Browsing by Author "Levkin, Pavel A."

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    3D Printing of Superhydrophobic Objects with Bulk Nanostructure
    (WILEY-V C H VERLAG GMBH, 2021-11-11) Dong, Zheqin; Vuckovac, Maja; Cui, Wenjuan; Zhou, Quan; Ras, Robin H.A.; Levkin, Pavel A.; Department of Applied Physics; Department of Electrical Engineering and Automation; Department of Bioproducts and Biosystems; Soft Matter and Wetting; Robotic Instruments; Karlsruhe Institute of Technology
    The rapid development of 3D printing (or additive manufacturing) technologies demands new materials with novel properties and functionalities. Superhydrophobic materials, owing to their ultralow water adhesion, self-cleaning, anti-biofouling, or superoleophilic properties are useful for myriad applications involving liquids. However, the majority of the methods for making superhydrophobic surfaces have been based on surface functionalization and coatings, which are challenging to apply to 3D objects. Additionally, these coatings are vulnerable to abrasion due to low mechanical stability and limited thickness. Here, a new materials concept and methodology for 3D printing of superhydrophobic macroscopic objects with bulk nanostructure and almost unlimited geometrical freedom is presented. The method is based on a specific ink composed of hydrophobic (meth)acrylate monomers and porogen solvents, which undergoes phase separation upon photopolymerization to generate inherently nanoporous and superhydrophobic structures. Using a desktop Digital Light Processing printer, superhydrophobic 3D objects with complex shapes are demonstrated, with ultralow and uniform water adhesion measured with scanning droplet adhesion microscopy. It is shown that the 3D-printed objects, owing to their nanoporous structure throughout the entire volume, preserve their superhydrophobicity upon wear damage. Finally, a superhydrophobic 3D-printed gas-permeable and water-repellent microfluidic device and a hierarchically structured 3D-printed super-oil-absorbent are demonstrated.
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    Nanoliter deposition on star-shaped hydrophilic–superhydrophobic patterned surfaces
    (2018-08-16) Chang, Bo; Kivinen, Oskari; Pini, Ivana; Levkin, Pavel A.; Ras, Robin; Zhou, Quan; Department of Applied Physics; Department of Bioproducts and Biosystems; Department of Electrical Engineering and Automation; Soft Matter and Wetting; Robotic Instruments; Department of Applied Physics; Karlsruhe Institute of Technology
    Nanoliter sized droplet deposition has gained increasing importance in many biomedical, chemical, and microfluidic applications and in materials synthesis. In this paper, we report a simple method for rapid and high-throughput deposition of nanoliter-sized droplets by dragging a larger droplet on star-shaped hydrophilic–superhydrophobic patterned surfaces. Dragging a droplet on the patterned surface causes water to adhere to hydrophilic patterns. As the larger mother droplet detaches from a star-shaped pattern, a small daughter droplet is deposited on the pattern. Star-shaped hydrophilic patterns with a distinct number of spikes are fabricated and investigated. Systematic tests are carried out to study the influence of different process parameters including the volume of a mother droplet, the dragging velocity, the number of spikes and the dragging directions to the deposition process. The results indicate that creating microarrays by dragging large droplets on patterned hydrophilic–superhydrophobic surfaces yield a reliable, cost-efficient, high-accuracy and easily scalable deposition. The volume of the daughter droplet grows with the velocity of the mother droplet and the number of spikes in a pattern, and decreases with the volume of the mother droplet.
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    Superoleophobic Slippery Lubricant-Infused Surfaces: Combining Two Extremes in the Same Surface
    (2018-08) Dong, Zheqin; Schumann, Martin F.; Hokkanen, Matti J.; Chang, Bo; Welle, Alexander; Zhou, Quan; Ras, Robin H.A.; Xu, Zhenliang; Wegener, Martin; Levkin, Pavel A.; Department of Applied Physics; Department of Electrical Engineering and Automation; Department of Bioproducts and Biosystems; Soft Matter and Wetting; Robotic Instruments; Karlsruhe Institute of Technology; East China University of Science and Technology
    The ability to create superoleophobic surfaces repellent toward low-surface-tension liquids is important for various applications, and has been recently demonstrated using re-entrant or doubly re-entrant microtopography. Liquid droplets on such surfaces feature composite liquid–solid–air interfaces, whereas composite liquid–lubricant–air interfaces would have potential for additional repellency. Here, the development of a novel slippery superoleophobic surface with low adhesion is demonstrated via combining doubly re-entrant microtopography with slippery lubricant-infused porous surfaces. This is realized by using 3D direct laser writing to fabricate doubly re-entrant micropillars with dedicated nanostructures on top of each pillar. The top nanostructures stabilize the impregnated slippery lubricant, while the re-entrant geometry of the micropillars prevents lubricant from spreading. The slippery layer reduces the adhesion of liquid to the pillars, as proved using scanning droplet adhesion microscopy (SDAM), while the doubly re-entrant micropillars make the surface superoleophobic. This novel interface combining two extremes, superoleophobicity and slippery lubricant-infused surface, is of importance for designing superoleophobic and superhydrophobic surfaces with advanced liquid repellent, anti-icing, or anti-fouling properties.