Unlocking the Secret of Lasting Slippery Surfaces Inspired by Nature

Inspired by the slippery surfaces of the Nepenthes pitcher plant, researchers at University College London (UCL) have developed a new type of surface coating that can resist contamination from bacteria, minerals, and even ice for much longer than existing solutions. Their groundbreaking findings were recently published in Advanced Materials and mark a major advancement in creating more durable, slippery surfaces for industries like aerospace and marine engineering.

The Nepenthes pitcher, a carnivorous tropical plant, uses its slippery, rounded rim to make prey fall into its tall, tubular structure. Surfaces inspired by this plant’s unique ability can resist contamination from a wide range of substances. However, a major challenge has been that these artificial surfaces quickly lose their lubricating layer, limiting their effectiveness. Professor Manish Tiwari and his team at UCL’s Mechanical Engineering Department have discovered an innovative solution to this problem by designing surfaces with ultra-tiny pores that can hold onto lubricants for much longer.

“We’ve found that by carefully designing these pores to allow the lubricant to penetrate deeply into the material and by tweaking the internal chemical environment, we can prevent the lubricant from leaking out,” explained Dr. Vikramjeet Singh and Dr. Jianhui Zhang, lead authors of the study.

The new design relies on advanced materials called metal-organic frameworks (MOFs), which consist of metal ions and organic molecules arranged in a porous, sponge-like structure. MOFs are known for their ability to trap and store different substances and can be adjusted at the molecular level, making them useful for gas storage, chemical reactions, and now, for creating slippery surfaces that last.

Why This Discovery Matters

Traditional methods for creating slippery surfaces often use a process called photolithography, which creates larger pores—typically greater than 10 nanometers (nm)—and results in a weak grip on the lubricant. In contrast, MOFs are produced with sub-nanometer pores (less than 1 nm) that create an exceptionally strong hold on the lubricant. This means the lubricant stays in place much longer, even under the stress of high-speed water impacts, ice formation, and bacterial buildup.

In their study, Professor Tiwari’s team introduced a three-step strategy to make sure the lubricant chains remain securely locked in place within the tiny MOF pores. They first leveraged the unique structure of MOFs to create high capillary pressure, which helps draw and hold the lubricant in place. Second, they ensured the size of the lubricant molecules was small enough to fit inside the pores. Lastly, they customized the chemical environment within the pores to enhance the bond between the lubricant and the surface.

Putting the New Surface to the Test

Through extensive testing, including experiments and molecular simulations, the UCL team confirmed that this design effectively traps lubricant within the MOF pores. The slippery coating remained intact and effective even when exposed to harsh conditions, resisting ice buildup and bacterial contamination. These results suggest that the new surface technology could be invaluable in settings that require durability under dynamic conditions, such as in marine and aerospace engineering.

Looking ahead, the researchers are excited to refine and scale this technology to make it more accessible for practical applications. Their vision includes developing a faster, more scalable process for fabricating these surfaces, allowing industries to benefit from this lasting, low-maintenance technology.

The study, featured in the Advanced Materials Journal, represents a promising step forward in the design of robust, long-lasting slippery surfaces, offering the potential to transform various industries with coatings that stay slippery and clean, even in the toughest environments.

• Designing Impact Resistance and Robustness into Slippery Lubricant Infused Porous Surfaces (Advanced Materials)
• Dr Vikaramjeet Singh's UCL Profile
• Professor Manish K Tiwari's UCL Profile