Browsing by Subject "Anisotropic wetting"

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Open Access
Micro and nanotextured polymer fibers for open microfluidics
(2016-01) Yunusa, Muhammad
Microfluidics is the science of controlling low volumes of fluids in a microchannel. It is used in diverse area of applications such as chemical and biological analysis. Benefits of microfluidics are fast analysis, short reaction times, and portability of device. Current fabrication techniques of lab-on-a-chip microfluidic devices are soft lithography and micromachining. However, these methods suffer from design limitations such as flexibility of product, high cost, integration of external components, and biocompatibility. Surface textured polymer fibers are utilized as a novel platform for the fabrication of affordable microfluidic devices. Fibers are produced by thermal drawing technique tens of meters-long at a time and comprise twenty continuous and ordered V-grooves channels on their surfaces. Extreme anisotropic wetting behavior due to capillary action along the grooves of fibers is observed after surface modifications with polydopamine (PDA) coating and Ultraviolet/Ozone (UV/O) treatment. Three-dimensional arrays of flexible fibers spontaneously spread liquid on predefined paths without the need of external pumps or actuators. In addition, surface modification with organically modified silica nanoparticles was added on top of the V-grooves to enhance the hydrophobicity of the fiber surfaces. Surface textured fibers are well suited for the fabrication of flexible, robust, lightweight and affordable microfluidic devices which is believed to expand the role of microfluidics in a scope of fields including drug discovery, medical diagnostics and monitoring food and water quality.
Open Access
Nonlinear laser lithography to control surface properties of stainless steel
(Elsevier BV, 2015) Orazi, L.; Gnilitskyi, I.; Pavlov, I.; Serro, A. P.; Ilday, S.; Ilday, F. O.
In the present work a novel method to improve the surface properties of stainless steel is presented and discussed. The method, based on the use of a high repetition rate femtosecond Yb fibre laser, permits generation of highly reproducible, robust, uniform and periodic nanoscale structures over a large surface area. The technique is characterized by high productivity, which, in its most simple form, does not require special environmental conditioning. Surface morphology is scrutinized through SEM and AFM analyses and wettability behaviour is investigated by means of the sessile drop method using distilled-deionized water. It is shown that optimization of process parameters promotes anisotropic wetting behaviour of the material surface.