  We propose the realization of capacitive temperature sensors based on the
concept of displacement amplification. Our design features two high coefficient
of thermal expansion (CTE) metallic layers separated by a low-CTE dielectric
layer; conductive and dielectric layers are then separated by a thin air gap
and glued together at a few locations. As the temperature increases, the
high-CTE layer tends to expand more than the low-CTE one. Owing to the
constraint to planar expansion imposed by the low-CTE layer, this results in
large out-of-plane displacements of the high-CTE layer -- hence the
displacement amplification term. In our case, the high-CTE layer buckles and
causes a reduction of the gap between conductive and dielectric layers; in
turn, this results in a large change of capacitance. First, we illustrate the
concept via numerical simulations. Then, we realize a low-cost prototype of
such sensor by using aluminum foil as conductor, paper as dielectric, and by
gluing the layers together with cyanoacrylate. Our results demonstrate the
potential of this simple design as a route towards efficient and low-cost
temperature sensors.
