Diving micro-robot

Abstract

The invention relates to a microrobot (10) configured to move in a propulsion direction in a viscoelastic anatomical environment, comprising:-a body (12) extending along a body axis (X),-a navigation head (14) extending along a head axis (H) and assuming a given configuration relative to the body,-a propulsion element (16) extending along a propulsion axis (A) and having an outer surface (18) with a helical external thread (20), the external thread assumes a given configuration with respect to the body,-a drive device (22) configured to drive the propulsion element in rotation about a propulsion axis (A). The microrobot includes an orienting device (24) configured to vary a given configuration of at least one of the navigation head and the external thread relative to the body in order to vary the propulsion direction.

Description

Technical Field

[0001] The present invention relates to a micro-robot configured to navigate inside a viscoelastic material by generating and propagating cracks inside the viscoelastic material. Background Art

[0002] In minimally invasive surgery, especially neurosurgery, reaching deep and functional structures without causing damage is a major challenge.

[0003] Thanks to microtechnology, it has become possible to introduce fully autonomous micro-robots inside the organs of a subject (e.g., the brain). However, most micro-robots in the prior art can only be propelled in viscous liquids (e.g., blood or cerebrospinal fluid) by thrusters. On the other hand, it is well known that at least part of the brain is a solid viscoelastic organ.

[0004] In materials science and continuum mechanics, viscoelasticity is the property of a material to exhibit both viscous and elastic characteristics when subjected to deformation. Viscous materials, such as water, resist shear flow when a stress is applied and strain linearly over time. Elastic materials strain when stretched and immediately return to their original state once the stress is removed. Viscoelastic materials combine both of these properties and thus exhibit time-dependent strain. Sometimes, viscoelastic materials can be regarded as solid materials.

[0005] Therefore, in a solid viscoelastic environment such as the brain, it is very difficult to propel a micro-robot by a thruster because the brain is elastic (it can store energy and release it back into the environment). Using such a thruster in the brain should meet specific criteria to break through this elastic barrier (which is a characteristic of the material) and enter it, otherwise the thruster and the micro-robot will remain in place, blocked from entering the material.

[0006] Therefore, effectively penetrating and moving through viscoelastic biological tissue is a challenge.

[0007] In this context, the present invention aims to propose a micro-robot having an efficient propulsion mechanism in a solid viscoelastic environment such as the brain. In order to be able to move inside a solid viscoelastic material, the micro-robot must first open (or generate) a crack, then it must widen it in order to be able to enter it, and finally enter it in order to be able to move inside the environment.

[0008] Another important requirement is that the micro-robot should be able to move in the organ while limiting as much as possible the physiological damage it causes to the organ. Therefore, it is important that the generated and propagated cracks are as precisely oriented as possible and as small as possible.

[0009] Another important requirement is that the microrobot should be able to move within an organ while minimizing the physiological damage it causes to the organ.

[0010] To address these technical and biological limitations, for medical and surgical purposes, in the solid matter of the brain, the extracellular matrix of the brain parenchyma, and in other viscoelastic organs such as the pancreas or the liver, an energy-efficient means of propulsion is to extend cracks by skillfully inserting a device, in particular by inserting a microrobot into the above-mentioned organ or organ region.

[0011] Such a microrobot should be technically equipped and configured to at least extend existing cracks and, in some embodiments, even generate cracks into which it can then dive in order to navigate within the organ or organ region.

[0012] To extend such cracks, a rotating tip including a pitch (but not limited to this) can be used. Thus, by rotating within the material, the rotating pitch is able to widen existing cracks (or generate new cracks) and further extend their openings forward while allowing the microrobot to advance like a screw.

[0013] The object of the present invention is to propose a microrobot that is technically capable of navigating in a biological viscoelastic environment along a navigation route with as little invasiveness and destructiveness as possible in a controlled manner. Summary of the Invention

[0014] Accordingly, the present invention relates to a microrobot configured to move in a viscoelastic anatomical environment along a propulsion direction, the microrobot comprising:

[0015] - a body extending along a body axis,

[0016] - a navigation head extending along a head axis between a free distal tip and a proximal base, the navigation head presenting a given configuration relative to the body,

[0017] - a propulsion element extending along a propulsion axis and presenting an outer surface with a helical external thread, the external thread presenting a given configuration relative to the body,

[0018] - a drive device configured to drive the propulsion element to rotate relative to the body about the propulsion axis,

[0019] The microrobot further comprises orientation means configured to change at least one of the given configurations of the navigation head and the external thread relative to the body to change the propulsion direction of the microrobot.

