axis X2 of the propulsion element 2. The main axis X2 of the propulsion element 2 is defined here, as in the previous embodiments, as the central axis of the deformable part 20, which is substantially perpendicular to the plane of the distal plate 230 of the rear part 23 to which the deformable part 20 is fixed. The helical spring forming the front sub-part 20A of the deformable part 20 comprises three flexible legs 22, 24, 26 that are arranged helically around the main axis X2 between the front part 21 of the propulsion element and the oscillating disc 30.

[0073] In this eleventh embodiment, the rear subsection 20B of the deformable part 2 includes at least one guide element 3, 5, 7 based on an electroactive material, such as the ionic electroactive polymer PEDOT. More specifically, in this eleventh embodiment of the present invention, the deformable part 2 includes three guide elements 3, 5, 7 forming a guide segment 3, 5, 7. Each of the three guide segments 3, 5, 7 is reversibly deformable under the influence of an electrical energy supply and is connected to a power source. At rest, the three guide segments 3, 5, 7 have the same length. As clearly shown in FIG. 15 , the guide segments 3, 5, 7 are isotropically distributed around the main axis X2 of the propulsion element 2, which allows for optimized steering of the propulsion element. Each of the three guide segments 3, 5, 7 forms a leg extending between the rear part 23 of the deformable part 2 and the oscillating disk 30. More specifically, the three guide segments are arranged spirally around the main axis X2 between the rear subsection 23 of the propulsion element 2 and the oscillating disk 30. As already mentioned, each guide segment 3, 5, 7 is adapted to, upon electrical energy supply, cause its deformation to tilt the oscillating disk 30. This is shown in FIG. 16. When each of the three guide segments 3, 5, 7 is activated, the oscillating disk 30 tilts in a different direction, thus generating a rotational oscillating movement. This rotational oscillating movement causes the propulsion element 2 to rotate. For each guide segment 3, 5, 7, the axis of rotation generated by the deformation of the guide segment intersects the main axis X2 of the propulsion element and the axes of rotation generated by the deformation of each of the other two guide segments. Therefore, also in this embodiment, despite the presence of the oscillating disk 30, the guide segments 3, 5, 7 are directly coupled to the flexible legs 22, 24, 26 and together form a single multifunctional group ensuring both rotation and propulsion. The present invention does not feature any combination of different elements each of which ensures a distinct function.

[0074] As can be seen from the above examples, the propulsion and steering device according to the invention allows a microstructure to be reliably and precisely moved in 3D space by coordinately activating, on the one hand, the rotation of the propulsion elements about at least two rotation axes transverse to each other and to the main axis, and, on the other hand, the deformation of the deformable parts of the propulsion elements, which generates the propulsion of the microstructure. Advantageously, the ability to independently activate the energy supply for each guide element and, if present, for the linear actuators, allows any spatial and temporal combination to be considered for activating the rotation and deformation of the deformable parts of the propulsion elements. In particular, the rotation and deformation can be activated simultaneously or sequentially as desired, which allows the microstructure to move according to a desired trajectory in its environment.

[0075] It should be noted that at the millimeter scale, the smallest elements moving in a low Reynolds environment require a lot of energy. The friction forces involved are considerable. Although it depends on the type of friction (dry, viscous, etc.) and the size of the robot, it is still known that, in general, a low Reynolds number means that surface forces dominate compared to volume forces. In this case, it is therefore more appropriate to optimize the overall size of the robot rather than, for example, its weight.

[0076] Therefore, the smaller the device and the fewer functional elements it contains, the less energy is expended to move said device. Due to its small size and the reduced number of functional elements (made possible by the multifunctional aspect of the different elements, in particular the guide segments), the present invention allows for significant energy savings for a given movement.

[0077] The invention is not limited to the examples described and shown.

[0078] In particular, in the aforementioned examples, the deformable portion of the propulsion element is a helical spring including one, two, or three flexible legs. Alternatively, the deformable portion of the propulsion element may comprise a helical or non-helical spring with any number of flexible legs, or else a deformable structure other than a spring, such as a bellows. The deformable portion of the propulsion element may also include a combination of a spring and a bellows, where each pleat of the bellows is located, for example, in a turn of the spring and the bellows jacket fills the space between successive turns of the spring.

