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

The research team, comprised of Dr. Xianming (Simon) Dai, an associate professor of mechanical engineering, along with graduate researcher Dr. Deepak Monga and Dr. Yaqing Jin, an assistant professor, was exploring ways to innovate surfaces to improve condensation efficiency. Upon examination, they noted that the surface collected more liquid—specifically, condensates, which are droplets formed by condensation—than they had anticipated based on established thermodynamic theories. This divergence from expectation prompted a deep-seated investigation, which ultimately spurred the development of a new theoretical framework for heat transfer that accounts for dynamic condensation processes and fluid behaviors under these conditions.

Typically, condensation science relies heavily on older theoretical models that inadequately reflect the behaviors observed in modern experimental setups, particularly those involving advanced materials and engineered surfaces. The novelty of the UTD team’s findings lies in the recognition that some areas of their surface, previously thought inactive in the condensation process, were indeed contributing to the accumulation of fluid—a form of condensation that was invisible to the naked eye and thus unrecognizable under classical theory. This revelation challenges the entrenched notions of condensation as purely a macroscopic phenomenon while shedding light on the minuscule yet impactful contributions of smaller, inconspicuous droplets.

Dr. Monga’s observations highlighted the importance of examining the speed at which condensates formed and were subsequently shed from surfaces. He remarked on the inadequacy of classical heat transfer equations, which failed to account for the rapid removal capabilities inherent in their newly innovated surfaces. By introducing parameters that factor in the frequency at which these microscopic droplets disappear once they coalesce, the research team was able to refine the theoretical model, thereby enhancing its accuracy when predicting condensation dynamics.

The implications of their newly developed theory extend far beyond academic curiosity. By optimizing surfaces that facilitate quicker condensation and droplet removal, this research holds transformative potential for practical applications. Efficient water harvesting technologies that rely on air moisture capture—especially in arid regions—could experience substantial advancements, allowing for sustainable water supply innovations without reliance on electricity or complex infrastructure. This aligns with goals to address global water scarcity challenges, leveraging nature’s processes to yield vital resources.

Dr. Jin’s contribution to the project focused on utilizing state-of-the-art imaging systems to visualize the behaviors of water droplets as they formed and moved across the engineered surfaces. By combining particle image velocimetry with high-resolution microscopic imaging, the research team recorded fluid dynamics at a scale previously inaccessible, further validating their revised model. This experimental approach not only fortified their theoretical assertions but illustrated the sophisticated interplay between fluid characteristics and surface interactions during the condensation process—a crucial aspect that classical models failed to encapsulate.

The breadth of this research extends into the realm of advanced refrigeration technologies, which could similarly benefit from these new insights. Traditional systems that utilize evaporative cooling can see improvements through enhanced surface designs informed by this research. The role of condensation in the cooling cycle—a process governed largely by how well surfaces manage condensate—is central to optimizing energy efficiency in such systems. Thus, the implications of refining heat transfer models are cascading across various engineering disciplines, heralding a new era of efficient system designs.

Additionally, Monga’s ongoing work based on the findings from this study was recently showcased at The American Society of Mechanical Engineers’ 2024 Summer Heat Transfer Conference, where it earned recognition for excellence in presentation. This achievement reflects not only personal accolades but also the broader interest and enthusiasm surrounding the innovations stemming from UTD’s research initiatives.

Supported through prestigious funding from the Defense Advanced Research Projects Agency, the National Science Foundation’s Faculty Early Career Development Program, and the Department of Energy, this research exemplifies how collaborative and well-resourced endeavors can lead to groundbreaking outcomes in science and engineering. The interdisciplinary nature of the team—integrating mechanical engineering with advanced imaging technologies—addresses a crucial niche in scientific inquiry that promises to yield further advancements in the study of heat transfer and condensation mechanisms.

While the theoretical underpinnings of mechanical condensation processes have long remained unchanged, the findings from UTD represent a turning point in how these processes are understood and utilized. The recognition of rapid dynamics, previously overlooked, opens up intriguing possibilities not just in water harvesting and refrigeration, but potentially in diverse applications spanning the fields of energy, manufacturing, and materials science. The collaboration between rigorous experimentation and theoretical exploration performed by the UTD team stands as a testament to the power of innovative thinking in engineering.

As researchers continue to interrogate the boundaries of classical physics, this burgeoning new domain holds promise for producing educational paradigms and industrial practices that are more efficient, sustainable, and aligned with the pressing needs of our time. The developments in condensation science are poised to resonate in academic literature and broader industry applications alike, revealing the pivotal role surface design and fluid dynamics play in the continuing evolution of heat transfer technologies.

In summary, the UTD research team’s contributions to the understanding of condensation, supported by comprehensive scientific methodology and innovative imaging techniques, has led to the formulation of a new theoretical framework that significantly enhances current models. As they advance their findings, the broader scientific community and industry stand to benefit from insights that challenge traditional notions and catalyze advancements in both science and technology across multiple sectors.

Subject of Research: Dynamics of condensation on advanced surfaces
Article Title: Dynamic condensation model of rolling droplets for high-performance heat transfer
News Publication Date: 13-Mar-2025
Web References: Water Harvesting
References: Newton DOI
Image Credits: The University of Texas at Dallas

Keywords

Condensation, Heat Transfer, Mechanical Engineering, Water Harvesting, Fluid Dynamics, Thermal Sciences, Surface Design, Innovative Materials.