An electromechanical microsystem including an electromechanical transducer, a deformable diaphragm and a cavity hermetically containing a deformable medium keeping a constant volume under the action of an external pressure change. The deformable diaphragm forms a wall of the cavity and has at least one free area so as to be elastically deformed. The electromechanical transducer is configured so that its movement depends on the change in the external pressure, and vice versa. The free area cooperates with an external member so that its deformation induces, or is induced by, a movement of the external member. Thus, the electromechanical microsystem is adapted to displace the external member or to detect a movement of this member, the electromechanical microsystem includes at least one pin, configured to bear on a peripheral portion of the free area so that a deformation of the free rea causes an inclination of the pin.

TECHNICAL FIELD

The present invention relates to the fields of electromechanical microsystems. For example, it finds a particularly advantageous application in the actuation or the displacement of objects, including over relatively large distances. It also finds application in gripping devices that allow capturing or expelling small-sized objects. The invention also finds application in the field of contact detection. Thus, it could be implemented to make sensors.

PRIOR ART

In many applications, it might be needed to displace, capture or expel microscopic, and possibly nanoscopic, objects, and/or needed to detect the movements of such objects. There are microsystems that allow this.

In the case where these microsystems are actuators or gripping devices, their performances are assessed in particular on the following parameters: the amplitude of the movement, the exerted force, the accuracy of the generated movement or else the accuracy of the detection or the expulsion of an object. In the case where these microsystems are sensors, their performances are assessed in particular on the following parameters: the capability to detect a movement over a significant amplitude and the accuracy of the measurement.

Otherwise, whether the microsystems consist of actuators, gripping devices or sensors, what is aimed is that they offer good performances in terms of bulk, energy consumption and capability to work in frequency.

All known solutions have low performances for at least one of these parameters. In general, the existing microsystems have performances that are too unsatisfactory for a combination of these parameters.

An object of the present invention is to provide an electromechanical microsystem which has improved performances in comparison with the existing solutions, at least for one of the above-mentioned parameters, or which has a better trade-off between at least two of the aforementioned parameters.

The other objects, features and advantages of the present invention will appear upon examining the following description and the appended drawings. It goes without saying that other advantages could be incorporated.

SUMMARY

To achieve this objective, according to one embodiment, an electromechanical microsystem is provided comprising:at least one electromechanical transducer comprising a portion movable between a balance position, off-load, and an out-of-balance position, under load,at least one deformable diaphragm,a first deformable cavity, delimited by walls, at least one portion of the deformable diaphragm forming at least one portion of a first wall selected amongst said walls of the cavity, the cavity being configured to hermetically contain a deformable medium capable of keeping a substantially constant volume under the action of a change of an external pressure exerted on the deformable medium through one of the walls of the cavity.

The movable portion of the electromechanical transducer is configured so that its movement depends on said change in the external pressure, or conversely its movement induces a change in the external pressure. Said at least one portion of the deformable diaphragm has at least one area freely deformable, preferably elastically, as a function of said change in the external pressure.

The free area has an outer perimeter and a peripheral portion which extends from the outer perimeter and up to a central portion of the free area.

Typically, the suggested electromechanical microsystem allows obtaining an inclination of the pin according to an angle having a large amplitude in comparison with the deformation of the diaphragm. It is then possible to obtain large strokes, even with an electromechanical microsystem with small dimensions. In particular, the second end of the pin, i.e. the end of the pin opposite to its end bearing on the diaphragm, is displaced over a large travel range.

Typically, the displacement of the second end of the pin may be performed over a travel length that could be expressed in an angular form. Typically, the second end of the pin is displaced by an angle of at least 45°, and preferably comprised between 0° and 90°.

Hence, the provided electromechanical microsystem presents a particularly effective solution to make:an actuator with a large stroke. Such an actuator enables the displacement of an object or of an external member displaced by the pin(s), typically with an amplitude in the range of 100 μm.a gripping device. By providing for several pins over the free area of the diaphragm, in particular over its peripheral portion, it is possible to make the ends of the different pins approach each other so as to allow grasping, capturing or holding an object between the pins. Conversely, it is possible to control the detachment of the pins so as to allow releasing or expelling an object. Similarly, by providing for at least one pin whose free end is shaped so as to cooperate with an object to grasp it, the displacement of the pin allows capturing or releasing an object. It is also possible to provide for the material of the pin enabling the capture of an object, by adhesive forces or magnetic forces.a sensor, typically allowing detecting a displacement imposed on at least one pin. This displacement may be a displacement according to a curved trajectory.

Thus, the electromechanical microsystem as introduced hereinabove is able to to displace the pin or to detect a movement imposed on the latter, and that being so while featuring, in a way that could be easily modulated depending on the targeted applications, a sufficient capability in terms of displacement amplitude and/or a sufficient capability in terms of deployed force and/or a capability to detect movement, and possibly capture, an object and/or a sufficient capability to work in frequency and/or a size compatible with the targeted applications, and/or a reduced energy consumption.

Another aspect of the invention relates to an opto-electro-mechanical system or microsystem comprising at least one electromechanical microsystem as introduced hereinabove and at least one optical microsystem.

Preferably, the optical microsystem comprises at least one mirror, preferably based on silicon. The opto-electro-mechanical system is configured so that the movement of the movable portion of the electromechanical transducer cause a displacement, preferably an inclination, of the at least one mirror.

Another aspect of the invention relates to a method for manufacturing an electromechanical microsystem as introduced hereinabove, comprising, and possibly being limited to, deposition and etching steps, quite common in the microelectronics industry. Indeed, the electromechanical microsystem may be manufactured by common means of the microelectronics industry, which confers on its manufacturer all of the advantages resulting from the use of these means, including a great flexibility in terms of sizing, energy of adhesion between the different deposits, thickness of the different deposits, extent of etching, etc.

According to one example, the method for manufacturing the electromechanical microsystem comprises the following steps:a step of forming, over a substrate, at least one portion of the electromechanical transducer, thena step of depositing the deformable diaphragm, thena step of forming an open cavity over the deformable diaphragm, thena step of filling with the deformable medium and closing the cavity, anda step of etching the substrate to form a front face (FAV) of the electromechanical microsystem.

The drawings are provided as examples and do not limit the invention. They consist of schematic principle representations intended to facilitate understanding of the invention and are not necessarily to the scale of practical applications. In particular, the thicknesses of the different illustrated layers, walls and members do not necessarily represent reality.

DETAILED DESCRIPTION

According to one example, in the absence of deformation, the free area of the diaphragm primarily extends in a plane (xy), called off-deformation plane or rest plane, and the perpendicular to the tangent at a given point of the free area extends according to a direction T1perpendicular to the off-deformation plane.

According to one example, when the diaphragm is deformed, the perpendicular to the tangent at a given point of the peripheral portion of the free area extends according to a direction T1, inclined with respect to the direction T1, by an angle αi (the angle αi being measured in a plane perpendicular to the off-deformation plane).

According to one example, the angle αi increases when getting away from the central portion and approaching the outer perimeter of the free area.

According to one example, the electromechanical microsystem is configured so that a deformation of the free area of the diaphragm causes an inclination of the pin in a plane perpendicular to a plane (xy) in which an outer face of the diaphragm primarily extends when the diaphragm is not deformed.

According to one example, the inclination may be measured by an angle α contained in a plane perpendicular to the plane xy.

According to one example, the pin primarily extends according to a longitudinal direction.

When the diaphragm is not deformed, the longitudinal direction of the pin is substantially perpendicular to a plane (xy) in which an outer face of the diaphragm primarily extends when the diaphragm is not deformed. The pin may have a cylindrical shape. According to an alternative embodiment, the pin does not have a cylindrical shape. For example, it may have a curved shape.

According to one example, the pin has a first end by which it bears on the peripheral portion of the free area and a second end opposite to the first end.

According to one example, the electromechanical microsystem is configured so that a deformation of the free area of the diaphragm causes an inclination of the first end in the direction of the central portion of the free area.

According to one example, the pin extends between the first end and the second end primarily according to a longitudinal direction. Alternatively, the pin has a curved shape or extends according to several different directions.

According to one example, the free area has a central portion extending from a centre of the free area and a peripheral portion disposed around the central portion.

According to one example, the peripheral area is continuous. It has a solid contour.

Alternatively, it has an open contour.

According to one example, the central portion comprises a centre of the free area, the centre corresponds for example to the barycentre of the free area.

According to one example, the free area forms a disk, an ellipse or a polygon and said centre corresponds to the barycentre of the free area.

According to one example, the free area is delimited by an outer perimeter, the pin being located at a minimum distance D122from the outer perimeter, such that D122is smaller than k times a distance D124,D122being measured between the pin and the point of the outer perimeter the closest to the pin, andthe distance D124being measured between this same point and the centre of the free area,k being less than 0.7, preferably k being less than 0.5, preferably k being less than 0.3.

According to an alternative embodiment, the central portion does not form a disk, an ellipse or a polygon. The central portion may surround at least partially the electromechanical transducer. For example, the central portion may have an elongate shape. This elongate shape may extend according to several sections having different directions.

According to one example, the electromechanical microsystem comprises a plurality of pins, each bearing on the peripheral portion of the free area so that a deformation of the free area of the diaphragm causes an inclination of the pins.

According to one example, the pins have a free end, opposite to the end by which they bear on the peripheral portion of the free area, the pins being shaped so that a deformation of the free area of the diaphragm selectively causes an approach or a separation of their free ends.

