Mohammod Aminuzzaman

Photochemical surface modification and characterization of double-decker-shaped polysilsesquioxane hybrid thin films

The surface modification of a double-decker-shaped polysilsesquioxane (DDPSQ) film by deep ultraviolet (UV) irradiation (λ = 185 and 254 nm) was studied in the presence of atmospheric oxygen at room temperature. The change in the surface structure of a DDPSQ hybrid film was observed by means of contact angle measurements, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Exposure to deep UV light was found to convert the surface of DDPSQ film from hydrophobic to hydrophilic due to the formation of silanol groups (Si–OH) on the DDPSQ film. Measurements of FT-IR and XPS indicate that the Si–O–Si cage structure of DDPSQ was converted to the Si–O–Si network structure of SiO2 through cleavage of the Si–O–Si cage with deep UV irradiation. The irradiated DDPSQ film surface is very smooth with a root-mean-square (RMS) roughness of 0.34 nm. Moreover, to demonstrate the effect of surface modification of a DDPSQ film on the adhesion of metals, we fabricated silver (Ag) micropatterns on the deep UV modified DDPSQ film by laser-induced pyrolysis of a film prepared from liquid-dispersed Ag nanoparticles. The Ag micropatterns show an excellent adhesion to the modified DDPSQ surface as assessed by the Scotch tape test.

Immobilization of a fluorinated polymer Langmuir–Blodgett monolayer on a solid substrate for surface nanocoating

N-(1H,1H-Pentadecafluorooctyl)methacrylamide copolymers containing carboxyl groups as reactive moieties were prepared to explore a novel method for surface nanocoating materials. All the copolymers form stable monolayers on a water surface. Those monolayers can be transferred onto solid substrates, thereby creating Y-type Langmuir–Blodgett (LB) films. Contact angle and critical surface tension measurements were used to characterize the surfaces of the copolymer LB films. The copolymer monolayer can be immobilized onto solid substrates that are modified with an aminosilane coupling agent through heat treatment. We monitored the immobilization process using water contact angle and X-ray photoelectron spectroscopy (XPS) measurements. The immobilized monolayer on SiO2 surface yields a smooth surface at the nanoscale, which was observed using atomic force microscopy.

Submicron writing by laser irradiation on metal nano-particle dispersed films toward flexible electronics

The requirement for microwiring technology by a wet process has significantly increased recently toward the achievement of printable and flexible electronics. We have developed the metal microwiring with a resolution higher than 1 μm by the laser direct writing technique using Ag and Cu nano-particle-dispersed films as precursors. The technique was applied to the microwiring on a flexible and transparent polymer film. The metallization is caused in a micro-region by focused laser beam, which reduces the thermal damage of the flexible polymer substrate during the metallization process. The laser direct writing technique is based on the efficient and fast conversion of photon energy to thermal energy by direct excitation of the plasmon absorption of a metal nano-particle, which provides Cu microwiring with a low resistivity owing to the inhibition of the surface oxidation of the Cu nano-particle.

Surface Modification of Microchannels with Fluorinated Polymer Langmuir-Blodgett Films

The Langmuir-Blodgett(LB)technique was utilized to control surface properties of narrow microchannel walls at the molecular scale. Fluorinated amphiphilic polymer(pC7F15MAA)was synthesized and its ultrathin films were prepared by the LB technique. Microchannel was fabricated with glass substrates. A laminar flow of water in hydrophilic and hydrophobic microchannels was monitored in situ using an optical microscope equipped with a digital CCD camera. Shape of meniscus was clearly monitored with 250 ms time-resolution. The fluorinated polymer LB film can be a good candidate to control water motion in the microchannel.