  Active microelectromechanical systems can couple the nanomechanical domain
with the electronic domain by integrating electronic sensing and actuation
mechanisms into the micromechanical device. This enables very fast and
sensitive measurements of force, acceleration, or the presence of biological
analytes. In particular, strain sensors integrated onto MEMS cantilevers are
widely used to transduce an applied force to an electrically measurable signal
in applications like atomic force microscopy, mass sensing, or molecular
detection. However, the high Young's moduli of traditional cantilever materials
(silicon or silicon nitride) limit the thickness of the devices, and therefore
the deflection sensitivity that can be obtained for a specific spring constant.
Using softer materials such as polymers as the structural material of the MEMS
device would overcome this problem. However, these materials are incompatible
with high-temperature fabrication processes often required to fabricate high
quality electronic strain sensors. We introduce a pioneering solution that
seamlessly integrates the benefits of polymer MEMS technology with the
remarkable sensitivity of strain sensors, even under high-temperature
deposition conditions. Cantilevers made using this technology are inherently
fluid compatible and have shown up to 6 times lower force noise than their
conventional counterparts. We demonstrate the benefits and versatility of this
polymer/ceramic/semiconductor multi-layer fabrication approach with the
examples of self-sensing AFM cantilevers, and membrane surface stress sensors
for biomolecule detection.
