Patent Description:
The ability to reach deep and functional structures without damage is a major challenge in mini-invasive surgery, especially in neurosurgery. Thanks to microtechnologies, it becomes possible to send a fully autonomous microrobot inside an organ of a subject, such as a brain. However, the propulsion of a microrobot in an environment at low Reynolds number, as in the brain, is a challenge because of absence of inertia and presence of relatively high drag forces due to the small size of the microrobot. Another important requirement is that the microrobot should be capable of moving in an organ while limiting as much as possible the physiological damage that its passage causes to the organ.

<CIT> discloses a micro-robot aimed at circulating through a viscous environment, in particular inside a human body.

In this context, the invention is intended to propose a microrobot having a highly efficient propulsion mechanism in a viscous environment at low Reynolds number, while preserving as much as possible the integrity of the environment in which it is displaced.

The invention is defined in appended independent claim <NUM>. Further embodiments are defined in appended dependent claims.

This invention thus relates to a micro-robot configured to move along a propulsion direction by vibrations, said micro-robot comprising a body configured to vibrate, and an actuator configured to generate vibrations causing the micro-robot to move, said micro-robot further comprising a steering system which comprises a resonating structure configured to be secured to the micro-robot, the resonating structure comprising:.

wherein the actuator is configured to generate vibrations in a range of frequencies including the proper activation resonance frequency of each weight-resonator, wherein the resonating structure displays at least two states:.

Thus, this solution achieves the above objective. In particular, it allows the obtaining of a rotation of the micro-robot solely based on the movements (energy) generated by the micro-robot itself (more precisely by the micro-motor of the micro-robot), thus avoiding the addition of extra-energy which might lead to further elements or devices to be added inside the patient or additional energy to be conveyed to the micro-robot, all which might lead to increase risks of damaging the environment in which the micro-robot moves.

The device according to the invention may include one or more of the following characteristics, taken in isolation from one another or in combination with one another:.

The invention will be better understood, and other aims, details, characteristics and advantages thereof will emerge more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given by way of illustration. purely illustrative and non-limiting examples, with reference to the accompanying drawings.

Please note that in the present application, the term "weight-resonator" is given a wide definition: It is not necessarily just resonators based on their weight. They might also include foils and bi-stable or multi-stable elements which enable to play with the shape of the part and the internal tensions that generate several stable states. Those enable to go from one stable state to another by bringing energy. This is achieved, as will be explained further below in detail, by the change of a resonance frequency which maximizes the available/conducted energy.

As can be seen on <FIG>, the steering system <NUM> according to the present invention, is aimed at being part of a micro-robot <NUM> configured to move inside a fluidic environment, more precisely along a propulsion direction following a propulsion axis X. This movement along the propulsion direction happens by vibration inside the fluidic environment.

The micro-robot <NUM> thus comprises a body <NUM> comprising an actuator <NUM> configured to generate vibrations. More precisely, in the represented embodiments, the actuator <NUM> is a vibrating motor <NUM> which comprises a coil <NUM> and a magnet <NUM>. The coil <NUM> extends along the propulsion direction X and surrounds the magnet <NUM>. The magnet <NUM> is activable by the coil <NUM> and is configured to move back and forth along the propulsion direction X. The movement of the magnet <NUM> induces a compression/decompression movement of a propulsion spring <NUM> also part of the vibrating motor <NUM> and also extending along the propulsion direction X. Said propulsion spring <NUM> allows the movement of a series of external pilis or cilia <NUM> which enable the micro-robot <NUM> to be put in motion inside the fluidic environment.

Many fluidic environments can be targeted, but specifically all bodily fluids are concerned. Those bodily fluid are, for example, blood, cerebra spinal fluids, urine, bile liquid, lymph fluid, aqueous humor. Those fluids all present a viscosity close to that of water.

As can be further seen on <FIG>, the steering system <NUM> according to the present invention comprises an elongated resonating structure <NUM> aimed at being secured to the micro-robot <NUM>.

This elongated resonating structure <NUM> comprises:.

The respective proper activation resonance frequencies fA, fA1, fA2 of each weight-resonator <NUM> is different from the proper activation resonance frequencies fA, fA1, fA2 of the other weight-resonators <NUM>. The actuator <NUM> is configured to generate vibrations in a range of frequencies including the proper activation resonance frequency fA, fA1, fA2 of each weight-resonator <NUM>. The elongated resonating structure <NUM> displays at least two states:.

