Moisture effects on nano-mechanical properties of epoxy-based materials

The nanoindentation of epoxy-based material has been conducted successfully using SU-8 as an example. In such a small scale characterization, it is noticed that moisture has a little effect on the change of bulk material properties in terms of Young's modulus and hardness, probably due to hydrolysis. However, there is an observable change of SU-8 under the optical microscope when the specimens were moisture conditioned. Even though moisture has only a minimal effect on the bulk material properties, it results in a detrimental effect on the interface fracture energy eventually leading to a premature failure of the bonded system, causing a durability problem, which has been reported in various research studies. It is envisioned that the overall deterioration of SU-8 is originated from its interface when bonded with other materials.