Microactuator
A microactuator has a proximal end configured to receive an electrical signal and a distal end configured to be inserted into a fenestration of an otic bone to provide access through the lateral wall of the cochlea of a subject. The microactuator includes a piezoelectric transducer assembly having a piezoelectric transducer disposed on a membrane (the piezoelectric transducer having a smaller dimension than a corresponding dimension of the membrane), a hermetically sealed fluid cavity filled with a fluid sealed at a first end to a first side of the piezoelectric transducer assembly and at a second end to a diaphragm, a second cavity containing a vacuum or a gas sealed at a first end to a second side of the piezoelectric transducer assembly and at a second end to an end cap.
1 . A microactuator comprising:
a proximal end and a distal end, the proximal end configured to receive an electrical signal, the distal end configured to be inserted into a fenestration of an otic bone of a subject;
a piezoelectric transducer membrane assembly, the piezoelectric transducer membrane assembly including a piezoelectric transducer disposed on a membrane, the piezoelectric transducer having a smaller axial cross-sectional dimension than a corresponding axial cross-sectional dimension of the membrane;
a fluid cavity containing a fluid sealed at a first end to a first side of the piezoelectric transducer membrane assembly and at a second end to a diaphragm; and
a back cavity sealed at a first end to a second side of the piezoelectric transducer membrane assembly and at a second end to an end cap.
2 . The microactuator of claim 1 , wherein the back cavity is partially evacuated.
3 . The microactuator of claim 1 , wherein the back cavity is totally evacuated.
4 . The microactuator of claim 1 , wherein the back cavity contains a gas.
5 . The microactuator of claim 4 , wherein the gas comprises air.
6 . The microactuator of claim 4 , wherein the gas comprises argon.
7 . The microactuator of claim 4 , wherein the gas comprises nitrogen.
8 . The microactuator of claim 1 , wherein the piezoelectric transducer membrane assembly has a circular axial cross-section.
9 . The microactuator of claim 8 , wherein the piezoelectric transducer has a circular axial cross-section and the dimension is a diameter.
10 . The microactuator of claim 9 , wherein the membrane is circular and has a larger diameter than the diameter of the piezoelectric transducer.
11 . The microactuator of claim 1 , wherein the fluid comprises water.
12 . The microactuator of claim 1 , wherein the fluid comprises saline.
13 . The microactuator of claim 1 , wherein the fluid cavity and the back cavity are circular in axial cross-section.
14 . The microactuator of claim 1 , wherein the piezoelectric transducer has a thickness in a range of from about 25 um to about 500 um.
15 . The microactuator of claim 1 , wherein the membrane has a thickness in a range of from about 5 um to about 100 um.
16 . The microactuator of claim 1 , wherein the diaphragm has a thickness in a range of from about 5 um to about 100 um.
17 . The microactuator of claim 1 , further comprising:
an implantable sleeve configured for permanent insertion into a fenestration in an otic bone of a subject,
wherein the microactuator is configured to fit into and lock to the sleeve.
18 . The microactuator of claim 17 , further comprising an O-ring disposed about the microactuator and configured to be in contact with the microactuator and the sleeve when installed in the subject.
19 . The microactuator of claim 1 , further comprising:
a sealant cavity disposed at the proximal end of the microactuator and filled with a sealant; and
lead wires coupled to the microactuator within the sealant cavity.
20 . The microactuator of claim 19 , wherein the sealant comprises silicone.
21 . The microactuator of claim 1 , wherein the fluid cavity includes at least one sealable port.
22 . A method for fabricating a microactuator having a proximal end and a distal end, the proximal end configured to receive an electrical signal, the distal end configured to be inserted into a fenestration of an otic bone of a subject, the method comprising:
forming a microactuator flange having a first cylindrical portion at a proximal end with a first circular axial cross-section having a first diameter, a second cylindrical portion at a distal end with a second circular axial cross-section having a second diameter smaller than the first diameter;
attaching a microactuator distal membrane to the distal end of the microactuator flange assembly to form a sealed flange assembly;
forming a piezoelectric transducer membrane assembly by attaching a piezoelectric transducer having a first circular cross-section with a first diameter to a membrane having a second circular cross-section with a second diameter, the second diameter larger than the first diameter;
attaching a lead between the piezoelectric transducer and a first electrical contact of a microactuator end cap;
assembling the sealed flange assembly, the piezoelectric transducer membrane assembly and the microactuator end cap into a partial microactuator assembly having a fluid cavity and a back cavity;
assembling a feed-through flange to the partial microactuator assembly, the feed-through flange defining a sealant cavity;
filling the fluid cavity with a fluid;
sealing the fluid cavity;
attaching lead wires to the microactuator at the sealant cavity; and
filling the sealant cavity with a sealant and curing it.
23 . The method of claim 22 , further comprising:
placing an O-ring around the microactuator flange.
24 . The method of claim 22 , further comprising:
evacuating the back cavity.
25 . The method of claim 22 , further comprising:
filling the back cavity with a gas.