Design and Evaluation of an Active Micro-Scale Ball and Socket Joint

Micro-scale articulated joints enable development of advanced micro-manipulators and micro-robots. This paper describes the design, fabrication, and evaluation of a novel active micro-scale ball and socket joint. The ball is chosen to be a magnetic micro-particle of spherical morphology. A micro-pit that seats the ball along with a liquid meniscus based microgripper together act as the socket. Application of an external magnetic field enables actively orienting the ball in any desired direction. A simplified analysis is performed to describe the functioning of the joint. Subsequently, the joint is fabricated and experimentally demonstrated to achieve orientation changes from 0° to 90° about X-axis and Y-axis. Finally, the joint is integrated on to the probe of an atomic force microscope (AFM), thereby enabling active re-orientation of the probe tip in three dimensions. The probe is employed to image a standard sample, and the resulting image is shown to be free of artifacts and identical to that obtained using a conventional AFM probe. This demonstrates the ability of the joint to firmly grip the AFM tip during imaging.