Photo-fluidic behavior of azopolymer toward micro/nano patterning and robust superomniphobic surface

Abstract

Azobenzene polymers exhibit extraordinary molecular behavior upon light irradiation. For example, when linearly polarized light is irradiated, the azobenzene molecules are aligned in a direction perpendicular to the polarization as they undergo repeated/reversible trans-cis-trans isomerization cycling. Interestingly, the light-responsive molecular behavior results in macroscopic behavior of azobenzene polymer, called directional photo-fluidization. The rep-resentative characteristic of the behavior is that the azobenzene polymer behaves like fluid even below its $T_g/T_m$ under irradiation. More importantly, the photofluidic mass-migration is anisotropic in a direction parallel to the light polarization. Such polarization-dependent, flu-idic movement can be usefully used in various applications ranging from mi-cro/nanostructuring to superomniphobic surface. This thesis is classified in 6 main parts. In Chapter 1, azobenzene polymers and their light-responsive behaviors are presented as follows: i) the light-responsive molecular behav-ior of azobenzene molecules, ii) the light-responsive macroscopic behavior of azobenzene polymer (i.e. the directional photofluidic behavior of azobenzene polymer), and iii) the rele-vant applications in macro/nano-fabrication (i.e. directional photofluidization lithography). In Chapter 2, the development of heat-free, solvent-free and curing-free imprint lithography that is enabled by an important discover of vertical-directional photofluidization is present-ed. In Chapter 3, an efficient way to transfer micro/nano-patterns to functional material (i.e. silicon wafer) is presented, where it exploits azobenzene polymer as etch-mask that produce diverse patterns ranging from few microns to 100 nm with vertical sidewall profile. In Chapter 4, a pragmatic method creating polymeric mushroom-structures that produce flexi-ble and robust superomniphobic surface is discussed. In Chapter 5, the development of alumina-patterning method that provide structural reconfigurability and fab-simplicity is presented. Finally, in Chapter 6, brief summary of this thesis is presented..