[0020] In this way, the solution is able to achieve the above objectives. In particular, it is able to change the propulsion direction of the microrobot in a controlled manner, thereby precisely controlling the navigation route of the robot in the viscoelastic environment.

[0021] The system according to the present invention may include one or more of the following features, which may be used independently of each other or in combination with each other:

[0022] - The drive device may also be configured to also drive the navigation head to rotate,

[0023] - A given configuration of the external thread may include a given inclination angle of the head axis relative to the body axis, and the orientation device may be configured to change the given inclination angle of the head axis relative to the body axis,

[0024] - The orientation device may include a pivot connection configured to rotate the propulsion element relative to the body along at least one pivot axis,

[0025] - A given configuration of the external thread of the propulsion element may include a given inclination angle of the propulsion axis relative to the body axis, and the orientation device may be configured to change the given inclination angle of the propulsion axis relative to the body axis,

[0026] - The orientation device may include a pivot connection configured to rotate the propulsion element relative to the body along at least one pivot axis,

[0027] - The drive device may include a support shaft that connects the proximal base of the navigation head to the body and includes a pivot connection,

[0028] - The support shaft may be fixed to the engine body by a section of flexible material,

[0029] - The support shaft may be made of flexible material,

[0030] - The support shaft may also connect the propulsion element to the body,

[0031] - The configuration of the external thread may include the pitch of the external thread, and the orientation device may be configured to change the pitch of the external thread,

[0032] - The orientation device may include a series of connectors movably mounted inside the propulsion element and connected to the external thread, the connectors having a relative positioning with respect to each other that varies according to the angular position with respect to the outer surface of the propulsion element,

[0033] - The series of connectors may be configured such that the relative position of the connectors with respect to the outer surface of the propulsion element varies between:

[0034] o A first relative position, in which the outer surface is in a first relative angular position, the connectors in the first relative position being spaced apart from each other by a respective first distance, the first distance being a minimum value,

[0035] o The second relative position, in which the outer surface is in the second relative angular position, and the connecting members in the second relative position are spaced apart from each other by a corresponding second distance, the second distance being the maximum value.

[0036] - The series of connecting members may include:

[0037] o An internal central connecting member located inside the propulsion element, and the central connecting member may be inclined relative to the propulsion axis inside the propulsion element.

[0038] o At least two lateral connecting members that extend between the central connecting member and the external thread. Description of the Drawings

[0039] Referring to the accompanying drawings, by reading the following detailed illustrative description of the embodiments of the present invention in an illustrative manner, the present invention can be better understood, and other objects, details, features, and advantages will also become clearer. The embodiments of the present invention are given only for illustrative purposes and are not restrictive:

[0040] - Figure 1a is a schematic diagram of the present invention according to a first embodiment.

[0041] - Figure 1b is the same schematic diagram as Figure 1a and presents different given configurations.

[0042] - Figure 2 is a detailed schematic diagram of a support shaft according to an embodiment of the present invention.

[0043] - Figure 3a and Figure 3b are schematic diagrams presenting two different given configurations of a second embodiment of the present invention.

[0044] - Figure 4a and Figure 4b are schematic diagrams presenting two different given configurations of a third embodiment of the present invention.

[0045] - Figure 5 is a detailed schematic diagram of a specific orientation device according to an embodiment of the present invention.

[0046] - Figure 6a and Figure 6b are schematic diagrams presenting two different given configurations of a fourth embodiment of the present invention.

[0047] - Figure 7a and Figure 7b are schematic diagrams presenting two different given configurations of a fifth embodiment of the present invention. Detailed Description of the Invention

[0048] As can be seen from the different figures, the present invention relates to a micro-robot 10 configured to move in a viscoelastic anatomical environment along a propulsion direction.

[0049] Such a viscoelastic environment can be, for example, the extracellular matrix of the brain.

[0050] According to the present invention, the micro-robot 10 comprises:

[0051] - a body 12 extending along a body axis X,

[0052] - a navigation head 14 extending along a head axis H between a free distal tip 14a and a proximal base 14b,

[0053] - a propulsion element 16 extending along a propulsion axis A and having an outer surface 18 with a helical external thread 20,

[0054] - a drive device 22 configured to drive the propulsion element 16 to rotate relative to the body 12 about the propulsion axis A.

[0055] The drive device 22 includes a rotor (or moving part) of an activatable motor (not shown) including a stator and a rotor. The motor is located inside the body 12. The stator can be part of the body 12.

