Patent Application
20220197014
This invention relates to the field of electromechanical microsystems. A particularly advantageous application is the actuation or movement of objects, in particular over relatively large distances. The invention is also applicable to the field of contact detection. It can thus be used to make sensors.
In various applications, there may be a need to move microscopic or even nanoscopic objects and/or a need to sense the movements of such objects. Microsystems are available that allow this.
When these microsystems are actuators, their performance is assessed in particular with respect to the following parameters: the amplitude of the movement, the force deployed and the precision of the movement generated. When these microsystems are sensors, their performance is assessed in particular with respect to the following parameters: the ability to sense a movement over a large amplitude and the measurement accuracy.
In addition, whether the microsystems are actuators or sensors, proper performance is sought in terms of size, energy consumption and ability to operate on a frequency basis.
All known solutions have poor performance for at least one of these parameters. In general, existing microsystems do not perform well enough for a combination of these parameters.
One of the purposes of this invention is to provide an electromechanical microsystem that has improved performance over existing solutions, at least for one of the above-mentioned parameters, or that provides a better compromise regarding at least two of the above-mentioned parameters.
It is a further purpose of this invention to provide an electromechanical microsystem that allows step-by-step movement, at least upward and downward, of an associated external member or that allows sensing of a movement, at least upward and downward, of an associated external member.
The other purposes, features and benefits of this invention will become apparent from the following description and accompanying drawings. It is understood that other benefits may be incorporated.
To achieve at least one of the above purposes, according to one embodiment, an electromechanical microsystem is provided comprising:
At least one part of the deformable diaphragm forms at least one part of a first wall of the said cavity walls.
The cavity is configured to hermetically contain a deformable medium capable of maintaining a substantially-constant volume under the action of a change in external pressure exerted on the deformable medium through one of the cavity walls.
The moving part of each electromechanical transducer is configured so that its movement is a function of the said external pressure change or conversely that its movement causes an external pressure change. At least a part of the deformable diaphragm has at least an area free to deform, preferably elastically, in response to the said external pressure change.
The moving parts of the two electromechanical transducers are configured so that:
According to an optional embodiment, the electromechanical microsystem includes at least three electromechanical transducers each comprising a part moving between an equilibrium, non-loaded position and an out-of-equilibrium, loaded position:
According to one example, the free area is configured to cooperate with at least one external member so that its deformation causes, or is caused by, movement of the external member.
The proposed solution is thus able to move an external member in step mode, towards the inside or outside of the cavity, and/or to sense a movement of this member, towards the inside or outside of the cavity.
The loading of at least one, if not each, electromechanical transducer is such that its moving part moves from its equilibrium position to a given non-equilibrium position. A subsequent absence of load preferably returns the moving part of the transducer to its equilibrium position. Each transducer can thus have a binary behaviour. The microsystem thus allows step-by-step actuation, or motion sensing, of the external member, even when the behaviour of each transducer is binary. Such a microsystem operates advantageously with simplified electronics.
Each transducer may be loaded:
Alternatively or additionally, the proposed solution allows the electromechanical microsystem to sense:
The electromechanical microsystem as introduced above is thus used to:
In the microsystem according to the said optional mode, the third transducer is used to:
Whether the third transducer makes it possible to achieve an intermediate or increased deformation with respect to the deformations achieved by loading one or both the other transducers, it is understood that, through the microsystem according to the said optional mode, at least three different deformations of the free area of the diaphragm can be achieved gradually or by steps.
It should be further noted that the microsystem according to the said optional mode is thus advantageously less sensitive to a fault in one of the transducers, as the ones that remain functional continue to allow the external member to be moved upwards and/or downwards, or an upwards or downwards movement of the external member to be sensed.
The proposed solution also allows the electromechanical microsystem to form a so-called long-travel actuator, i.e. typically allowing the external member to move over a stroke length of at least 30 μm or even 100 μm (10−6 metre). Similarly, the proposed solution allows the electromechanical microsystem to form a so-called long-travel sensor, typically allowing a movement of at least 30 μm or even 100 μm (10−6 metre) to be sensed.
The electromechanical microsystem as introduced above is thus capable of moving the external member in step mode or of sensing a movement of this member, while presenting, in an easily modulable way, depending on the applications in question, a sufficient capability in terms of amplitude of movement and/or a sufficient capability in terms of deployed force and/or a capability in terms of sensing movement over an amplitude and/or with a sufficient accuracy and/or a capability to operate on a frequency basis and/or a size compatible with the applications in question, and/or a reduced energy consumption.
Another aspect of the invention relates to an opto-electromechanical system or microsystem including at least one electromechanical microsystem as introduced above and at least one optical microsystem.
Another aspect of the invention relates to a process of manufacturing an electromechanical microsystem as introduced above, comprising, or even being limited to, ordinary microelectronic deposition and etching steps. The electromechanical microsystem can in fact be manufactured by ordinary microelectronic means, which gives its manufacturer all the benefits of using these means, including a great deal of latitude in terms of sizing, adhesion energy between the different deposits, thickness of the various deposits, etching area, etc.
