Microelectromechanical structure with motion limiter

1. A microelectromechanical structure, comprising:

a first element that includes a first element surface, and a second element that includes a second element surface, wherein at least one of the first element and the second element is mobile;

an element gap between the first element surface and the second element surface; wherein

one of the first and second element surfaces includes a convex contact surface and the other one of the first and second element surfaces includes a concave contact surface;

the convex contact surface includes a protrusion, and the concave contact surface includes an indentation;

the surface of the protrusion includes a first curved region;

the surface of the indentation includes a second curved region;

a radius of curvature in a vertex of the first curved region is a first radius of curvature;

a radius of curvature in a vertex of the second curved region is a second radius of curvature;

the first radius of curvature is smaller than the second radius of curvature such that the ratio of the first radius of curvature and the second radius of curvature is within a range of 0.5 to 1, and both the first radius of curvature and the second radius of curvature are at least two times the width of the element gap;

the microelectromechanical structure includes two impact elements for providing successively activated motion limiter stages, at least one of the impact elements including the convex contact surface and the concave contact surface;

a first impact element includes a flexural element and is induced into contact by closing of a first limiter gap in response to displacement of the mobile element in a specific direction;

a second impact element is induced into contact by closing of a second limiter gap in response to displacement of the mobile element in the specific direction, the second limiter gap being greater than the first limiter gap.

2. The microelectromechanical structure of claim 1 , wherein one of the first and second elements comprises an anchored element and the other of the first and second elements comprises a mobile suspended element.

3. The microelectromechanical structure of claim 1 , wherein the first element and the second element comprise mobile suspended elements.

4. The microelectromechanical structure of claim 2 , further comprising a suspension spring structure supporting the suspended element for motion with a degree of freedom.

5. The microelectromechanical structure of claim 4 , wherein the first element surface is aligned to a first line, the second element surface is aligned to a second line, and wherein the first line and the second line are parallel to each other.

6. The microelectromechanical structure of claim 1 , wherein the first element comprises a structural layer element, and wherein the first element surface comprises a side surface of the structural layer element.

7. The microelectromechanical structure of claim 1 , wherein the protrusion extends to the element gap, and wherein the indentation comprises a recess that extends away from the element gap.

8. The microelectromechanical structure of claim 5 , wherein the first curved region and the second curved region are aligned such that an axis connecting a vertex of the first curved region and a vertex of the second curved region is aligned to a first direction that is perpendicular to the first line and the second line.

9. The microelectromechanical structure of claim 1 , wherein the projection of the first curved region is within the projection of the second curved region on the first or the second element surface.

10. The microelectromechanical structure of claim 1 , wherein the flexural element provides a spring constant in the specific direction, the spring contact being configured to provide a restoring force greater than adhesive force of the contact in the second impact element.

11. A microelectromechanical device, comprising the microelectromechanical structure of claim 1 .