Design and optimization of cantilevered magnetostrictive film-substrate microactuator

Abstract

The exact solution for the bending problem of a free-end point loaded filmsubstrate cantilever with arbitrary film-to-substrate thickness ratio is obtained by using the basic mechanical equilibrium equation. And then the problem of design and optimization for microactuator buildup of film-substrate cantilever is discussed by taking into account the effect of geometrical and physical parameters of the cantilever components. Furthermore, the optimal condition for actuator application is presented and some theoretical problems are clarified. The results show that, in general, the greater the film-to-substrate thickness ratio, the higher the ability of taking load, namely the larger the exerted force of the cantilever when the thickness of substrate is kept constant. When the total thickness of the cantilever is kept constant, however, the free-end exerted force will experience a maximum and this maximum value of the exerted force will decrease with the increasing film-to-substrate stiffness ratio. Meanwhile, the optimal thickness ratio corresponding to this maximum exerted force also decreases with the increasing stiffness ratio. Whether for the cases of fixed substrate or fixed total thickness, the influence of Poisson's ratio of two cantilever components on the exerted force is remarkable, and should not be neglected. magnetic film-substrate system, cantilever, deflection, actuator, exerted force Microactuator [1,2] and microsensor [3] are the most important topic of current research on microelectromechanical system (MEMS) [1][2][3][4][5] , in which the microelectromechanical device made of nano-magnetostrictive materials possess many advantages over the piezoelectric devices, such as non-contact driving, high load and large response at low field. Especially, the cantilevered film-substrate system made of giant magnetostrictive material is the most promising for the making of microsensors and microactuators [6] . Since the cantilever actuating system is based on the

Modelling of the magnetostrictive trilayer cantilever for actuators

“…In fact, they applied an unloaded cantilever theory to the calculation of the exerted force without considering the influence of the external load. This led to the conclusion that the deflection of the cantilever will disappear everywhere in the case where the free-end deflection is forced to be zero by a point loaded, which is inconsistent with the standard assumptions that are generally made for a point loaded cantilever beam [23].…”

“…The four-parameter model [21] has achieved much improvement in describing the bending state of a cantilever with arbitrary thick film [22]. But this theory had omitted the role of the external load for a cantilever actuator and thus obtained erroneous results when applied to model the actuators [23].…”

Analysis of film strain and stress in a film-substrate cantilever system

“…With regard to its validity and integrality, Iannotti et al's theory [26] achieved much improvement. But a cantilever system consisting of two active materials was considered in their paper, so the results are too complicated to be applied to such universal cases as the arbitrary Poisson's ratio configuration [30,31] . Moreover, most of the recent work discussed the application of film-substrate cantilever to the MEMS devices such as sensors and actuators [23,[25][26][27][28][29] .…”

Modeling of Bimorph Type Cantilever for Actuators

“…A series of work was devoted to model the behaviors of such a GMS film-substrate system as sensors and actuators in the last decades [4]- [9]. But most of them have encountered some difficulties when applied to predict and optimize the cantilever actuator [10], [11].…”