Narayanan Ramakrishnan

Sliding Contact Micro-Bearing for Nano-Precision Sensing and Positioning

Applications involving sub-nanometer, relative, in-plane motion between two substrates require precise control of gap-spacing between substrates for, both position-sensing as well as for signal transduction between the substrates. A method of passive gap-spacing control using MEMS-fabricated rigid spacers is proposed. A model to design a low-friction and low-wear interface between the sliding substrates is developed. Prototype parts with hard-coated interfaces and with and without lubrication were fabricated and tested. Sliding friction coefficients of 0.1-0.15 or less and wear life of millions of sliding cycles were achieved on prototype parts. Better results are predicted for MEMS-scale devices.

Nano-Positioning of a Electromagnetic Scanner with a MEMS Capacitive Sensor

Abstract This paper presents the control design and experimentation of a prototype electromagnetic scanner with an integrated capacitive linear and rotational position sensor for small form factor probe storage. An array of probe heads is to be precisely positioned in X/Y linear and rotation directions so that high areal density (>1 terabit/in 2 ) and high data throughput can be achieved. The scanner has X/Y motion capabilities with a linear stroke of about 300 µm. It can also generate rotational motion with offset actuators to compensate for disturbances, mechanical tolerance and nonlinearities. System characterization, modeling, MIMO control design and simulation, and preliminary experimental results are presented. The feasibility of rotation control with the developed capacitive sensor and offset actuators is experimentally confirmed.