Based on an example, the process of manufacturing the electromechanical microsystem system includes the following steps:
The purposes, aims and features and benefits of the invention will become clearer from the detailed description of one embodiment thereof which is shown by the following accompanying drawings in which:
The drawings are given as examples and do not place any limit on the invention. They are schematic diagram representations intended to facilitate understanding of the invention and are not necessarily on the scale of practical applications. In particular, the thicknesses of the various layers, walls and members shown are not necessarily representative of reality. Also, the lateral dimensions of the piezoelectric elements, the free area of the diaphragm and/or the stops are not necessarily representative of reality, especially when considered in relation to each other.
Before beginning a detailed review of embodiments of the invention, optional features are set forth below which may optionally be used in combination or alternatively.
According to one example, two of the said at least two electromechanical transducers extend, on at least one of the cavity walls, at a distance from the free area of the deformable diaphragm. In particular, they do not extend around the free area.
According to the above particular example, the first electromechanical transducer is shaped like a disc of radius R1 and the second electromechanical transducer is shaped like a ring extending in a radial extension R2 around the disc formed by the first electromechanical transducer. The sum of the radius R1 of the disc formed by the first electromechanical transducer and the radial extension R2 of the ring formed by the second electromechanical transducer is preferably less than 900 μm, or preferably less than 600 μm, or preferably less than 300 μm.
In addition to or as an alternative to the previous example, the radial extension R2 of the ring formed by the second electromechanical transducer is about twice as small as the radius R1 of the disc formed by the first electromechanical transducer.
According to the preceding example, with the microsystem comprising a third electromechanical transducer, and with the first and second electromechanical transducers contained within the boundaries of a circular area of given radius known as the “total radius” and noted Rtot, with the said circular area comprising two parts, a first disc-shaped part centred on the said circular area and a second ring-shaped part extending around the first part, the said at least one first electromechanical transducer being contained more particularly within the first part of the circular area and the said at least one second electromechanical transducer being contained more particularly within the second part of the circular area. The first part of the circular area has a radius R2/3 substantially equal to two thirds of the total radius and the second part of the circular area has an extension E1/3 substantially equal to one third of the total radius. This ensures that, when the first and second electromechanical transducers include a PZT-based piezoelectric element, the first and second electromechanical transducers have opposing movements relative to each other.
In addition or as an alternative to the previous example, the second electromechanical transducer may be configured such that a movement of its moving part from its equilibrium position to its non-equilibrium position causes an increase in the external pressure acting on the deformable medium and the deformable diaphragm may be configured such that an increase in the external pressure acting on the deformable medium causes a deformation of the free area of the deformable diaphragm tending to move it away from the cavity (more specifically to move it away from a fixed cavity wall such as the wall opposite to the wall formed in part by the diaphragm). The electromechanical microsystem can thus be configured so as to cause a movement of the external member in a first direction, corresponding to a movement of the external member away from the cavity.
In addition to the previous feature, the first electromechanical transducer may be configured such that a movement of its moving part from its equilibrium position to its non-equilibrium position causes a deformation of the free area of the deformable diaphragm tending to move it towards the cavity (more specifically to move it towards a fixed cavity wall such as the wall opposite to the wall formed in part by the diaphragm). The electromechanical microsystem can thus be configured so as to cause a movement of the external member in a second direction, this second direction tending to move it towards the external member of the cavity (more specifically, move it towards a fixed cavity wall such as the wall opposite the wall formed in part by the diaphragm).
According to an example of the optional embodiment, the third electromechanical transducer extends over at least one of the walls of the cavity and over an annular area around the free area of the deformable diaphragm. The annular area over which the third electromechanical transducer extends may define the extension of the free area of the deformable diaphragm. The third electromechanical transducer may then be remote from the first and second electromechanical transducers and/or not be arranged around the first and second electromechanical transducers.
According to another example of the optional embodiment, the microsystem comprises, an alternative to or in addition to the third electromechanical transducer according to the previous example, at least one further ring-shaped electromechanical transducer and extending around the first disc-shaped electromechanical transducer or around the second ring-shaped electromechanical transducer. The moving part of the said at least one other electromechanical transducer, when the latter comprises a PZT-based piezoelectric element, is deformed under load, in opposite directions to each other, according to whether it is contained:
According to another example of the optional embodiment, the microsystem comprises, as an alternative to or in addition to the third electromechanical transducer and/or to the said at least one other electromechanical transducer, at least two other electromechanical transducers extending, on at least one of the walls of the cavity, at a distance from the free area of the deformable diaphragm and from the first and second electromechanical transducers and being arranged neither around the free area of the deformable diaphragm, nor around the first and second electromechanical transducers, a first of the said at least two other disc-shaped electromechanical transducers and a second of the said at least two other ring-shaped electromechanical transducers extending around the disc formed by the first of the said at least two other electromechanical transducers. The said at least two other electromechanical transducers may then have the same features as the first and second electromechanical transducers as introduced above.
According to one example, the deformable diaphragm has a plurality of free areas, which may differ in shape and/or size.
When the free area is configured to cooperate with at least one external member so that its deformation causes, or is caused by, a movement of the external member, the free area of the deformable diaphragm is configured to cooperate with the external member via a pin attached to the said free area, preferably in contact with the said free area, and more specifically in contact with an outer face of the free area.
