Microsystem switches

• US 20040252936A1
• Filed: 08/05/2004
• Published: 12/16/2004
• Est. Priority Date: 07/05/2001
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Widmar, Roland W., Rothuizen, Hugo E., Despont, Michel, Vettiger, Peter, Drechsler, Ute
• Granted Patent: US 7,146,067 B2
• Time in Patent Office: Days
• US Class Current: 385/18
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/3514 the reflective optical element moving along a line so as to translate into and out of the beam path, i.e. across the beam path
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3546 NxM switch, i.e. a regular array of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/3576 Temperature or heat actuation thermal forces controlling reflecting elements in general G02B26/0866; thermo-optic devices G02F1/0147
• CPC Class Codes: G02B 6/358 Latching of the moving element, i.e. maintaining or holding the moving element in place once operation has been performed; includes a mechanically bistable system
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2001/0042 Bistable switches, i.e. having two stable positions requiring only actuating energy for switching between them, e.g. with snap membrane or by permanent magnet
• CPC Class Codes: H01H 2001/0084 with perpendicular movement of the movable contact relative to the substrate
• CPC Class Codes: H01H 2061/006 Micromechanical thermal relay
• CPC Class Codes: H01H 61/02 wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively

Abstract

A microsystem switch (1, 20, 25, 30, 33) has a support (2) defining a recess (3), and a flexible bridge (6) is mounted on the support (2) bridging the recess (3). The bridge (6) is shaped so as to hold selectively a concave stable state, in which the bridge bulges into the recess (3), and a convex stable state in which the bridge bulges out of the recess (3). The switch includes an actuator (8, 9; 26, 27) for effecting flexing of the bridge (6) between the stable states, and a switching element (7, 31, 34) is mounted on the bridge (6) such that movement of the bridge between the stable states moves the switching element between an on position and an off position. According to another design, a microsystem switch (40, 55) has a support (41) defining a recess (42), and an elongate torsion member (44) is mounted on the support (41) bridging the recess (42). A flexible bridge (43, 56) is mounted on the support (41) bridging the recess (42) in a direction substantially perpendicular to the torsion member (44). The bridge (43, 56) is connected to the torsion member (44) at the cross-point thereof so that a first section of the bridge extends between the cross-point and one side of the recess (42) and a second section of the bridge extends between the cross-point and the opposite side of the recess (42). The bridge (43, 56) is shaped so as to hold selectively a first stable state, in which the first section of the bridge bulges into the recess and the second section of the bridge bulges out of the recess, and a second stable state in which this configuration is reversed. A switching element (45) is mounted at the cross-point of the bridge (43, 56) and torsion member (44), and an actuator (46a, 46b; 58a, 58b) is again provided for effecting flexing of the bridge (43, 56) between the stable states. Here, movement of the bridge (43, 56) between the stable states effects twisting of the torsion member (44) and rotation of the switching element (45) between an on position and an off position. Switching devices incorporating these switches, and switching apparatus comprising arrays of such switching devices, are also provided.

Claims

1. A microsystem switch (1, 20, 25, 30, 33) comprising:

a support (2) defining a recess (3);

a flexible bridge (6) mounted on the support (2) and bridging the recess (3), the bridge (6) being shaped so as to hold selectively a concave stable state, in which the bridge bulges into the recess (3), and a convex stable state in which the bridge bulges out of the recess (3);

an actuator (8, 9;

26, 27) for effecting flexing of the bridge (6) out of each of the stable states into the other of the stable states; and

a switching element (7, 31, 34) mounted on the bridge (6) such that movement of the bridge between the stable states moves the switching element between an on position and an off position.

2. A switch as claimed in claim 1 wherein the bridge comprises a flexible membrane (6).

3. A switch as claimed in claim 1 or claim 2 wherein the actuator comprises a pair of bimorph actuation layers (8, 9;

26, 27), each bimorph actuation layer extending over a respective portion of the bridge (6) to form therewith a bimorph structure such that differential expansion in the bimorph structure on activation of the bimorph actuation layer exerts a force causing flexing of the bridge out of one stable state into the other stable state, the arrangement being such that activation of one of said layers (8, 9;

26, 27) causes flexing of the bridge out of the convex stable state into the concave stable state, and activation of the other layer causes flexing of the bridge out of the concave stable state into the convex stable state.

4. A switch as claimed in claim 3 wherein each bimorph actuation layer comprises a heater (8, 9;

26, 27), having a thermal expansion coefficient different to that of said respective portion of the bridge (6), whereby heating of the heater produces said differential expansion.

5. A switch as claimed in claim 4 wherein the heaters (8, 9) are disposed on the same surface of the bridge (6) on opposite sides of the switching element (7, 31, 34), the thermal expansion coefficient of one heater being greater than that of said respective portion and the thermal expansion coefficient of the other heater being less than that of said respective portion.

6. A switch (25) as claimed in claim 4 wherein the heaters (26, 27) are disposed on opposite surfaces of the bridge (6) and on opposite sides of the switching element.

7. A switch as claimed in any preceding claim wherein the bridge (6) is mounted on a substantially flat surface of the support (2) and the recess (3) is formed in said surface of the support.

8. A switch as claimed in any preceding claim wherein the bridge (6) has a substantially symmetrical curved profile in cross-section along the extent of the bridge across the recess (3), and wherein the switching element (7, 31, 34) is mounted substantially mid-way along said extent.

9. A switch as claimed in any preceding claim wherein the switching element (7, 31, 34) is mounted on the side of the bridge (6) remote from the recess (3).

