Browsing by Keyword "Contact angle"
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Item Effects of ion implantation on nano-topographic properties(2007-08-05) Braceras, I.; Briz, N.; García, F.; Muñoz, R.; Viviente, J.L.; Onate, J.I.; INGENIERÍA DE SUPERFICIES; SG; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Tecnalia Research & InnovationIt is well known that surface properties at nano-scale are determinant in a number of applications, such as sensors, biomedical and optical devices. Nevertheless, relations between surface treatment parameters and their effects on topography at the nano-scale, surface energy or light reflectivity are often poorly understood. In this study, a non fluorescent glass material (Knittel) was selected and subjected to ion implantation treatments with different parameters and species, including Ar, Ne, C, N, CO and NH2. The resulting surface topography at the nano-scale was studied by Atomic Force Microscopy (AFM) and the surface energy was evaluated with the contact angle method. Additionally, the modifications induced on optical properties, i.e. reflection, were evaluated with two different wavelength lasers. The results showed remarkable differences in surface nano-topographies and contact angles (from 15° to 70°) that were obtained. Furthermore, the effects of ion implantation parameters had also very significant consequences on background noise effects, of great importance for optical properties. It was found that the best implantation treatment corresponded to N2 + ions implanted to a dose of 3×1017 ions/cm2 at an energy of 30 keV. This treatment resulted in a adequate contact angle, producing a nano-textured surface with potential features for a good attachment and orientation of deposited bio-molecules, and a very low background fluorescence, hence allowing a high degree of scanning sensitivity, for application on DNA microarrays. The study has shown that ion implantation represents a powerful tool for modifying key properties on surfaces that play an important role in the response elicited on living tissue and bio-molecules, which is notoriously relevant for the application as bio-sensors.Item Influence of the contact angle on the wettability of horizontal-tube falling films in the droplet and jet flow modes(2018-06) Fernández de Arroiabe, Peru; Martinez-Urrutia, Asier; Peña, Xabier; Martinez-Agirre, Manex; Bou-Ali, M. Mounir; Tecnalia Research & Innovation; SISTEMAS TÉRMICOS EFICIENTESWettability has a key impact on the performance of LiBr-H2O horizontal-tube falling film absorbers working under typical operating conditions. Therefore, it is necessary to study the influence of the wettability properties on the film hydrodynamics and wetted area. This work analyses the influence of the contact angle (0° – 120°) on the transient film hydrodynamics and the wetted area in the droplet and jet flow modes (7 ≤ Re ≤ 53). The comparison between two-dimensional and three-dimensional models evidences that three-dimensional models are needed for incomplete wetting conditions. The influence of the contact angle on both the film hydrodynamics and wetted area is demonstrated using 3D unsteady CFD model. Furthermore, the results indicate that each Reynolds number has a maximum contact angle to wet the whole tube steadily. When the value of the contact angle is lower than this maximum value, the contact angle has not influence on the wetting ratio. In contrast, at higher values, the wetting ratio decreases as the contact angle increases.