Acoustic tweezers

Abstract

Electroacoustic device that includes a body, an electrode to be electrically powered, named hot electrode, and an electrode to be electrically grounded, named ground electrode. The body includes a piezoelectric part or the electroacoustic device further including a piezoelectric part different from the body. The hot electrode includes a hot track spiraling around a spiral axis. The radial step between two consecutive coils of the hot track decreasing radially from the spiral axis. The hot electrode and the ground electrode are arranged on the piezoelectric part such as to define a wave transducer configured to generate a focalised ultrasonic vortex propagating in the body and/or, when a fluid medium is acoustically coupled with the electroacoustic device, in the fluid medium.

Claims

1. Electroacoustic device comprising a body, an electrode to be electrically powered, named hot electrode, and an electrode to be electrically grounded, named ground electrode, the body comprising a piezoelectric part or the electroacoustic device further comprising a piezoelectric part different from the body, the hot electrode comprising a hot track spiraling around a spiral axis, the radial step between two consecutive coils of the hot track decreasing radially from the spiral axis, the hot electrode and the ground electrode being arranged on the piezoelectric part such as to define a wave transducer configured to generate a focalised ultrasonic vortex propagating in the body and/or, when a fluid medium is acoustically coupled with the electroacoustic device, in said fluid medium.

2. Electroacoustic device according to claim 1, wherein the wave transducer is configured for the body to be located in between the hot electrode and a focal locus of the focalised ultrasonic vortex.

3. Electroacoustic device according to claim 1, wherein the ground electrode is provided on the face of the piezoelectric part wherein the hot track is provided.

4. Electroacoustic device according to claim 3, wherein the ground track is provided on the face of the piezoelectric part opposite to the face wherein the hot track is provided.

5. Electroacoustic device according to claim 1, wherein the piezoelectric part is different from the body, the body being arranged on a face of the wave transducer and is acoustically coupled with the wave transducer.

6. Electroacoustic device according to claim 1, wherein the ground electrode comprises at least one ground track spiraling around the spiral axis.

7. Electroacoustic device according to claim 1, comprising a plurality of at least N hot electrodes, with N being at least 2 and at least one electrode of the plurality comprising a hot track spiraling around the spiral axis.

8. Electroacoustic device according to claim 7, wherein the ground track is provided between two adjacent hot tracks.

9. Electroacoustic device according to claim 7, wherein the ground electrode comprises at least M ground tracks, with M being at least 2, each ground track defining at least one spiral coil, the radial step between two adjacent coils of two adjacent ground tracks decreasing from the spiral axis.

10. Electroacoustic device according to claim 7, further comprising a control unit for electrically powering the hot electrodes and being configured for controlling each electrode pair consisting of a hot electrode and the ground electrode, such that said each pair generates a volume acoustic wave in the piezoelectric part, the phase shift between the volume acoustic waves generated by two adjacent electrodes pairs being of 2π/N.

11. Electroacoustic device according to claim 7, wherein at least two hot electrodes each comprise a single hot track defining at least one spiral coil, the step distance between two adjacent coils of the two respective adjacent hot tracks decreasing from the spiral axis.

12. Electroacoustic device according to claim 7, wherein two adjacent hot tracks are provided on the same face of the piezoelectric part or two adjacent hot tracks are provided on two opposite faces of the piezoelectric part.

13. Electroacoustic device according to claim 7, wherein the ground electrode comprises a ground coating extending over a face of the piezoelectric part and superimposed with the hot track of each hot electrode of the plurality of N hot electrodes.

14. Electroacoustic device according to claim 13, wherein the ground electrode is superimposed with at least two adjacent hot tracks of two adjacent electrodes of the plurality of hot electrodes, said adjacent hot tracks being provided on the same face of the piezoelectric part, and with a gap separating said two adjacent hot tracks.

15. Electroacoustic device according to claim 7, wherein each ground track is completely superimposed with the hot track of a respective hot electrode of the plurality of hot electrodes, and vice-versa.

16. Electroacoustic device according to claim 7, wherein the piezoelectric part is provided in between the gap between the hot tracks of two adjacent hot electrodes.

17. Electroacoustic device according to claim 1, wherein the body comprises in the piezoelectric part, the hot electrode and the ground electrode comprising respective hot track and ground track provided on a same face of the body, both the hot track and ground track spiraling around the spiral axis Z.

