Unobstructing microdevices for self-clearing implantable catheters
A self-clearing actuator configured to be positioned in a pore providing fluid communication into a central lumen of a ventricular catheter body is described. The actuator extends into a central bore via a cantilever beam having a first end emanating at the central bore and a second end terminating at the actuator, wherein the actuator is configured to reciprocate within the central bore between a first position extending downward at an angle into the central bore and a second position substantially at or above the external surface of the catheter. The cantilever beam is stressed, e.g. via a composite compress layer, such that it is preloaded to nominally curve downward to extend the actuator into the second position. The actuator is preferably a magnet responsive to magnetic field such that the magnetic field drives the actuator toward the first position.
1. An apparatus for self-clearing a flow pore in a human implant, comprising:
a housing configured to be disposed in a flow pore of the implant;
said housing comprising a central bore spanning between an upper surface and a lower surface of the housing, the central bore providing fluid communication into said flow pore; and
an actuator plate extending from the upper surface of the housing into the central bore via a cantilever beam;
the cantilever beam having a first end emanating at the central bore and a second end terminating at the actuator plate;
the actuator plate configured to reciprocate within the central bore between a first position extending downward at an angle into the central bore and a second position substantially at or above the upper surface of the housing;
wherein the cantilever beam is stressed such that it is preloaded to nominally curve downward to extend the actuator plate in the first position;
wherein the actuator plate comprises a magnet responsive to magnetic field such that the magnetic field drives the actuator plate toward the second position;
wherein in the cantilever beam comprises a composite material having a first low-stress layer and a second compressed layer; and
wherein the second compressed layer preloads the cantilever beam to nominally curve in the first position.
2. An apparatus as recited in claim 1 , wherein in the second position the actuator plate and cantilever beam are configured to be substantially parallel with the upper surface.
3. An apparatus as recited in claim 2 , wherein the actuator plate is shaped and sized such that it covers a substantial portion of the central bore in the second position.
4. An apparatus as recited in claim 1 , wherein the second layer is sized to have a thickness that controls the angle at which the actuator plate extends into the bore.
5. An apparatus as recited in claim 1 , wherein the second layer comprises PECVD silicon nitride.
6. An apparatus as recited in claim 5 , wherein the first layer comprises LPCVD silicon nitride.
7. An apparatus as recited in claim 1 , wherein the first layer of the cantilever beam, the actuator plate, and the upper surface of the housing are all micro-machined from one contiguous layer of material.
8. An apparatus as recited in claim 1 , further comprising:
a second actuator plate extending from the upper surface of the housing into the central bore via a second cantilever beam;
wherein the second actuator plate extends from an opposing end of the central bore from the first actuator plate such that second actuator plate is interdigitating with said first actuator plate.
9. An apparatus as recited in claim 8 , wherein the first actuator plate is magnetically charged in a different direction than the first actuator plate, such that the magnetic field causes the second actuator to curve in an opposite direction than the first actuator plate.