C. Universal Needle Clamping and Loading Mechanism To design a needle driver that allows a large variety of standard needles to be used, a new clamping device rigidly connect the needle shaft to the driving motor mechanism is developed as shown in Fig. 3. It consists of three components made of ABS plastic: collet, collet nut and collet screw shaft. This structure is a collet mechanism and a hollow screw is twisted to fasten the collet thus rigidly locks the needle shaft on the clamping device. The clamping device is connected to the rotary motor through a timing belt. An eccentric pulley tensioner that is concentric with the rotary piezoelectric motor can freely adjust the distance between the motor and the clamping mechanism. The clamping device is generic in the sense that each collet can accommodate a wide range of standard medical needle diameters. The overall needle diameter range for three collets is from 25 Gauge (0.5144mm)to 16 Gauge (1.651mm). By this token, it can not only fasten brachytherapy needles but also biopsy needle or most other standard needles instead of designing some specific structure to hold the needle as those in [15]. The plastic needle guide with quick release mechanism, collet, nut and guide sleeve have direct contact with the needle and are low lost and disposable