18. Electroacoustic device according to claim 1 wherein the hot track draws a line along a polar coordinate R(θ), from a center C, said polar coordinate being obtained by solving equation (i) $\begin{array}{cc}{\psi }_0={\mu }^{\left(N\right)}\left(\stackrel{\_}{\psi }+\pi ,-{\stackrel{\_}{\sigma }}_N\right)-\alpha \left(\stackrel{\_}{\psi }+\pi ,-{\stackrel{\_}{\sigma }}_N\right)+\omega s_{\mathrm{ref}}h\left(\theta ,\phi ,\stackrel{\_}{\psi },{\stackrel{\_}{\sigma }}_N\right)\sqrt{R^2+z^{{\left(N\right)}^2}}+\frac{\pi }{4}\zeta & \left(i\right)\end{array}$ wherein $\begin{array}{cc}\tan \phi =-\frac{R}{z^{\left(N\right)}},& \left(\mathrm{ii}\right)\end{array}$ with z(N) being the distance along axis Z between the face of the piezoelectric part on which the hot track is provided and the focal locus 2 of the vortex ψ.sub.0.sup.(R) is the phase of the electric potential coupled to the vortex by piezoelectric effect at height along axis Z on the plane where the hot track is provided, the equation (i) being solved when this phase is constant along an electrode, μ.sup.(N)(ψ+π,−σ.sub.N) is the phase of the angular spectrum at the focal locus of the vortex with ψ and σ.sub.N being beam stirring angles, preferably μ.sup.(N)=−mψ with m being a positive integer number, α(ψ+π,−σ.sub.N) is the piezoelectric coupling coefficient, ω is the wave pulsation of the vortex, S.sub.ref is a reference speed, h(θ,φ,ψ,σ.sub.N) is the dimensionless fly time of the wave, which reads $\begin{array}{cc}h=\frac{1}{s_{\mathrm{ref}}}\left(s_r\left(\psi ,{\sigma }_0\left({\sigma }_N\right)\right)\sin \phi \cos \left(\psi -\theta \right)+\cos \phi \underset{n=0}{\overset{N-1}{.Math.}}{s}_z^{\left(n\right)}\left(\psi ,{\sigma }_n\left({\sigma }_N\right)\right){\gamma }_n^{n+1}\right)& \left(\mathrm{iii}\right)\end{array}$ where ${\gamma }_n^{n+1}=\frac{z^{\left(n+1\right)}-z^{\left(n\right)}}{z^{\left(N\right)}},$ with Z.sup.(N) being the distance between the first interface of a material n stacked onto the piezoelectric part and the plane containing the hot track, in case n medium are stacked onto the piezoelectric part, n=0 corresponding to the plane containing the hot track, s.sub.r(ψ,σ.sub.0(σ.sub.N)) and s.sub.z.sup.(n)(ψ,σ.sub.n(σ.sub.N)) components of the wave slowness vector in the cylindrical coordinate system with the propagation direction being referred by angles ψ and σ; s.sub.r(ψ,σ.sub.0(σ.sub.N)) is independent of the material due to propagation laws, and is for instance chosen as being equal to s.sub.r.sup.(0)(ψ,σ.sub.0(σ.sub.N)) which is the radial component of the wave slowness in the piezoelectric part; each wave, which forms the vortex by interference of multiples waves, propagates in medium n along a direction expressed with angles ψ and σ.sub.n being the azimuthal and inclination angles respectively from axis Z measured from the focal locus of the vortex, and σ.sup.0 being the refraction angle of the material constitutive of the piezoelectric part; angle ψ is independent from the material wherein the wave propagates while the refraction angle σ.sub.n is obtained by solving the Snell-Descartes relationship
s.sup.(n)(ψ,σ.sub.n)sin σ.sub.n=s.sup.(N)(ψ,σ.sub.N)sin σ.sub.N,  (iv); a man skilled in the art knows how to compute the slownesses from the material's properties for any kind of wave using solid acoustics methods well known in the art; S.sub.Z.sup.(n) is given by the following dispersion relationship
s.sub.z.sup.(n)(ψ,σ.sub.n)=√{square root over (s.sup.(n)(ψ,σ.sub.n).sup.2−s.sub.r(ψ,σ.sub.0(σ.sub.N)).sup.2)}  (v), and $\frac{\pi }{4}\zeta$ is the Gouy phase of the vortex, wherein ζ is the signature, i.e. the difference between the number of positive eigenvalues and the number of negative eigenvalues of the Hessian matrix A of function h evaluated at ψ, σ.sub.N $\begin{array}{cc}A=\left(\begin{array}{cc}\frac{1}{{\sin }^2{\sigma }_N}\frac{{\partial }^2}{\partial {\psi }^2}h& \frac{1}{\sin {\sigma }_N}\frac{{\partial }^2}{\partial \psi \partial \sigma }h\\ \frac{1}{\sin {\sigma }_N}\frac{{\partial }^2}{\partial \psi \partial \sigma }h& \frac{{\partial }^2}{\partial {\sigma }^2}h\end{array}\right){|}_{\stackrel{\_}{\psi },{\stackrel{\_}{\sigma }}_N}& \left(\mathrm{vi}\right)\end{array}$ To solve equation (i), once the 4 variable function h(θ,φ,ψ,σ.sub.N) is obtained, the beam stirring angles ψ, σ.sub.N are obtained, using numerical well known methods, as solutions of the following differential equation systems $\begin{array}{cc}\{\begin{array}{c}\frac{\partial }{\partial {\sigma }_N}h=0,\\ \frac{1}{\sin {\sigma }_N}\frac{\partial }{\partial \psi }h=0.\end{array}& \left(\mathrm{vii}\right)\end{array}$

