Nanocomposite effects on the coefficient of thermal expansion modification for high performance electro-thermal microactuator

We employ a low-temperature stress-free electroplated nickel (EL) process with the addition of uniformly dispersed nanoparticles of diamond (< 500 nm) or SiO₂ (< 80 nm) to investigate "nanocomposite effects" for the first time on the modification of the thermal expansion coefficient (CTE) and other mechanical properties of nickel and its correlation to power and reliability improvement of electro-thermal microactuators. Experimental results show that these material parameters can be either enhanced or deteriorated via the incorporation of different kind of nanopowders. Although the mechanical strength enhancement can be attributed to the intrinsic characteristics of the nanoparticle based on the rule of mixture, the discrepancy of CTE modification can only be explained with distinct composite microstructures which result in the performance improvement of the electro-thermal microactuator. This work has led to a possible research direction in the development of MEMS using the nanocomposites.