According to one example, the pins are shaped so that a deformation of the free area of the diaphragm selectively causes a contact or a separation of the free ends of the pins.

According to one example, the pins are distributed over the peripheral portion so that the approach of their free ends allows grasping between the free ends and/or holding between the diaphragm and the pins an object that is external the electromechanical microsystem. The approach of their free ends allows forming a cage above the free area of the diaphragm.

This embodiment allows obtaining a particularly reliable and accurate gripping device. Furthermore, the large angular stroke of the pins, allows capturing and releasing objects with relatively large sizes in comparison with the size of the pins and with the size of the electromechanical microsystem.

In this embodiment, the object is not fastened to the electromechanical microsystem. All the more so, it is not fastened to the pins.

According to another embodiment, the object is an external member.

According to one example, the pin(s) is/are configured to cooperate with an object forming an external member so that the movement of the movable portion of the electromechanical transducer depends on a displacement of the pin(s) driven by the external member or conversely the movement of the movable portion of the electromechanical transducer induces a displacement, in particular an inclination, of the external member through the pin.

This embodiment allows obtaining a reliable and accurate actuator or a sensor. The large angular stroke of the pins enables a displacement of the external member over a relatively large travel in comparison with the size of the pin(s) and with the size of the electromechanical microsystem.

The pin(s) may be configured to cooperate with the external member through a guide secured to the external member, so as to enable an automatic positioning of the external member on the pin(s).

The pin(s) may be configured so as to be able to be secured to the external member by gluing or magnetically, the adhesive energy of the pin(s) on the free area of the deformable diaphragm being preferably higher than that of the pin(s) on the external member. An attachment, possibly removable, of the pin(s) and of the external member is thus provided for which is could be greatly modulated in terms of holding force.

According to one example, the electromechanical microsystem further comprises at least one lateral stop, preferably supported by said first wall of the cavity configured to guide the movement of the external member.

According to one example, the pin extends from the free area of the deformable diaphragm beyond said at least one lateral stop. According to an alternative example, the pin extends from the free area of the deformable diaphragm short within said lateral stop.

According to one example, the pin is fastened on said free area, preferably in direct contact with said free area.

According to one example, the electromechanical microsystem comprises a plurality of electromechanical transducers.

According to one embodiment, the electromechanical transducers are separated from each other. Their movable portions are not in contact. Alternatively, they are contiguous.

According to one example, an electromechanical transducer surrounds, at least partially, and possibly entirely, one or several other electromechanical actuator(s), in particular their movable portion. Furthermore, they may be actuated independently from each other.

Preferably, each electromechanical transducer has a movable portion configured so that its movement depends on said change in the external pressure, or conversely so that its movement induces a change in the external pressure exerted on the deformable medium through one of the walls of the cavity.

Thus, the electromechanical microsystem includes several electromechanical transducers for a cavity.

According to one example, at least some of the electromechanical transducers of said plurality are configured so that, under load, their movable portions induce deformations of the free area of the diaphragm causing an inclination of the at least one pin in the same direction.

Thus, at least some of these electromechanical transducers each allows displacing the at least one pin according to the same direction and each over one amplitude. The overall inclination of the pin results from the cumulated displacement of the movable portions of these electromechanical transducers. Thus, the electromechanical microsystem has a step-by-step operation; this allows limiting the addressing voltage.

The electromechanical transducers may be loaded simultaneously or successively. The amplitude of displacement of the pin induced by each electromechanical transducer may be identical or different.

According to one example, at least some of the electromechanical transducers of said plurality are configured so that, under load, their movable portions, induce deformations of the free area of the diaphragm in two opposite directions causing an inclination of the at least one pin in two opposite directions.

Thus, at least two of these electromechanical transducers allow displacing the at least one pin according to two opposite directions. Hence, these two electromechanical transducers are antagonist. Thus, at least one of these electromechanical transducers allows inclining the pin according to a first direction and at least another one of these electromechanical transducers allows inclining the pin according to a second direction opposite to the first direction. This allows increasing even more the amplitude of the inclination that is possible for the pin.

These two antagonist electromechanical transducers may be separated from each other by a non-zero distance. Alternatively, one of these electromechanical transducers may surround the other electromechanical transducer, preferably entirely. According to another embodiment, the same transducer allows performing these two alternating movements. For this purpose, it is possible to use a transducer made of AlN for example.

According to one example, the electromechanical microsystem comprises several free areas, separated from each other by a non-zero distance.

These free areas may be formed by the same diaphragm. Alternatively, these free areas may be formed by distinct diaphragms.

According to one example, the free area is freely deformable, preferably elastically, as a function of said change in the external pressure.

Preferably, the electromechanical microsystem as introduced hereinabove is devoid of any optical element, such as a lens, in particular a variable-focus one.

The pin is not fastened at the centre of the free area of the deformable diaphragm. In this manner, the movement of the pin is not a translational movement perpendicular to the wall of the cavity which is partially formed by the deformable diaphragm.

At least one portion of the electromechanical transducer forms a portion of the wall of the cavity which is partially formed by the deformable diaphragm. According to this feature, the electromechanical microsystem has a structure that is not open-through, leaving the other walls of the cavity free so as to be able implement other functions therein or so as to enable them to remain inert, for an increased integration capability in particular in an opto-electro-mechanical microsystem.

The electromechanical transducer may extend, directly or indirectly, over the deformable diaphragm, and preferably around the free area of the deformable diaphragm. Furthermore, the electromechanical transducer may have annular shape whose circular centre defines the extent of the free area of the deformable diaphragm.

The movable portion of the electromechanical transducer may have a surface at least twice as large, and possibly 5 times larger, and preferably at least ten times larger than the surface of the free area of the deformable diaphragm, and possibly than the surface of the free areas of the deformable diaphragm. The larger the surface of the transducer in comparison with the surface of the free area, the higher will be the amplitude of deformation of the free area of the diaphragm.

Preferably, the deformable diaphragm is configured so that its free area could be deformed with an amplitude of at least 50 μm, possibly of at least 100 μm, and possibly of at least 1,000 μm according to a direction perpendicular to the plane in which it primarily extends when it is at rest. Thus, without tearing and/or without any significant wear, the electromechanical microsystem offers the ability to address numerous and various application requiring a large stroke, the latter being defined where appropriate by the considered technical field.

According to one example, at least one portion of the electromechanical transducer forms a portion of said first wall of the cavity.

According to one example, the electromechanical transducer extends, directly over the deformable diaphragm, i.e. the electromechanical transducer is directly in contact with the deformable diaphragm. Alternatively, the electromechanical transducer extends indirectly over the deformable diaphragm, i.e. at least one element or one intermediate layer is disposed between the electromechanical transducer and the deformable diaphragm. Preferably, the electromechanical transducer extends around the free area of the deformable diaphragm.

According to one example, the electromechanical transducer completely surrounds the free area of the deformable diaphragm, the electromechanical transducer preferably having an annular shape whose circular centre defines the extent of the free area of the deformable diaphragm.

The electromechanical microsystem may further comprise at least one lateral stop configured to guide the movement of the pin or of the external member when present. According to an optional example, the lateral stop is supported by the wall of the cavity which is partially formed by the deformable diaphragm. According to an optional example, said at least one lateral stop extends opposite to the cavity.

Thus, it is possible to:limit, in a controlled, reliable and reproducible manner, the inclination of the pin during the movement of the movable portion of the electromechanical transducer, and/orenable a self-positioning of the external member with respect to the free area of the deformable diaphragm, and/orprotect the deformable diaphragm, and more particularly its free area, in particular from a possible pull-out, when affixing or gluing the external member.

According to one example, the free area of the deformable diaphragm is configured to cooperate with the external member via the pin fastened on said free area.

The pin may extend from the free area of the deformable diaphragm beyond said at least one lateral stop.

Alternatively, the pin may extend from the free area of the deformable diaphragm short within said at least one lateral stop. The electromechanical microsystem according to either one of these two features offers a satisfactory capability to adapt to a wide range of external members and applications.

The electromechanical microsystem may further comprise a so-called bottom stop supported by the wall of the cavity opposite to the free area of the deformable diaphragm, said bottom stop extending in the cavity towards the free area. It has a shape and dimensions configured to limit the deformation of the free area of the deformable diaphragm so as to protect the deformable diaphragm, and more particularly its free area, in particular from a possible pull-out, when affixing or gluing the external member. Moreover, the so-called bottom stop is shaped so as to limit the contact surface between the diaphragm and the wall of the cavity opposite to the free area of the deformable diaphragm. Alternatively or complementarily, the bottom stop is shaped so as to limit the contact surface between the diaphragm and the wall of the cavity opposite to the free area of the deformable diaphragm. This allows avoiding the diaphragm adhering to this wall.

The electromechanical transducer may be a piezoelectric transducer, preferably comprising a PZT-based piezoelectric material.

The electromechanical transducer may be a transducer with a static operation. Alternatively or complementarily, the electromechanical transducer may be a transducer with a vibratory operation at least at one resonance frequency, said at least one resonance frequency being preferably lower than 100 kHz, and even more preferably lower than 1 kHz.

The deformable medium hermetically contained in the cavity may comprise at least one amongst a fluid and/or a liquid, and microbeads, the fluid preferably having a viscosity in the range of 100 cSt at ambient temperature and pressure.

