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Courage + Khazaka electronic GmbH

Drop Angle Meter DM 300 - Compact, high-quality instrument for analyzing wettability and spreadability of materials on the skin

Drop Angle Meter DM 300 - Compact, high-quality instrument for analyzing wettability and spreadability of materials on the skin

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Drop Angle Meter DM 300

Compact, high-quality instrument for analyzing wettability and spreadability of materials on the skin

 

Characterizing the shape of a drop of water on a surface and determining its contact angle is a well-known method to analyze wettability, skin’s free surface energy, its tension and its hydrophilic/hydrophobic properties.

Wettability is the ability of a liquid to maintain contact with a solid surface. Wettability can be wanted or not (repellence or spreadability).
 

  • Method

    When a defined droplet is applied to a solid medium (here: skin), the liquid forms a certain shape (drop shape). The point at which the skin, liquid and air meet determines the contact angle.

    drop angle measurement principle

    The relationship between the contact angle, the skin surface free energy, the liquid surface tension and the interfacial tension between skin and liquid is defined by Young’s equation:

    γS = γL cosθ + γSL

    θ: Contact angle
    γS: Surface free energy of the solid
    γL: Surface tension of the liquid
    γSL: Interfacial tension between solid and liquid

    The larger the contact angle the lower the wettability, the lower the contact angle the better the wettability.In literature the relation between wettability of a substance and contact angle are defined as follows:

    • Contact angle < 90° = hydrophilic surface
    • Contact angle > 90° = hydrophobic surface
    Translated for the skin, higher wettability indicates more moisture at the skin surface. It is also linked to the sebum content of the skin as sebum makes the skin more hydrophilic. Dry skin shows correspondingly lower wettability. Skin surface free energy and wettability are also related. Skin with lower surface energy generally shows lower wettability properties.

     

    DM wettability text

    high                          contact angle                                                          low
     low wettability high
     low adhesiveness high
     small skin’s free energy large

     

    Drop Angle Meter DM 300

     

    With the Drop Angle Meter, the inner forearm is placed on a comfortable rest, which can be moved vertically and tilted in order to have the skin surface where the drop is applied to absolutely levelled to prevent the water from running or disintegrating. The compact system features a very uniform diffuse LED light source and a high-resolution camera, which takes the macro image of the drop on the skin from the side, which is then analyzed in the software. All data, images, and even videos are saved in the database and can conveniently be filtered and exported.

    The camera can be moved in x, y and z direction (up and down as well and back and forth and vertically), to perfectly match the best depth of focus for each drop size. The solid system features height adjustable feet to compensate unevenness of the working surface.

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