[0056] The drive device 22 can be located inside or outside the body 12. The drive device 22 includes motion transmission means. These motion transmission means are connected to the activatable motor and enable the motion generated by the activated motor to be transmitted to the elements in the micro-robot 10 that require motion. More specifically, the drive device 22 is configured to drive the propulsion element 16 to rotate. This is shown in Figure 7a and 7b In these embodiments, the drive device 22 only drives the propulsion element 16 to rotate about the propulsion axis A. In these embodiments, the navigation head 14 is not driven to rotate by the drive device 22. As will be apparent from the following, although the navigation head 14 is not driven to rotate by the drive device 22, the navigation head 14 can change its orientation to change the direction of the micro-robot 10. In Figure 1a 、 1b 、3a, 3b, 4a, 4b, 6a and 6b of the embodiments, the drive device 22 is also configured to drive the navigation head 14 to rotate. In these embodiments, the navigation head 14 and the propulsion element 16 are the same technical element.

[0057] The motion transmission means of the drive device 22 can be, for example, a series of filaments made of a smart material (such as nitinol or an electroactive polymer such as PEDOT), which are regularly distributed around the body axis X (see Figure 1a 、 1b and 7a, 7b). In Figure 3a andFigure 3b In embodiments, these filaments are also coupled to a central line structure to optimize the directional performance. In another embodiment (not shown), the drive device 22 may include a central drive rod. In such an embodiment, the support shaft 24 may be part of the drive device 22. The drive device 22 is also capable of including an external drive cylinder that is directly connected to the motor and further connected to the proximal base 14b of the navigation head 14. The external drive cylinder is capable of being connected to the proximal base 14b of the navigation head through a bellows-like element 23 (see, for example, Figure 3a and 3b ). The bellows-like element 23 may also be a wire. Nevertheless, the bellows has the technical advantage of being a sealing element and thus being able to be used as a housing or envelope, thereby being able to protect the elements located within the bellows from the viscoelastic environment. When the rotation of the propulsion element 16 is from the periphery of the motor of the body 12, it has the technical advantage of transmitting stronger torque to the rotating propulsion element 16.

[0058] In some embodiments, the navigation head 14 is connected to the rotor of the activatable motor through the support shaft 24, and the support shaft 24 connects the proximal base 14b of the navigation head 14 to the motor. The support shaft 24 extends along the body axis X. In some embodiments, the propulsion element 16 is also connected to the rotor of the activatable motor through the support shaft 24. In these embodiments, the navigation head 14 and the propulsion element 16 are preferably (but not necessarily) the same technical element. In some alternative embodiments, for example Figure 7a and Figure 7b 's embodiments, the propulsion element 16 extends around the support shaft 24.

[0059] In some alternative embodiments, the navigation head 14 is connected to the rotor of the activatable motor through a bellows or a wire-like element 25. In the rest position, the bellows or the wire-like element 25 extends along the body axis X. Due to its structure, the bellows or the wire-like element 25 allows the navigation head 14 to tilt smoothly and easily relative to the body 12 in any possible direction. In some embodiments, the propulsion element 16 is also connected to the rotor of the activatable motor through the bellows or the wire-like element 25. In some embodiments, the bellows or the wire-like element 25 surrounds the support shaft 24.

[0060] The body 12 is capable of carrying a variety of functional elements, such as electronic devices, sensors, drug cargo, or other tools or elements. Possibly, the body 12 is formed by continuous body parts, and each body part includes one or more of the above functional elements. Two adjacent body parts can be connected to each other through a flexible connection. The body 12 is connected to the stator of the activatable motor. The stator does not move direction. More precisely, the stator does not rotate by itself along the body axis X. Its technical purpose is to serve as a directional reference.

[0061] The navigation head 14 presents a generally conical or spiky shape. Thus, the diameter of the free distal tip 14a of the navigation head 14 is significantly smaller than the diameter of the proximal base 14b of the navigation head 14. This shape can be slightly distorted or bent. More precisely, the free distal tip 14a can present a variable length and can be bent and / or distorted along its length. The shape can be conical, arrow-shaped, convex or concave.

[0062] The function of the navigation head 14 is to expand cracks in the viscoelastic environment in which the micro-robot 10 has to navigate and, sometimes according to the embodiment, to create cracks. The shape of the navigation head 14 influences the overall shape of the cracks produced and must therefore have some specific technical characteristics. The main technical characteristics of the navigation head 14 are its sharpness and its coefficient of friction with the viscoelastic medium (which should be a minimum). Since the micro-robot 10 cannot navigate inside a solid material (the elastic part of the viscoelastic environment), it is necessary to create cracks within said environment. The micro-robot 10 can then navigate within said cracks towards its destination.

