Highly linear and large spring deflection characteristics of a Quasi-Concertina MEMS device

In this work a Quasi-Concertina (QC) spring capable of a high linear range, large deflections, high out-of-plane compliance, and low in-plane compliance for MEMS applications is presented. These features are essential for high accuracy out-of-plane measurements such as those required in self-sensing nanoindentation atomic force microscopy (AFM) probes or molecular mass sensors. The spring constant and first mode resonant frequency of the spring was determined analytically and verified numerically. The QC springs were microfabricated using a purposely developed stiction free process. Force–displacement tests on the QC springs have shown them to be in good agreement with the analytical and finite element analysis performed. The measurement results show that the QC springs fabricated have an out-of-plane spring constant of 5.5 N/m, 0.129 N/m, and 0.156 N/m, remain 99% linear to a deflection of 100 μm, 1080 μm, and 931 μm respectively, and can have a total deflection before fracture of as much as 8000 μm.