Regardless of the embodiment, the state B, A, A<NUM>, A<NUM> of the elongated resonating structure <NUM>, is determined by the activation or deactivation of the weight-resonators <NUM> as will be explained further below.

As will be explained further below, the activation and deactivation frequencies fB, fA, fA1, fA2 of the weight-resonator <NUM> are induced by the vibrations of the micro-robot body <NUM> (mor particularly the vibrations induced by the micro-motor comprised within the body <NUM> of the micro-robot) when the micro-robot <NUM> is moving along its propulsion direction.

More particularly regarding <FIG>, the elongated resonating structure <NUM> further comprises a distribution of multi-stable element <NUM> secured to the micro-robot <NUM>. Each multi-stable element <NUM> displays at least two stable configurations and is deformable between those at least two stable configurations:.

Depending on the embodiments, the multi-stable element <NUM>, the weight-resonator <NUM> and the steering structure <NUM> can be the same technical element or distinct elements. For example, in the embodiment depicted on <FIG>, the multi-stable element <NUM>, the weight resonator <NUM> and the steering structure <NUM> are all distinct technical elements. However, regarding the embodiment depicted on <FIG>, the multi-stable element <NUM>, the weight-resonator <NUM> and the steering structure <NUM> are the same technical element. In this case, the different proper activation frequencies fA, fA1, fA2 could be dedicated to, for example, the control the shape of the weight-resonator <NUM> (or multi-stable element <NUM>). One could have a frequency for semi-closure, another for full closure, for example.

More precisely regarding the embodiment depicted on <FIG>, <FIG> and <FIG>, the elongated resonating structure <NUM> comprises three multi-stable elements <NUM>, equidistantly distributed around the body <NUM> of the micro-robot <NUM> (see <FIG>). Each multi-stable elements <NUM> is associated to a weight-resonator <NUM> having a specific proper activation frequency fA. This specific proper activation frequency fA being different from the proper activation frequencies fA of the other weight-resonator <NUM> associated to the other multi-stable elements <NUM>. In this example, each multi-stable element <NUM> is a bi-stable pre-compressed beam <NUM> between <NUM> and a few mm in length, made of polymers, glass or metal such as stainless steel or alliage. In this particular embodiment, each beam <NUM> connects the steering structure <NUM> and the weight-resonator <NUM>. Each beam <NUM> has two extremities, and each extremity is secured to the micro-robot <NUM>. More precisely, each beam <NUM> is secured in a small open cavity of the body <NUM> of the micro-robot <NUM>. As already mentioned, each beam <NUM> presents a first stable configuration CA in which it bends inwards the cavity of the micro-robot <NUM> and a second stable configuration CB in which it bends outwards the cavity of the micro-robot <NUM>. The first stable configuration CA corresponds to the activated steering state A, the second stable configuration CB corresponds to the non-activated steering state B. In its non-activated steering state B, the pre-compressed beam <NUM> is bent in a first direction, away from the body <NUM> of the micro-robot <NUM>. In its activated steering state A, the pre-compressed beam <NUM> is bent in a second direction, towards the body <NUM> of the micro-robot <NUM> and thus different from the first direction.

Still considering the embodiment on <FIG> and <FIG>, the steering structure <NUM> comprises a retractable steering foil <NUM> displaying an open and a retracted configuration with regards to the body <NUM> of the micro-robot <NUM> (see <FIG>). As will be explained later, the configuration of the steering foil <NUM> is determined by the state of the elongated resonating structure <NUM> of the steering system <NUM>. The foils could be made of many different flexible materials such as metals such as copper or alliage metals, glass or polymers among others. Size can vary from about <NUM> to a few mm. More precisely, the non-activated steering state B of the elongated resonating structure <NUM> induces a retracted configuration of the retractable steering foil <NUM>. On the other hand, the activated steering state A of the elongated resonating structure <NUM> induces an open configuration of the retractable steering foil <NUM>.

Still considering <FIG>, each weight-resonator <NUM> comprises a resonating mass connected to the beam <NUM>. This mass can be of any suitable shape, for example a bead or a cube. Depending on the embodiment the resonating mass could also be embedded in the beam <NUM> by extra thickness or an extension of the shape of the beam <NUM>. The activation of the resonating mass of the weight-resonator <NUM> thus induces a configuration change in the beam <NUM>. The configuration change of the beam 22a further induces a configuration change of the corresponding steering foil <NUM>.

