Active micromechanical motion amplifiers using the mechanical resonance modulated by variable stiffness springs

This paper presents active micromechanical motion amplifiers, inspired from the amplification principle of outer hair cells in cochlea, achieving the displacement amplification using the mechanical resonance modulated by variable stiffness springs. The proposed active micromechanical motion amplifiers modulate the resonant carrier motion using the variable stiffness springs whose stiffness changes depending on the input motion. We have designed, fabricated, and characterized two types of the amplifiers A and B, each having the variable stiffness spring designed to obtain different displacement gains. In the experimental study, we characterized the ratio of output stiffness change to input motion as 1.82 N/m/μm and 0.636 N/m/μm for the variable stiffness springs A and B, respectively. The displacement gains of the amplifiers A and B were measured as different values of 5.62 and 2.62, respectively. Therefore, we experimentally verified that the displacement gain of the proposed active micromechanical motion amplifier can be adjusted by the variable stiffness spring design. The present micromechanical motion amplifiers are capable to amplify the displacement based on the active amplification mechanism, thus having the potential to be used in high-sensitivity microsensors.