19. Electroacoustic device according claim 1, wherein the stack consists of a piezoelectric part and a body, the body being thicker than the piezoelectric part, and made of a an isotropic material, and the hot track draws a line along a polar coordinate R(θ), from a center C which equation is $\begin{array}{cc}R\left(\theta \right)=\sqrt{{\left(\frac{{\psi }_0+m\theta }{\omega s}\right)}^2-z^{{\left(N\right)}^2}}& \left(\mathrm{viii}\right)\end{array}$ with m being an integer, s being the slowness of the vortex in the body, ψ.sub.0 being a constant, ω being the pulsation of the vortex, and z.sup.(N) being the distance along axis Z between the face of the piezoelectric part on which the hot track is provided and the focal locus of the vortex.

20. Electroacoustic device according to claim 1, wherein the width of the hot track radially varies from the center.

21. Electroacoustic device according to claim 1, comprising a support to which the wave transducer is attached, the support comprising a handle adapted to be gripped by a hand of a user or by a robotic arm, or comprising a stage and a base, the stage being adapted to move along at least one directions relative to the base.

22. Electroacoustic device according to claim 21, the electroacoustic device being in the form of a pen or the displacement of the stage being actuated by means of a motor or manually.

23. Method for manipulating a fluid medium or at least one object being embedded in the fluid medium, the method comprising the successive steps consisting in: generating a focalised ultrasonic vortex with the electroacoustic device according to claim 1, positioning the fluid medium such that the focal locus of the focalised ultrasonic vortex is provided in the bulk of the liquid medium, such as to generate an acoustic trap or an acoustic streaming to which the fluid medium and/or the object are submitted.

24. Method according to claim 23, comprising, manipulating the object through displacement of the wave transducer of the electroacoustic device relative to the fluid medium or manipulating the fluid by means of acoustic streaming.

Description

(1) The invention may be better understood from a reading of the detailed description that follows, with reference to exemplary and non-limiting embodiments thereof, and by the examination of the appended drawing, in which:

(2) FIG. 1 illustrates, from a perspective view, an electroacoustic device according to a first embodiment of the invention;

(3) FIGS. 2 and 3 illustrate views along the spiral axis of a face of the wave transducer of the electroacoustic device of FIG. 1 and its opposite face respectively,

(4) FIG. 4 illustrates a side view of an axial cross section of the electroacoustic device of FIG. 1,

(5) FIG. 5 illustrates a side view of an axial cross section of the electroacoustic device of FIG. 1 implemented for manipulating an object,

(6) FIG. 6 illustrates a side view of an axial cross section of a variant of the electroacoustic device of FIG. 1,

(7) FIGS. 7 and 8 illustrate respectively a face view and a side view of an axial cross section of a variant of the electroacoustic device of FIG. 1,

(8) FIG. 9 illustrates a side view of an axial cross section of another variant of the device of FIG. 1,