[0079] Additionally, if the propulsion and steering device comprises a dedicated linear actuator for actuating the deformation of the deformable part of the propulsion element to extend / contract, the linear actuator may comprise actuators other than the aforementioned electromagnetic transducers, including electromagnetic coils and permanent magnets. In particular, if the deformable part has a sealed outer casing, such as when it comprises a bellows, the actuator for actuating the deformation of the deformable part to extend / contract may be a pump, and the extension / contraction of the deformable part may be obtained by alternating inflow / outflow of fluid into the internal volume of the deformable part, actuated by the pump.

[0080] Furthermore, in the aforementioned examples implementing guide segments containing active materials, the active materials of the different guide segments are all of the same nature. Alternatively, the propulsion and steering device according to the present invention may include several guide segments with active materials of different compositions or properties. For example, guide segments containing electroactive materials may be combined with guide segments containing bimetallic elements, or guide segments containing photoactive materials may be combined with guide segments containing electroactive materials or bimetallic elements, with different energy supply connections for activating the guide segments being adapted accordingly. Guide segments based on active materials may also be combined with guide coils of the type of coils in the embodiments of Figures 8-12.

[0081] If the propulsion and steering device comprises guide coils as guide elements for generating rotation of the propulsion element, arrangements of the guide coils other than those of the embodiments of Figures 8 to 12 can of course also be considered, in particular the number of guide coils can be any number greater than or equal to two, the guide coils being possibly arranged tandem, next to each other or even concentrically, combined or not combined with a linear actuation coil.

[0082] Advantageous arrangements not shown in the figures include, for example, three guide coils distributed around the main axis of the propulsion element with their central axes substantially parallel to the main axis and equidistant from one another; six guide coils distributed around the main axis of the propulsion element with their central axes substantially parallel to the main axis and equidistant from one another. In these two cases, the guide coils are optionally arranged without a linear actuation coil at the rear of the propulsion element, where actuation of the deformation of the deformable section to expand / contract along the main axis is obtained by simultaneously supplying electrical energy to all guide coils, while actuation of the rotation of the magnet relative to its rest position, which causes rotation of the propulsion element about an axis of rotation transverse to the main axis, is obtained by selectively powering the guide coils; or, arranged at the rear of the propulsion element in combination with a linear actuation coil, where actuation of the deformation of the deformable section to expand / contract along the main axis is obtained by powering the linear actuation coil, while actuation of the rotation of the magnet relative to its rest position, which causes rotation of the propulsion element about an axis of rotation transverse to the main axis, is obtained by selectively powering the guide coils.

[0083] Finally, an invention has been described for the propulsion and steering of microrobots intended to move in viscous or viscoelastic substances, such as cerebrospinal fluid or the extracellular matrix of a subject's brain. Alternatively, the propulsion and steering device according to the invention can of course be implemented to move other types of microstructures in the medical field or other fields; in particular, the device according to the invention can be used for the propulsion and steering of steerable flexible tubes such as stents or catheters.

Claims

1. 10 －５ ~10 －１ 1. An autonomous device (1) for propelling and steering a microstructure (10), including a flexible tube or a microrobot, in a fluid having a low Reynolds number comprised between - a propulsion element (2) with a main shaft (X ) connecting the front (21) and rear (23) of said propulsion element (2); ２ a propulsion element (2) including at least one deformable portion (20) that can be expanded / contracted along a - at least two guide elements (3, 5, 7; 43, 45) which, under the influence of an energy supply by their respective connections (83, 85, 87; 63, 65) to an energy source, are in contact with each other and with the main axis (X ２ at least two guide elements (3, 5, 7; 43, 45) adapted to generate a rotation of said propulsion element (2) about a first rotation axis and a second rotation axis, respectively, that intersect with said guide element (3, 5, 7; 43, 45); a linear actuator (4) configured to successively activate the extension / retraction cycles of the deformable part (20) of the propulsion element (2), said linear actuator (4) comprising a permanent magnet (41) attached to the front part (21) and an electromagnetic coil (42) attached to the rear part (23); a control unit (9), activating the linear actuator (4) to actuate a linear deformation of the deformable part (20) extending / contracting along the main axis (X 2 ); Selectively controlling one or more of said connections to electrical energy sources (83, 85, 87, 63, 65) actuates said propulsion element (2) to rotate about at least one axis transverse to said main axis (X2) in a manner coordinated with deformation of said deformable portion (20) of said propulsion element (2) to expand / contract along said main axis (X2). a control unit (9) configured to: Equipped with The guide element (3, 5, 7; 43, 45) further comprises at least two guide segments (3, 5, 7) based on an active material that is reversibly deformable under the influence of an energy supply by respective connection to an energy source (83, 85, 87), each guide segment (3, 5, 7) being adapted to move, by its deformation under the influence of an energy supply, the main axis (X ２ adapted to generate a rotation of said propulsion element (2) about an axis of rotation transverse to the control unit (9) is configured to actuate the single element propulsion element (2) and generate propulsion and rotation of the autonomous device (1) by actuation of the single element; the control unit (9) is configured to coordinate the actuation of the rotation of the propulsion elements (2) and the actuation of the deformation of the deformable part (20) in extension / contraction along the main axis (X 2 ) in order to obtain a desired movement and trajectory of the microrobot (10) in the material in which it moves; Autonomous device (1).

