Influence of Crack Growths on the Performances of Cantilever based MEMS Devices: Design and Simulations M. Tariq Jan ∗ , Nor Hisham B Hamid, Mohd Haris B Md Khir, Muhammad Shoaib, Asif Mirza Department of Electrical and Electronic Engineering Universiti Teknologi PETRONAS,Tronoh, Perak, Malaysia ∗ Department of Physics, KUST, Kohat, KPK, Pakistan. tariqjan@kust.edu.pk Abstract—There is a great need to design experimental setup to deal with the fundamental material issues in MEMS. Cantilever being the active part of MEMS is modeled using COMSOL Multiphysics. The model is simulated for small cracks ranging from Nano to Micro-meter. The cracks are produced at the anchor of MEMS device subjected to variations in Eigen frequencies, Stress levels and Tip displacements of cantilever beam and is measured in association with crack growths. These factors are simulated in order to predict the ultimate lifetime in the form of total number of cycles to failure in association with variations in applied stress levels and with the help of Statistical distribution and Paris’s law. The Paris’s law is utilized by integrating it between the upper and lower limits (crack sizes) that results in predicting the useful lifetime of the cantilever based MEMS device. The simulated results show that at resonance frequency the probability of crack growth is less due to its stress-less and free vibration. The tip displacement of the cantilever also contributes in deterioration in resonance frequency. Moreover, periodically increase in applied stresses result in rapid crack growth. Index Terms—Cantilevers, Eigen frequency, stress levels, tip- displacements, Number of cycles to failure. I. I NTRODUCTION The size of the Microelectromechanical Systems (MEMS) is getting reduced day by day in order to enhance their performance. The small sized micro-components will expe- rience various loading cycles (i.e mechanical, thermal or chemical) that results in altering the structure, morphology or composition of these devises. Hence being vital for the design and maintenance planning of various structural parts; the fatigue lifetime prediction and reliability evaluation are the two rousing problems in spite of the extensive research. A method based on fracture mechanics and crack growth analysis is among one of the methodologies utilizing for fatigue life- time prediction. MEMS consists of miniature mechanical and electromechanical components that are fabricated utilizing the techniques of microfabrications. MEMS devices (sensors and actuators) are having unique mechanical functionalities that can be transformed into an electrical signal by the microelectric counterpart connected on the same chip. MEMS devices are categorized as relative simple structures having no moving parts to complex structures consisting of several moving sur- faces. Based on the structural formation of MEMS, some com- ponents such as membrane, comb figures and cantilever within the structure receive input stimuli (mechanical moments) and transform it to other form of energy. MEMS lifetime prediction has become necessary, as they are frequently being used in automobiles, aircrafts, medical, bio-medical and agriculture, where failure of these structures can turn to be dangerous and fatal [1]. Lifetime of MEMS sensors and actuators is consequently one of the most rising anxiety among the MEMS experts in order to ensure the long term reliability [2], [3]. Silicon and its oxides are the most common materials of which the MEMS structures are being fabricated. It is found that these materials are vulnerable to fatigue [4], [5] that in turns results in unpredictable lifetime of MEMS structures. Even though, the basic structural properties of silicon and its oxides are still under observations [6]. Nevertheless, reports regarding lifetime and fatigue damage accumulation of silicon are comparatively rare and on the other hand there is no well-known method adopted or available with the help of which the lifetime of MEMS can be predicted [7]. Frac- ture mechanics-based crack growth analysis is proposed for the lifetime prediction [8]. An Equivalent Initial Flaw Size (EIFS) model was utilized for this purpose. Jalamahmadi et al. [9] studied the fatigue lives of MEMS devices based on Voronoi Finite Element Method (VFEM). They also described the occurrence of damage and crack formation under cyclic loading by damage mechanics. Paris’s law can reflect the failure mechanism and is usually used to be a method to predict fatigue life. A generalized equation of Paris’ law is proposed in [10] for the fatigue crack propagation depending on the applied stress level. In this study cantilever being an active component besides membrane and comb-fingers is chosen which is composed of silicon and its oxides. Upon actuations of cantilever based MEMS devices, it receives cracks of nano levels that tends to degrade its performances in terms of 1) changes in Eigen fre- quency, 2) stresses level at the anchor and 3) tip displacement; that results in longer amplitude of the cantilever. Lifetime of the device is predicted by integrating Paris’s law with the help of statistical distributions in association with the applied stress, crack growths and known actuation period. All studies have been carried out in simulation environments. The rest of the paper is organized as follows. The fatigue in MEMS devices 978-1-4799-4653-2/14/$31.00 c 2014 IEEE