According to the previous example, the pin may be attached in the centre of each free area of the deformable diaphragm. In this way, it is ensured that the movement of each pin is a translational movement perpendicular to the plane within which the cavity wall is contained, which is partly formed by the deformable diaphragm, when the diaphragm is not deformed.
Several pins may be provided.
Each pin may be configured to cooperate with the external member via a guide integral with the external member, so as to allow automatic positioning of the external member each the pin.
Each pin may be configured to be bonded to the external member by adhesion or magnetism, the energy with which the pin adheres to the free area of the deformable diaphragm preferably being greater than that with which the pin adheres to the external member. A connection, possibly removable, between each pin and the external member is thus provided which is largely adjustable in terms of holding force.
According to one example, each free area is free to deform, preferably elastically, in response to the said external pressure change.
The electromechanical microsystem as introduced above is preferably free of any optical element, such as a lens, in particular a variable focus lens.
At least a part of each electromechanical transducer forms a part of the cavity wall that is partially formed by the deformable diaphragm. The electromechanical microsystem according to this feature has a non-through structure, leaving the other walls of the cavity free so as to be able to carry out other functions thereon or so as to allow them to remain inert, for an increased integration capacity in particular in an opto-electromechanical microsystem.
Each electromechanical transducer can extend, directly or indirectly, over the deformable diaphragm.
According to one example, the moving part of at least one, or even of each, of the said at least two electromechanical transducers is integral with an area of the deformable diaphragm over which it extends, so that a movement of the said moving part causes a corresponding movement of the said area of the deformable diaphragm.
The deformable diaphragm is preferably configured so that its free area is capable of being deformed with an amplitude of at least 50 μm, or even of at least 100 μm, or even of at least 1000 μm, in a direction perpendicular to the plane in which it primarily extends when at rest. Without tearing and/or without significant wear, the electromechanical microsystem thus offers the ability to meet the requirements of many different applications requiring a large amount of travel, the latter being defined by the technical field concerned.
The moving part of at least one, or even each, of the said at least two electromechanical transducers may have a surface area at least twice as large as a surface area of the said free area of the deformable diaphragm. The surface area of the moving parts of the transducers is preferably at least 5 times or even 10 times or even 20 times larger than the surface area of the free area of the deformable diaphragm, or even than the surface area of the free areas of the deformable diaphragm.
The electromechanical microsystem may further comprise at least one lateral stop configured to guide the movement of an external member, when the free area is configured to cooperate with the said external member so that its deformation causes, or is caused by, a movement of the external member.
The said at least one lateral stop may be supported by the cavity wall that is partially formed by the deformable diaphragm. According to an optional example, the said lateral stop extends away from the cavity.
It is thus possible to:
According to one example, when the free area is configured to cooperate with an external member so that its deformation causes, or is caused by, a movement of the external member and that the free area of the deformable diaphragm is configured to cooperate with the external member via a pin attached to the said free area:
the pin may extend from the free area of the deformable diaphragm beyond the said at least one lateral stop or
the pin may extend from the free area of the deformable diaphragm within the at least one lateral stop.
The electromechanical microsystem according to either of the latter two alternatives provides satisfactory adaptability with a wide variety of external members and applications.
The electromechanical microsystem may further comprise at least one so-called bottom stop supported by the cavity wall opposite the free area of the deformable diaphragm, the said at least one bottom stop extending into 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, from any possibility of being torn off, in particular when the external member is transferred or stuck. Furthermore, the said at least one bottom stop may be shaped to limit the contact surface between the diaphragm and the cavity wall opposite the free area of the deformable diaphragm. This prevents the diaphragm from adhering to this wall.
At least one, and preferably each, of at least two electromechanical transducers may be a piezoelectric transducer, preferably comprising a PZT-based piezoelectric material.
If each electromechanical transducer is a piezoelectric transducer comprising a PZT-based piezoelectric transducer and the microsystem only includes two electromechanical transducers contained within the boundaries of a given circular area of given radius known as the “total radius” and noted Rtot, with the said circular area comprising two parts, a first disc-shaped part centred on the said circular area and a second ring-shaped part extending around the first part, the first electromechanical transducer is preferably not contained entirely within the first part of the circular area, but extends beyond it, or the second electromechanical transducer is preferably not contained entirely within the second part of the circular area, but extends beyond it into the first part.
At least one, and preferably each, of the electromechanical transducers may be a statically-operating transducer. Alternatively or additionally, at least one, and preferably each, of the electromechanical transducers may be a vibratory-operating transducer with at least one resonant frequency, the said at least one resonant frequency being preferably less than 100 kHz, and even more preferably less than 1 kHz.
The deformable medium hermetically contained in the cavity may comprise at least one, preferably liquid, fluid. The fluid preferably has a viscosity of about 100 cSt (1 cSt=10-6 m2/s) at ambient temperature and pressure.
According to a non-limiting embodiment example, the fluid has a compressibility of between 10−9 and 10−10 Pa−1 at 20° C., for example, of about 10−10 Pa−1 at 20° C., without these values being limiting.
The electromechanical microsystem as introduced above may further include a plurality of deformable diaphragms and/or a plurality of free areas per deformable diaphragm.