10. A switch (20) as claimed in any preceding claim wherein the bridge (6) is formed with a spring structure (21) on each side of the switching element (7) in a direction along the extent of the bridge across the recess (3) to facilitate flexing of the bridge out of each stable state into the other stable state.

11. A switch (30, 33) as claimed in any one of claims 1 to 10 wherein the switching element comprises an electrical contact (31, 34).

21. A switch (1, 20, 25, 40, 55) as claimed in any one of claims 1 to 10 and 12 to 20 wherein the switching element comprises an optical element (7, 45).

22. A switch as claimed in claim 21 wherein the optical element comprises a mirror.

23. Switching apparatus comprising an array of switches as claimed in any preceding claim.

24. An optical switching device comprising:

a switch (1, 20, 25, 40, 55) as claimed in claim 21 or claim 22;

and

a waveguide structure (10, 50) having an optical waveguide (11, 12, 51) and defining a cavity (13, 52) intersecting the waveguide;

wherein the switch (1, 20, 25, 40, 55) is disposed relative to the waveguide structure (10, 50) such that movement of the bridge (6, 43, 56) between said stable states moves the optical element (7, 45) in said cavity (13, 52) between the on position, in which the optical element intersects the optical path defined by the waveguide (11, 12, 51), and the off position in which the optical element does not intersect the optical path.

25. A switching device as claimed in claim 24 wherein:

the waveguide structure (10, 50) has a pair of crossed waveguides (11, 12;

51) and the cavity (13, 52) intersects both waveguides at the cross-point thereof;

the optical element (7, 45) comprises a mirror; and

the switch (1, 20, 25, 40, 55) is disposed relative to the waveguide structure (10, 50) such that, in the on position, the mirror is arranged to reflect light from one waveguide into the other.

26. Optical switching apparatus comprising an array of optical switching devices as claimed in claim 24 or claim 25.

27. Optical switching apparatus comprising an array of optical switching devices as claimed in claim 25 wherein:

the waveguide structures of the devices are provided by a waveguide array chip (50) and the switches of the devices are provided by a switch array chip (53);

the waveguides (51) are arranged in a grid on the waveguide array chip (50);

the mirror of each switch is mounted on the side of the bridge remote from the recess; and

the switch array chip (53) is disposed relative to the waveguide array chip (50) such that the mirror of each switch is located for movement between the on and off positions in the cavity (52) at the cross-point of a respective pair of waveguides (51).

12. A microsystem switch (40, 55) comprising:

a support (41) defining a recess (42);

an elongate torsion member (44) mounted on the support (41) and bridging the recess (42);

a flexible bridge (43, 56) mounted on the support (41) and bridging the recess (42) in a direction substantially perpendicular to the torsion member (44), the bridge (43, 56) being connected to the torsion member (44) at the cross-point thereof so that a first section of the bridge extends between the cross-point and one side of the recess (42) and a second section of the bridge extends between the cross-point and the opposite side of the recess (42), wherein the bridge (43, 56) is shaped so as to hold selectively a first stable state, in which the first section of the bridge bulges into the recess and the second section of the bridge bulges out of the recess, and a second stable state in which the first section of the bridge bulges out of the recess and the second section of the bridge bulges into the recess;

an actuator (46a, 46b;

58a, 58b) for effecting flexing of the bridge (43, 56) out of each of the stable states into the other of the stable states; and

a switching element (45) mounted at the cross-point of the bridge (43, 56) and torsion member (44);

wherein movement of the bridge (43, 56) between the stable states effects twisting of the torsion member (44) and rotation of the switching element (45) between an on position and an off position.

13. A switch as claimed in claim 12 wherein the cross-point is located substantially mid-way along the extent of each of the bridge (43, 56) and torsion member (44) across the recess (42).

14. A switch as claimed in claim 12 or claim 13 wherein the bridge comprises a flexible membrane (43, 56) and the torsion member comprises a torsion bar (44).

15. A switch as claimed in any one of claims 12 to 14 wherein the switching element (45) is mounted on the side of the cross-point remote from the recess (42).

16. A switch as claimed in any one of claims 12 to 15 wherein the switching element (45) comprises a substantially planar element mounted for rotation substantially in the plane thereof between the on and off positions.

17. A switch (40) as claimed in any one of claims 12 to 16 wherein the actuator comprises a pair of bimorph actuation layers (46a, 46b), each bimorph actuation layer extending over a said section of the bridge (43) to form therewith a bimorph structure such that differential expansion in the bimorph structure on activation of the bimorph actuation layer (46a, 46b) exerts a force causing flexing of the bridge (43) out of one stable state into the other stable state, the arrangement being such that activation of one of said layers (46a, 46b) causes flexing of the bridge out of the first stable state into the second stable state, and activation of the other layer causes flexing of the bridge out of the second stable state into the first stable state.

18. A switch as claimed in claim 17 wherein each bimorph actuation layer comprises a heater (46a, 46b) having a thermal expansion coefficient different to that of said section, whereby heating of the heater produces said differential expansion.

19. A switch as claimed in claim 18 wherein the heaters (46a, 46b) are disposed on the same surface of the bridge (43), one on the first section of the bridge and the other on the second section of the bridge.

20. A switch (55) as claimed in any one of claims 12 to 16 wherein the support comprises a conductive substrate (59) and the actuator comprises a conductive layer (58a, 58b) on each of the first and second sections of the bridge (56), whereby application of a voltage between the substrate (59) and the conductive layer (58a, 58b) on a said section pulls that section towards the recess.