In the embodiment presented in <FIG>, <FIG> and <FIG>, the multi-stable element <NUM> is a multi-stable shell <NUM> comprising a stack of several sheets. The multi-stable elements could be made of many different flexible materials who have this multi-stable state capacity when shaped appropriately such as copper. Size can vary from about <NUM> to a few mm.

In this embodiment, the multi-stable shell <NUM> displays a non-activated steering state B, in this state none of the shells oppose a resistance to the movement of the system by blocking the flow of the liquid, and several activated steering states A<NUM>, A<NUM>. Each activated steering state A<NUM>, A<NUM> is associated to a different proper activation resonance frequency f<NUM>, f<NUM>. In those activated states, a shell is positioned in a way that oppose the flow, this creates an asymmetry and induces a rotation in the direction to which the shell is exposed.

According to further embodiments depicted, in particular, on <FIG> and <FIG>, the steering system <NUM>, and more particularly the elongated resonating structure <NUM>, comprises at least one mobile cilium <NUM>. In some embodiment, the elongated resonating structure <NUM> comprises at least one, preferably a group of mobile cilia <NUM>. This at least one mobile cilium <NUM> can be part of the series of external pilis or cilia <NUM> which enable the micro-robot <NUM> to be put in motion inside the fluidic environment (see paragraph [<NUM>]). The at least one mobile cilium <NUM> may also be an independent technical element from said series of external pilis or cilia <NUM>.

In the embodiments of <FIG> and <FIG>, the at least one cilium <NUM> is part of the steering structure <NUM>. In this embodiment, the steering structure further is configured to enable a preferential activation of one single cilium <NUM> over the other cilia <NUM>. In order to achieve this, the steering structure may comprise a foil carried by said at least one cilium <NUM>. The foil can present different orientations depending on the configuration and/or position of the at least one cilium <NUM>. Those different configurations/positions enable the steering structure <NUM> to control the propulsion direction of the micro-robot <NUM>.

Each cilium <NUM> is secured to the body <NUM> of the micro-robot <NUM>, preferably on the head portion of the micro-robot <NUM>. More precisely, each <NUM> is secured to a mobile part <NUM> of the body <NUM> of the micro-robot <NUM>. This mobile part <NUM> is connected to the propulsion spring <NUM> of the vibrating motor <NUM> and moves in accordance with said propulsion spring <NUM>. Depending on the movements of the propulsion spring <NUM>, said mobile part <NUM> can be centred or off-centred around the the propulsion direction X. Each cilium <NUM> is thus configured to be put in motion by the vibration of the micro-robot <NUM>, more particularly by the movement of the propulsion spring <NUM> of the motor (actuator) <NUM>.

In this embodiment, the propulsion string <NUM> comprises several strands <NUM> from which some are equipped weight-resonators <NUM> (see <FIG>). Thus, in this embodiment, the elongated resonating structure <NUM> comprises at least one strand <NUM> of the propulsion spring <NUM> of the vibrating motor/actuator <NUM>.

More particularly, in the embodiment depicted on <FIG>, <FIG>, <FIG> and <FIG>, each strand <NUM> carrying a weight-resonator <NUM> is part of the multi-stable element <NUM> of the steering system <NUM>. Each weight-resonator <NUM> is, similarly to the precedingly detailed embodiments, activable over a proper activation resonance frequency fA, fA1, fA2 and deactivated under a given deactivation frequency fB. As can be seen on <FIG>, the propulsion spring <NUM> comprises three independent strands <NUM> and each strand <NUM> carries a weight-resonator <NUM> which is activable over a different proper activation frequency fA, fA1, fA2. As hinted at in <FIG>, the different weight-resonator <NUM> present different sizes and shapes, leading to different proper activation frequencies fA, fA1, fA2. In an alternative embodiment, the different proper activation frequencies fA, fA1, fA2 could be dedicated to, for example, the control the shape of the weight-resonator <NUM>. One could have a frequency for semi-closure, another for full closure.

In this embodiment (<FIG>, <FIG>, <FIG> and <FIG>), the activation of the elongated resonating structure <NUM> in its at least one activated steering state A, A<NUM>, A<NUM> (see <FIG>), and more particularly the activation of each weight-resonator <NUM> induces a retractation of the corresponding strand <NUM> of the propulsion spring <NUM>.