According to a non-limiting embodiment, the fluid has a compressibility comprised between 10−9and 10−10Pa−1at 20° C., for example in the range of 10−10Pa−1at 20° C., without these values being restrictive.

The electromechanical microsystem as introduced hereinabove may further comprise a plurality of deformable diaphragms and/or a plurality of free areas per deformable diaphragm and/or a plurality of electromechanical transducers.

Said at least one optical microsystem of the opto-electro-mechanical microsystem as introduced hereinabove may comprise at least one mirror also referred to as micro-mirror, preferably silicon-based.

According to one example, the opto-electro-mechanical system is configured so that the movement of the movable portion of the electromechanical transducer causes a displacement of the at least one mirror.

By “electromechanical microsystem”, it should be understood comprising at least one mechanical element and at least one electromechanical transducer made in the micrometric scale with means of the microelectronics industry. The electromechanical transducer could detect a movement of the mechanical element; the electromechanical microsystem then serves as a sensor. Alternatively or complementarily, the mechanical element could be set in movement (actuated) thanks to a force generated by the electromechanical transducer. The electromechanical microsystem then serves as an actuator or gripping device.

The electromechanical transducer may be powered by electric voltages produced with neighbouring electronic circuit.

A “microsystem” is a system whose outer dimensions are smaller than 1 centimetre (10−2metres) and preferably than 1 millimetre (10−3metres).

Most often, an electromechanical transducer serves as an interface between the mechanical and electrical domains. Nonetheless, by “electromechanical transducer”, it should herein be understood a piezoelectric transducer, as well as a thermal transducer, the latter serving as an interface between the mechanical and thermal domains. An electromechanical transducer may comprise a movable portion between a balance position, off-load, and an out-of-balance position, under load. In the case where the transducer is piezoelectric, the load is electric. In the case where the transducer is thermal, the load is thermal.

When mention is made of the centre of the cavity, this centre is defined geometrically by considering the centre of a cavity having a non-deformed free area of the deformable diaphragm.

By “lower” and “higher”, it should be understood “lower than or equal to” and “higher than or equal to”, respectively. Equality is excluded by the use of the terms “strictly lower” and “strictly higher”.

By a parameter “substantially equal to/higher than/lower than” a given value, it should be understood that this parameter is equal to/higher than/lower than the given value, more or less 20%, possibly 10%, of this value. By a parameter “substantially comprised between” two given values, it should be understood that this parameter is at least equal to the lowest given value, more or less 20%, possibly 10%, of this value, and at most equal to the highest given value more or less 20%, possibly 10%, of this value.

As this will be described in more details later on, depending on its configuration and its use, the electromechanical microsystem1according to the invention may ensure several functions:as an actuator, it could allow displacing an object such as an external member2by tilting it in a first direction, (for example to the left) as illustrated inFIGS.3A and7A, or in a second direction (for example to the right), as illustrated inFIGS.3B and7B,As a gripping device, it could allow capturing or expelling an object3as illustrated inFIG.6B, grasping an object3as illustrated inFIG.6C, or else holding an already captured object3as illustrated inFIG.6D,As a sensor, it could allow detecting a displacement, in particular an inclination. The features allowing ensuring these different functions will now be described in details with reference to the figures.

FIGS.1and2are block diagrams, respectively of sectional and top views, of an example of the electromechanical microsystem1according to the invention.FIGS.3A and3Billustrate the electromechanical microsystem ofFIGS.1and2, during use.

InFIG.1, an electromechanical transducer11, a deformable diaphragm12and a cavity13configured to hermetically contain a deformable medium14, are illustrated

Before describing the different embodiments of the invention illustrated in the figures in more details, note that each of these illustrations schematically represents an embodiment of the electromechanical microsystem which has a structure that is not open-through. More particularly, in the different illustrated embodiments, the electromechanical transducer11and the deformable diaphragm12is located at the front face FAV of the electromechanical microsystem1. This structure type is particularly advantageous to the extent that the rear face FAR of the electromechanical microsystem1could participate only in a passive manner, and in particular without being deformed, in the actuator and/or gripping device and/or sensor function of the electromechanical microsystem1. More particularly, the rear face FAR of an electromechanical microsystem1with a structure that is not open-through according to the invention may, in particular, form a face by which the electromechanical microsystem1could be easily mounted on a support and/or may form a face by which the electromechanical microsystem could be easily functionalised further.

Nonetheless, the invention is not limited to electromechanical microsystems with a structure that is not open-through. The invention also relates to so-called electromechanical microsystems1with an open-through structure wherein the electromechanical transducer11and the deformable diaphragm12are arranged over distinct walls of the cavity13, whether these walls are adjacent or opposite to each other.

The electromechanical transducer11comprises at least one movable portion111. The latter is configured so as to move or be moved between at least two positions. A first one of these positions is in a balance position reached and held when the electromechanical transducer11is not loaded, for example whether by an electric current powering it or by a force urging it off its balance position. A second position of the movable portion111of the electromechanical transducer11is reached when the electromechanical transducer11is loaded, for example whether by an electric current powering it or by a force urging it off its balance position. The electromechanical transducer11could be kept in either one of the above-described first and second positions, and thus have a binary behaviour, or could further be kept in any intermediate position between its balance position and its largest separation or largest deformation position, with respect to equilibrium.

In the illustrated example, when the electromechanical transducer11is not loaded, its movable portion111extends primarily in a plane parallel to the plane xy of the orthogonal reference frame xyz illustrated inFIG.1.

Preferably, the electromechanical transducer11is a piezoelectric transducer. Each electromechanical transducer11comprises at least one piezoelectric material mechanically coupled to another element, described as a support or beam. The term beam does not limit, in any manner whatsoever, the shape of this element.

In a known manner, one property of a piezoelectric material is to be stressed when subjected to an electric field. When stressed, it is deformed. Mechanically associated to the support, the piezoelectric material seizes the support with it and then displaces the latter. The area of the support that could be displaced corresponds to the movable portion111. It is this displacement property that is used to form an actuator.

Similarly, under the action of a mechanical stress, a piezoelectric material is electrically polarised. Thus, when the support is moved, it deforms the piezoelectric material which induces an electric signal. It is this property that is used to form a sensor.

Hence, from this example, yet this remains possibly true for each of the other considered embodiments of the electromechanical transducer11, it arises that the electromechanical microsystem1according to the invention could operate as an actuator and/or as a gripping device and/or as a sensor.

Even more preferably, the electromechanical transducer11is a piezoelectric transducer comprising a PZT-based (lead zirconate titanate) piezoelectric material. In this case, the movable portion111of the electromechanical transducer11could, under load, move with a more significant displacement (because of the piezoelectric coefficient d31) than with many other piezoelectric materials. Nonetheless, PZT being a ferroelectric material, such a piezoelectric transducer preferably operates in one single actuation direction (movement of its movable portion111in one direction) irrespective of the polarity of its electric power supply, while a piezoelectric transducer based on a non-ferroelectric material could preferably operate in both directions (movement of its movable portion111in two opposite directions). Alternatively or complementarily, the electromechanical transducer11may be a (non-ferroelectric) piezoelectric transducer based on a material adapted to enable its movable portion111to move in opposite directions with respect to its balance position, for example as a function of the polarity of its electric power supply. For example, such a material is a material based on aluminium nitride (AlN).

Alternatively or complementarily, the electromechanical transducer11may be or comprise a thermal transducer.

The deformable diaphragm12may be based on a polymer, and is preferably based on PDMS. The properties of the deformable diaphragm12in particular its thickness, its surface area and its shape may be configured so as to confer on the deformable diaphragm12, and more particularly on the area121of this diaphragm which is freely deformable, a targeted stretch capacity, in particular according to the targeted application.

The cavity13may feature a rotational symmetry or axisymmetry around an axis z perpendicular to the plane xy, as illustrated inFIG.2. Alternatively, the cavity may have, when viewed from the top, a polygonal shape, for example as illustrated inFIGS.17A to17Dwhich will be described in detail later on.

As illustrated in particular inFIGS.1,3A and3B, the cavity13has more to particularly walls131,132,133hermetically containing the deformable medium14. In the illustrated examples, the wall132of the cavity13forms the rear face FAR of the electromechanical microsystem1. The wall131opposite to the wall132is formed at least partially by at least one portion of the deformable diaphragm12. Thus, the wall131is deformable. Next, the wall131may sometimes be referred to as the first wall. It is located at the front face FAB of the electromechanical microsystem1. At least one lateral portion133joins the walls131and132together. It should be noted that the hermeticity of the cavity13requires the deformable diaphragm12being itself watertight, or made watertight, in particular at its free area121. Preferably, the walls132,133remain fixed when the diaphragm is deformed.

In turn, the deformable medium14could keep a substantially constant volume under the action of a change in the external pressure. In other words, it may consist of an incompressible or barely compressible medium the deformation of which preferably requires little energy. For example, it consists of a liquid.

