Method for measuring liquid-drop contact angle on solid surface and device thereof

A solid surface and measurement method technology, applied in the field of measurement, can solve the problems of not considering the influence of gravity, not considering the influence, and not being able to give the contact angle well, so as to improve the measurement accuracy and expand the measurement range.

Active Publication Date: 2009-09-23
TSINGHUA UNIV
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AI-Extracted Technical Summary

Problems solved by technology

At present, even the most advanced contact angle measuring instrument in the world cannot give the value of the contact angle very well when the droplet is relatively large or the contact angle is relatively large (such as superhydrophobic materials). big error
One of the main reasons for the error is that the influence of gravity is not considered when measuring the c...
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Method used

Utilize above-mentioned measurement device, at first material sample 5 is placed on loading platform 4, utilizes microinjector 6 to drop the liquid of known volume on sample surface, after drop reaches balance, utilizes optical imaging system, CCD The camera and computer acquire the image of the shape of the droplet on the sample plane, and use the method of image matching to process and analyze the shape of the droplet through the computing software, and calculate the contact angle of the droplet. If the s...
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Abstract

The invention relates to a method for measuring a liquid-drop contact angle on a solid surface and a device thereof, which are used for measuring the contact angles of the liquid drops with different mediums and different sizes on the solid surface. The method comprises the following steps of: according to one-to-one correspondence between a liquid drop volume and a liquid drop contact angle, obtaining a plurality of liquid drop profiles which correspond to different contact angles, thus establishing a database used for storing different liquid drop profiles; when in measuring, fixing a sample on an earthquake isolation platform, and dropping the liquid with known volumes on the surface of the sample by utilizing a micro-injector; after the liquid drops achieve balance, acquiring a liquid drop image on the surface of the sample by utilizing an optical imaging system, a CCD camera and a computer; utilizing an image matching method to carry out processing and analyzing to the shapes of the liquid drops by computer software, and then carrying out calculation to obtain contact angles of the liquid drops; and matching the liquid drop profiles obtained by experimental measurements with the liquid drop profiles in the database so as to determine the corresponding contact angles. Compared with the existing method, the method takes the influence of volume and weight of the liquid drop in to consideration, thus improving the measuring precision.

Application Domain

Technology Topic

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  • Method for measuring liquid-drop contact angle on solid surface and device thereof
  • Method for measuring liquid-drop contact angle on solid surface and device thereof
  • Method for measuring liquid-drop contact angle on solid surface and device thereof

Examples

  • Experimental program(1)

Example Embodiment

[0034] Examples:
[0035] Such as image 3 As shown, the specific implementation is divided into two parts: 1) establishing a database; 2) calculating the contact angle in real time. The specific operations for establishing a database are:
[0036] 1) Given the initial physical constants of the measured droplet: surface tension coefficient, density, volume. In the process of numerical solution, given initial boundary conditions (given contact angle θ, w 0 =0, the width r of any given adhesion zone 0 | w=0 And the pressure difference between the inside and outside of the droplet at the base ΔP 0 | w=0 ).
[0037] 2) Solve by shooting method (the formula of shooting method is r i | w=0 =r 0 +Δr, ΔP i | w=0 =ΔP 0 +ΔP);
[0038] 3) Determine whether the final boundary conditions are met (that is, the condition V=V for program termination 0 , dw dr | r 1 = 0 = 0 Is it satisfied?). If yes, store the drop profile represented by this set of data, if not, go back to step 2) and continue to solve with the shooting method;
[0039] 4) Establish a database by continuously changing the droplet volume and contact angle to store the x and y coordinate values ​​of the contours of different contact angles corresponding to a certain volume range.
[0040]The specific operation of real-time calculation of contact angle is:
[0041] 1) Start the contact angle measuring instrument and contact angle measuring software;
[0042] 2) Enter the initial parameters of the droplet: liquid density, surface tension coefficient, droplet volume;
[0043] 3) Use a micro syringe to inject droplets of corresponding volume;
[0044] 4) The measurement software automatically obtains the contour of the droplet;
[0045] 5) Find contour lines from the database and match them;
[0046] 6) Judging the accuracy requirements (controlled by the error function), if the required accuracy is met, the matching stops, if not, the search and matching will continue;
[0047] 7) Give the value of the contact angle obtained by 6);
[0048] 8) End
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Description & Claims & Application Information

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