[0063] Different from the usual crack theory where cracks propagate in a straight line, the micro-robot 10 according to the present invention must be able to rotate / turn in all possible directions (left and right, up and down) to change its trajectory. Thus, the micro-robot tilts its navigation head 14 towards a specific direction to orient the crack. Then, the micro-robot 10 advances in that specific direction to expand the crack in that specific direction.

[0064] Thus, the micro-robot 10 according to the present invention can control its trajectory inside the viscoelastic material by:

[0065] - Controlling the crack orientation by controlling the tilt of the navigation head 14 before crack generation,

[0066] - Controlling the propulsion of the micro-robot 10 inside the generated crack, thus controlling the crack propagation.

[0067] Regardless of its shape, the navigation head 14 always presents a given configuration relative to the body 12. The concept of configuration in the context of the present application will be described in further detail below.

[0068] In some embodiments, the navigation head 14 and the propulsion element 16 are the same technical element. More specifically, in these embodiments, the navigation head 14 forms the free distal or front end of the propulsion element 16 (e.g., see Figure 1a , 1b or 4a, 4b), and the propulsion element 16 is of an integral conical shape.

[0069] As described above, the propulsion element 16 has an outer surface 18 with a helical external thread 20 (e.g., see Figure 1a , 1b, 2a, 2b or 7a, 7b). According to an embodiment, the external thread 20 can be constituted by a single continuous helical blade 200 (see Figure 1a and Figure 1b ), or by a series of small blades 202 aligned in a helical manner around the outer surface 18 of the propulsion element 16 (see Figure 6a and 6b ). Similar to the navigation head 14, the external thread 20 always presents a given configuration relative to the body 12.

[0070] Once the given configuration of the external thread 20 is defined and once the propulsion element 16 starts to move (rotational movement) by means of the drive device 22, the propulsion element 16 functions as a screw or an impeller and enables the microrobot 10 to move in the propulsion direction. Thus, the microrobot 10 according to the present invention can be analogized to a system where a screw drills into a solid material such as a wall or a wooden board.

[0071] In the present invention, the term "configuration" is defined as in the Collins Online Dictionary: "the way in which a group of things are arranged". Thus, the term "configuration" includes the relative positions of elements with respect to each other. According to an embodiment, the configuration of the navigation head 14 relative to the body 12 and the configuration of the external thread 20 of the propulsion element 16 relative to the body 12 can be independent of each other (meaning that the configuration of the navigation head 14 can be changed without affecting the configuration of the external thread 20 of the propulsion element 16, and the configuration of the external thread 20 of the propulsion element 16 can also be changed without affecting the configuration of the navigation head 14), or they can also be interdependent on each other (meaning that a change in the configuration of the navigation head 14 will result in a change in the configuration of the external thread 20, and a change in the configuration of the external thread 20 will also result in a change in the configuration of the navigation head 14).

[0072] Considering the embodiments of 7a and 7b, the given configuration of the navigation head 14 includes the inclination angle α1 of the head axis H with respect to the body axis X.

[0073] Considering Figure 1a , 1b and the embodiments of 2a, 2b, the given configuration of the external thread 20 of the propulsion element 16 relative to the body 12 includes the inclination angle α2 of the propulsion axis A of the propulsion element 16 with respect to the body axis X.

[0074] In Figure 1a , 1b , 2a and 2b embodiments, the navigation head 14 is part of the propulsion element 16, and the given inclination angles α1 and α2 are the same angle. The given configuration of the navigation head 14 and the given configuration of the external thread 20 are interdependent and cannot be changed without changing the other.

[0075] InFigure 7a and 7b In the embodiment of Figure 7a and 7b , only the navigation head 14 can be oriented, and the tilt angle α1 can vary, while the configuration of the propulsion element 16 relative to the body 12 remains constant. Therefore, the given configuration of the external thread 20 and the given configuration of the navigation head 14 are independent of each other.

[0076] Considering the embodiments of 4a, 4b, 6a, and 6b, the configuration of the external thread 20 of the propulsion element 16 relative to the body 12 includes the pitch of the external thread 20. The pitch of the external thread 20 is thus variable along the outer surface 18 of the propulsion element 16.

