All compliant electrode

Abstract

The invention relates to a dielectric transducer structure comprising a body of elastomeric material that is provided with an electrode arrangement on each of two boundary surfaces lying oppositely to one another. At least one boundary surface comprises a corrugated area that comprises heights and depths. The aim of the invention is to improve the compliance to elastic deformations of the dielectric transducer structure. To this end, the heights and depths are arranged in both perpendicular directions of the boundary surface.

Claims

1. A dielectric transducer structure comprising a body of elastomeric material, wherein the body on each of two boundary surfaces lying oppositely to one another is provided with an electrode arrangement, wherein at least one boundary surface comprises at least one corrugated area, wherein the at least one corrugated area comprises heights and depths where the heights and depths are arranged along both perpendicular directions (X, Y) of the boundary surface wherein the corrugation peak to peak amplitudes (H.sub.x, H.sub.y) are different in the two perpendicular directions (X, Y) and wherein the electrode arrangement has a substantially constant thickness (h).

2. The dielectric transducer structure according to claim 1, wherein the heights and depths are arranged periodically at least along one of the two perpendicular directions (X, Y).

3. The dielectric transducer structure according to claim 2, wherein the heights and depths are periodic along both of the perpendicular directions (X, Y), with corrugation periods (P.sub.x, P.sub.y) and corrugation peak to peak amplitudes (H.sub.x, H.sub.y).

4. The dielectric transducer structure according to claim 1, wherein that the heights and depths have a sinusoidal-like shape along at least one of the perpendicular directions (X, Y).

5. The dielectric transducer structure according to claim 1, wherein the electrode arrangement covers the at least one corrugated area completely.

6. The dielectric transducer structure according to claim 1, wherein there are no lines of substantially equal height in the at least one corrugated area.

7. The dielectric transducer structure according to claim 1, wherein the ratio of corrugation peak to peak amplitude (H.sub.x, H.sub.y) to the thickness (h) of the electrode arrangement lies in the range of 30 to 60.

8. The dielectric transducer structure according to claim 2, wherein that the heights and depths have a sinusoidal-like shape along at least one of the perpendicular directions (X, Y).

9. The dielectric transducer structure according to claim 3, wherein that the heights and depths have a sinusoidal-like shape along at least one of the perpendicular directions (X, Y).

10. The dielectric transducer structure according to claim 2, wherein the electrode arrangement covers the at least one corrugated area completely.

11. The dielectric transducer structure according to claim 3, wherein the electrode arrangement covers the at least one corrugated area completely.

12. A dielectric transducer structure comprising a body of elastomeric material, wherein the body on each of two boundary surfaces lying oppositely to one another is provided with an electrode arrangement, wherein at least one boundary surface comprises at least one corrugated area, and wherein the at least one corrugated area comprises heights and depths where the heights and depths are arranged along both perpendicular directions (X, Y) of the boundary surface wherein the corrugation peak to peak amplitudes (H.sub.x, H.sub.y) are different in the two perpendicular directions (X, Y), wherein the heights and depths are periodic along both of the perpendicular directions (X, Y), with corrugation periods (P.sub.x, P.sub.y) and corrugation peak to peak amplitudes (H.sub.x, H.sub.y), and wherein the sum of the corrugation peak to peak amplitudes (H.sub.x, H.sub.y) of both perpendicular directions (X, Y) is less than or equal to one quarter of the mean thickness (B) of the body between the two boundary surfaces.

13. The dielectric transducer structure according to claim 12, wherein the corrugation period (P.sub.x, P.sub.y) is substantially equal to the corresponding corrugation peak to peak amplitude (H.sub.x, H.sub.y) in at least one of the two perpendicular directions (X, Y).

14. The dielectric transducer structure according to claim 12, wherein that the heights and depths have a sinusoidal-like shape along at least one of the perpendicular directions (X, Y).

15. The dielectric transducer structure according to claim 12, wherein the electrode arrangement covers the at least one corrugated area completely.

16. A dielectric transducer structure comprising a body of elastomeric material, wherein the body on each of two boundary surfaces lying oppositely to one another is provided with an electrode arrangement, wherein at least one boundary surface comprises at least one corrugated area, and wherein the at least one corrugated area comprises heights and depths where the heights and depths are arranged along both perpendicular directions (X, Y) of the boundary surface wherein the corrugation peak to peak amplitudes (H.sub.x, H.sub.y) are different in the two perpendicular directions (X, Y), wherein the heights and depths are periodic along both of the perpendicular directions (X, Y), with corrugation periods (P.sub.x, P.sub.y) and corrugation peak to peak amplitudes (H.sub.x, H.sub.y), and wherein the corrugation period (P.sub.x, P.sub.y) is substantially equal to the corresponding corrugation peak to peak amplitude (H.sub.x, H.sub.y) in at least one of the two perpendicular directions (X, Y).

