接触角仪选购指南There are a lot of contact angle meters or contact angle measurement instruments with different measuring method or made by different manufactory. And, quality and working accuracy of these contact angle meters or contact angle measurements instrument is quite differ from each other. How to choice most suitable contact angle meter for us is more important. This article will show you how to begin your contact angle measuring experience by choosing the most suitable contact angle meter from different manufactory in worldwide.1, Startup choosing contact angle meter fromWhat material do you want to measure and whats you purpose to measure contact angle?Material which you want to measure is always taken seriously when one choose contact angle meter. Actually, material such as fiber (especially measuring contact angle between resin and single fiber, or single fiber with super-hydrophobic surface), powder (with contact angle above 80) and uneven surface is difficult to measure contact angle. All of these need special ways to measure contact angle. (Email us to get more information about measurement of contact angle for these conditions)Material with Super-Hydrophilic (contact angle below 3) surface (such asaluminum foil ofair conditioning) or super-hydrophobic (contact angle above 140) surface (such as lotus leaf or water strider leg) is also difficult to measure contact angle. General method of contact angle meter is useless in this condition.So, when you measure such material as described above, you should tell it to you supplier and ask them for a suitable solution.The second thing we should consider is outline dimensions of measuring sample, especially size of one side and thickness of sample, because to capture small droplet image, work distance of lens is usually not very long (max. word distance of lens with 0.20X auxiliary lens is about 360mm). And in commercial contact angle meter, work distance of lens is usually about 170mm and it can used to measure contact angle for sample with size of one side about 300mm. As an alternative when we measure contact angle for especially large sample such as LED displayer, we use prism to refract the observation angle and background light. (Refer portable contact angle meter model SL200P series).The third thing that need to be considered is concave sample. Due to view of lens is side-looking, contact angle of concave sample cannot be measured using normal sessile drop method. We should use top-side view to measure contact angle of such sample and use ADSA-D method to calculate contact angle.2, Choose contact angle meter based on measuring methodThere are about ten methods to measure contact angle (refer: surface science techniques, Gianangelo Bracco Bodil Holst editors, springer 2013, ISBN 978-3-642-34243-1, for more information), including the following methods:2.1 Direct measurement by telescope-goniometer:This is usually called as contact angle goniometer. The most widely used technique of contact angle measurement is a direct measurement of the tangent angle at the three-phase contact point on a sessile drop profile. The first commercial contact angle goniometeris designed by W.A.Zisman, and was manufactured by Ramehart instrument company. Usually, contact angle meter with camera but without complexity algorithm (such as drop shape analysis system) is also called as contact angle goniometer. Most manufactorys contact angle measurement instrument is fall into this category except contact angle measurement instrument with drop shape analytical system. Refer 2.10 drop shape analysis system for more information.2.2 Captive bubble method:Instead of forming a sessile drop on the surface of solid, an air bubble is formed beneath the solid sample, which is immersed in the testing liquid. This method is very useful for material with Super-Hydrophilic (contact angle below 3) surface (such as aluminum foil ofair conditioning) or super-hydrophobic (contact angle above 140) surface (such as lotus leaf or water strider leg).2.3Tilting plate method:This method is rarely used due to its poor precise and operation inconvenient.2.4Wilhelmy balance method:The Wilhelmy balance method is a widely used technique that indirectly measures contact angle on a solid sample. The Wilhelmy balance technique is an indirect force method. It is usually used to measure dynamic contact angle of smooth and known wetting length. And sometimes, it is maybe an alternative solution when one want to check sessile drop method. Some manufactory that dont make optical method will always emphasize advantage of this method and ignore its disadvantage. So, we must be sure what we really want, then you will make a good choice.It has several advantages over conventional optical methods. First, the task of measuring an angle is reduced to the measurements of weight and length, which can be performed with high accuracy and without subjectivity. Second, the