High-Throughput Stamping of Hybrid Functional Surfaces

Abstract

Hydrophobic–hydrophilic hybrid surfaces, sometimes termed biphilic surfaces, have shown potential to enhance condensation and boiling heat transfer, anti-icing, and fog harvesting performance. However, state of art techniques to develop these surfaces have limited substrate selection, poor scalability, and lengthy and costly fabrication methods. Here, we develop a simple, scalable, and rapid stamping technique for hybrid surfaces with spatially controlled wettability. To enable stamping, rationally designed and prefabricated polydimethylsiloxane (PDMS) stamps, which are reusable and independent of the substrate and functional coating, were used. To demonstrate the stamping technique, we used silicon wafer, copper, and aluminum substrates functionalized with a variety of hydrophobic chemistries including heptadecafluorodecyltrimethoxy-silane, octafluorocyclobutane, and slippery omniphobic covalently attached liquids. Condensation experiments and microgoniometric characterization demonstrated that the stamped surfaces have global hydrophobicity or superhydrophobicity with localized hydrophilicity (spots) enabled by local removal of the functional coating during stamping. Stamped surfaces with superhydrophobic backgrounds and hydrophilic spots demonstrated stable coalescence induced droplet jumping. Compared to conventional techniques, our stamping method has comparable prototyping cost with reduced manufacturing time scale and cost. Our work not only presents design guidelines for the development of scalable hybrid surfaces for the study of phase change phenomena, it develops a scalable and rapid stamping protocol for the cost-effective manufacture of next-generation hybrid wettability surfaces.

Spatial Control of Condensation: The Past, the Present, and the Future

“…This is supplemented by a long list of subtractive (i.e., where an initially deposited hydrophobic coating is removed) and additive fabrication methods developed to create chemical patterns. The subtractive fabrication methods already utilized for nucleation control include: ion beam, [55,63] laser ablation, [66] stamping, [67] selective plasma etch, [68] and photolithographic lift-off. [69] Potentially, to achieve nanoscale biphilic patterning, many of these could be combined with bottom-up self-assembly.…”

“…Hoque et al created 75 µm pitch droplet arrays on both flat and nanostructured surfaces. [67,85] Their method excels by being highly durable with good stamp durability and without the need to reapply hydrophobic agents to the stamp as it is a subtractive process where the hydrophobic coating was uniformly applied prior to the stamping. He et al functionalized the micropores (having a 20 µm pitch) of a micro-nanoporous aluminum surface with hydrophilic polymer to enable quick nucleation, controllable coalescence, and high-efficiency self-removal of the microdroplets.…”

“…created 75 µm pitch droplet arrays on both flat and nanostructured surfaces. [ 67,85 ] Their method excels by being highly durable with good stamp durability and without the need to reapply hydrophobic agents to the stamp as it is a subtractive process where the hydrophobic coating was uniformly applied prior to the stamping. He et al.…”

Lubricant self-replenishing slippery surface with prolonged service life for fog harvesting

“…| https://mc03.manuscriptcentral.com/friction are generally recognized as the three stages of fog harvesting [22,59]. First, the fog-capture process based on a humidifier is captured by small droplets from a mist flow by a surface, in which the oil-infused slippery surfaces have a higher droplet nucleation density than HBSs [37]. Water condensation is the process whereby the volumes of the droplets increase gradually.…”

“…They have a high nucleation density of water droplets in the fogcapture process, which shortens the distance between water droplets and promotes the condensation of water droplets. The slippery property not only promotes the further condensation of water droplets but also allows the water droplets to slide off the surface easily [29,30,37]. Hence, SLIPSs have a higher fog-harvesting efficiency than HBSs and HHSs.…”