Nano-G accelerometer using geometric anti-springs

We report an ultra-sensitive seismic accelerometer with nano-g sensitivity, using geometric anti-spring technology. High sensitivity is achieved by an on-chip mechanical preloading system comprising four sets of curved leaf springs that support a proof-mass. Using this preloading mechanism, stiffness reduction up to a factor 26 in the sensing direction has been achieved. This increases the sensitivity to acceleration by the same factor. The stiffness reduction is independent of the proof-mass position, preserving the linear properties of the mechanics and due to its purely mechanical realization, no power is consumed when the accelerometer is in its preloaded state. Equivalent acceleration noise levels below 2ng/√Hz have been demonstrated in a 50 Hz bandwidth, using a capacitive half-bridge read-out.