Design, fabrication and experimental validation of a MEMS periodic auxetic structure

Auxetic structures are attracting increasing interest because of their large variety of applications at both the macro and micro scales. In this work, an innovative auxetic unit cell is presented, numerically studied, fabricated at the microscale and experimentally tested. Its versatility in terms of stiffness and Poisson's ratio and its compatibility with commercial Micro Electro-Mechanical Systems (MEMS) fabrication processes suggest applications such as motion conversion and amplification mechanism in MEMS devices or on-chip biaxial tests. A MEMS auxetic and periodic structure exhibiting an overall equivalent Poisson's ratio lower than -1 is then proposed. The static and dynamic behaviours are studied both numerically and through a simplified analytical model. Experimental results confirm the simulated behaviour of the structure thus verifying the first MEMS auxetic structure with electrostatic actuation and capacitive readout.