New materials with near-perfect water repellency offer potential for self-cleaning surfaces in cars and buildings.
Scientists from Karlsruhe Institute of Technology (KIT) and the Indian Institute of Technology Guwahati (IITG) have developed a surface material that repels water droplets almost completely. Using an entirely innovative process, they changed metal-organic frameworks (MOFs) – artificially designed materials with novel properties – by grafting hydrocarbon chains. The resulting superhydrophobic (extremely water-repellent) properties are interesting for use as self-cleaning surfaces that need to be robust against environmental influences, such as on automobiles or in architecture. The study was published in the Materials Horizons journal.
Superhydrophobic Surfaces from MOFs
Metal-organic frameworks (MOFs) are made of metal ions connected by organic linkers, forming a porous, sponge-like structure. Their remarkable surface area — just two grams can cover the size of a football field — makes them valuable for applications like gas storage, carbon dioxide separation, and advanced medical technologies.
Beyond their internal pores, the outer surfaces of MOFs also offer unique properties. Researchers enhanced these surfaces by grafting hydrocarbon chains onto thin MOF films, creating a water-repellent material with a contact angle of over 160 degrees. A higher contact angle means better hydrophobicity, as water droplets form a nearly spherical shape instead of spreading out.
“With our method, we are able to achieve superhydrophobic surfaces with contact angles that are significantly higher than those of other smooth surfaces and coatings,” explains Professor Christof Wöll from KIT’s Institute of Functional Interfaces. “Although the wetting properties of MOF powder particles have been explored before, the use of monolithic MOF thin films for this purpose is a groundbreaking concept.”
The team attributes these results to the brush-like arrangement (polymer brushes) of the hydrocarbon chains on the MOFs. After being grafted to the MOF materials, they tend to form “coils” – a state of disorder that scientists call “high-entropy state,” which is essential for its hydrophobic properties. The scientists asserted that this state of the grafted hydrocarbon chains could not be observed on other materials.
It is remarkable that the water contact angle did not increase even when they used perfluorinated hydrocarbon chains for grafting, i.e. substituting hydrogen atoms with fluorine. In materials such as Teflon, perfluorination brings about superhydrophobic properties. In the newly developed material, however, it decreased the water contact angle significantly, as the team found out. Further analyses in computer simulations confirmed that the perfluorinated molecules – in contrast to hydrocarbon chains – could not assume the energetically favorable high-entropy state.
Insights from Surface Roughness and Theoretical Analysis
In addition, the scientists varied the surface roughness of their SAM@SURMOF systems in the nanometer range, thereby further reducing the water adhesion strength. Even with extremely small inclination angles, water droplets started rolling off, and their hydrophobic and self-cleaning properties were significantly improved.
“Our work also includes a detailed theoretical analysis, which links the unexpected behavior shown in experiments to the high-entropy state of the molecules grafted to the MOF films,” says Professor Uttam Manna from IITG’s Chemistry department. “This study will change the design and production of next-generation materials with optimum hydrophobic properties.”
Reference: “Functionalization of monolithic MOF thin films with hydrocarbon chains to achieve superhydrophobic surfaces with tunable water adhesion strength” by Evgenia Bogdanova, Modan Liu, Patrick Hodapp, Angana Borbora, Wolfgang Wenzel, Stefan Bräse, André Jung, Zheqin Dong, Pavel A. Levkin, Uttam Manna, Tawheed Hashem and Christof Wöll, 15 November 2024, Materials Horizons.
DOI: 10.1039/D4MH00899E
News
Global Nanomaterial Regulation: A Country-by-Country Comparison
Nanomaterials are materials with at least one dimension smaller than 100 nanometres (about 100,000 times thinner than a human hair). Because of their tiny size, they have unique properties that can be useful in [...]
Pandemic Potential: Scientists Discover 3 Hotspots of Deadly Emerging Disease in the US
Virginia Tech researchers discovered six new rodent carriers of hantavirus and identified U.S. hotspots, highlighting the virus’s adaptability and the impact of climate and ecology on its spread. Hantavirus recently drew public attention following reports [...]