(9) FIG. 10 illustrates from a perspective view an electroacoustic device according to a second embodiment of the invention,

(10) FIG. 11 illustrates a side view of an axial cross section of the electroacoustic device of FIG. 10 for manipulating an object,

(11) FIG. 12 illustrates the definition of reference points for expressing equations (i) to (x),

(12) FIG. 13 illustrates a method implemented to define the specific shape of the hot electrode for generating a focalized ultrasonic wave,

(13) FIG. 14 illustrates a side view of an axial cross section of another example of electroacoustic device according to the invention,

(14) FIG. 15 illustrates, from a perspective view, another example of the electroacoustic device according to the invention, and

(15) FIG. 16 illustrates a side view of an axial cross section of the electroacoustic device of FIG. 15.

(16) In the drawing, the respective proportions and sizes of the different elements are not always respected for sake of clarity.

(17) FIGS. 1 to 5 illustrate a first embodiment of the electroacoustic device 5.

(18) The electroacoustic device according to FIGS. 1 to 5 comprises a piezoelectric part 7 in the shape of a plate of thickness e.sub.s equal to 120 μm, presenting an upper face and a lower face. It is made of a LiBNO.sub.3 Y-cut at 35°.

(19) The electroacoustic device also comprises a body 10, represented on FIG. 5, made of borosilicate glass, having a thickness e.sub.b of 6.5 mm. The body is acoustically coupled to the piezoelectric part by means of a coupling media 12, for instance optical adhesive NOA61 of Norland Product.

(20) Two hot first 15 and second 17 electrodes are provided on the upper face 20, and each comprise a contact brush 22a-b for connecting the hot electrodes to a control unit 24 which provides electrical power to the first and second electrodes. The first, respectively the second hot electrode comprise a first 25, respectively second 27 hot track spiraling around a common spiral axis Z, which is normal to the upper face. The first, respectively the second hot track comprise several coils, the inner coil of each of the first and second hot track encircling a central zone 30 defined on the upper face. In a variant which is not represented, the electroacoustic device can comprise more than 2, notably 4 hot electrodes, all comprising hot tracks spiraling around the spiral axis Z.

(21) As it can be observed on FIGS. 2 and 4, the first and second hot tracks spiral are such that the radial step Δr between two adjacent coils of the first, respectively second hot tracks decreases from the center. For instance, the radial step between the radially inner adjacent coils and the radially outer adjacent coils decreases from 136 to 115 μm.

(22) The electroacoustic device comprises a ground electrode 35, which as for the embodiment illustrated on FIGS. 1 to 4, consists in a ground coating 36 extending partially over the lower face 37 opposite to the upper face. The first and second electrodes, the ground electrode and the piezoelectric part define a wave transducer 41. The ground electrode is electrically connected to the ground 40. As illustrated on FIG. 3, where the hot electrodes provided on the upper faces are drawn as dashed patterns, the ground coating entirely cover the first and second hot track. The first track and the ground coating on the one hand, and the second track and ground coating on the other hand define first 42 and second 44 electrode pairs which when electrically powered generates respectively first W.sub.1 and second W.sub.2 volume ultrasonic waves that deform the piezoelectric part. In particular, the control unit is adapted for delivering electrical power to the first and second electrodes such that the phase shift between first and second volume ultrasonic wave is equal to π.

(23) Furthermore, as illustrated in FIG. 5, the body 10 is provided on top of the upper face 20, such that the first 15 and second 17 hot electrodes are sandwiched in between the piezoelectric part 7 and the body.

(24) The electroacoustic device comprises a base provided on the face opposite to the one facing the wave transducer. The base is a plate made of borosilicate glass of thickness e.sub.a of 150 μm. The base can be moved in at least two directions transverse to the spiral Z. An interface liquid of thickness less than 10 μm is provided between the base and the body.

(25) A sound absorber 50 made for instance of PDMS is provided on the base, which defines a cavity 55 containing a fluid medium 58, preferably a liquid medium. An object 60 is embedded in the fluid medium.

(26) When powering the hot electrodes, the wave transducer is deformed by the first W.sub.1 and second W.sub.2 volume ultrasonic waves propagating substantially along a direction parallel to the spiral axis, in the piezoelectric part.

