The research, published in the journal PLOS ONE on 18 September 2026, describes a hybrid antifouling material that combines two distinct strategies operating at different length scales. The team fabricated coatings of zinc oxide nanorods on three differently patterned polymer surfaces, labeled D1, D2, and D3 in the study. Each polymer substrate carried its own microscale texture, and the zinc oxide nanorods added a second, nanoscale layer of structure on top. This hierarchical architecture, in which micro- and nanostructured features coexist on a single surface, is central to the design philosophy. In nature, many organisms deter fouling not through chemical warfare alone but through precisely sculpted surface topographies, and the Omani team sought to mimic and enhance this principle with a functional semiconductor material known for its antimicrobial properties.

Zinc oxide has attracted considerable attention in materials science because it combines several useful characteristics in a single compound. It is a wide-bandgap semiconductor, it can be grown into elongated nanorod crystals with high surface area under relatively mild laboratory conditions, and it exhibits antibacterial activity through well-documented mechanisms. When zinc oxide nanostructures interact with water, they can release zinc ions, which are toxic to many microorganisms at sufficient concentrations. They can also generate reactive oxygen species, chemically aggressive molecules that damage cell membranes, proteins, and DNA. By growing dense forests of these nanorods directly onto textured polymer surfaces, the researchers created materials in which both the physical topography and the chemical activity of the coating could contribute to fouling resistance simultaneously.

To evaluate how well the hybrid surfaces performed, the team subjected them to laboratory tests under flow conditions, an important detail because real marine equipment rarely sits in stagnant water. Flow alters how microorganisms approach, contact, and adhere to surfaces, so testing under flowing conditions provides a more realistic assessment than simple static immersion. Two representative fouling organisms were chosen: the bacterium Escherichia coli, a widely used model organism in antibacterial testing, and Amphora sp., a marine diatom. Diatoms are single-celled algae with silica shells and are among the earliest and most problematic colonizers of submerged surfaces, forming slimy biofilms that pave the way for larger fouling organisms. The researchers also assessed the acute toxicity of the coated surfaces using larvae of the whiteleg shrimp, Litopenaeus vannamei, a commercially important aquaculture species whose sensitivity makes it a useful indicator of environmental risk.

One of the most striking physical changes induced by the nanorod coating was a dramatic shift in wettability. The uncoated patterned polymer surfaces exhibited water contact angles of roughly 80 to 90 degrees, values typical of moderately wettable materials that water spreads across fairly readily. After the zinc oxide nanorods were applied, the contact angles climbed to approximately 150 to 165 degrees, placing the surfaces in the range considered highly water-repellent or superhydrophobic. At such angles, water droplets bead up and roll off easily, sitting atop the textured surface rather than wetting it. This behavior matters for antifouling because many marine organisms need a hydrated interface to attach successfully, and surfaces that resist wetting can present a formidable first barrier to colonization.

The biological results revealed a nuanced picture in which the underlying micropattern proved just as important as the coating itself. Bacterial attachment was reduced by 60.3 percent on the coated D1 surface, by 48.8 percent on coated D2, and by only 5.8 percent on coated D3. The diatom results followed a different pattern: coverage fell by 9.9 percent on coated D1 but by 72.9 percent on coated D2 and 71.8 percent on coated D3. In other words, the surface that best suppressed bacteria was not the one that best suppressed diatoms, and the surface with the weakest antibacterial effect still performed admirably against algal settlement. This divergence underscores a key insight of the study: antifouling performance is not a simple function of the coating material but emerges from the interplay between the nanorods and the specific geometry of the micropattern beneath them.

The researchers attributed the observed antifouling effects to a combination of mechanisms acting in concert. The release of zinc ions and the generation of reactive oxygen species provide direct chemical pressure against attached microorganisms. Surface wettability alters the initial interaction between organism and substrate, making adhesion energetically less favorable. Finally, the interaction between the microscale polymer patterns and the nanoscale zinc oxide structures shapes how cells encounter and contact the surface at the micrometer scale, influencing whether they can establish stable attachment. Because each mechanism operates differently against different organisms, the balance among them determines the overall antifouling profile of a given surface design, which helps explain why the three patterns produced such distinct results.

