Supersensitive linear pressure transducer
Apparatus and methods for a MEMS-fabricated variable capacitor. In one embodiment the capacitor is a comb drive comprising a plurality of plates interdigitated with a corresponding blades. As the plates move relative to the blades, the capacitance of the sensor changes. The capacitor is sufficiently sensitive to measure respiratory pressure in an animal.
1. A microfabricated variable capacitor, comprising:
a stator including a plurality of electrically conductive plates each spaced apart from one another, each said pair of adjacent plates forming a channel between, each of said plates being in a first common electrical communication;
a rotor including a plurality of electrically conductive blades, said rotor being suspended relative to said stator such that each of said blades is received within a corresponding one of said channels and each said blade includes an area that overlaps with an area of an adjacent said plate, each of said blades being in a second common electrical communication;
a flexible diaphragm; and
a suspension system for flexibly coupling said rotor and said diaphragm, said system configured and adapted to apply a load from the diaphragm to the stator in one direction and unable to substantially apply a load from the diaphragm to the stator in another direction;
wherein the capacitance between the first electrical communication and the second electrical communication varies in correspondence to the overlapping areas between each said blade and an adjacent plate.
2. The capacitor of claim 1 wherein said suspension system couples to said rotor such that no net torque is exerted on the suspension system by the rotor.
3. The capacitor of claim 1 wherein said plates are planar and said blades are planar.
4. The capacitor of claim 1 wherein said plates are circular about an axis and said blades are circular about the same axis.
5. The capacitor of claim 1 wherein said rotor includes a centrally located hub, and said blades are cantileveredly supported from said hub.
6. The capacitor of claim 5 which further comprises a cantilever arm supporting said blades, one end of said arm being coupled to said hub, each said blade extending from said arm in a direction transverse to the direction from the hub to the other end of said arm.