The Fabrication of Functional Surfaces via Multiscale Deposition Methods

Abstract

In this thesis, we report novel multiscale deposition methods for fabricating functional surfaces. The processes using polymer and aerosol process have various advantages such as fast, cost-effective, easy material preparation and atmospheric environment process. We fabricated functional surfaces which have selective wettability, controllable wettability and energy conversion properties using those advantages. First, we present that a thin layer of polydimethyl siloxane (PDMS) in the nano-thickness(< 100 nm) can be generated multiple times (> 10) by utilizing irreversible bonding with oxygen plasma treatment and controlled interfacial fracture. The clean cleavage is attributed to the built-in stress at the fracture interface during the plasma treatment, resulting in the repetitive formation of a smooth membrane of ~5 nm roughness from the bulk PDMS. And then, we controlled height of transferred pattern via oxygen plasma treatment conditions and intrinsic characteristics of PDMS stamp. The method can be used to transfer various micro- and nanopatterns without a residual layer as well as to form nanogrooves of controlled dimension. Also, we achieved highly specific protein immobilization on the patterned surface of a solid substrate in a site-directed manner. Next, we investigated about magnetic responsive and superhydrophobic pillar arrays via spray method. The magnetic pillars grow following magnetic field direction during spray process, represent enormous deflection under the magnetic force. From the fabrication result, we analyzed structure change and wetting characteristics of the pillars as strength of magnetic field and number of coating. Size of pillar was increased by repeated coating process and it makes the pillars become more hydrophobic. Furthermore, dual-roughness of pillars dramatically decreased the CA hysteresis of the pillar arrays. The large bending of the pillars generates geometrical potentials decrease the droplet ROAs on the structure. By the active property, we adjust sliding direction of the droplet by orientation of the magnet and we show active droplet manipulation and mixing result on the pillar structure via only structural modulation. Furthermore, formed ice particle under subzero temperature could be removed by motion of the magnetic pillar. Finally, we present fabrication process to make the components of the solid oxide fuel cell (SOFC) using Electrospray deposition (ESD) method which can deposit a uniform membrane through simple step and evaluated its performances. The components of the SOFC such as anode functional layer (AFL), electrolyte layer, cathode functional layer (CFL) and cathode layer could be fabricated by ESD method followed by annealing process. Especially, we could get dense membrane and porous structure using ESD process. During annealing process, the morphology of the membrane is determined by the amount of the binder. In the low concentration of the binding polymer, the porous membrane is fabricated but in the high concentration, dense membrane morphology is attained. As a result, we could adjust the morphology of the ceramic membrane via ESD method and the concentration of polymer binder. Structure of cathode and electrolyte was optimized by controlling the amount of polymer binder, also their electrochemical characteristics were measured. The power density of the fabricated ESD-SOFC was 660 mW/cm2 power density at 650 °C.