Abstract
This study presents the effect of temperature on the mechanical and tribological properties of SU-8 polymer. The temperature of investigated samples increasing during testing and the variation of mechanical and tribological properties were monitored. The samples for tests were SU-8 hard baked at different temperatures. The hard bake temperature changes the mechanical and tribological properties of polymers. The aim of this research work is the reliability design improvement of SU-8 microstructures from electro-thermally actuated devices where a thermal gradient produces the softening and modification of SU-8 behavior. As a function of the hard baked temperature, different mechanical and tribological properties were experimentally determined using the atomic force microscopy (AFM) technique. The mechanical properties of interest are the modulus of elasticity and hardness. The investigated tribological properties involve the adhesion and friction forces. The modulus of elasticity and hardness decrease if the operating temperature increases based on the thermal relaxation of material and their viscoelastic behavior. The adhesion force between AFM tip and investigated samples increases if the operating temperature increases, respectively. The same evolution was experimentally observed in the case of friction force. Moreover, for the same testing temperature, the modulus of elasticity and hardness increase, and the adhesion and friction forces decrease if the SU-8 is hard baked at high temperature.
Highlights
The SU-8 is an epoxy-based negative photoresist material that was first developed and patented by IBM in 1989 [1,2]
The surface parameters have an important influence on the adhesion and friction effects from Microelectromechanical Systems (MEMS) devices with movable components
In order to determine the effect of hard bake temperature on the surface parameters of investigated polymers, the surfaces scanning was carried out by using the non-contact mode of atomic force microscopy (AFM) (NC-AFM)
Summary
The SU-8 is an epoxy-based negative photoresist material that was first developed and patented by IBM in 1989 [1,2]. This material has adequate mechanical properties that make it capable of flexible structures manufacturing or as a support for other components. The SU-8 is directly used as a polymeric material to produce mechanical components in the area of Microelectromechanical Systems (MEMS) [3,4]. This polymer exhibits good biocompatibility and has been successfully implemented in Bio-MEMS [5,6]. This material is insoluble in water and after polymerization has good chemical durability [3]. The SU-8 allows obtaining surfaces with good roughness, which is a basic need for reliability design of MEMS structures with adequate mechanical and tribological characteristics [3]
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