Lena Mammen

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Coating is an essential step in adjusting the surface properties of materials. Superhydrophobic coatings with contact angles greater than 150° and roll-off angles below 10° for water have been developed, based on low-energy surfaces and roughness on the nano- and micrometer scales. However, these surfaces are still wetted by organic liquids such as(More)
A droplet deposited or impacting on a superhydrophobic surface rolls off easily, leaving the surface dry and clean. This remarkable property is due to a surface structure that favors the entrainment of air cushions beneath the drop, leading to the so-called Cassie state. The Cassie state competes with the Wenzel (impaled) state, in which the liquid fully(More)
Describing wetting of a liquid on a rough or structured surface is a challenge because of the wide range of involved length scales. Nano- and micrometer-sized textures cause pinning of the contact line, reflected in a hysteresis of the contact angle. To investigate contact angles at different length scales, we imaged water drops on arrays of 5 μm high(More)
Surface roughness on different length scales is favourable for superhydrophobic behaviour of surfaces. Here we report (i) an improved synthesis for hybrid raspberry-like particles and (ii) a novel method to obtain superhydrophobic films of good mechanical stability. Polystyrene spheres with a diameter of 400 nm-1 microm are decorated with silica colloids <(More)
We demonstrate the fabrication of superhydrophobic surfaces consisting of micropillars with hydrophobic sidewalls and hydrophilic tops, referred to as Janus micropillars. Therefore we first coat a micropillar array with a mono- or bilayer of polymeric particles, and merge the particles together to shield the top faces while hydrophobizing the walls. After(More)
The effect of nanoroughness on contact angles and pinning is investigated experimentally and numerically for low-energy surfaces. Nanoroughness is introduced by chemical vapor deposition of tetraethoxysilane and was quantified by scanning force microscopy. Addition of a root-mean-square roughness of 2 nm on a flat surface can increase the contact angle(More)
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