  We show that the Casimir force gradient can be quantitatively measured with
no contact involved. Results of the Casimir force measurement with systematic
uncertainty of 3% are presented for the distance range of 100-600 nm. The
statistical uncertainty is shown to be due to the thermal fluctuations of the
force probe. The corresponding signal to noise ratio equals unity at the
distance of 600 nm. Direct contact between surfaces used in most previous
studies to determine absolute distance separation is here precluded. Use of
direct contact to identify the origin of distances is a severe limitation for
studies of the Casimir forces on structured surfaces as it deteriorates
irreversibly the studied surface and the probe. This force machine uses a
dynamical method with an inserted gold sphere probe glued to a lever. The lever
is mechanically excited at resonant frequency in front of a chosen sample. The
absolute distance determination is achieved to be possible, without any direct
probe/sample contact, using an electrostatic method associated to a real time
correction of the mechanical drift. The positioning shift uncertainty is as low
as 2 nm.