The said at least one optical microsystem of the opto-electromechanical system as introduced above may include at least one, preferably silicon-based, mirror also referred to as a micromirror.
According to one example, the opto-electromechanical system is configured such that each movement of the moving part of at least one, preferably each, electromechanical transducer causes a movement of the at least one mirror.
Alternatively or additionally, the opto-electromechanical system may include a plurality of electromechanical microsystems each having at least a free area arranged opposite a part of the same optical microsystem, such as a mirror. Preferably, the electromechanical microsystem cooperates with the mirror in an area that is not in the centre of the mirror but, for example, in a corner of the mirror. This results in an opto-electromechanical system or microsystem with a large capacity to adapt its optical orientation.
The term “electromechanical microsystem” means a system including at least one mechanical element and at least one electromechanical transducer made on a micrometric scale by microelectronic means. The mechanical element can be set in motion (actuated) by a force generated by the electromechanical transducer. The latter can be powered by electrical voltages generated with nearby electronic circuits. Alternatively or additionally, the electromechanical transducer can sense a movement of the mechanical element; the electromechanical microsystem then acts as a sensor.
A “microsystem” is a system whose external dimensions are less than 1 centimetre (10−2 metres) and preferably less than 1 millimetre (10−3 metres).
Most often, an electromechanical transducer acts as an interface between the mechanical and electrical domains. However, the term “electromechanical transducer” refers both to a piezoelectric transducer and a thermal transducer, the latter acting as an interface between the mechanical and thermal domains. An electromechanical transducer may comprise a part moving between an equilibrium, non-loaded position and an out-of-equilibrium, loaded position. When the transducer is piezoelectric, the loading is electrical. When the transducer is thermal, the loading is thermal.
When reference is made to the centre of the cavity, this centre is defined geometrically as the centre of a cavity with an undeformed free area of the deformable diaphragm.
“Below” and “above” mean “not greater than” and “not less than”, respectively. Equality is excluded by the use of the terms “strictly less than” and “strictly greater than ».
A parameter that is “substantially equal to/above/below” a given value means that the parameter is equal to/above/below the given value within plus or minus 20% or even 10% of that value. A parameter that is “substantially between” two given values means that the parameter is at least equal to the smaller given value within plus or minus 20% or 10% of that value and at most equal to the larger given value within plus or minus 20% or 10% of that value.
This schematic diagram may represent a structure with no rotational or revolutionary symmetry about an axis perpendicular and centred with respect to the surface of the deformable diaphragm as shown, as well as a structure extending, for example, in a substantially invariant manner, perpendicularly to the shown cross-sectional view and symmetrical for a first part with respect to a plane perpendicular and centred with respect to the referenced area 121 and for a second part with respect to a plane perpendicular and centred with respect to the referenced area 111a.
Before further describing the various embodiments of the invention shown in the appended figures, it should be further noted that each of these illustrations schematically represents an embodiment of the electromechanical microsystem according to the invention which has a non-through structure. More particularly, in the electromechanical transducers 11, 11a, 11b, 11c and 11d and the deformable diaphragm 12 are located on the front FAV of the electromechanical microsystem 1. This type of structure is particularly advantageous in that the rear FAR of the electromechanical microsystem 1 can participate only passively, and in particular without deforming, in the actuator and/or sensor function of the electromechanical microsystem 1. More particularly, the rear FAR of an electromechanical microsystem 1 with a non-through structure according to the invention may in particular form a face by which the electromechanical microsystem 1 may be easily fitted to a support (referenced 32 in
However, the invention is not limited to electromechanical microsystems with a non-through structure. In its broadest acceptance, the invention also relates to so-called through-structured microsystems 1 in which at least one of the transducers 11, 11a, 11b, 11c and 11d and the deformable diaphragm 12 are arranged on mutually distinct walls of the cavity 13, regardless of whether these walls are adjacent or opposite each other.
With reference to
In the example shown, when an electromechanical transducer 11, 11a, 11b is not loaded, its moving part 111, 111a, 111b extends primarily in a plane parallel to the plane xy of the orthogonal reference frame xyz shown in
At least one, and preferably each, electromechanical transducer 11, 11a, 11b is preferably a piezoelectric transducer. It is known that such a transducer converts an electrical power supply into a movement of its moving part 111, 111a, 111b from its equilibrium position to a non-equilibrium position and/or converts a movement of its moving part 111, 111a, 111b from its equilibrium position to a non-equilibrium position into an electrical signal. It is thus apparent from this example, but potentially remains true for each of the other contemplated embodiments of the electromechanical microsystem 1 according to the invention, that the latter can operate as an actuator and/or as a sensor. As an actuator, it may allow an external member 2 to be moved up and/or down, as shown in
At least one, if not each, electromechanical transducer 11, 11a, 11b is even more preferably a piezoelectric transducer comprising a PZT (Lead Titano-Zirconate) based piezoelectric material. In this case, the moving part 111, 111a, 111b of the transducer 11, 11a, 11b is able to move when subjected to a load with a more significant movement (due to the piezoelectric coefficient d31) than with many other piezoelectric materials. However, since PZT is a ferroelectric material, such piezoelectric transducers each preferentially operate in a single actuation direction (movement in a single direction of their moving part 111, 111a, 111b) regardless of the polarity of its power supply, whereas a piezoelectric transducer based on a non-ferroelectric material can preferentially operate in both directions (movement in two opposite directions of their moving part 111, 111a, 111b). Alternatively or additionally, at least one or each electromechanical transducer 11, 11a, 11b may be a piezoelectric (non-ferroelectric) transducer based on a material suitable for allowing its moving part 111, 111a, 111b to move in opposite directions relative to its equilibrium position depending on the polarity of its power supply. Such a material is, for example, an aluminium-nitride-based material (AlN).
