Diatom attachment inhibition: limiting surface accessibility through air entrapment

Area of Science:

• Materials Science
• Marine Biology
• Surface Chemistry

Background:

• Marine biofouling is a persistent challenge for submerged surfaces, leading to increased drag and maintenance costs.
• Existing antifouling strategies like foul-releasing paints and self-polishing coatings have limitations.
• Understanding early-stage settlement mechanisms is key to developing effective antifouling solutions.

Purpose of the Study:

• To investigate the marine antifouling behavior of surfaces with engineered sub-micron holes in nanoparticle coatings.
• To determine the relationship between pore size, interfacial air pockets, and the settlement of marine diatoms.
• To assess the role of hierarchical nano/micro length scales in biofouling resistance.

Main Methods:

• Fabrication of nanoparticle coatings with controlled sub-micron pore sizes (0.420-0.765 μm).
• Marine antifouling assay using Amphora coffeaeformis (diatom) attachment over 5 hours.
• In-situ measurement of interfacial air pocket size and morphology using synchrotron small-angle X-ray scattering (SAXS).
• Macroscopic wettability measurements including contact angle and sliding angle.

Main Results:

• Surfaces demonstrated resistance to Amphora coffeaeformis attachment.
• Attachment inhibition correlated with pore size, with larger pores (0.765 μm) showing highest resistance.
• Interfacial air pocket accessibility, influenced by pore size and morphology, governed diatom attachment.
• Macroscopic wettability (contact angle ~160°, sliding angle <5°) was independent of pore size and not indicative of fouling resistance.

Conclusions:

• Hierarchical surface structures combining nano/micro scales are critical for early-stage marine biofouling control.
• Sub-micron pore size engineering in nanoparticle coatings offers a promising strategy for marine antifouling.
• Interfacial air pockets play a significant role in preventing initial biological settlement on engineered surfaces.