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چکیده
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A B S T R A C T The design and engineering of suitable structures for enhancement of the hydrophobic property of a surface is one of the most challenging problems. In order to achieve a superhydrophobic structure we have designed and fabricated Mn nano-sculptured thin films with different shapes and dimensions, namely helical squares and helical pentagons on glass substrates. The contact angle (CA) of three liquids; a–bromonaphtalene (apolar), water and formamide (polar) to these surfaces was measured and the surface free energy was calculated. Changes to the geometry of the structure produced results ranging from hydrophilic (CA = 51) to superhydrophobic (CA = 152). The superhydrophobic structure is a helical square shaped structure with high porosity (deposited at 83) which also shows the rose petal effect with the additional property of high adhesion. The resemblance of this structure to that of gecko feet, which shows both high adhesion forces and superhydrophobic property is discussed. All structures investigated in this work showed negative spreading coefficients with highest values for the largest contact angle for each type/shape of structure. The superhydrophobic sample also acts as a sticky surface which is confirmed by hysteresis of the contact angle obtained from advancing and receding contact angles measurements. The influence of the volume of liquid drop and different surface morphologies on the wetting transition from Cassie–Baxter to Wenzel states is also reported.
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