Alternatively or additionally, at least one or each electromechanical transducer 11, 11a, 11b may be or include a thermal transducer.
The deformable diaphragm 12 may be polymer based, and is preferably PDMS (polydimethylsiloxane) based. The properties of the deformable diaphragm 12, in particular its thickness, surface area and shape, can be configured to provide the deformable diaphragm 12, and in particular an area 121 of the diaphragm that is free to deform, with an expected stretchability, in particular depending on the intended application.
The cavity 13 as shown in particular in
It should also be noted that, in order to more easily ensure the hermetic sealing of the cavity 13:
The walls 132, 133 preferably remain fixed as the diaphragm is deformed.
The deformable medium 14 is in turn capable of maintaining a substantially constant volume under the action of an external pressure change. In other words, it can be an incompressible or weakly compressible medium the deformation of which preferably requires little energy. For example, it is a liquid.
Since at least part of the wall 131 of the cavity 13 is formed by at least part of the deformable diaphragm 12, it is understood that any change in external pressure exerted on the deformable medium 14 can be compensated for by a substantially proportional deformation of the deformable diaphragm 12, and more particularly its free area 121, and/or by a movement of the moving part 111, 111a, 111b of one of the electromechanical transducers 11, 11a, 11b. When one of the transducers 11, 11a, 11b is loaded, this compensation is more particularly related to a conversion of the external pressure change exerted on the deformable medium 14 into a stretching of the deformable diaphragm 12. It is understood that, for the sake of reproducibility of the actuation or motion sensing offered by the electromechanical microsystem 1 according to the invention, it is preferable for any deformation of the deformable diaphragm 12 to be elastic, and not plastic, to ensure that the deformable diaphragm 12 returns to the same state of least stretch, or maximum relaxation, whenever it is no longer loaded.
The deformable medium 14 may more particularly include at least one, preferably liquid, fluid. The parameters of the liquid will be adjusted according to the intended applications. This ensures that any change in external pressure exerted on the deformable medium 14 causes a substantially proportional deformation of the free area 121 of the deformable diaphragm 12. The fluid may be a liquid or liquid based, such as oil, or may be a polymer or polymer based. According to one example, the fluid is based on or consists of glycerine. In this way, in addition to a substantially proportional deformation of the diaphragm 12, the deformable medium 14 is able to occupy, in particular, the volume created by stretching the free area 121 of the deformable diaphragm 12 opposite the centre of the cavity 13.
It is understood from the above that the electromechanical microsystem 1 is configured so that each movement of an electromechanical transducer 11, 11a, 11b depends on a change in the external pressure exerted on the deformable medium 14, in order to provide the actuator function of the electromechanical microsystem 1, and conversely, in order to provide the sensor function of the electromechanical microsystem 1. More particularly, when the electromechanical microsystem 1 acts as an actuator, at least one of the electromechanical transducers 11, 11a, 11b is loaded so as to exert an external pressure change on the deformable medium 14 and thereby cause the deformation of the deformable diaphragm 12. Conversely, when the electromechanical microsystem 1 acts as a sensor, the deforming of the diaphragm 12 exerts an external pressure change on the deformable medium 14 which causes a movement of the moving part 111, 111a, 111b of one of the electromechanical transducers 11, 11a, 11b.
As shown in
More particularly, the cooperation between the free area 121 of the deformable diaphragm 12 and the external member 2 may be achieved via a finger, also referred to as a pin 122, which is attached to the free area 121. The terms “finger” and “pin” may be interchanged. The term “pin” is not limited to parts with a constant cross-section, let alone cylindrical parts.
As shown in
Additionally or alternatively, the external member 2 may be structured to include a guide through which the external member 2 cooperates with the pin 122. This guide can also help to prevent the pin 122 from tilting when it moves. It will be seen later that the limitations thus achieved in terms of lateral deflection of the pin 122 may be further enhanced by the provision of at least one lateral stop 15 extending from a part of the wall 131 located outside the free area 121 of the deformable diaphragm 12.
In a non-limiting way, the pin 122 being bonded to or magnetized to the external member 2 may allow the pin 122 and the external member 2 to be made integral with each other. The energy with which the pin 122 adheres to the free area 121 of the deformable diaphragm 12 is preferably greater than that with which the pin 122 adheres to the outer member 2. The energy with which the pin 122 adheres to the free area 121 can be a result of ordinary technological steps in the field of microelectronics. Since this adhesion energy can thus be estimated or measured, it is easy to obtain by bonding, for example using an ad hoc resin or through magnetisation, for example, adhesion that is of lower energy than the energy with which the pin 122 adheres to the deformable diaphragm 12. It is thus understood that the connection between the pin 122 and the external member 2 can thus be largely adjusted in terms of holding force. This modularity may make it possible, in particular, to make the connection between the pin 122 and the external member 2 removable, for example to allow the same electromechanical microsystem 1, according to the invention, to be arranged successively with several external members 2 with each of which it would be connected and then disconnected.
