Here, ε 0 is the vacuum permittivity, d is the distance between the membrane and the bottom electrode, t m is the membrane's thickness, ν is the poisson's ratio, a is half the edge length of the cavity, Y is the biaxial modulus of the membrane, and σ 0 is the prestress. Note, this approximation assumes a simple parallel arrangement of the membrane and the bottom electrode and neglects changes of the electric field due to the deformation of the actuated membrane. However, for the range of small deflections (h << d)