We developed a facile nano-fabrication method to generate nanostructures by the nano-indenting and the nano-imprinting of core-shell particles on a polymer surface.  The particle array was achieved by spreading and compressing the particles over the water surface and transferring the particle monolayer onto the substrate with the LB technique.  Then, heat-treatment of the particle-arrayed substrate was carried out by the UV irradiation or the incubation in a temperature-controlled incubator.  This heat-treatment caused denting of particles into the substrate without any pressing.  Then, this nanostructured substrate was immersed into ethanol and treated by ultrasonication to remove the particles from the substrate.  Nanoholes were produced and their size and depth were tunable by controlling particle arrangement and heat-treatment.  Next, we investigated the relation between the annealing temperature and the depth of the particle denting to elucidate a mechanism of the particle nano-indenting.  The height of bumps, which is the distance from the polymer surface to the top of the particle, was measured with AFM at different temperatures.   With increasing the incubation time at a constant temperature, the average height gradually decreased and leveled off.  The initial change of the height, which reflects the rate of indenting, became steeper with increasing the temperature.  It is thought that the plastic flow of the polymer substrate was induced by annealing above its Tg and thereby the arrayed particles could undergo denting into the substrate through surface deformation.  This also suggests that the gravitational force, which is proportional to the particle mass, and intermolecular forces, which reflects the affinity between the substrate surface and the particle surface, are important to determine the shear stress.  We hope that the nanostructures generated by this nano-fabrication method would be applied for advanced materials and devices such as antireflection film, micro flow channels, biochips and novel tissue cultured substrates.

Indentation and imprinting by core-shell particles to create nanostructures over the polymer surface

247th National Meeting (2014)

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