17. The dielectric transducer structure according to claim 16, wherein the corrugation peak to peak amplitude (H.sub.x) of one of the perpendicular directions (X) is at least 50% larger than the corresponding peak to peak amplitude (H.sub.y) of the other perpendicular direction (Y).

18. The dielectric transducer structure according to claim 16, wherein that the heights and depths have a sinusoidal-like shape along at least one of the perpendicular directions (X, Y).

19. The dielectric transducer structure according to claim 17, wherein that the heights and depths have a sinusoidal-like shape along at least one of the perpendicular directions (X, Y).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the invention will now be described with reference to the accompanying drawings.

(2) FIG. 1 shows a dielectric transducer structure according to the invention in a cut view,

(3) FIG. 2 shows the same dielectric transducer structure according to FIG. 1 in a cut view perpendicular to the view of FIG. 1,

(4) FIG. 3 shows a top 2D view of the boundary surfaces of the dielectric transducer structure.

(5) FIGS. 4A&B show isometric views of one of the boundary surfaces of the dielectric transducer structure for two different peak heights.

(6) FIG. 5 shows an isometric top view of one of the boundary surfaces of the dielectric transducer structure.

DETAILED DESCRIPTION

(7) FIG. 1 and FIG. 2 show a dielectric transducer structure 1, comprising a body of elastomeric material 2. The body 2 has two boundary surfaces 3, 4 lying oppositely to one another. The boundary surfaces 3, 4 are corrugated along a first direction X as well as along a second direction Y, wherein the first direction X is perpendicular to the second direction Y. The two perpendicular directions X, Y would be parallel to corresponding flat, uncorrugated boundary surfaces. Along each of the directions X, Y the corrugation includes heights 5 as well as depths 6. A third direction Z is perpendicular to both directions X and Y.

(8) Each of the boundary surfaces 3, 4 is provided with an electrode arrangement 7, 8. In the given embodiment the electrode arrangement 7, 8 has a substantially constant thickness h. The electrode arrangements 7, 8 may be deposited on the boundary surfaces 3, 4 using vapor deposition or electrolytic techniques, and may contain or consist of a metal such as copper or silver.

(9) In FIG. 2 the same dielectric transducer structure is shown as in FIG. 1. In this case, a different direction for the cut view has been chosen. The dielectric transducer structure shows two different profiles of corrugation along the two directions X and Y. The corrugation profile in this case is of a sinusoidal-like shape in both of the directions X, Y. Consequently, the heights 5 and depths 6 of the corrugation profiles are periodic with a period P.sub.x in the direction X and with a period P.sub.y in the direction Y. Furthermore, in this case, there will also be characteristic peak to peak amplitudes H.sub.x and H.sub.y in both directions X and Y.

(10) In the given embodiment according to FIGS. 1, 2 and 3 the corrugation peak to peak amplitudes H.sub.x, H.sub.y in the two directions X, Y are chosen to be different. In particular, H.sub.x is in this case 50% larger than H.sub.y. This way it is ensured that there are no extended lines of substantially equal height in Z-direction in the boundary surface, the straight lines of surface topology.

(11) Mathematically one embodiment profile of a surface topology according to the present invention can be expressed by the following function:
z=f(x,y)=?*Hx*Sin(2*pi*x/Px)+?*Hy*Sin(2*pi*y/Py),a.

(12) where Sinus naturally could be replaced by Cosinus or any other periodic expression.

(13) x is the coordinate in length direction, y is the coordinate in width direction, z is the coordinate in thickness direction, Hx is corrugation depth in x-direction, Px is corrugation period in x-direction, Hy is corrugation depth in y-direction and Py is corrugation period in y-direction.

(14) In FIG. 3 a top view illustrating in 2D the surface topology having a corrugated profile formed extending in the X-direction having heights 5 and crests 6 and formed with period Px and peak amplitudes H.sub.x, and correspondingly a corrugated profile formed extending in the Y-direction having heights 5 and crests 6 and formed with period Py and peak amplitudes H.sub.y.

(15) The actual height at any X,Y position will be the sum of the actual heights at that position of the formed corrugation profiles extending in the X and Y directions. In the illustration the two periods are the same, P.sub.x=P.sub.y, and they are aligned such that with the same period a height 5 of the X-direction corrugation matches with a height 5 of the Y-direction corrugation, e.g. at a spot 20, and correspondingly a crest 6 matches a crest 6, e.g. at a spot 21. At the tops such as 20 no material will have been removed, or at least the minimum thickness of material has been removed, and at minimums such as 21 a maximum thickness of material has been removed.

