The campaniform sensillum is a displacement sensor found in the external skeleton
(cuticle) of insects, lobsters, spiders, etc. It is a hole extending through the cuticle
arranged such that its shape changes in response to loads. In specific directions The
shape change is rotated through 90° by the suspension of a bell-shaped cap whose
deflection is detected by a cell beneath the cuticle. It can be sensitive to
displacements of the order of 1 nm.
Engineering mechanics teaches that holes are commonly stress concentrators and
crack initiators, not sources of information for sensor engineers. The membrane in a
blind hole serves to amplify the strain in the wafer. However the sensitivity of strain
sensors could be further enhanced by learning from strain sensors found in biology,
for instance the campaniform sensillum of insects. Its unique structure yields strain
amplification that enables more sensitive strain detection, even when associated with
a stiff material.