Toxicity findings added a further layer of complexity to the design question. The zinc oxide-coated D1 surface showed the best overall balance between antifouling performance and low toxicity toward shrimp larvae, making it the most environmentally promising of the three designs. The coated D3 surface, by contrast, combined lower antibacterial performance with greater larval toxicity, an unfavorable pairing that illustrates why simply applying an antimicrobial nanocoating is not sufficient. The geometry of the underlying pattern can amplify or dampen both the beneficial and the harmful effects of the nanomaterial. For any future application, the study suggests, engineers must treat the surface pattern and the coating as a single integrated design problem rather than optimizing them independently.

Durability is another critical consideration for any material intended for marine service, and here the study offered encouraging preliminary evidence. Microscopic examination conducted after the biological experiments showed that the zinc oxide nanorods remained structurally intact, indicating that the coatings withstood the laboratory testing period without significant physical degradation. Coatings that shed nanoparticles or crumble under flow would pose both a performance problem and an environmental one, releasing engineered material into the water column. The structural stability observed in this work suggests that the nanorods were well anchored to their polymer substrates, although the researchers were careful to note that their experiments were conducted under controlled laboratory conditions rather than in the open ocean.

The path from laboratory promise to practical deployment remains a long one, and the authors were explicit about the limitations of the current work. Long-term field trials and further ecotoxicological assessments will be required before these coatings can be considered for real marine or industrial use. Seawater is a far more chemically complex and biologically diverse environment than any laboratory assay, and months or years of exposure introduce degradation pressures, seasonal variation in fouling communities, and ecological interactions that short-term tests cannot capture. Nevertheless, the findings point toward a promising direction: combining zinc oxide nanorods with deliberately designed micropatterned surfaces could eventually support antifouling applications on ship surfaces, aquaculture nets, water-intake systems, and other equipment exposed to marine environments. If subsequent trials confirm the laboratory results, such materials could offer a route to fouling control that reduces reliance on toxic chemical leaching, aligning with the growing regulatory and environmental pressure to make antifouling technology safer for the oceans it operates in.

Subject of Research: Antifouling performance of zinc oxide nanorod coatings on micropatterned polymer surfaces against marine microorganisms

Article Title: Can nanostructured surfaces help keep marine equipment clean?

Article References: Can nanostructured surfaces help keep marine equipment clean?. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: biofouling, zinc oxide nanorods, micropatterned polymers, antifouling coatings, marine science, Escherichia coli, Amphora diatom, superhydrophobic surfaces, reactive oxygen species, Litopenaeus vannamei, ecotoxicology, Sultan Qaboos University

Addressing this longstanding challenge, researchers at Rice University, under the guidance of assistant professor of mechanical engineering Daniel J. Preston, have unveiled a novel approach that sidesteps conventional wisdom. Rather than solely engineering the surface chemistry or texture, their breakthrough centers on manipulating heat transfer within the surface itself. By integrating a thin, thermally insulating layer beneath a widely available superhydrophobic spray coating, they have devised a multilayered insulated superhydrophobic (MISH) surface capable of repelling hot water droplets even as their temperatures near boiling—up to an unprecedented 90 degrees Celsius. This development, detailed in their recent publication in ACS Applied Materials & Interfaces, redefines the boundaries of superhydrophobic technology, pushing it well beyond previously accepted thermal limits.

Preston emphasizes the practicality and economic advantage of their method, noting that earlier high-performance hot-water-repellent coatings required sophisticated cleanroom nanofabrication steps and costs exponentially greater than their streamlined system. “Our MISH coating performs robustly in real-world conditions across various geometries—from curved pipes to industrial bowls—demonstrating scalability and ease of application,” Preston attests. This contrasts starkly with traditional superhydrophobic surfaces, whose delicate trapped air pockets collapse under heat stress, causing rapid functional decline.

The science underlying this advancement involves a nuanced interplay between surface texture, temperature gradients, and phase change phenomena. Classic superhydrophobic surfaces maintain a fragile air cushion atop microscale roughness, effectively minimizing water-solid contact area and adhesion. However, when a hot water droplet contacts a cooler textured surface, water evaporates locally and then recondenses within the surface’s microcavities. This recondensation forms liquid “bridges” that replace the insulating air pockets, anchoring droplets firmly and transitioning the surface into a wetted, sticky regime. Such thermal interactions impose severe operational limitations for industries working with hot fluids, including food processing, desalination, and sterile chemical manufacturing.