Since at least one portion of the first wall131of the cavity13is formed by at least one portion of the deformable diaphragm12, it should be understood that any change in the external pressure exerted on the deformable medium14could be compensated by a substantially proportional deformation of the deformable diaphragm12, and more particularly of its free area12(operation as an actuator or as a gripping device) and/or by a displacement of the movable portion111of the electromechanical transducer11(operation as a sensor). When the transducer11is loaded, this compensation is more particularly related to a conversion of the change in the external pressure exerted on the deformable medium14into a stretching of the deformable diaphragm12or a relaxation of the already stretched deformable diaphragm12. It should be recalled that the deformable medium14is preferably non-compressible and that these stresses are therefore preferably imparted with a conservation of the volume of the cavity13. It should be understood that, for reasons relating to the repeatability of the actuation or of the detection of the movement allowed by the electromechanical microsystem1according to the invention, it is preferably that any deformation of the deformable diaphragm12is elastic, and not plastic, in order to guarantee the return of the deformable diaphragm12to the same minimum stretch or maximum relaxation state, once it is no longer stressed.

As illustrated in each ofFIGS.1,3A and3B, the electromechanical transducer11may form a portion of the first wall131of the cavity13. Thus, the electromechanical transducer11and the deformable diaphragm12are placed on the same side of the cavity13. Advantageously, as mentioned hereinabove, the structures having this feature are not to open-through.

In this non-limiting example, the diaphragm12has an inner face12iconfigured to be in contact with the deformable medium14and an outer face12e. The inner face12iforms at least one portion of the wall131of the cavity13. The electromechanical transducer11, more specifically the movable portion111of the latter, has an inner face11idirected opposite, and preferably in contact with, the outer face12eof the diaphragm2. The electromechanical transducer11also has an outer face11e, opposite to the inner face11i, and directed towards the outside of the electromechanical microsystem1. Alternatively, it is possible to provide for one or several intermediate layer(s) being disposed between the outer face12eof the diaphragm12and the inner face11iof the electromechanical transducer11. The electromechanical microsystem1is configured so that the movement of the movable portion111of the electromechanical transducer11causes a displacement of the diaphragm12and therefore of the wall131which encloses the medium14.

Notice that, in each ofFIGS.1to3B:the electromechanical transducer11extends over the deformable diaphragm12, andthe deformable diaphragm12separates the electromechanical transducer11from the deformable medium14.

Furthermore, the electromechanical transducer11may advantageously be secured to the deformable diaphragm12at least over an area123located outside the free area121, and more particularly substantially adjacent to the free area121, so that any movement of the movable portion111of the electromechanical transducer11induces, in particular over this area123, a stretching or a relaxation of the deformable diaphragm12. Thus, in the example illustrated inFIG.3A, when the electromechanical transducer11is loaded so as to move downwards (as illustrated inFIG.3Aby the arrow extending from the electromechanical transducer11), a decrease in the external pressure exerted on the deformable medium14is observed, which induces the stretching of the deformable diaphragm12upwards, i.e. towards the centre of the cavity13.

More particularly, the deformable medium14may comprise at least one amongst a fluid and/or a liquid. The parameters of the liquid will be adapted according to the targeted applications. Thus, it is ensured that any change in the external pressure exerted on the deformable medium14induces a substantially proportional deformation of the free area121of the deformable diaphragm12. The fluid may consist of or be based on a liquid, to such as oil, or consist of or be based on a polymer. According to one example, the fluid is based on or consists of glycerine. Thus, in addition to a substantially proportional deformation of the diaphragm12, the deformation of the electromechanical transducer11, the capability of the deformable medium14to occupy in particular the volume created by stretching of the free area121of the deformable diaphragm12opposite to the centre of the cavity13is ensured.

In the case where the electromechanical microsystem1serves as an actuator or as a gripping device, the electromechanical transducer11is loaded so as to exert a change in the external pressure on the deformable medium14and therefore induce the deformation of the deformable diaphragm12. Conversely, when the electromechanical microsystem1serves as a sensor, the deformation of the diaphragm12exerts a change in the external pressure on the deformable medium14which induces a displacement of the movable portion111of the electromechanical transducer11and consequently generates an electric signal.

As illustrated inFIGS.1to3B, the electromechanical microsystem1is such that the free area121of the deformable diaphragm12is configured to cooperate with at least one finger, generally referred to as pin122. The terms “finger” and “pin” are interchangeable. The term “pin” is not limited to parts with a constant section and all the more to cylindrical parts.

More specifically, the pin122bears on an outer face12eof the free area121. In this manner, the deformation of the free area121induces, or is induced by, a movement of the pin122. Hence, it is through the free area121of the deformable diaphragm12that the electromechanical microsystem1displaces the pin122or detects a movement of the pin122. Thus, in the case where the electromechanical microsystem1serves as an actuator or a gripping device, the activation of the electromechanical transducer11deforms the diaphragm12which displaces the pin122. Conversely, in the case where the electromechanical microsystem1serves as a sensor, a pressure or a pull imposed on the pin122, for example by an external member2, generates a deformation (compression or tension) on the diaphragm12, which displaces the electromechanical transducer11and then ultimately generates a signal that could depend on this displacement.

In the case of an actuator or of a sensor, the displacement of the object or the detection of the displacement of the object could be performed through an external member2which cooperates with the pin122.

The electromechanical microsystem1may comprise several pins122. The pins122of the same electromechanical microsystem1, and possibly the pins122of the same free area121, may have different shapes and/or dimensions. In particular, the pins may have different heights. For example, this allows adapting to the objects that are to be displaced, captured, or whose displacement is to be detected, and possibly measured.

Positioning of the Pin122on the Diaphragm12

As illustrated inFIGS.1to18B, the pin122is not fastened at the centre of the free area121of the deformable diaphragm12. The pin122is positioned in an offset manner on the free area121.

In more detail and as illustrated inFIGS.1to3Bfor example, the free area121of the diaphragm12has a central portion125and a peripheral portion126which extends from the central portion125and up to a boundary, also referred to as outer perimeter129of the free area121. In the example illustrated inFIGS.1to3B, the diaphragm12forms a disk. The central portion125also forms a disk centred on a centre124of the free area121. The peripheral portion126forms a ring surrounding the central portion125.

For example, the outer perimeter129is defined by a cowl18which holds the diaphragm12. Thus, the diaphragm12is located between the cowl18and the deformable medium14. For example, this cowl18extends in the plane xy. It has at least one opening which defines the free area121. InFIGS.1and2, it appears that the cowl18extends over the entire surface of the cavity13, projected on the plane xy, except for an opening defining the free area121of the diaphragm12and for at least one other opening123in which a portion of the electromechanical transducer11, and in particular its movable portion111, is accommodated. The cowl18has an area127(illustrated in particular inFIG.1) that separates these two openings121and123.

The pin122is configured to bear on the peripheral portion126of the free area121so that a deformation of the free area121of the diaphragm12causes an inclination of the pin122.

According to one example, the pin122has a first end122abearing, directly or ndirectly, on the outer face12eof the free area121. It also has a second end122b. According to a non-limiting embodiment, the pin122extends, between its first end122aand its second end122b, primarily according to a unique direction, referred to as longitudinal direction122c. For example, the pin122has a cylindrical or tubular shape, with a circular, ovoid or polygonal section. When the free area121is deformed, its longitudinal direction122ctilts in a plane perpendicular to the plane xy.

According to an alternative embodiment, the pin122does not have a cylindrical shape. For example, it may have a curved shape. The features and technical advantages mentioned hereinbelow remain valid if the pin122has a curved shape or others.

Inclination of the Pin122

The inclination of the pin122will now be described in detail with reference toFIGS.3A and3B.

According to a non-limiting example, in the absence of deformation:the free area121of the diaphragm12extends primarily in the plane xy, called off-deformation plane, andthe perpendicular to the tangent of the diaphragm12, at a given point of the free area121, extends according to a direction T1perpendicular to the off-deformation plane.

When the diaphragm12is deformed, the perpendicular to the tangent at a given point of the peripheral portion126of the free area121extends according to a direction Ti, inclined with respect to the direction T1, by an angle αi. The angle αi is measured in a plane perpendicular to the off-deformation plane xy. The angle αi is illustrated inFIG.3A. When deformed, the free area121of the diaphragm12generally has a shape of sphere portion, a dome or a bell from its outer perimeter129. Thus, the angle αi increases when getting away from the central portion125and approaching the outer perimeter129.

In the illustrated example, the longitudinal direction122cof the pin122extends according to a direction T2perpendicular to the tangent of the diaphragm at the point where the end122aof the pin122bears on the free area121. Thus, when the free area121is deformed, the longitudinal direction122cof the pin122tilts. InFIG.3A, when the diaphragm12is deformed, the longitudinal direction122cof the pin forms an angle α2with the off-deformation direction122c.

With this schematic example, one could clearly see that the suggested electromechanical microsystem1allows for a particularly large angular stroke for a given deformation of the free area121of the diaphragm12. Thus, the suggested solution allows considerably amplifying the movement of the end122bof the pin122.

When the pin122is connected to an object such as an external member2, and:the electromechanical microsystem1serves as an actuator, this allows amplifying the angular stroke imposed on this external member2, andthe electromechanical microsystem1serves as a sensor, this allows detecting a displacement of the external member2.

The provided electromechanical microsystem1also offers many advantages when it serves as a gripping device. Next, these advantages will be described in details with reference toFIGS.4to6E.

A displacement of the movable portion111of the electromechanical transducer11in a first direction (herein primarily according to the axis z) causes a deformation of the free area121of the diaphragm12in a second direction opposite to the first direction, and induces an inclination of the pin122in a first direction. Thus, as illustrated inFIG.3Aand with reference to the reference frame xyz, the downward displacement of the movable portion of the electromechanical transducer11causes an upward deformation of the free area121of the diaphragm12, and a leftward inclination of the longitudinal direction122cof the pin122. Conversely, as illustrated inFIG.3B, an upward displacement of the movable portion111of the electromechanical transducer11causes a downward deformation of the free area121of the diaphragm12, and induces a rightward inclination of the original direction122cof the pin122.

