content_image/354822.jpg content_image/354821.jpg content_image/354820.jpg content_image/354819.jpg content_image/354818.jpg content_image/354817.jpg
and of the total force are not identical, interpolation was used to determine the values of A$_{k}$ ( a ) at the separations corresponding to the total lateral force. After determination of the coefficients A$_{k}$ ( a ) from the fit, the signal S C lat was subtracted from the data for the total deflection signal S tot $_{lat}$. The obtained deflection signal S el lat now corresponds to the lateral electrostatic force 

<img src='content_image/354822.jpg'>

The experimental force data in this equation were used to determine the calibration param- eter k$_{ben}$ and z$_{0}$ from the fit to the theoretical expression for the lateral electric force. 

To derive the analytic expression for the lateral electric force acting between the sinu- soidally corrugated surfaces of a sphere and a plate, we start with the electrostatic energy in sphere-plane configuration with smooth surfaces [47, 48] 

<img src='content_image/354821.jpg'>

Here, the integration constant ˜ c is equal to [47] 

where 0 ≤ θ ≤ 1, and c$_{i}$ are defined in Eq. (2). 

<img src='content_image/354820.jpg'>

Using the PFA, we obtain the electrostatic energy between sinusoidally corrugated sur- faces of a sphere and a plate in the form 

<img src='content_image/354819.jpg'>

where z$_{s}$ − z$_{p}$ is given by Eqs. (3), (5) and (6). Using the definition of the lateral electric force [see the formula for the phase shift below Eq. (3)] 

and calculating all integrals in (17), we arrive at the result 

<img src='content_image/354818.jpg'>

<img src='content_image/354817.jpg'>