As shown in
In this non-limiting example, the diaphragm 12 has an inner face 12i configured to be in contact with the deformable medium 14 and an outer face 12e. The inner face 12i forms part of the first wall 131 of the cavity 13. In order to easily ensure the sealing of the cavity 13, the inner face 12i of the deformable diaphragm 12 forms the entire first wall 131 of the cavity 13. Each electromechanical transducer 11, 11a, 11b, more specifically the moving part 111, 111a, 111b thereof, has an inner face 11i facing, and preferably in contact with, the outer face 12e of the diaphragm 12. Each electromechanical transducer 11a, 11b also has an outer face 11e, opposite the inner face 11i, and facing the outside of the electromechanical microsystem 1. In order to easily ensure the hermetic sealing of the cavity 13, the inner face 11i of each electromechanical transducer 11, 11a, 11b is preferably entirely in contact with the outer face 12e of the diaphragm 12. One or more intermediate layers may be provided between the outer face 12e of the diaphragm 12 and the inner face 11i of each transducer 11, 11a, 11b. The electromechanical microsystem 1 is configured such that the movement of the moving part 111, 111a, 111b of each electromechanical transducer 11, 11a, 11b causes a deformation of the diaphragm 12 and thus of the first wall 131 which encloses the medium 14.
Note that in
In addition, each electromechanical transducer 11, 11a and 11b may advantageously be integral with the deformable diaphragm 12. In particular, as the electromechanical transducer 11a and 11b do not define the free area 121 of the deformable diaphragm 12, they can advantageously be integral with the deformable diaphragm 12 over an area 123ab located outside the free area 121, and more particularly over an area 123ab distant from the free area 121, so that any movement of the moving part 111a, 111b of each of these transducers 11a, 11b causes, in particular in this area 123ab, the deformable diaphragm 12 to be stretched or relaxed. Thus, in the example shown in
Still, in the example shown in
According to the example shown in
It should be noted, that in its equilibrium position, the moving part 111, 111a, 111b of each electromechanical transducer 11, 11a, 11b, and more generally one, or even each, transducer, cannot be flat, but may instead exhibit a deflection, known as the equilibrium deflection, which does not detract in any way, in terms of amplitude, from the movement or deflection capability of the electrically supplied transducer 11, 11a, 11b.
With reference to
The cover 18 extends in the xy-plane, for example. It has at least one opening that defines the area in which the moving part 111 of the third electromechanical transducer 11 extends and at least one opening in which the moving parts of the first and second electromechanical transducers 11a and 11b extend. In the area around the free area 121 of the deformable diaphragm 12, the cover 18 not only has the above-mentioned holding role, but may also act as lateral stops 15 (see below).
As shown in
In particular, when the partial overlap of the deformable diaphragm 12 by the third electromechanical transducer 11 is as shown in
In general, the deformable diaphragm 12 is preferably configured such that its free area 121 is capable of being deformed with an amplitude of less than 1 mm.
The deformation amplitude of the free area 121 is measured along a direction perpendicular to the plane in which the outer face 12e of the diaphragm 12 at rest mainly extends.
Also when the partial overlap of the deformable diaphragm 12 by the electromechanical transducer 11 is as shown in
Still when the partial overlap of the deformable diaphragm 12 by the third electromechanical transducer 11 is as shown in
The radius R1 of the disc 11a is, for example, between a few tens and a few hundreds of microns, and is typically equal to 200 microns. The radial extension R2 of the area extending around the disc 11a is, for example, between a few tens and a few hundreds of microns, and is typically equal to 100 microns. When the first and second transducers 11a and 11b are spaced apart, the radial extension of this spacing is, for example, between 1 and 10 microns, and is typically equal to 5 microns. It is understood here that as each of the first and second electromechanical transducers 11a and 11b has its own moving part 111a, 111b, the moving part of one of the two transducers 11a and 11b can be loaded independently from, and in particular alternately to, the moving part of the other of the two transducers 11a and 11b.
In a configuration in which the first and second electromechanical transducers 11a and 11b are contained within the boundaries of a circular area of given radius known as the “total radius” and noted Rtot, with the said circular area comprising two parts, a first disc-shaped part centred on the said circular area and a second ring-shaped part extending around the first part, the said at least one first electromechanical transducer 11a may be contained within the first part of the circular area and the said at least one second electromechanical transducer 11b may be contained within the second part of the circular area. Then, if the first part of the circular area has a radius R2/3 substantially equal to two thirds of the total radius and if the second part of the circular area has an extension E1/3 substantially equal to one third of the total radius, the deformation of the moving part 111a of the first electromechanical transducer 11a then opposes, and more particularly in an opposite direction in the direction of the z-axis, the deformation of the moving part 111b of the second electromechanical transducer 11b. It is then possible, even when each of the two transducers 11a and 11b includes a PZT-based piezoelectric transducer, to alternately cause, depending on which of the two transducers 11a and 11b is loaded, a movement away from and towards the free area 121 of the diaphragm 12 with respect to at least one wall among the walls 132, 133 of the cavity 13. For example, the first electromechanical transducer 11a is configured to move upwards, i.e. away from the centre of the cavity 13, when loaded, and the second electromechanical transducer 11b is configured to move downwards, i.e. towards the centre of the cavity 13, when loaded.
