Characterisation of PolyVinyl Alcohol (PVA) as a water-soluble sacrificial layer for affordable surface micromachining

• Main Author: Jijo Mathen Varghese
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/53592
• Institution: Nanyang Technological University

Micro-Electro Mechanical Systems (MEMS) play a significant role in many industries today. These include aerospace, automotive, biomedical, optical display and wireless communication. MEMS are very small devices that can sense, think, communicate and even act. This makes them the backbone of many industries. As the sizes of these devices gets smaller and smaller to the micro- or nano-scale, the fabrication process becomes a challenge. There are numerous methods of creating such devices. One such method is the use of sacrificial layers in surface micromachining. Currently the common sacrificial layers that are used require acids, that are highly corrosive and toxic, to dissolve them. This is harmful not just to the people handling it but also to the environment. Thus a safer means of creating such devices is essential. Imagine being able to form such devices with solvents that are extremely safe and environmentally friendly. Water is one such solvent, and that is why it important to obtain a sacrificial layer that can be dissolved using water and still be able to function just as well as other sacrificial layers. PolyVinyl Alcohol (PVA) is a polymer that is soluble in water. Therefore this study focused on the possibility of using PVA as a water-soluble sacrificial layer. Experiments were carried out to form PVA film from solid PVA and then structural layers were deposited on top of the PVA. The structural layers used were Norland Optical Adhesive (NOA), epoxy resin and cyanoacrylate. The PVA was then dissolved away using water to form channels. This process resembles the basic steps required to create micro-devices using a sacrificial layer. It was found that PVA can be used as a water-soluble sacrificial layer for surface micromachining. However, success in using PVA depends heavily on the choice of structural layer, because certain materials such as NOA and epoxy resin alter the solubility of PVA. Nevertheless, with further process development, the use of PVA as a sacrificial layer could result in the elimination of toxic solvents from MEMS fabrication.