Abstract A surface-micromachined force sensor using tuning forks as resonant transducers has been designed, fabricated, and successfully tested. This sensing technique shows great promise for the measurement of very small forces at high bandwidths. In this paper, the models used in the design of this sensor are presented. These models include expressions for the natural frequency and sensitivity of the forks, an expression for the force magnification due to the suspension design, and a model to both predict and correct for the uneven loading of the tuning fork tines. Finite element results are discussed and initial testing data are presented and compared with the design models. The tuning fork natural frequencies of 227 kHz and 229 kHz are within 3% of the model estimate. The frequency matching between the tuning forks on a single device is within 1%. The observed force sensitivity is also very close to the model prediction of 4.26 Hz/nN. Output drift and asymmetric sensitivity are observed, and it is hypothesized that nonlinear effects and problems with the amplitude control system are the cause.
Roessig et al. (Sun,) studied this question.