According to one example, and with reference toFIG.1, the pin122, more specifically its first end122a, is located at a minimum distance D122from a point128of the outer perimeter129, such that D122is smaller than k times the distance D124measured between this same point128and the centre124of the free area121.

The point128is the point of the outer perimeter129the closest to the pin122. Preferably, k is less than 0.7, preferably k is less than 0.5 and preferably k is less than 0.3. More generally, the more the pin122will be positioned proximate to the boundary of the free area121, the larger will be the inclination of the pin122for the same deformation of the diaphragm12. Thus, the amplitude of the obtained stroke is increased.

Attachment of the Pin122and of the External Member2

Without limitation, a gluing or a magnetisation of the pin122on the external member2could allow securing the pin122and the external member2together. Preferably, the energy of adhesion of the pin122on the free area121of the deformable diaphragm12is higher than that of the pin122on the external member2. The energy of adhesion of the pin122on the free area121could be obtained through technological steps that are ordinary in the microelectronics industry. Thus, since this adhesive energy could be estimated or measured, it is, for example, easy to obtain by gluing, for example using an ad hoc resin, or by magnetisation, an attachment that has a lower energy than the energy with which the pin122is secured to the deformable diaphragm12. Hence, it should be understood that the attachment between the pin122and the external member2is thus greatly modular in terms of holding force. In particular, this modularity could allow making the attachment between the pin122and the external member2removable, for example in order to enable the same electromechanical microsystem1according to the invention to e successively arranged with several external members2with each it would be secured, to and then detached.

Referring toFIGS.4to6E, an embodiment wherein the electromechanical microsystem forms a gripping device will now be described. All of the features and all of the technical effects mentioned before with reference to the embodiments ofFIGS.1to3Bare still perfectly applicable and combinable with the embodiments that have just been described with reference toFIGS.4to6E. In particular, each of the previously-mentioned embodiments could have several pins122distributed over the free area121of the diaphragm12.

The electromechanical microsystem1illustrated inFIGS.4and5comprises several pins122. Preferably, these pins122are disposed in the peripheral area126of the free area121of the diaphragm12. The electromechanical microsystem1is shaped so that the ends122bof the pins122approach each other, or depart from each other according to the deformation of the free area121.

As illustrated inFIG.6A, when the movable portion111of the electromechanical transducer11is immersed in the deformable medium14, the free area121is deformed while getting away from the deformable medium14and the free ends122bof the pins122get away from each other. It is then possible to receive or capture an object3between the pins122, as illustrated inFIG.6B.

Conversely, as illustrated inFIGS.6C to6E, when the movable portion111of the electromechanical transducer11gets away from the deformable medium14, the free area121is deformed while approaching the deformable medium14or while being immersed in the latter. The free ends122bof the pins122then approach each other.

It is then possible to grasp an object3, for example between the ends122b, as illustrated inFIG.6C. For example, this allows performing afterwards a step of treating the object3, by suitable equipment. This treatment may comprise the modification of the object3, for example by applying a coating thereon. This treatment may also comprise a step of analysing the object3, the analysis may for example be optical, biological or else chemical.

As illustrated inFIG.6D, approaching the free ends122bof the pins122also allows enclosing the object3between the pin122and the diaphragm12. Approaching their free ends122ballows forming a cage holding an object3whose minimum dimension is larger than the space between two adjacent pins122. Afterwards, it is possible to provide for displacing this object3. For example, this embodiment could find application in objects sorting.

As illustrated inFIG.6E, depending on the dimension of the pins122and on the dimension of the diaphragm12, it is possible to provide for the free ends122bcoming into contact with each other. For example, this embodiment allows grasping objects with a very small size, such as millimetric, and possibly micrometric, objects.

For these embodiments wherein it is desired to grasp/capture/enclose/release an object3between the pins122, at least two pins122are provided. Preferably, more than two pins are provided. This number of pins122is adapted according to the size of the object3to be held.

Preferably, the pins are evenly disposed over the peripheral portion126of the free area121of the diaphragm12.

In the example illustrated inFIG.5, eight pins122are disposed over the peripheral area126. These pins are disposed in pairs symmetrically with respect to the centre124of the free area121.

More generally, these pins122are disposed symmetrically with respect to an apex of the diaphragm12in its maximum deformation state. Typically, the pins122are disposed over the same diameter Ø of the free area121. This is illustrated inFIG.6.

Preferably, the number of pins122is greater than two. Preferably, it is greater than three. Preferably, the pins121are evenly disposed around the central portion125of the free area121.

Another use of the electromechanical microsystem comprising at least two pins consists in stretching a deformable object. For example, such an object may be a deformable diaphragm (distinct from the deformable diaphragm12), that would be attached on the at least two pins, so that the displacement of at least one of them, or of several ones of them in different, and possibly opposite, directions stretches the deformable diaphragm. Preferably, these at least two pins are disposed symmetrically with respect to the centre of the free area121of the deformable diaphragm12.

According to an alternative example, the pins122are not symmetrically distributed and/or are not evenly distributed over the peripheral portion126.

Referring toFIGS.7A to7C, other embodiments will now be described.

These other embodiments differ from the previous ones by the arrangement of the free area121with respect to the electromechanical transducer11. All of the other features mentioned hereinabove with reference to the previous embodiments are still perfectly applicable and combinable with the other embodiments illustrated inFIGS.7A and7B. Similarly, all of the features and numerical values mentioned hereinbelow are perfectly to applicable and combinable with the previously-descried embodiments. In particular, for simplicity, one single pin122is represented in this example. Of course, the electromechanical microsystem1may comprise more than one pin122.

Arrangement of the Free Area121

In the previous embodiments, the free area121is separated from electromechanical transducer11. Thus, a non-zero distance separates the free area121and the electromechanical transducer11. For example, this non-zero distance is materialised by an area127of the cowl18, as illustrated inFIG.1.

In the embodiments ofFIGS.7A to7C, the free area121is surrounded, at least partially, by at least one electromechanical transducer11. As illustrated inFIGS.7A to7C, the electromechanical transducer11completely surrounds the free area121. The electromechanical transducer11and the free area121could then be contiguous.

More specifically, as illustrated inFIG.7C, the electromechanical transducer11is in the form of a ring with a radial extent denoted R2and defines a circular free area121with a radius denoted R1. Note that the electromechanical transducer11is not limited to an annular shape, but could have other shapes, and in particular an oblong or oval shape, a triangular, rectangular shape, etc., defining a corresponding plurality of shapes of the free area121of the deformable diaphragm12. This illustration applies in particular for a rotational symmetry or axisymmetry. Nevertheless, a corresponding illustration for a structure symmetrical with respect to the surface of the free area121could similarly be provided which would consist in particular of the representation of three strips, adjacent in pairs, where the central strip would represent the free area121of the deformable diaphragm12and whose lateral strips would represent the movable portion of the involved electromechanical transducer(s)11.

In particular when the partial overlap of the deformable diaphragm12by the electromechanical transducer11is as illustrated inFIG.7Cand the electromechanical transducer11is a piezoelectric transducer comprising a PZT-based piezoelectric material, it is interesting that the movable portion111of the electromechanical transducer11has a urface at least twice as large, possibly at least 5 times larger, and preferably at least ten times larger than the surface of the free area121of the deformable diaphragm12. Henceforth, the deformable diaphragm12is configured so that its free area121could be deformed with an amplitude of at least 50 μm, for example substantially equal to 100 μm, and possibly of several hundred μm. In general, the deformable diaphragm12is configured so that its free area121could be deformed with an amplitude lower than 1 mm. This deformation is measured according to a direction perpendicular to the plane in which the outer face12eof the diaphragm12primarily extends at rest. Without tearing and/or without any significant wear, the electromechanical microsystem1allows for a hydraulic amplification of the action and thus offers the capability to address numerous and various applications requiring a large stroke. In this context, the electromechanical microsystem1illustrated inFIGS.7A to7Cmay be defined as an actuator with a large angular stroke.

The electromechanical microsystem1illustrated inFIG.7Aenables an inclination of the pin122to the left when the electromechanical transducer11is loaded. The electromechanical microsystem1illustrated inFIG.7Benables an inclination of the pin122to the right when the electromechanical transducer11is loaded.

Also when the partial overlap of the deformable diaphragm12by the electromechanical transducer11is as illustrated inFIG.7Cand the electromechanical transducer11is a piezoelectric transducer comprising a PZT-based piezoelectric material, but with reference toFIGS.8A and8Bdiscussed in more details hereinbelow, the electromechanical transducer11may comprise, more particularly, a support305, also referred to as beam305, and a PZT-based piezoelectric element302, the latter being configured to induce a deformation of the support305. The term beam305does not limit the shape of the support305. In this example, the beam305forms a ring. The thickness of the piezoelectric element302may be substantially equal to 0.5 μm and the thickness of the beam305may be comprised for example between a few μm and several tens μm, for example substantially equal to 5 μm.