(27) The wave transducer transmits said volume ultrasonic waves to the bulk of the body wherein they define a focalized ultrasonic vortex FV which focal locus (wherein the acoustic intensity is the lowest) is located in the cavity. By displacing the base relatively to the body, the object can be brought close to the focal locus. It can then be manipulated and notably be entrapped along the spiral axis.

(28) The electroacoustic device illustrated in FIG. 6 differs from the one illustrated on FIG. 1 by a recess 65 formed in the piezoelectric part, provided radially between the first 15 and second 17 hot electrodes, and consisting in a groove spiraling around axis Z. The spiraling groove comprises at least one coil, in the present case, 4 coils. As illustrated the radial width Δ.sub.c of a coil of the groove can decrease from the spiral axis Z. In a variant, it can be constant. The recess limits the propagation of a diaphonic transverse volume or surface acoustic wave in the substrate.

(29) The electroacoustic device illustrated on FIGS. 7 and 8 differs from the one illustrated on FIG. 1 by the fact the ground electrode comprises two first 70 and second 75 ground tracks instead of the ground coating, and both connected to the ground 40.

(30) The ground tracks are provided on the lower face 37 of the piezoelectric part opposite to the one on which the first and second hot electrodes are provided.

(31) The first, respectively the second ground track is completely superimposed on the first, respectively the second hot track, and vice versa. They define first 42 and second 44 electrode pairs.

(32) The electroacoustic device illustrated on FIG. 9 differs from the one illustrated on FIG. 8 by the following features.

(33) On the upper face, instead of the second hot electrode of the device of FIG. 1, a ground track 78 is provided, which has a shape and position relative to the spiral Z which are identical to the second hot electrode of the device of FIG. 8.

(34) On the lower face, instead of the second ground electrode of the device of FIG. 1, a hot track 79 is provided, which has a shape and position relative to the spiral Z which are identical to the second hot electrode of the device of FIG. 8.

(35) FIGS. 10 and 11 illustrate a second embodiment of the invention. The electroacoustic device according to the second embodiment differs from the embodiment illustrated on FIG. 1 by the fact it comprises a body 10 consisting of a piezoelectric part 7 made of LiNbO.sub.3 Y-cut having a thickness 150 microns, having an upper face and a lower face opposite to the upper face, and by the fact a ground electrode 80 and a hot electrode 85 are provided on the same face of the body, in the present case on the lower face. They comprise respective ground and hot tracks spiraling around a spiral axis Z.

(36) The hot and ground spiraling tracks define an intertwined pattern of coils of the respective track on the face where they are disposed.

(37) Furthermore, the electroacoustic device comprises a base provided on the face opposite to the one facing the wave transducer. The base is a plate made of borosilicate glass of thickness e.sub.a of 150 μm. The base can be moved in at least two directions transverse to the spiral axis Z. An interface gel of thickness less than 10 μm is provided between the base and the body.

(38) A sound absorber 50 made for instance of PDMS is provided on the base, which defines a cavity 55 containing a fluid medium 58, preferably a liquid. An object 60 is embedded in the fluid medium.

(39) The hot and ground tracks are conformed such that the local deformation of the piezoelectric part in between two adjacent coils they induce, when the hot track is electrically powered by mean of the control unit, interfere to define a focalized ultrasonic vortex propagating in the body and focusing in the cavity containing the fluid medium. By displacing the base relatively to the body, the object can be manipulated.

(40) FIG. 12 illustrates the location of a Cartesian coordinate system for defining a spherical vortex such as for instance defined by equation (x), which focal locus is referred by point 2 and intercepts the plane, referred by n=0, on which the electrodes are provided, for instance being the face 20 of the piezoelectric part.

(41) FIG. 13 aims at illustrating the resolution of equations (i) to (vii), in the case the vortex FV propagates in the body being the piezoelectric part from the hot track towards the focal locus 2 over a distance z.sup.(N) along axis Z. The vortex FV comprises 3D lines along which the phase is constant, named equi-phase lines. For instance, along an equi-phase line 99, the phase of the vortex is the same at points 100a to 100c. The projection, along the line 117 that joins the focal locus 2 and points 100a to 100c, of equi-phase line 99 is a plane line which is set by parameter R(θ) expressed from the center C on the surface where the tracks are provided. In other words, the intersection of the phase of the focalized ultrasonic vortex onto the plane where the hot track has to be provided yields the drawing of the hot track. This is for instance mathematically expressed by the set of equations (i) to (viii). By forming at least one hot track drawing said line R(θ), an ultrasonic vortex focalizing at focal point 2 can be generated. The example of FIG. 13 corresponds to a specific case of the resolution of the set of equations (i) to (viii), wherein the electroacoustic device comprise a single body being the piezoelectric part. It will appear clearly to the skilled worker that the method illustrated here above can be applied to any other variant of the invention, for instance in case the electroacoustic device comprises a piezoelectric part, a body different from the piezoelectric part, and optionally other substrate(s) provided on top of the body.

