MEMS resonant load cells for micro-mechanical test frames: feasibility study and optimal design

Creative Commons License

Torrents A., Azgin K., Godfrey S. W., Topalli E. S., AKIN T., Valdevit L.

JOURNAL OF MICROMECHANICS AND MICROENGINEERING, vol.20, no.12, 2010 (SCI-Expanded) identifier identifier


This paper presents the design, optimization and manufacturing of a novel micro-fabricated load cell based on a double-ended tuning fork. The device geometry and operating voltages are optimized for maximum force resolution and range, subject to a number of manufacturing and electromechanical constraints. All optimizations are enabled by analytical modeling (verified by selected finite elements analyses) coupled with an efficient C++ code based on the particle swarm optimization algorithm. This assessment indicates that force resolutions of similar to 0.5-10 nN are feasible in vacuum (similar to 1-50 mTorr), with force ranges as large as 1 N. Importantly, the optimal design for vacuum operation is independent of the desired range, ensuring versatility. Experimental verifications on a sub-optimal device fabricated using silicon-on-glass technology demonstrate a resolution of similar to 23 nN at a vacuum level of similar to 50 mTorr. The device demonstrated in this article will be integrated in a hybrid micro-mechanical test frame for unprecedented combinations of force resolution and range, displacement resolution and range, optical (or SEM) access to the sample, versatility and cost.