In addition, it is advantageous for the radial extension R2 of the second transducer 11b to be about half the radius R1 of the first transducer 11a. In such a configuration, the moving part 111a of the first transducer 11a and the moving part 111b of the second transducer 11b can be moved or deflected with a substantially equal amplitude, when the transducers are alternately and substantially equally loaded.
Also when the partial overlap of the deformable diaphragm 12 by the two transducers 11a and 11b is as shown in
Each of the first and second electromechanical transducers 11a and 11b more particularly consist of a member comprising a beam 305 and a PZT-based piezoelectric element 302, the latter being configured to cause a deflection of the beam 305. The thickness of the piezoelectric element 302 may be substantially equal to 0.5 μm and the thickness of the beam 305 is, for example, between a few microns and several tens of microns, for example, 5 μm. In such a configuration, when R1 is equal to 200 microns and R2 is equal to 100 microns, the amplitude of movement of the moving parts 111a, 111b of the transducers 11a and 11b may reach a value equal to a few tens of microns, in particular when a voltage of a few tens of volts is applied across one or other of the transducers 11a and 11b.
It is immediately apparent from
It is again immediately apparent from
Without tearing and/or significant wear, the electromechanical microsystem 1 allows for hydraulic amplification of the action and thus offers the ability to meet the requirements of many different applications requiring a large amount of travel. In this context, the electromechanical microsystem 1 shown in
It is again apparent from
The third and fourth transducers 11c and 11d are, in the example shown in
The transducers 11a, 11b, 11c and 11d according to the second embodiment of the invention are preferably concentric. Two radially successive electromechanical transducers 11a, 11b, 11c and 11d are either spaced apart or adjacent to each other. Their moving parts are, for example, separated from each other by a distance noted e in
In the embodiment shown in
The deformation of the moving parts 111a and 111c of the transducers 11a and 11c can advantageously oppose the deformation of the moving parts 111b and 111d of the transducers 11b and 11d. For this purpose, the transducers 11a and 11c may be contained within a disc of radius less than ⅔ of the total radial extension R1+R3+R2+R4 of the transducers.
Alternatively, the transducer 11a may be contained within a first circular area of radius less than two-thirds of the total radial extension R1+R3+R2+R4 of the transducers and the other three transducers 11b, 11c and 11d may extend beyond the first circular area over an annular radial extension area of less than one-third of the total radial extension R1+R3+R2+R4 of the transducers.
Another alternative involves considering that the three transducers 11a, 11b and 11c are located in the first circular area with a radius of less than two thirds of the total radial extension R1+R3+R2+R4 and that the fourth electromechanical transducer 11d is located in the annular area with a radial extension of less than one third of the total radial extension R1+R3+R2+R4 of the transducers.
As already discussed above with reference to the embodiment shown in
It is understood that an additional advantage, with respect to the first embodiment schematically shown in
In such a configuration, when the transducers 11a and 11c are contained within a disc of radius less than ⅔ of the total radial extension R1+R3+R2+R4 of the transducers:
It is understood that the configuration shown in
It should be noted here that the electromechanical microsystem 1 according to the second embodiment is not limited to the example shown comprising two additional transducers 11c and 11d (each having an annular shape) in relation to the first embodiment. More particularly, the second embodiment extends to a case comprising a single additional annular-shaped transducer and a case comprising more than two additional annular-shaped transducers.
A third embodiment is shown in
A fourth embodiment is shown in
It is understood from the example shown in
It should be noted that in
It should be noted that the scope of the appended claims does not preclude a microsystem combining different sets of the aforementioned transducers 11, 11a, 11b, 11c and 11d. Thus, and by way of non-limiting examples, the embodiment shown in
It should be noted that, regardless of which of the embodiments of the electromechanical microsystem according to the invention described above is used, each electromechanical transducer 11, 11a, 11b, 11c, 11d is not limited to an annular or disc shape, respectively, but may take on other shapes, and in particular a hollow or solid oblong, oval, triangular, rectangular, etc. shape, depending on the transducer considered. The illustrations in
In particular, when the partial overlap of the deformable diaphragm 12 by the electromechanical transducers is as shown in
As already mentioned above, each electromechanical transducer 11, 11a, 11b, 11c, 11d more particularly consists of an element comprising a beam 305 and a PZT-based piezoelectric element 302, the latter being configured to cause a deflection of the beam 305. The thickness of the piezoelectric element 302 may be substantially equal to 0.5 μm and the thickness of the beam 305 is preferably between a few microns and several tens of microns, for example, substantially equal to 5 μm.
