The Status of PTB’s Nanonewton Force Facility

The nanonewton force facility of Physikalisch-Technische Bundesanstalt (PTB), Germany, has been significantly improved. We demonstrate the possibility of using the facility as a calibration device that can accurately determine spring constants of soft cantilevers (k <; 0.1 N · m
^-1
) with traceability to the SI units. This paper is described the possibility of increasing the range of the measured forces to 1 mN. We demonstrate the possibility of using PTB's nanonewton force facility to accurately determine and compensate for the contact potential difference. To measure the contact potential difference and at the same time the distance between a force sensor and a measured object, a new three-voltage method was developed. For a so-called “plan- plan geometry,” the results of measuring the contact potential difference and the distance in vacuum are presented. A new method of adjusting the parallelism of the plates is also presented. The method used to measure the negative light pressure (light-induced force), which had previously been only theoretically predicted, and the first results of the measurement are presented as well.