Still when the partial overlap of the deformable diaphragm12by the electromechanical transducer11is as illustrated inFIG.7Cand the electromechanical transducer11is a piezoelectric transducer comprising a PZT-based piezoelectric material, the radius R1of the free area121of the deformable diaphragm12may be substantially equal to 100 μm and the radial extent R2of the electromechanical transducer11(typically its radius if it is circular) may be substantially equal to 350 μm. The references R1and R2are illustrated inFIG.7C. In such a configuration, the movable portion111of the electromechanical transducer11may be displaced or deflected with an amplitude for example substantially equal to 15 μm when subjected to an electric voltage for example substantially equal to 10 V for a beam305thickness substantially equal to 5 μm and a PZT thickness substantially equal to 1 μm.

Nonetheless, the invention is not limited to the different specific values given hereinabove which could be substantially adapted, depending on the targeted application, in particular to find a trade-off between the stretch factor and the expected amplitude of to deformation of the free area121of the deformable diaphragm12.

It should be noted that, in its balance position, the movable portion111of the electromechanical transducer11, and more generally the electromechanical transducer11, could be not flat, but could, on the contrary, be convex or concave at balance, which does not deprive the electrically-powered electromechanical transducer11in any manner from its capability to move or deflect, in terms of amplitude.

Note that, in particular when the electromechanical transducer11is a piezoelectric transducer, the electromechanical transducer11may advantageously be a transducer with a vibratory operation. Its resonance frequency is then preferably lower than 100 kHz, and even more preferably lower than 1 kHz. The vibratory dynamics thus obtained could allow reaching larger strokes than is the case in static operation, in particular by exploiting the related resonance phenomenon or reducing the consumption of the electromechanical microsystem for a given stroke.

Lateral Stops

The electromechanical microsystem1may further comprise one or several lateral stop(s)15forming an end-of-travel stop for the pin122or for the possible external member2supported by the pin122. The lateral stop(s)15are supported by the first wall131of the cavity13.FIGS.7A and7Billustrate such an embodiment. In this embodiment, the free area121of the diaphragm12is surrounded by the movable portion111of the electromechanical transducer11. More particularly, each lateral stop15extends opposite to the cavity13. For example, each lateral stop15extends from a non-movable portion of the electromechanical transducer11.

In the examples illustrated inFIGS.7A and7B, each lateral stop15may further have an action of holding a non-movable portion of the electromechanical transducer11in position, said non-movable portion being complementary with the movable portion111of the electromechanical transducer11. In this respect, the lateral stop(s)15coincide with the cowl18. For example, as illustrated inFIGS.8A and8B, the action of holding the non-movable portion of the electromechanical transducer11may be more particularly ensured by clamping thereof between the two lateral stops15and/or the cowl18, and in particular that one located at a central portion of the microsystem1, and the spacer306, as introduced hereinbelow, which materialises the lateral wall133of the cavity13; in this respect, the spacer306preferably extends towards the central portion of the microsystem1at least up to opposite the portion of the cowl18the closest to the central portion of the microsystem1.

With respect to this or these lateral stop(s)15, the pin122may extend, opposite to to the cavity13. The lateral stop(s)15contribute(s) in limiting the angular stroke of the pin122, and of the possible external member2associated to the pin122.

This also allows reducing the risk of pull-out of the deformable diaphragm12when affixing the external member2on the electromechanical microsystem1. Of course, for this purpose, the dimensions of the external member2are preferably configured so that the latter abuts on the lateral stops15upon fastening thereof on the pin122. Of course, the dimensions and the shapes of the stops15and of the external member2should be adapted so that the latter abut on the lateral stop15located to the right of the electromechanical microsystem.

Note herein that, depending on the extent of the external member2, the lateral stops15may also serve as a top stop limiting the approach of the external member2to the electromechanical microsystem1. This particularity may also allow inducing a detachment of the pin122and of the external member2from each other by pulling the pin122in a position lower than that possibly reached by the external member2as the matter abuts on the top of the lateral stops15. More specifically, the lateral stops15have a stop surface configured to stop the displacement of the member2. The electromechanical microsystem1is configured so that when the displacement of the member2is stopped in its displacement, according to a given direction, by the lateral stops15, the pin122could carry on its displacement, in this same direction. Thus, the pin122is detached from the member2.

Bottom Stop

As illustrated in each ofFIGS.7A and7B, the electromechanical microsystem1may further comprise one or several stop(s) at the end of travel, called bottom stops16. This or these bottom stop(s)16are supported by the wall132of the first cavity13which is opposite to the wall131formed at least partially by the deformable diaphragm12. It extends in the first cavity13towards the free area121of the deformable diaphragm12. Preferably, this bottom stop16has a shape and dimensions configured to limit the deformation of the free area121of the deformable diaphragm12so as to protect the deformable diaphragm12, and more particularly its free area121, from a possible pull-out, in particular when affixing the pin122or the external member2on the electromechanical microsystem1. Alternatively or complementarily, the bottom stop16is shaped so as to limit the contact surface between the diaphragm12and the wall132of the cavity13opposite to the free area121of the deformable diaphragm12. This allows avoiding the diaphragm12adhering and sticking to this wall132.

Embodiments of the invention that are more specific than those described to hereinabove are illustrated inFIGS.8A and8Bwherein the same references as inFIGS.7A and7Brefer to the same objects.

First of all, it is observed therein that each illustrated electromechanical transducer11comprises a support305, also referred to as beam305, and a piezoelectric material302configured to deform the support305when an electric voltage is applied thereto. The term beam305does not limit the shape of this support. In this example, the beam305forms a ring.

A comparison betweenFIGS.8A and8Bshows that the piezoelectric material302could be located on either side of the neutral fibre of the set forming the beam305. It is thanks to this alternative that a piezoelectric material whose deformation is not sensitive to the polarisation of the electric current flowing therethrough still allows deforming the beam305in either direction.

More particularly, inFIG.8A, the piezoelectric material302is located under the beam305, and therefore under the neutral fibre of the set, i.e. it is located between the beam305and the diaphragm12. When an electric current flows through the piezoelectric material302, it retracts and displaces the beam305with it. A free end305aof the beam bends downwards, displacing with it a portion of the diaphragm12connected to the beam305. In turn, by volume conservation, the free area121of the diaphragm moves upwards, thereby causing the upward displacement of the pin122and the inclination thereof, herein to the left. This case corresponds to that illustrated inFIG.7A. Preferably, another end305bof the beam305remains fixed. For example, this other end305bis secured to a fixed wall306of the cavity13and to possible lateral stops15. According to another embodiment, it is possible to provide for the end305B being fastened to a cowl of the electromechanical microsystem1. The cowl or the cavity of the electromechanical microsystem1is intended to be fastened on a support or a frame.

InFIG.8B, the piezoelectric material302is located above the beam305, i.e. the beam305is located between the piezoelectric material302and the diaphragm12. When an electric current flows through the piezoelectric material302, it retracts and displaces the beam305with it. A free end305aof the beam bends upwards, pulling with it the portion of the diaphragm12connected to the beam305. In turn, by volume conservation, the free area121of the diaphragm moves downwards, thereby causing the downward displacement of the pin122and the inclination thereof, herein to the right. This case corresponds to that illustrated inFIG.7B.

InFIGS.8A and8B, one could also observe the different heights that the pin122could have in comparison with the height of the lateral stops15. Herein again, one could observe that the lateral stops15and the bottom stops16could have different shapes, and in particular a parallelepiped shape, a frustoconical shape, a substantially pyramidal shape, etc.

InFIGS.8A and8B, one could further observe that the movable portion111of the electromechanical transducer11could be substantially defined by the extent of the piezoelectric material302with respect to the extent of the beam305.

InFIGS.8A and8B, access openings for an electrical connection of the electrodes are represented. In these examples, these openings form vias17through the cowl18. In this example, the vias17cross the entire thickness of the beam305. The thickness e305of the beam302is measured according to a direction perpendicular to the plane in which the faces12eand12iof the diaphragm12primarily extend. The thickness e305is referenced inFIGS.8A and8B.

More particularly,FIGS.8A and8Billustrate third and fourth embodiments of the invention which have been obtained through deposition and etching steps which could be considered as ordinary in the microelectronics industry. More particularly, the electromechanical microsystem1according to the third embodiment illustrated inFIG.8Ahas been obtained through the succession of steps illustrated byFIGS.9A,10A,11A,12A,13A,14A and15Aand the electromechanical microsystem1according to the fourth embodiment illustrated inFIG.8Bhas been obtained through the succession of steps illustrated byFIGS.9B,10B,11B,12B,13B,14B and15B. Thus, two manufacturing methods are illustrated each leading to one of the electromechanical microsystems1illustrated inFIGS.8A and8B.

At least one common feature of these manufacturing methods is that they comprise:a step of forming, over a substrate200, what is intended to form at least one portion of the electromechanical transducer11, thena step of depositing the deformable diaphragm12, thena step of forming at least one open cavity13over the deformable diaphragm12, thena step of filling with the deformable medium and closing the cavity13, anda step of etching the substrate200to form the front face FAV of the electromechanical microsystems illustrated inFIGS.8A and8B.

Examples of Steps of Manufacturing Methods

We successively describe each of the aforementioned manufacturing methods hereinbelow, starting with the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8A.