However, the invention is not limited to the various specific values given above, which can be largely adjusted, depending on the intended application, in particular to obtain a compromise between stretch factor and expected deformation amplitude of the free area 121 of the deformable diaphragm 12.
Note that, in particular when one of the electromechanical transducers is a piezoelectric transducer, it can advantageously be a transducer with a vibratory operation. Its resonant frequency is then preferably lower than 100 kHz, and even more preferably lower than 1 kHz. The vibratory dynamics thus obtained can make it possible to achieve greater deflections than in static operation, in particular by using the related resonance phenomenon, or to reduce the consumption of the electromechanical microsystem for a given deflection.
As already mentioned above, the electromechanical microsystem 1 may further comprise one or more lateral stops 15 supported by the wall 131 of the cavity 13. Each side stop 15 extends more particularly away from the cavity 13.
Relative to the side stops 15, the pin 122 may extend beyond or within the cavity 13.
The lateral stops 15 may also be configured to allow the external member 2 to be guided and self-positioned on the electromechanical microsystem 1. It further contributes to limiting, or even eliminating, the risk of the deformable diaphragm 12 being torn off when the external member 2 is transferred to the electromechanical microsystem 1. It should be noted here that, depending on the extension of the external member 2, the side stops 15 can also act as an upper stop limiting the movement of the external member 2 towards the electromechanical microsystem 1. When the free area is configured to cooperate with at least one external member so that its deformation causes, or is caused by, a movement of the external member, this feature may also cause the pin 122 and the external member 2 to disengage from each other by pulling the pin 122 to a lower position than the one that the external member 2 may have reached due to the fact that the latter abuts against the top of the lateral stops 15. More specifically, the side stops 15 then have a stop surface area configured to stop the movement of the member 12. The electromechanical microsystem 1 is configured so that, when the movement of the member 12 is stopped, in a given direction, by the side stops 15, the pin 122 can continue its movement, in the same direction. The pin 122 thus disengages from the member 12.
As shown in
A more specific embodiment of the invention than the one described above with reference to
First, it is observed that each electromechanical transducer 11, 11a, 11b shown includes a beam 305 and a piezoelectric material 302 configured to deform the beam 305 when it is supplied with electrical power. More particularly, the first and second transducers 11a and 11b share a common beam 305, with their piezoelectric elements 302 being arranged opposite different areas of the beam 305.
It is also noted that the piezoelectric elements 302 of the transducers 11, 11a and 11b are all located on the same side of the beam 305 or equivalently of the neutral fibre of these transducers. As mentioned above, this embodiment, which is in principle consistent with that shown in
It is understood that the piezoelectric element 302 of the first transducer 11a is designed to primarily deform the beam 305 in a central area of the area 123ab into which the piezoelectric elements of the first and second transducers 11a and 11b extend, whereas the piezoelectric element 302 of the second transducer 11b is designed to primarily deform the beam 305 in an area peripheral to the said central area.
It is further apparent from
It should also be noted that each cover 18 and each side stop 15 discussed above are also formed by carrying out the technological steps, the result of which is shown in
Another aspect of the invention relates to an opto-electromechanical system 3 as shown in
It should also be noted that, because of the possibility offered by each electromechanical microsystem 1, according to the invention, of acting on the optical microsystem 31 by moving it upwards and downwards in step mode, the achievable angles of tilt of the optical microsystem 31 are thus advantageously increased by an amplitude, relative to electromechanical microsystems that do not allow operation in step mode. Better control at each instant and better reproducibility of the tilt angle of the optical microsystem 31 are achieved since each potentially achieved tilt angle belongs to a predetermined set of tilt angles, due to the potentially binary operation of the transducers used.
It should be further noted that it may be advantageous, in the context of the incorporation of an electromechanical microsystem 1 according to the first aspect of the invention with an opto-electromechanical microsystem 3 according to the second aspect of the invention, for the electromechanical microsystem 1 used to be chosen from the ones described above (and envisaged below) which do not include a third transducer 11. Indeed, due to the decentring of the free area 121 of the deformable diaphragm 12 relative to the area 123ab over which the first and second electromechanical transducers 11a and 11b extend, it is then possible to arrange the free areas 121 of the four electromechanical microsystems 1 as close as possible to the corners or centre of the optical microsystem 31, and in particular potentially closer than would be possible with electromechanical microsystems in each of which the free area 121 of the deformable diaphragm 12 would be centred on the area 123 of a third electromechanical transducer 11 as schematically illustrated in
The invention is not limited to the previously described embodiments and extends to all embodiments covered by the claims.
In particular, the embodiments described above mostly include at least three electromechanical transducers. However, the microsystem 1 according to the first aspect of the invention may only include two electromechanical transducers.
A first schematic representation of an example of such a microsystem 1 is obtained by considering, in
A second schematic representation of an example of a microsystem 1 according to the first aspect of the invention comprising two electromechanical transducers is obtained by considering, in
A third schematic representation of an example of a microsystem 1 according to the first aspect of the invention comprising two electromechanical transducers is provided considering, in
In addition, other applications than those described above are possible. For example, the electromechanical microsystem 1 can be arranged in a micropump, or even in a micropump array system, or in a haptic system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 13826 | Dec 2020 | FR | national |