(42) FIG. 14 illustrates another embodiment of the electroacoustic device 5 according to the invention. The electroacoustic device 5 has the general shape of a pen 128 which can be grasped by a user. It comprises a support 130 extending along an extension axis and to which a wave transducer 41 is attached. The wave transducer is provided at an extremity of the support. The wave transducer comprises a body 10 consisting in a piezoelectric part 7. First 15 and second 17 hot electrodes are provided on a face of the body and a ground electrode 36 is provided on the other part of the body in a fashion as already illustrated in FIG. 4. The electroacoustic device further comprises a quarter wavelength layer 135 provided on top of the face where the first and second hot electrodes are provided and on top of said hot electrodes. The quarter wavelength filter is made of an electrically isolating material to prevent any electric shunt as it will appear here below. In a variant, the ground electrode and the first and second hot electrodes can all be provided respectively on the face of the piezoelectric part which faces the support.

(43) The electroacoustic device can be used for manipulating an object in the following manner.

(44) A container 110 comprising an opening 111 and defining a cavity 112 is filled with a fluid medium 120, preferably a liquid medium, in which an object 122 is embedded. The electroacoustic device is handled by a user such that the wave transducer is immersed in the liquid.

(45) When an electrical voltage is applied to the electroacoustic device by means of a power generator, not represented, first W.sub.1 and second W.sub.2 volume ultrasonic waves are generated that deform the piezoelectric part. The wave transducer transmits said volume ultrasonic waves W.sub.1 and W.sub.2 directly in the fluid medium wherein they define a focalized ultrasonic vortex FV which focal locus, i.e. wherein the acoustic intensity is the lowest, is located in the cavity. By displacing the electroacoustic device 5 relatively to the container 110, the object 122 can be brought close to the focal locus. It can then be manipulated in 3D.

(46) FIG. 15 illustrates another embodiment of an electroacoustic device 5 according to the present invention.

(47) The electroacoustic device of FIG. 15 differs from the electroacoustic device of FIG. 1 in that it comprises a single hot electrode 125 and that the ground electrode 130 is arranged with the hot electrode on the same face of the piezoelectric part 7. In the present case, they are provided on the upper face 20 of the piezoelectric part.

(48) The ground electrode and the hot electrode each comprise a contact brush 135a-b to be connected to a control unit 140. The control unit provides different electrical potential to the ground electrode and to the hot electrode. The ground electrode is for example connected to a ground socket of the control unit, which electrical potential is defined as a reference, as being grounded 40.

(49) In particular, the electrical potentials of the hot electrode of the ground electrode can be out of phase the one with respect to the other by a phase equal to π.

(50) The hot electrode and the ground electrode comprise a hot track 145 and a ground track 150 respectively, which spiral around a common axis Z, normal to the upper face. The hot track, respectively the ground track, comprises several coils, the inner coil of each encircling a central zone 230 defined on the upper face.

(51) Furthermore, the hot track and the ground track are intertwined the other with the other.

(52) As it can be observed on FIG. 16, the ground track and the hot track are such that the radial step Δr′ between two adjacent coils 240a-b of the ground track, respectively the hot track decreases radially from the center.

(53) When the control unit provides an electrical power to the hot electrode, the ground electrode and the hot electrodes generate volume ultrasonic waves that deform the piezoelectric part. The ultrasonic waves can be transmitted to the bulk of the body to define a focalized ultrasonic vortex in the manner depicted in FIG. 5.

(54) As it appears throughout the present description, the electroacoustic device according to the invention improves the efficiency of manipulating an object embedded in a fluid medium. It further improves the selectivity, when manipulating a specific object among a population of objects.

(55) Of course, the invention is not limited to the specific embodiments detailed in the present description.