Instead of attempting to engineer ever more complex surface chemistries to resist this transition, the Rice team redirected focus toward heat flow management within the coating architecture. Zhen Liu, co-lead author and recent doctoral graduate from Preston’s lab, explains, “By incorporating a thin insulation layer—commonly a sprayable polyurethane foam—we dramatically reduce heat conduction from droplet to substrate. This impairs the evaporation-condensation cycles responsible for liquid bridge formation and preserves the air cushion critical for repellency.” The topcoat remains a commercially accessible superhydrophobic spray, emphasizing the method’s compatibility with off-the-shelf materials.

The MISH system’s two-layer design thus synergizes thermal insulation with superhydrophobic microtexture to mitigate inherent thermal defects. Experimental testing involved systematically heating coated samples and challenging them with hot water droplets under gravity to evaluate sliding behavior. Compared against conventional surfaces, MISH coatings exhibited significantly reduced droplet adhesion at elevated temperatures; droplets resisted sticking and rolled off effortlessly up to near-boiling points. Such empirical results aligned well with an accompanying heat transfer model that decoupled surface chemistry effects from insulation performance, validating the theoretical framework.

Additional rigorous tests replicated industrial scenarios by subjecting coatings to continuous hot water jets. While traditional coatings rapidly failed in these conditions, MISH surfaces, particularly those with thicker insulating layers, reliably repelled water jets, indicating promising durability and robustness. To further stress the system, coatings endured nearly two million droplet impacts over the course of a week-long exposure, mirroring extreme usage cycles. Whereas standard coatings lost repellency immediately, MISH-treated surfaces maintained their functionality past one million impacts before gradual degradation occurred. Detailed analyses revealed that failure initiated within the commercial topcoat’s material properties rather than the insulating design, suggesting that future iterations employing more thermally and chemically stable top layers could greatly extend lifespan.

To verify practical applicability beyond the laboratory, the team deployed MISH coatings on larger surfaces, including curved pipes and vessels, then subjected them to real hot liquids common in food and beverage industries such as hot milk, coffee, and split pea soup. Remarkably, these trials resulted in less than 1% residual wetness on MISH surfaces versus over 30% residue on standard superhydrophobic coatings—an outcome with direct implications for reducing contamination, simplifying cleaning, and decreasing waste in commercial settings.

Preston acknowledges that while this innovation marks a significant leap forward, further research is needed to improve long-term durability, particularly at elevated temperatures and in chemically harsh environments. This future work is poised to explore advanced insulating materials, novel nanostructured top layers, and manufacturing techniques transcending simple spray coatings to create even more resilient superhydrophobic surfaces with sustained high-temperature performance. The promise of cost-effective, scalable, and broadly applicable coatings holds potential to transform how industries handle hot liquids, enhancing efficiency and environmental sustainability.

By fundamentally addressing the geothermal root of superhydrophobic failure rather than its symptoms, this approach revolutionizes the design paradigm for water-repellent materials. It exemplifies how merging fundamental thermal physics with practical engineering can unlock exponential gains in performance without prohibitive cost. Co-lead author Rawand Rasheed, a Rice alumnus and CEO of Preston’s spinout company Helix Earth, underscores this synergy: “Our findings highlight that deep scientific understanding married with real-world engineering pragmatism yields massive advancements, heralding a new era of hot-water-repellent technology.”

In summary, the MISH coating represents an exciting and scalable breakthrough in surface science. Its combination of thermal insulation and microtextured superhydrophobicity defies previous thermal constraints, allowing surfaces to maintain their coveted water-repelling properties even near boiling temperatures. As future research hones durability and expands applications, this technology is poised to catalyze significant improvements in industries reliant on hot liquids. By preventing hot water from sticking and fouling surfaces, MISH coatings pave the way for cleaner, more efficient, and less wasteful industrial processes worldwide.

Subject of Research: Mechanical engineering, Superhydrophobic surfaces, Thermal insulation

Article Title: Scalable Hot-Water-Repellent Superhydrophobicity via Thermal Insulation

News Publication Date: 9-Jan-2026

Web References: 10.1021/acsami.5c17943

Image Credits: Jorge Vidal/Rice University

Keywords

Mechanical engineering, Surface structure, Mechanical properties