The first step of this method is illustrated inFIG.9A. It consists in providing a substrate200over which extends a stack of layers which may successively comprise, starting from one face of the substrate200:a first insulating layer201, for example based on silicon oxide, which may be deposited by Plasma-Enhanced Chemical Vapour Deposition (or PECVD),a layer202intended to form the beam305of the electromechanical transducer11, this layer202being for example based on amorphous silicon and may be deposited by Chemical Vapour Deposition (or CVD) at subatmospheric pressure (or LPCVD) or through the use of SOI-type (standing for Silicon On Insulator) structure,a second insulating layer203, for example based on silicon oxide and which may be deposited by PECVD,a layer204intended to form a so-called lower electrode, for example based on platinum and which may be deposited by Physical Vapour Deposition (or PVD),a layer205made of a piezoelectric material, for example based on PZT, and which may be deposited through sol-gel process, anda layer206intended to form a so-called upper electrode, for example based on platinum and which may be deposited by PVD.

The second step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Ais illustrated inFIG.10A. It comprises:etching of the layer206so as to form the upper electrode301of the electromechanical transducer11,etching of the layer205so as to form the piezoelectric elements302of the electromechanical transducer11, andetching of the layer204so as to form the lower electrode303of the electromechanical transducer11.

Note that each of these etchings may be carried out by lithography, and preferably by plasma etching, or by a wet chemical process.

The third step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Ais illustrated inFIG.11A. It comprises:the deposition of a passivation layer207, for example based on silicon oxide and/or silicon nitride, may be deposited by PECVD,opening, through the passivation layer207, of an area for resuming contact per electrode, this opening may be carried out for example by lithography, and preferably by plasma etching, or by a wet chemical process,the deposition of a layer intended to form an electric line304per electrode, the layer being for example based on gold and may be deposited by PVD, andetching of the previously deposited layer so as to form an electric line304per electrode, this etching being carried out for example by lithography, and preferably by plasma etching, or by a wet chemical process.

The fourth step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Ais illustrated inFIG.12A. It comprises the deposition of a polymer-based layer208intended to form the deformable diaphragm12. For example, this layer208is deposited by spin coating. For example, the polymer based on which the layer208is formed is based on PDMS.

The fifth step of the method for manufacturing an electromechanical microsystem1as illustrated inFIG.8Ais illustrated inFIG.13A. It comprises the formation of at least one spacer306intended to form at least one portion of said at least one lateral wall133of the cavity13. The formation of the spacer(s) may comprise rolling of a photosensitive material based on which the spacer(s) is/are formed, insulation, and then the development of the photosensitive material. Said photosensitive material may be based on a polymer, and in particular based on Siloxane. Rolling of the photosensitive material may comprise rolling of a dry film of said material.

The sixth step of the method for manufacturing an electromechanical microsystem1as illustrated inFIG.8Ais illustrated inFIG.14A. According to an optional embodiment, this step comprises the deposition of glue210at the top of each spacer306, this deposition could be carried by screen-printing or by dispensing. It comprises fastening, for example by gluing, at the top of the spacer(s) (possibly through the glue210), a second substrate211which could be structured so as to comprise at least one amongst a through vent212and a bottom stop16as described hereinabove. In an alternative embodiment, depending on the nature of the spacer, the latter could serve as glue. Upon completion of this sixth step, the cavity13is formed which is open by at least one through vent212.

The seventh step of the method for manufacturing an electromechanical microsystem1as illustrated inFIG.8Ais illustrated inFIG.15A. It comprises filling, preferably under vacuum, the cavity13with the deformable medium14as described hereinabove, for example by dispensing through the through vent212. It also comprises the tight closure of the at least one through vent212, for example by dispensing a sealing material213at the mouth of each through vent212, the sealing material213being for example based on an epoxy glue.

An additional step allows obtaining the electromechanical microsystem1as illustrated inFIG.8A. It comprises etching of the substrate200. This etching may be carried out by lithography, and preferably by plasma etching, or by a wet chemical process. Afterwards, it comprises etching of the layer202and of the insulating layers201,203so as to form at least one beam305of the electromechanical transducer11, expose a portion of the deformable diaphragm12and form all or part of the pin122of the possible lateral stops15.

Note that, following the above-described steps of manufacturing the electromechanical microsystem1as illustrated inFIG.8A, the pin122is in the form of a stack extending directly from the deformable diaphragm12opposite to first cavity13while successively presenting the material of the insulating layer201, the material forming the beam305, the material of the insulating layer203and the material forming the substrate200. It should be noticed that the pin122is not centred on the free area121.

Also note that, following the above-described steps of manufacturing the electromechanical microsystem1as illustrated inFIG.8A, each of the possible lateral stops15is in the form of a stack extending, directly or indirectly, from the deformable diaphragm12opposite to the cavity13while successively presenting the material of the insulating layer201, the material forming the beam305, the material of the insulating layer203and the material forming the substrate200.

The method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Bis described hereinbelow.

The first step of this method is illustrated inFIG.9B. It consists in providing a substrate400over which extends a stack of layers which may successively comprise, starting from one face of the substrate400:a first insulating layer401, for example based on silicon oxide, which may be deposited by PECVD-Enhanced Chemical Vapour Deposition,a layer402intended to form a so-called lower electrode, for example based on platinum and which may be deposited by PVD,a layer403made of a piezoelectric material, for example based on PZT, and which may be deposited through sol-gel process, anda layer404intended to form a so-called upper electrode, for example based on platinum and which may be deposited by PVD.

The second step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Bis illustrated inFIG.10B. It comprises:etching of the layer404so as to form the upper electrode301of the electromechanical transducer11,etching of the layer403so as to form the piezoelectric elements302of the electromechanical transducer11, andetching of the layer402so as to form the lower electrode303of the electromechanical transducer11.

Note that each of these etchings may be carried out by lithography, and preferably by plasma etching, or by a wet chemical process.

The third step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Bis illustrated inFIG.11B. It comprises:the deposition of a passivation layer405, for example based on silicon oxide and/or silicon nitride, may be deposited by PECVD,opening, through the passivation layer207, of an area for resuming contact per electrode, this opening may be carried out for example by lithography, and preferably by plasma etching, or by a wet chemical process,the deposition of a layer intended to form an electric line304per electrode, the layer being for example based on gold and may be deposited by PVD, andetching of the previously deposited layer so as to form an electric line304per electr ode, this etching being carried out for example by lithography, and preferably by plasma etching, or by a wet chemical process, thenthe deposition of a passivation layer406, for example based on silicon oxide and/or silicon nitride, may be deposited by PECVD.

The fourth step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Bis illustrated inFIG.12B. It comprises the deposition of a layer intended to form the beam305of the electromechanical transducer11, this layer being for example based on amorphous silicon and may be deposited by PVD. Afterwards, it may comprise a step of planarising the layer deposited before. Afterwards, it comprises etching of the layer deposited before so as to form at least one beam305of the electromechanical transducer11. This etching being carried out for example by lithography, and preferably by plasma etching, or by a wet chemical process.

The fifth step of the method for manufacturing the electromechanical microsystem1as illustrated inFIG.8Bis illustrated inFIG.13B. It comprises:the deposition of a polymer-based layer407intended to form the deformable diaphragm12. For example, this layer407is deposited by spin coating. For example, the polymer based on which the layer407is formed is based on PDMS, andthe formation of at least one spacer306intended to form at least one portion of said at least one lateral wall133of the cavity13.

The formation of the spacer(s)306may comprise rolling of a photosensitive material based on which the spacer(s) is/are formed, insulation, and then the development of the photosensitive material. Said photosensitive material may be based on a polymer, and in particular based on Siloxane. Rolling of the photosensitive material may comprise rolling of a dry film of said material.

The sixth step of the method for manufacturing an electromechanical microsystem1as illustrated inFIG.8Bis illustrated inFIG.14B. Where appropriate, it comprises the deposition of glue408at the top of each spacer306. According to an optional example, this deposition may be carried by screen-printing or by dispensing. It comprises gluing, at the top of the spacer(s)306(possibly through the glue408), a second substrate411which could be structured so as to comprise at least one amongst a through vent412and a bottom stop16as described hereinabove. In an alternative embodiment, depending on the nature of the spacer, the latter could serve as glue. Upon completion of this sixth step, the cavity13is formed which is open by at least one through vent412.

The seventh step of the method for manufacturing an electromechanical microsystem1as illustrated inFIG.8Bis illustrated inFIG.15B. It comprises filling, preferably under vacuum, the cavity13with the deformable medium14as described hereinabove, for example by dispensing through the at least one through vent212. It also comprises the tight closure of the at least one through vent212, for example by dispensing a sealing material213at least at the mouth of each through vent212, the sealing material213being for example based on an epoxy glue.

An additional step allows obtaining the electromechanical microsystem1as illustrated inFIG.8B. It comprises etching of the substrate200. This etching may be carried out by lithography, and preferably by plasma etching, or by a wet chemical process. Afterwards, it comprises etching of the insulating layer401, so as to expose a portion of the deformable diaphragm12and form all or part of the pin122of the possible lateral stops15.

Note that, following the above-described steps of manufacturing the electromechanical microsystem1as illustrated inFIG.8B, the pin122is in the form of a stack extending directly from the deformable diaphragm12opposite to the cavity13while successively presenting the material of the insulating layer401and the material forming the substrate200. It should be noticed that the pin122is not centred on the free area121.

Also note that, following the above-described steps of manufacturing the electromechanical microsystem1as illustrated inFIG.8B, each of the possible lateral stops15is in the form of a stack extending, directly or indirectly, from the beam305opposite to the cavity13while successively presenting the material of the insulating layer401and the material forming the substrate200.