(16) If the two peak amplitudes are equal, Hx=Hy, then at the line (22) running through the points (23a, 23b) where one of the corrugations is at a peak and the other at a low then only material of one of the X or Y-direction corrugations is removed, the fraction of the one increasing and the fraction of the other more or less correspondingly decreasing following the line (22) to the next peak. This gives a line being substantially straight, at least seen in the plane, the line being substantially flat seen in the Z-direction (being the direction perpendicular to both the X and the Y directions of the plane). It may zig-zag slightly but this being too insignificant to give sufficient compliance (perhaps only 1-5 percent) for many purposes.

(17) If however the two peak amplitudes are different, Hx being different from Hy, then a corrugation of the line (22) would be formed in the Z-direction too.

(18) FIGS. 4A and 4B illustrate this situation where an isometric view of one of the boundary surfaces 3, 4 is shown looking into the X-Y plane. FIG. 4A show the situation where the peak amplitudes are equal, Hx=Hy, thus giving line (24) parallel to the X and Y plane extending from the position (23a) where the first of the corrugations is at a peak and the other at a low, to the next position (23b) where the situation is vice versa.

(19) FIG. 4B however show a situation where the two peak amplitudes are different, Hx being different from Hy, here the line (25) has a slow from position (23a) to (23b) where after it would drop again, thus giving a corrugation in the Z direction.

(20) In FIG. 5 an isometric top view of one of the boundary surfaces 3, 4 is shown. According to FIG. 3, the dielectric transducer structure 1 again is provided with a two-dimensional sinusoidal profile of corrugation in the boundary surfaces 3, 4. The height distance in Z-direction between the highest heights 5 and the deepest depths 6 of the boundary surface is in this case given by the sum H.sub.x+H.sub.y of the two one-dimensional peak to peak amplitudes. To ensure a high level of homogeneity of the electric field between the two electrode arrangements 7, 8, the sum H.sub.x+H.sub.y of the two one-dimensional peak to peak amplitudes should be less than or equal to one quarter of the mean thickness B of the body 2 between the boundary surfaces 3, 4.

(21) FIG. 5 also clarifies what is meant by a line of substantially equal height in one of the boundary surfaces 3, 4. If for example for a given two-dimensional sinusoidal profile of corrugation the peak to peak amplitudes H.sub.x, H.sub.y in both perpendicular directions X, Y are chosen to be the same, there will be periodic lines of equal height appearing in the boundary surface. Along these periodic lines the height in Z-direction will not change. Consequently, an electrode arrangement on the boundary surface will be more likely to break at such lines since the compliance to elastic deformation is much lower than in the rest of the corrugated area.

(22) For a two-dimensional sinusoidal profile of corrugation such lines of substantially equal height can be avoided by choosing different values for the two peak to peak amplitudes H.sub.x, H.sub.y in X- and Y-direction. Choosing the corrugation periods P.sub.x, P.sub.y to be different will not eliminate such lines for a sinusoidal profile.

(23) In contrast to that in the state of the art, the dielectric transducer structures are only compliant to elastic deformations in one of the two directions X, Y of the boundary surface. Thus, the dielectric transducer structure according to the invention allows for a broader scope of applications. At the same time, a risk of damage to the electrodes is reduced by achieving a much more homogeneous level of compliance to deformations in both directions of the boundary surface.

(24) The compliance to deformations can furthermore be expressed using a compliance factor F.sub.c, that can be different in both directions X, Y of the boundary surface 3, 4. The compliance factor F.sub.c can be related to an effective elastic modulus Y.sub.eff of the dielectric transducer structure via Y.sub.eff=Y.sub.flat/F.sub.c. In this case Y.sub.flat is the elastic modulus of a corresponding flat electrode arrangement of the same material and mean thickness. The compliance factor F.sub.c in one direction can then be estimated for small deformations from the bending beam theory to be F.sub.c?s/P (H/2h).sup.2 for periodic corrugation profiles. In this case s is the corrugation contour length for one period of corrugation, P is period of corrugation, H is the corresponding peak to peak amplitude and h is the thickness of the electrode arrangement. The factor of proportionality depends on the shape of the corrugation profile. Thus, the compliance factor F.sub.c can be different in both directions X, Y of the boundary surfaces 3, 4 but can be adjusted by choosing the corrugation periods P.sub.x, P.sub.y and the corrugation peak to peak amplitudes H.sub.x, H.sub.y according to the application. In contrast to that in the state of the art, the effective elastic modulus in one of the directions of the boundary surface will be given by the elastic modulus of a flat transducer structure and will thus be much higher than the effective elastic modulus in the direction of the corrugation. Consequently, the resulting problems as present in the state of the art can be avoided with a dielectric transducer structure according to the invention.

(25) The embodiments of the invention described above are provided by way of example only. The skilled person will be aware of many modifications, changes and substitutions that could be made without departing from the scope of the present invention. The claims of the present invention are intended to cover all such modifications, changes and substitutions as fall within the spirit and scope of the invention.