With the recent development of microfabrication technology, the measurement technology to evaluate geometric
quantities is demanded to assure their accuracy. In order to measure the 3D shape of these microcomponents, a novel
nano-CMM system has been developed based on an oscillated probing technique, which uses an optically trapped
particle. The particle as a probe is trapped by focused laser light using an objective in the air. The trapped particle is
laterally oscillated or circularly at the focal plane of the objective using AOD (acousto-optical deflector).
The motion of the trapped particle is induced by a trapping force toward a focal spot and damped by the viscosity of
the surrounding atmosphere. The frequency response of the oscillated particle typically agrees with the spring-mass-damper
model. On the other hand the response disagrees with the theoretical curve of the model at high frequency range,
i.e. 4.6% at 4000 Hz. It is considered the difference is caused from the numerical error for the fluid effect, which is given
by the stokes formula 6πη<i>r</i>
In this report, we construct a fluid simulation using SMAC method that calculates fluid resistance against an
oscillating sphere in noninertial frame of reference. The fluid effect is investigated in order to improve the model of the
sphere motion. 2D simulation indicates the same tendency in frequency response of the oscillating sphere with
amplitudes of 500 nm in 100-4000 Hz frequency range. 3D simulation could improve the measurement accuracy of
nano-CMM system as compared with 2D simulation.