More particularly, in this embodiment (<FIG>, <FIG>, <FIG> and <FIG>), each strand <NUM> presents a first stable configuration CA in which it presents a first length LA corresponding to an activated steering state A<NUM>, A<NUM> and a second stable configuration CB in which it presents a second length LB, corresponding to the non-activated steering state B. When the strand <NUM> is in its second stable configuration CB, its length LB is the same than the length of the other strands <NUM>. In this second stable configuration, the mobile part <NUM> of the body <NUM> of the micro-robot <NUM>, is centred with regards to an elongation axis X of the micro-robot <NUM>. Said elongation axis X is the same as the propulsion axis X already mentioned previously. When the strand <NUM> is in its activated configuration CA, its length changes and the mobile part <NUM> of the body <NUM> of the micro-robot <NUM> is off-centred. The activation of the elongated resonating structure <NUM> in one of its activated steering states A<NUM>, A<NUM> thus induces a break in the global symmetry of the body <NUM> of the micro-robot <NUM>.

Regarding the embodiments depicted respectively on <FIG>, <FIG>, <FIG> and <FIG>, <FIG> and <FIG>, it can also be said that the activation of the elongated resonating structure <NUM> in one of its activated steering states A<NUM>, A<NUM> induces a break in the global symmetry of the body <NUM> of the micro-robot <NUM>: the spreading of the foils 18a, 18b break the global rotational symmetry of the micro-robot <NUM>.

The length of each strand <NUM> depends on the activation/inactivation of each associated weight -resonator <NUM>. The length of each strand <NUM> thus depends on the vibration amplitude of the vibrating motor <NUM> and of the propulsion spring <NUM>, going from about <NUM> (it does not move) to an amplitude in hundreds of µm.

In the last depicted embodiment of the present invention (<FIG>, <FIG>, <FIG> and <FIG>), the at least one cilium <NUM> is also part of the elongated resonating structure <NUM>. However, it is also part of the steering structure <NUM> and of the multi-stable element <NUM>. As in the previous embodiment, each cilium <NUM> carries a foil in order to enable some steering of the micro-robot <NUM>.

In this embodiment, the weight-resonator <NUM> activable by the frequencies of the propulsion spring <NUM>, are carried by the cilia <NUM>. More particularly, each cilium <NUM> carries a weight-resonator <NUM> activable at a propre activation frequency fA, fA1, fA2.

In this embodiment, the at least one cilium <NUM> presents at least two stable states CA, CB, each stable state CA, CB being associated to a movement intensity. This way, each cilium <NUM> presents a first stable state CB correspondent to a first movement intensity IB. This first stable state CB corresponds to the non-activated state of the weight-resonator <NUM> carried by the cilium <NUM> and thus corresponds to the non-activated steering state B. The second stable state CA corresponds to a second movement intensity IA and thus to the activated steering state A. The second movement intensity IA being higher than the first movement intensity IB. All cilium <NUM> in the first stable state CB are moving (back and forth movements) with the same first movement intensity IB. Once one (or several) cilium (cilia) <NUM> is (are) activated, it (they) start(s) moving with a different intensity, the second movement intensity IA, thus inducing a break in the general symmetry of the micro-robot <NUM> which leads to a disequilibrium and eventually to a direction change.

As mentioned above, for each embodiment, the activation of the weight-resonator <NUM> induces the elongated resonating structure <NUM> to enter its at least one activated steering state A, A<NUM>, A<NUM>. On the other hand, the deactivation of the weight-resonator <NUM> induces the elongated resonating structure <NUM> to enter its non-activated steering state B.

When the elongated resonating structure <NUM> is in its non-activated steering state B, the propulsion direction of the micro-robot <NUM> is maintained the same and the micro-robot <NUM> moves straight forward along the propulsion axis X. However, when the elongated resonating structure <NUM> enters its at least one activated steering state A, A<NUM>, A<NUM>, the micro-robot <NUM> rotates and changes its propulsion direction.