FIG.16illustrates, in section, an embodiment corresponding to the embodiments illustrated inFIGS.1to3A.

Thus, the electromechanical transducer11does not surround the free area121of the diaphragm12. This embodiment allows having more freedom to adapt the dimension, the shape and the number of the free areas121, without the electromechanical transducer11imposing any constraint on these parameters. For example, for the same dimension of the electromechanical transducer11, this embodiment allows having a smaller extent of the free area121and therefore a larger deformation of the latter. The inclination that could be imposed to the pin122is then increased. Another benefit is to enable movements according to the axis in two opposite directions, i.e., upwards and downwards.

In this figure, all reference numerals correspond to the reference numerals ofFIGS.8A to15B.

InFIG.16, a strut19is represented. It may be in the form of a pillar or a low wall. This strut19allows supporting the diaphragm12. The deformable medium14surrounds this strut19. This strut19serves as a pillar inside the cavity13. Where appropriate, the strut19allows, for example together with the portion of the cowl18over it, stiffening a contour of the electromechanical transducer11, so that its deformation is converted, as much as possible, into a deformation of the diaphragm12. It is possible to provide for several struts19.

InFIG.16, the electromechanical transducer11is configured so as to bend downwards when it is loaded, as this is the case inFIG.9A. By replicating the structure of the electromechanical microsystem illustrated in thisFIG.16, it is perfectly possible to modify this electromechanical transducer11so that they bend upwards when it is loaded, as this is the case inFIG.9B.

To manufacture the electromechanical microsystem1illustrated inFIG.16or else its variant with a bent at the bottom of the electromechanical transducer11, it is possible to replicate and adapt without any difficulty the steps of the making processes described in detail with reference toFIGS.9A to15A and9B to15B.

Other Embodiments

Using the principles, the features and the technical effects mentioned with reference to the above-described embodiments, many variants may be considered. Some of its variants re briefly disclosed hereinbelow. All features and all technical effects mentioned in the following examples and in the above-described examples may be combined.

Relative Arrangement of the Electromechanical Transducer11and of the Free Area121of the Diaphragm12:

FIG.17Aillustrates an embodiment wherein the electromechanical transducer completely surrounds the free area121of the diaphragm12. This is also the case in the embodiments described inFIGS.8A to15B.

FIGS.1to6E and16illustrate embodiments wherein the free area121is remote from the electromechanical transducer11. This is also the case inFIGS.17B and17C. A fixed portion separates the free area121and the electromechanical transducer11. This fixed portion may be formed at least partially by the cowl18.

InFIG.17D, the electromechanical transducer11is partially surrounded by the free area121of the diaphragm12. A portion of the electromechanical transducer11is secured to a case of the electromechanical system1, for example to its cowl18. Another portion of the electromechanical transducer is surrounded by the free area121of the diaphragm12. In this example, the free area121has a “U”-like general shape around the electromechanical transducer11. Its central portion125then also has a “U”-like general shape. The outer perimeter129and the peripheral portion126surround the central portion125. Hence, pins122positioned on either side of the central portion125could be brought into contact with each other when the free area121is deformed. The pins122then define a gripping line which extends along the central portion125. In this example, this gripping also forms a “U”. For example, this allows adapting the gripping area to specific shapes of objects to be grasped, captured or held.

Shape of the Free Area121and of the Electromechanical Transducer11

The shapes of the free area121of the diaphragm12may be adapted with a great freedom according to the pursued objectives. For example, these objectives concern the amplitude of the inclination of the pins122or the shape that should be conferred on a gripping area ensured by the pins122.

InFIG.17A, the free area121has a disk-like shape. Its central portion125, its peripheral portion126and its outer perimeter129then also have a disk-like or circular shape.

InFIG.17B, the free area121has an oblong or ellipsoidal shape. Its central portion125, its peripheral portion126and its outer perimeter129then also have an to oblong or ellipsoidal shape.

InFIG.17C, the free area121has a polygonal shape, herein a square. Its central portion125, its peripheral portion126and its outer perimeter129then also have a polygonal shape.

InFIG.17D, the free area121forms an open contour. In this non-limiting example, this open contour forms a “U”-like shape.

Like the shape of the free area121, the shape of the electromechanical transducer11may be adapted as desired.

Number and Relative Arrangement of the Electromechanical Transducers

In the embodiments illustrated inFIGS.1to16, one single electromechanical transducer has been represented, for clarity.

Nevertheless, for each of these embodiments, it is possible to provide for several electromechanical transducers11for the same electromechanical microsystem1.

As illustrated in thisFIG.17B, the electromechanical transducers11a,11bmay be separated from each other, for example by a cowl portion18. Their movable portions are not then in contact.

As illustrated in thisFIG.17C, the electromechanical transducers11a,11bmay be juxtaposed. Nevertheless, they are not completely contiguous. Indeed, the piezoelectric materials of the two electromechanical transducers11a,11bshould be separated in order to be able to be individually polarised.

According to one example, the piezoelectric material of a first electromechanical transducer11bsurrounds, at least partially, and possibly completely, the piezoelectric material of one or several other electromechanical transducer(s)11a. The movable portions of these electromechanical transducers11a,11bare continuous.

Of course, the number of electromechanical transducers11may be greater than two.

The electromechanical transducers may be loaded simultaneously or successively. The amplitude of displacement of the pin122induced by each electromechanical transducer11may be identical or different.

The presence of several electromechanical transducers11in the same electromechanical microsystem1allows for various operating modes.

According to a first embodiment, the electromechanical transducers11a,11bare configured so that, under load, their movable portions induce deformations of the free area121causing an inclination of the pin(s)122in the same direction. The overall inclination of the pin(s) then results from a cumulated displacement of the movable portions of these electromechanical transducers11a,11b. This could allow limiting the addressing voltage.

Moreover, in the case where the electromechanical transducers11could be activated independently from each other or successively, the electromechanical microsystem then has a step-by-step operation. This allows controlling the inclination of the pin(s) with an even greater accuracy.

According to a second embodiment, which could be combined with the step-by-step embodiment, at least some of the electromechanical transducers11a,11bare configured so that, under load, they induce an inclination of the pin(s)122in two opposite directions. Hence, these two electromechanical transducers11a,11bare antagonist. Thus, at least one of these electromechanical transducers allows inclining the pin122according to a first direction and at least another one of these electromechanical transducers11a,11ballows inclining the pin122according to a second direction opposite to the first direction. This allows increasing even more the amplitude of the possible inclination of the pin122.

Number of Free Areas121

As illustrated inFIG.17C, it is possible to provide for several free areas121a,121bfor the same electromechanical microsystem1. For example, this may allow adapting the arrangement of the pins122to the objects to be displaced, grasped or captured. Moreover, the surface of each movable portion or movable portions of the transducers illustrated inFIG.17Cmay be at least 5 times, and possibly 10 times, and possibly 20 times, larger than the surface of the free areas121a,121bof the deformable diaphragm12.

Another aspect of the invention relates to an opto-electro-mechanical system3. A non-limiting example of such a system is illustrated inFIG.18A. The opto-electro-mechanical microsystem3illustrated in this figure comprises at least one electromechanical microsystem1as described hereinabove and at least one optical microsystem31. Preferably, the electromechanical microsystem1is mounted on a support of the opto-electro-mechanical microsystem3.

The optical microsystem31may comprise a silicon-based micro-mirror. Preferably, the pin122is not disposed at the centre of the mirror. This allows increasing even more the amplitude of the inclination of the mirror.

The optical microsystem31may be mounted directly over the at least one electromechanical microsystem1or be mounted through a frame. It may have dimensions substantially equal to 2 mm×5 mm and/or, at most, a thickness of about 700 μm.

In the case where the opto-electro-mechanical system3comprises at least two electromechanical microsystems1, each electromechanical microsystem1comprising one single pin122, the optical microsystem31may be fixed, directly or indirectly, at the upper ends of the pins. In this manner, by driving all pins in the same displacement, the optical microsystem31is displaced in a circular translational movement.

Thus, an opto-electro-mechanical microsystem3allowing for a broad capability of adaptation of its optical orientation is obtained.

In light of the previous description, it clearly appears that the invention allows obtaining an inclination of one or several pin(s)122with an angular stroke whose amplitude is large and perfectly controlled. This allows obtaining actuators, gripping devices, and possibly sensors, with a large stroke and with a great accuracy.

The invention is not limited to the previously-described embodiments and extends to all embodiments covered by the claims.

In particular, applications other than those described hereinabove may be considered. For example, the electromechanical microsystem1may be arranged in a system for self-assembling microelectronic components.

Moreover, in the case where the electromechanical microsystem1ensures a gripping function, it is possible to provide for a free end122bof the pin12allowing capturing an object of its own. For this purpose, it is possible to provide for this free end122bhaving a suitable shape or material. For example, the free end122bmay form a curved finger or hook for grasping an object. It may also have any other shape complementary with the object to grasp the latter. Furthermore, the material of the fee end122bof the pin122may participate in ensuring capture of an object on its own. For example, it is possible to provide for coating at least one portion of the pin122with an adhesive material or at least with a material that adheres with the material of the object to be captured. It is also possible to provide for the pin122comprising a magnetic or ferromagnetic material allowing capturing an object by means of a magnetic force.