[0077] Changing the given configuration of one or both of the navigation head 14 and / or the external thread 20 causes the micro-robot 10 to change its propulsion direction when moving forward in a viscoelastic environment. This configuration change can generate a new crack with a desired orientation in a viscoelastic environment, or it can also cause the micro-robot 10 to smoothly follow a path designed by an already existing crack (previously generated by the micro-robot 10 or not generated by the micro-robot).

[0078] To change the given configuration of the navigation head 14 and / or the external thread 20 of the propulsion element 16 relative to the body 12, the micro-robot 10 includes an orientation device 26. The orientation device 26 includes a series of interacting elements to change the given configuration of one or both of the external thread 20 and the navigation head 14. Thus, generally speaking, the orientation device 26 is configured to change the propulsion direction of the moving micro-robot 10. In other words, the change in the propulsion direction is achieved by changing the given configuration of at least one of the external thread 20 or the navigation head 14.

[0079] In some embodiments, the orientation device 26 is more precisely configured to change the given tilt angle α2 of the propulsion axis A of the propulsion element 16 relative to the body axis X. The orientation device 26 can also be configured to change the given tilt angle α1 of the head axis H of the navigation head 14 relative to the body axis X.

[0080] In these embodiments, the orientation device 26 can include a pivot connection 28 that is configured to tilt the navigation head 14 relative to the body 12 along at least one pivot axis. In some other embodiments of these embodiments, the orientation device 26 can include a pivot connection 28, including for example a ball and socket joint, that is configured to tilt the propulsion element 16 relative to the body 12 along one or more pivot axes. In these embodiments, the navigation head 14 is preferably part of the propulsion element 16. In some embodiments of these embodiments, the support shaft 24 includes a pivot connection 26 such that the navigation head 14 can tilt relative to the body 12 (see Figure 1a and 1b)。In some embodiments, the bellows or wire element 25 is part of a pivot connection 26. In some alternative embodiments, the support shaft 24 is fixed to the rotor of an activatable motor by a section of flexible material such as 3D printed resin, a specific polymer, or polyether ether ketone (PEEK).

[0081] In some other alternative embodiments, the support shaft 24 is made of a flexible material (see Figure 2 ). In some embodiments, the support shaft 24 includes smart material filaments as described above, and thus these smart material filaments allow the tilt of the navigation head 14 (and sometimes the propulsion element 16) when activated in a specific direction. In Figure 2 some of the alternative embodiments shown, the support shaft 24 includes a series of internal ducts. Each duct is under pressure, and by changing the pressure of one or more of these internal ducts, some tilting of the support shaft 24 can be achieved.

[0082] Generally speaking, the orientation device 26 is part of a compliant mechanism. In mechanical engineering, a compliant mechanism is defined as a flexible mechanism that achieves force and motion transmission through elastomeric deformation. Its motion comes partly or wholly from the relative flexibility of its components, rather than only from rigid body joints. The advantage of such a compliant mechanism is that there are no two (or more) components that can move relative to each other. This generally improves the robustness of the system, but limits its motion capabilities.

[0083] Considering Figure 4a 、 4b and the embodiments of 6a, 6b, the orientation device 26 is configured to change the pitch of the external thread 20 of the propulsion element 16. More precisely, with respect to these embodiments, the orientation device 26 includes a series of connecting elements 30, 32 movably mounted inside the propulsion element 16 and connected to the external thread 20. More precisely, the orientation device 26 includes:

[0084] - A central internal connecting element 32 located inside the propulsion element 16, which is tiltable within the propulsion element 16 relative to the propulsion axis A,

[0085] - At least two lateral connecting elements 30 that extend between the central connecting element 32 and the external thread 20.

[0086] Thus, all the connectors 30 exhibit a relative positioning with respect to each other that varies according to the angular position relative to the outer surface 18 of the propulsion element 16. In an embodiment where the propulsion element 16 has a single helical blade 200, the connectors 30 work together to vary the pitch of the single blade 200. In an embodiment where the propulsion element 16 has a series of small blades 202, each small blade 202 is connected to at least one connector 30 and its pitch can be varied independently of the other small blades 202. The second mechanism is similar to a helicopter blade pitch change mechanism.

[0087] Regardless of the shape of the external thread 20, a series of connectors 30 are configured such that the relative positioning of the connectors 30 varies between:

[0088] - a first relative position, in which the outer surface 18 is in a first relative angular position,

[0089] - a second relative position, in which the outer surface 18 is in a second relative angular position.