Considering the first embodiment (<FIG>, <FIG>, <FIG>, <FIG>), the vibration of the propulsion spring <NUM> induces the micro-robot <NUM> to vibrate at given frequencies. When the micro-robot <NUM> vibrates at the proper activation resonance frequency fA of one of the weight-resonators <NUM> of the elongated resonating structure <NUM>, the considered weight-resonator <NUM> starts vibrating. This vibration induces a configuration change in its associated pre-compressed beam 22a from its inactivated configuration CB to its activated configuration CA. This configuration change leads the associated steering foil <NUM> to be expanded. The elongated resonating structure <NUM> finds itself in its steering activated state A. The expansion of the steering foil <NUM> induces a rotation of the micro-robot <NUM> and a redefinition of the propulsion direction X (see <FIG>). When the vibration of the micro-robot <NUM> falls below the given deactivation frequency fB of the weight-resonator <NUM>, the weight-resonator <NUM> is deactivated and the pre-compressed beam <NUM> falls back into its inactivated configuration CB. The steering foil <NUM> is thus retracted and the elongated resonating structure <NUM> falls back in its inactivated steering state B. The frequency and/or amplitude of the motor <NUM> is changed to go from one resonant frequency related to a specific state to another related to another state.

Regarding the second embodiment (<FIG>, <FIG>, <FIG>), the functioning is similar to the precedent embodiment, with exception that the vibrating of the propulsion spring <NUM> activates directly the multi-stable shell 22b, which changes configuration and induces the micro-robot <NUM> to rotate.

Considering the fourth embodiment (<FIG>, <FIG>, <FIG>, <FIG>), it has to be specified that each cilium <NUM> vibrates at a given intensity, said vibration being induced by the vibrations of the vibrating motor (actuator) <NUM> of the micro-robot <NUM>. When the micro-robot <NUM> vibrates at the proper activation resonance frequency fA of one of the weight-resonators <NUM> of the elongated resonating structure <NUM>, the considered weight-resonator <NUM> starts vibrating. This vibration induces a configuration change in its associated strand <NUM>, more precisely a modification of its length from its second length LB defining its inactivated state CB, to its first length LA defining its activated state CA. This change in length induces a break in the global symmetry of the body <NUM> of the micro-robot <NUM> and the at least one cilium <NUM> undergoes a shift in its vibration axis, thus inducing a rotation of the micro-robot <NUM> (see <FIG>).

Regarding the last embodiment (<FIG>, <FIG>, <FIG> and <FIG>), when the micro-robot <NUM> vibrates at the proper activation resonance frequency fA of one of the weight-resonators <NUM> of the elongated resonating structure <NUM>, the considered weight-resonator <NUM> starts vibrating. This vibration induces a configuration change in the vibration intensity of the associated cilium <NUM>. The cilium <NUM> then changes from its first movement intensity IB (corresponding to the steering non-activated state B of the elongated resonating structure <NUM>) to its movement intensity IA (corresponding to the steering activated state A of the elongated resonating structure <NUM>). The activated cilium <NUM> thus vibrates at a different speed and a different amplitude from the other cilia <NUM> (or the series of external pilis or cilia <NUM>) and this induces a rotation of the micro-robot <NUM> (see <FIG>).

This rotation of the micro-robot <NUM> most likely happen by a succession of jolts, creating a discrete cumulation of several small rotational movements leading to the desired final rotation. This enables an additional layer of precision and security.

Claim 1:
Micro-robot (<NUM>) configured to move along a propulsion direction by vibrations, said micro-robot (<NUM>) comprising a body (<NUM>) comprising an actuator (<NUM>) configured to generate vibrations causing the micro-robot (<NUM>) to move,
said micro-robot (<NUM>) further comprising a steering system (<NUM>) which comprises a resonating structure (<NUM>) configured to be secured to the micro-robot (<NUM>), the resonating structure (<NUM>) comprising:
- a steering structure (<NUM>) aimed at controlling the propulsion direction,
- a distribution of weight-resonators (<NUM>), each weight-resonator (<NUM>) being configured to be activated by a proper activation resonance frequency (fA, fA1, fA2), the respective proper activation resonance frequencies (fA, fA1, fA2) of the weight-resonators (<NUM>) being different from each other,
wherein the actuator (<NUM>) is configured to generate vibrations in a range of frequencies including the proper activation resonance frequency of each weight-resonator,
wherein the resonating structure (<NUM>) displays at least two states:
- at least one activated steering state (A, A<NUM>, A<NUM>), in which at least one of the weight-resonators is activated at the proper activation resonance frequency to change the propulsion direction of the micro-robot (<NUM>),
- a non-activated steering state (B), in which none of the weight-resonators is activated at its proper activation resonance frequency so as to maintain the propulsion direction of the micro-robot (<NUM>).