Thermoregeneration of Fouling‐Inhibiting Plastrons on Conductive Laser‐Induced Graphene Coatings by Joule Heating

Abstract

Superhydrophobic surfaces are capable to resist the adhesion of organisms through a surface bound air layer, known as a plastron. However, the lifetime of such plastrons is limited and their decay results in the loss of the protective barrier against organism attachment. Here a method is established to replenish the plastron by Joule heating of electrically conductive, superhydrophobic laser‐induced graphene (SLIG) coatings. Local heating with a DC current reduces the water solubility of gases and the growth of an initial microplastron into a macroplastron through gas nucleation at the liquid–air interface is observed. Small temperature differences between the surface and the surrounding water could induce this effect. Different SLIG surfaces are challenged against biofouling by the diatom Navicula perminuta under dynamic conditions and it is shown that surfaces with intact plastron resist diatom accumulation. Surfaces without the protective air layer are found to accumulate high amounts of diatoms. The results underline the promising potential of plastron‐based antifouling approaches because plastrons can be stabilized for extended times. This strategy could be applied to many other materials for an effective protection against fouling organism.

Fouling Inhibition by Replenishable Plastrons on Microstructured, Superhydrophobic Carbon‐Silicone Composite Coatings

“…As reported previously [ 22,30 ] the increase of the temperature of water close to a heated surface reduces the solubility of air, which leads to a growth and thus a replenishment of the plastron. As shown in Figure 5D‐F, the temperature increase underwater is only 1–3°C, and thus much lower than in air, but nonetheless, the plastron grew on the various surfaces over a time span of 2–3 h. Immediately after immersion (0 h) all surfaces exhibited parts with noticeable reflecting areas, indicating the presence of a microplastron.…”

“…[22] Among the different approaches to counteract limited plastron longevity is the thermoregeneration of the air layers. [22,30] While initial studies used a heating pad, to initiate the temperature increase near the surface to initiate the growth of the plastron, conductive coatings allow to use of direct Joule heating, to increase their temperature. This resulted in lower energy consumption and enhanced the versatility of the applications.…”

“…Superhydrophobic surfaces can either be prepared from rough hydrophobic materials or from rough non-hydrophobic materials which are subsequently functionalized with a hydrophobic chemistry. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Rough surfaces can be produced by different methods like chemical etching, plasma etching, laser ablation, sol-gel processes, and recently 3D printing. [32] While most of these methods require chemical treatments and complicated preparation protocols, 3D printing is a cost-effective, rapid, and easy method to produce superhydrophobic surfaces.…”

“…running a heating current across the conductive coating. [ 30 ] The temperature increase leads as described above to a growth of the plastron over time.…”

Self-Driven Gas Spreading on Mesh Surfaces for Regeneration of Underwater Superhydrophobicity

“…44−47 Nonetheless, the implementation of these techniques often complicates surface design and presents challenges for large-scale applications. Intermittent or continuous energy input also increases costs, as some methods involve integrating electrolysis or heating devices, 35,36,44 raising concerns about energy conversion efficiency. In addition, the spreading of the gas on superhydrophobic surfaces is a prerequisite for plastron restoration.…”