[0090] In the first relative position, the connectors 30 are spaced apart from each other by a first distance, which is a minimum value. In the second relative position, the connectors 30 are spaced apart from each other by a second distance, which is a maximum value.

[0091] This particular embodiment enables an asymmetrical variation of the pitch of the external thread 20 to be achieved. The orientation of the propulsion element 16 and the orientation of the navigation head 14 are not changed, but the given configuration of the external thread 20 is still altered, and the micro-robot 10 presents a closer pitch on one side of the outer surface 18 of the propulsion element 16 while presenting a more distant pitch on the other opposite side of the outer surface 18.

Claims

1. A micro-robot (10) configured to move in a viscoelastic anatomical environment along a propulsion direction, the micro-robot (1) comprising: - A body (12) extending along a body axis (X), - A navigation head (14) extending along a head axis (H) between a free distal tip (14a) and a proximal base (14b), the navigation head (14) presenting a given configuration relative to the body (12), - A propulsion element (16) extending along a propulsion axis (A) and presenting an outer surface (18) with a helical external thread (20), the external thread (20) presenting a given configuration relative to the body (12), - A drive device (22) configured to drive the propulsion element (16) to rotate about the propulsion axis (A) relative to the body (12), wherein the micro-robot (10) further comprises an orientation device (24) configured to change at least one of the given configurations of the navigation head (14) and the external thread (20) relative to the body (12) to change the propulsion direction of the micro-robot (10).

2. The micro-robot (10) according to the previous claim, wherein, The drive device (22) is further configured to also drive the navigation head (14) to rotate.

3. The micro-robot (10) according to any one of the preceding claims, wherein, The given configuration of the external thread (20) includes a given inclination angle (α1) of the head axis (H) relative to the body axis (X), and wherein the orientation device (26) is configured to change the given inclination angle (α1) of the head axis (H) relative to the body axis (X).

4. The micro-robot (10) according to the previous claim, wherein, The orientation device (26) includes a pivot connection (28) configured to enable the navigation head (14) to rotate relative to the body (12) about at least one pivot axis.

5. The micro-robot (10) according to any one of the preceding claims, wherein, The given configuration of the external thread (20) of the propulsion element (16) includes a given inclination angle (α2) of the propulsion axis (A) relative to the body axis (X), and wherein the orientation device (26) is configured to change the given inclination angle (α2) of the propulsion axis (A) relative to the body axis (X).

6. The micro-robot (10) according to the previous claim, wherein, The orientation device (26) includes a pivot connection (28) configured to enable the propulsion element (16) to rotate relative to the body (12) about at least one pivot axis.

7. The micro-robot (10) according to any one of the preceding claims, wherein, The drive device (22) includes a support shaft (24) connecting the proximal base (14b) of the navigation head (14) to the body (12) and including the pivot connection (28).

8. The micro-robot (10) according to the previous claim, wherein, The support shaft (24) is fixed to the engine body (12) by a section of flexible material.

9. The microengine according to claim 7 or 8, wherein, The support shaft (24) is made of flexible material.

10. The micro-robot (10) according to claims 7 to 9, wherein, The support shaft (24) also connects the propulsion element (16) to the body (12).

11. The micro-robot (10) according to any one of the preceding claims, wherein, The configuration of the external thread (20) includes the pitch of the external thread (20), and wherein the orientation device (26) is configured to change the pitch of the external thread (20).

12. The micro-robot (10) according to the previous claim, wherein, The orientation device (26) includes a series of connecting members (30) movably mounted inside the propulsion element (16) and connected to the external thread (20), and the connecting members (30) have relative positions with respect to each other that vary according to the angular position with respect to the outer surface (18) of the propulsion element (16).

13. The micro-robot (10) according to the previous claim, wherein, The series of connecting members (30) are configured such that the relative position of the connecting members (30) with respect to the outer surface (18) of the propulsion element (16) varies between: - A first relative position, where the outer surface (18) is at a first relative angular position, and the connecting members (30) in the first relative position are spaced apart from each other by a corresponding first distance, which is a minimum value; - A second relative position, where the outer surface (18) is at a second relative angular position, and the connecting members (30) in the second relative position are spaced apart from each other by a corresponding second distance, which is a maximum value.

14. The micro-robot (10) according to claim 12 or 13, wherein, The series of connecting members (30) includes: - An internal central connecting member (32) located inside the propulsion element (16), and the central connecting member (32) is capable of tilting with respect to the propulsion axis (A) inside the propulsion element (16); - At least two lateral connecting members (30) extending between the central connecting member (32) and the external thread (20).

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