2. 2. The autonomous device (1) of claim 1, wherein at least one guide segment (3, 5, 7) comprises an electroactive material or a bimetallic element, and the autonomous device (1) comprises an electrical energy source (83, 85, 87) connected to the guide segment (3, 5, 7) for activating its deformation.

3. 3. The autonomous device (1) of claim 1 or claim 2, wherein at least one guide segment (3, 5, 7) comprises a light-active material, and the autonomous device (1) comprises a radiation source (83', 85', 87') from which radiation light is emitted opposite the guide segment (3, 5, 7) to activate its deformation.

4. At least two of the guide segments (3, 5, 7) are deformed along the main axis (X ２ activating the deformation of the deformable parts (20) of the propulsion elements (2) that expand / contract along the main axis (X ２ 4. The autonomous device (1) according to any one of claims 1 to 3, configured to actuate the rotation of the propulsion element (2) about an axis of rotation transverse to the axis of rotation of the propulsion element (2).

5. The guide element comprises at least two electromagnetic guide coils (43, 45) each provided with a respective connection (63, 65) to a source of electrical energy, which together with a magnet (41) fixed to the propulsion element (2) form an electromagnetic transducer (4), the magnet (41) being oriented in a rest position relative to the main axis (X) of the propulsion element (2). ２ ) and each guide coil (43, 45) is adapted to generate, under the influence of an electrical energy supply, a rotation of the magnet (41) relative to its rest position, so as to rotate the main axis (X) of the propulsion element. ２ 5. The autonomous device (1) according to any one of claims 1 to 4, adapted to cause rotation of the propulsion element (2) about an axis of rotation transverse to the axis of rotation of the propulsion element (2).

6. It further comprises linear actuation electromagnetic coils (42) provided with respective connections (62) to a source of electrical energy, which also form together with the magnets (41) fixed to the propulsion element (2) an electromagnetic transducer (4), the linear actuation electromagnetic coils (42) being adapted to rotate in the direction of the main axis (X) under the influence of an electrical energy supply. ２ ) to generate a movement of the magnet parallel to the main axis (X ２ 6. The autonomous device (1) according to claim 5, adapted to cause a deformation of the deformable part (20) of the propulsion element (2) extending / contracting along a

7. The control unit (9) controls the main shaft (X ２ 7. The autonomous device (1) according to any one of claims 1 to 6, further configured to actuate the deformation of the deformable part (20) of the propulsion element (2) by extension / contraction along a

8. The main axis (X ２ 8. The autonomous device (1) according to claim 1, further comprising an actuator (41, 42) including an electromagnetic transducer or a pump configured to actuate the deformation of the deformable part (20) of the propulsion element (2) to extend / contract along a

9. Autonomous device (1) according to any one of claims 1 to 8, characterized in that the at least two guide elements (3, 5, 7; 43, 45) are positioned radially outside the deformable part (20).

10. The autonomous device (1) according to any one of claims 1 to 8, characterized in that the deformable part (20) comprises an oscillating disc (30) arranged between the front part (21) and the rear part (23), and the at least two guide elements (3, 5, 7; 43, 45) are arranged between the rear part (23) and the oscillating disc (30).

11. A method for propelling and steering a microstructure (10) including a flexible tube or a microrobot, comprising: - introducing said microstructure (10) into a fluid with a low Reynolds number comprised between 10 -5 and 10 -1 using an autonomous device (1) for propulsion and steering according to any one of claims 1 to 9; - selectively controlling, by means of said control unit (9), one or more of said connections to sources of electrical energy (83, 85, 87, 63, 65) to actuate said propulsion elements (2) to rotate about at least one axis transverse to said main axis (X 2 ) in a manner coordinated with the deformation of said deformable parts (20) of said propulsion elements (2) to extend / contract along said main axis (X 2 ); A method comprising:

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