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Title: Proton beam writing of 3D-microstructure for microfluidics and MEMS applications
Author: Alshehri, Saad
ISNI:       0000 0004 5918 6436
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2016
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This thesis describes the use of proton beam writing (PBW) for the fabrica- tion for microfluidic and microelectromechanical system (MEMS) devices. In particular, the fabrication of three-dimensional (3D) micro or nanostruc- tures with high aspect ratios is of growing interest in these fields. PBW is the only technique that has the capability to satisfy these requirements while providing full control of the geometrical parameters, such as the sur- face roughness and side wall angle. This technique is a direct microfabri- cation method that employs a focused, energetic (MeV) proton beam to structure the input pattern in resist materials. In the present work, a network of buried channels is fabricated as part of a project to develop a functional microfluidic device for neuronal studies and self-powered microfluidics (capillary micropump). Proton beam with energies of 0.75 to 2.5 MeV is used to fabricate the channels in 3D with a minimum feature size of approximately 1 μm and depths of 40 to 60 μm. The roughness of the sidewalls of the written channels is approximately 3 nm root mean square roughness (Rrms). Radio frequency (RF) MEMS switches, which consist of an overhanging structure, are also written using PBW, and new MEMS switch designs are proposed. These designs are constructed so as to provide full control of the main cantilever beam parameters, such as the thickness, spring constant, and actuation. The three main stages of the lithography process, i.e., pre-exposure, expo- sure, and post-exposure, are investigated and optimised for application to poly(methyl methacrylate)(PMMA), pure SU-8 polymer, and SU-8/silver- nanoparticle nanocomposites (SU-8/AgNp). During the exposure process, the proton beam energies, doses, and scanning method are also optimised, in order to attain a good-quality structure (i.e., a robust structure with smooth and straight walls). The mechanical and electrical properties of the nanocomposites, which are irradiated with a range of proton beam doses, are measured. Note that the structures written in this work are numerically validated prior to the writing process using COMSOL Multiphysics �R software. The fluid flow in the written buried channels is investigated using numerical methods.
Supervisor: Webb, R. P. Sponsor: Royal Embassy of Saudi Arabia Cultural Bureau in London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available