Regarding a bimorph's structure

[PhyIsOhSoHard]

Can anyone explain to me why a bimorph has a metal in between the two piezo-layers?

 

[Baluncore]

Maybe it provides the common electrical connection to the far end of the bimorph cantilever.

 

[PhyIsOhSoHard]

Maybe it provides the common electrical connection to the far end of the bimorph cantilever.

Are you sure? I've tried searching for it many places but I just can't find anything about it.

 

[Baluncore]

Are you sure? I've tried searching for it many places but I just can't find anything about it.

No, I'm not sure which is why I say maybe.
It is an educated guess in that to control the two piezo elements independently will require a minimum of three electrical connections.
One of those terminals will be common to both piezo elements and so must reach to the far end of the device.
The metal will be repeatably stretched and contracted as the structure walks. Being on the neutral axis will minimise the metal length change.

 

[Baluncore]

See; www.piezo.com/tech2intropiezotrans.html

Parallel Operation: Parallel operation refers to the case where the supply voltage is applied to each layer individually. This means accessing and attaching wires to each layer. A 2-layer bending element wired for parallel operation requires three wires (one attached to each outside electrode and one attached to the center shim), as shown in Figure-18. For the same motion, a 2-layer element poled for parallel operation needs only half the voltage required for series operation.

There are also fabrication and structural advantages.

The metal shim sandwiched between the two piezo layers provides mechanical strength and stiffness while shunting a small portion of the force.

The brass shim reinforcement laminated between the two piezoelectric layers is an economical approach to producing a rugged actuator.