Thermal bimetallic microactuators by Ni and Ni-diamond nanocomposite

In previous investigation, it was found that Ni-diamond nanocomposite fabricated by adding nano-diamond particles in nickel plating could enhance coefficient of thermal expansion (CTE). Here thermal bimetallic microactuators made of Ni and Ni-diamond nanocomposite are proposed, fabricated, and tested. By controlling plating sequence of Ni and Ni-diamond nanocomposite, two types of the thermal bimetallic microactuators, including upward displacement and downward displacement types, are developed. Due to the same low process temperature in electroplating these two layers, the residual thermal stress and initial deformation of fabricated thermal bimetallic microactuators are small. Since two materials in the bimetallic actuators are Ni-based, the bonding strength between Ni and Ni-diamond nanocomposite is found to be strong. From vibration test, after 10⁹ cycles, the resonant frequency remains unchanged. From thermal cycling test, the fabricated thermal bimetallic microactuator shows good interfacial bonding strength with only 0.002 % deviation of resonant frequency and 13.5 % deviation of tip deflection after 1,000 continuous thermal cycles.