Sessile drop technique

About: Sessile drop technique is a research topic. Over the lifetime, 2827 publications have been published within this topic receiving 68943 citations.

Hemocompatibility of Poly(acrylonitrile-co-N-vinyl-2-pyrrolidone)s: Swelling Behavior and Water States

Abstract: Hemocompatibility is an essential aspect of blood contacting polymers. Knowledge of the relationship between polymer structure and hemocompatibility is important in designing such polymers. In this work, the effect of swelling behavior and states of water on the hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone) (PANCNVP) films was studied. Platelet adhesion and plasma recalcification time tests were used to evaluate the hemocompatibility of the films. Considering the importance of surface properties on the hemocompatibility of polymers, static water contact angles were measured by both sessile drop and captive bubble methods. It was found that, on the film surface of PANCNVP with a higher NVP content, adhered platelets were remarkably suppressed and the recalcification time was longer. The total water content adsorbed on the PANCNVP film was determined through swelling experiments performed at temperatures of interest. Differential scanning calorimetry and thermogravimetric analysis were used to probe the states of water in the films. Based on the results from these experiments, it was hypothesized that the better hemocompatibility of PANCNVP films with higher NVP contents was due to their higher free water content, because water molecule exchange at the polymer/liquid interface, facilitated by a high free water content, is unfavorable for the formation of surface bound water, which causes poor hemocompatibility. [diagram in text].

X-ray computed microtomography for drop shape analysis and contact angle measurement

Abstract: The interaction between an atomized fluid and a solid surface has a great importance in many fields, both in adiabatic conditions and when heat transfer is involved. To investigate the behavior of many drops in contact with a surface, the first step is to study a single one of them and in that, surface wettability is key parameter. Wettability analyses are usually performed by contact angle measurement, in most cases using the sessile drop or captive bubble techniques. Such techniques require optical acquisition of a side view of the drop or bubble, with a series of drawbacks when conventional optics are used, in particular for not uniform, not planar or rough base surfaces. X-ray micro-computed tomography is therefore used to acquire a 3D scan of a drop gently deposited on a surface, with the aim to reconstruct the drop surface and to perform contact angle measurements on true cross-sections of the drop-surface couple. Comparison with contact angle measurements performed on conventional images is performed. The results evidence that the proposed technique is very promising for surface characterization and to get more accurate and detailed information about wettability characteristics.

An analytical solution for determination of small contact angles from sessile drops of arbitrary size.

Abstract: An analytical solution to the capillary equation of Young and Laplace is derived that allows determination of the static contact angle based on the volume of a sessile drop and the wetted area of the substrate. This solution does not require numerical integration to determine the drop profile and accounts for surface deformation due to gravitational effects. Calculation of the static contact angle by this method is remarkably simple and accurate when the contact angle is less than 30°. A natural scaling arises in the solution, which provides indication of when a drop is small enough so as to neglect gravitational influences on the surface shape which, for small contact angles, is generally less than 1 μl. The technique described has the simplicity of the spherical cap approximation but remains accurate for any size of sessile drop.

Surface modification of silicone rubber by ion implantation

Abstract: A study has been made on the wettability, structure, and chemical states of ion implanted silicone rubbers. C + , N 2 + , O 2 + , and Ar + ion implantations were performed at energies of 50 and 100 keV at room temperature. The fluences ranged from 10 12 to 10 17 ions/cm 2 . Ion implantation caused the surface roughness to increase 2–3 times. Wettability was estimated by means of the sessile drop method using water, of which the results showed that the contact angle of water decreased from 98.9° to 48° as the fluence increased. The results of XPS measurements showed that implanted elements formed a Gaussian-like distribution, host elements were redistributed and no change in binding energies of O 1s , C 1s and Si 2p occurred. Results of FT-IR-ATR showed that ion implantation broke up original chemical bonds to form new radicals, the amounts of which are related to the fluences. It is concluded that the change in wettability may be caused by formation of new radicals rather than roughening of the surface under ion implantation.