A materials and methods study for the fabrication process of thermal actuator microelectromechanical systems

Abstract

The conventional production process of MEMS, silicon micromachining, is expensive and lengthy. Printing and coating techniques such as screen printing, inkjet printing, and blade coating could be a solution to this problem, reducing costs and turnover time. In this study, the materials and production process for a thermal actuator MEMS is selected and tested. The structure of the print is as follows: the substrate, the sacrificial layer, and the structural layer. After depositing this layer, the sacrificial material is dissolved and removed to achieve a freestanding structure. PVA, PMMA, and PEO are tested for their usability in the process as a sacrificial material. The main criterium for the sacrificial layer is that it can be dissolved after the production process with no negative impact on the MEMS. For the structural material, a silver nanoparticle and microflake ink are tested. PVA was selected as a sacrificial material because of its dissolving under 15 min. in water of 85°C. It was applied using blade coating. For the structural material, screen printing was found most suitable. Both inks are strong enough to support a freestanding actuator up to 9mm long, however, the nanoparticle ink was brittle and broke down easily. In thermoelectric testing, temperatures of 170°C were achieved for both inks which translates to simulated deflections of up to 224µm. A proof of concept achieved deflections of 100µm, however, further optimisation of the process and design is needed due to deformations that occur in the structure.