and as long as the conditions h << a and t m << h are fulfilled, this model is expected to provide a useful description of the deflection of the membrane with increasing bias voltage. Figure presents a plot of the applied bias voltage V versus the deflection h of the membrane's central point. A fit to the data according to Equation 5 is shown as solid line. Note, in order to fulfil the condition of small deflections (h << d) the data used for producing the fit function, were limited to deflections between 0.1 µm and 1.7 µm. Within this range, the fit function shows good agreement with the data. With the exception of the membrane's prestress all parameters of Equation 5 could be measured and estimated or are known from literature (Supporting Information, Section S4). Hence, the membrane's prestress was extracted as the only free fit parameter, providing a value of ∼1.4 MPa. This value is smaller than the prestress values determined by the above-presented AFM bulge tests. We assume that this discrepancy results from the different geometry and size of the through holes and the cavity of the substrates used for AFM bulge tests and electrostatic actuation, respectively. The square-root-like shape of the fit function for deflections up to ∼1 µm suggests that the behavior of the membrane at small deflections was mainly governed by the membrane's residual stress (second term of Equation ). Plotting the data on a log/log scale returns a slope of 0.67, confirming that the prestress dominated the membrane's behavior in the range of small deflections (Supporting Information, Section S4). For deflections exceeding 1 µm the first term of Equation 5 becomes more important as indicated by the slight positive curvature of the plotted data and the fit between ∼1 µm and ∼1.7 µm.