Studies detail high rates of long COVID among healthcare, dental workers
Researchers have estimated approximately 8% of Americas have ever experienced long COVID, or lasting symptoms, following an acute COVID-19 infection. Now two recent international studies suggest that the percentage is much higher among healthcare workers [...]
Melting Arctic Ice May Unleash Ancient Deadly Diseases, Scientists Warn
Melting Arctic ice increases human and animal interactions, raising the risk of infectious disease spread. Researchers urge early intervention and surveillance. Climate change is opening new pathways for the spread of infectious diseases such [...]
Scientists May Have Found a Secret Weapon To Stop Pancreatic Cancer Before It Starts
Researchers at Cold Spring Harbor Laboratory have found that blocking the FGFR2 and EGFR genes can stop early-stage pancreatic cancer from progressing, offering a promising path toward prevention. Pancreatic cancer is expected to become [...]
Breakthrough Drug Restores Vision: Researchers Successfully Reverse Retinal Damage
Blocking the PROX1 protein allowed KAIST researchers to regenerate damaged retinas and restore vision in mice. Vision is one of the most important human senses, yet more than 300 million people around the world are at [...]
Differentiating cancerous and healthy cells through motion analysis
Researchers from Tokyo Metropolitan University have found that the motion of unlabeled cells can be used to tell whether they are cancerous or healthy. They observed malignant fibrosarcoma [...]
This Tiny Cellular Gate Could Be the Key to Curing Cancer – And Regrowing Hair
After more than five decades of mystery, scientists have finally unveiled the detailed structure and function of a long-theorized molecular machine in our mitochondria — the mitochondrial pyruvate carrier. This microscopic gatekeeper controls how [...]
Unlocking Vision’s Secrets: Researchers Reveal 3D Structure of Key Eye Protein
Researchers have uncovered the 3D structure of RBP3, a key protein in vision, revealing how it transports retinoids and fatty acids and how its dysfunction may lead to retinal diseases. Proteins play a critical [...]
5 Key Facts About Nanoplastics and How They Affect the Human Body
Nanoplastics are typically defined as plastic particles smaller than 1000 nanometers. These particles are increasingly being detected in human tissues: they can bypass biological barriers, accumulate in organs, and may influence health in ways [...]
Measles Is Back: Doctors Warn of Dangerous Surge Across the U.S.
Parents are encouraged to contact their pediatrician if their child has been exposed to measles or is showing symptoms. Pediatric infectious disease experts are emphasizing the critical importance of measles vaccination, as the highly [...]
AI at the Speed of Light: How Silicon Photonics Are Reinventing Hardware
A cutting-edge AI acceleration platform powered by light rather than electricity could revolutionize how AI is trained and deployed. Using photonic integrated circuits made from advanced III-V semiconductors, researchers have developed a system that vastly [...]
A Grain of Brain, 523 Million Synapses, Most Complicated Neuroscience Experiment Ever Attempted
A team of over 150 scientists has achieved what once seemed impossible: a complete wiring and activity map of a tiny section of a mammalian brain. This feat, part of the MICrONS Project, rivals [...]
The Secret “Radar” Bacteria Use To Outsmart Their Enemies
A chemical radar allows bacteria to sense and eliminate predators. Investigating how microorganisms communicate deepens our understanding of the complex ecological interactions that shape our environment is an area of key focus for the [...]
Psychologists explore ethical issues associated with human-AI relationships
It's becoming increasingly commonplace for people to develop intimate, long-term relationships with artificial intelligence (AI) technologies. At their extreme, people have "married" their AI companions in non-legally binding ceremonies, and at least two people [...]
When You Lose Weight, Where Does It Actually Go?
Most health professionals lack a clear understanding of how body fat is lost, often subscribing to misconceptions like fat converting to energy or muscle. The truth is, fat is actually broken down into carbon [...]
