Nanonewton force generation and detection based on a sensitive torsion   pendulum
  In this paper, we introduce the experiment based on a sensitive torsion pendulum for measuring and calibrating small forces at nanonewton scale. The force standard for calibration is the universal gravitation between four masses separated by known distances. It is realized by two test masses suspended as the part of torsion pendulum and two source masses on a rotation table. Two force generation mechanisms, optical force from radiation pressure and electrostatic force by capacitive actuation unit, are designed and will be calibrated by the gravitation force. We present our recent results of radiation pressure measurements, and describe the design of capacitive displacement sensing/actuating unit. 
Sheng-Jui Chen and Sheau-Shi Pan