Inside a plant’s vasculature, like this cross section of a linden tree branch, resides a water transport molecule that has inspired WashU chemical engineers to develop a PFAS alternative that uses plant waste and fatty acids to produce water-proof coatings. The research is a big step toward the eventual goal of replacing forever chemicals with nontoxic alternatives.
Image Credit: Scientific Frontline / AI generated
Scientific Frontline: Extended "At a Glance" Summary: Superhydrophobic Lignin-Integrated Particles (SLIP)
The Core Concept: Superhydrophobic lignin-integrated particles (SLIP) are a biodegradable, nontoxic, plant-inspired alternative to polyfluoroalkyl substances (PFAS) used to create water-proof coatings.
Key Distinction/Mechanism: SLIP utilizes lignin (a plant waste material) linked to fatty acids and a polylactic acid (PLA) binder to replicate the molecular structure of suberin, a natural waterproof molecule found in plant vascular tissue. Unlike PFAS, which persists indefinitely in the environment and causes toxic biological effects, SLIP exhibits high superhydrophobicity, mechanical robustness, and ultraviolet stability, yet degrades into harmless organic matter.
Origin/History: Developed by researchers at Washington University in St. Louis and published in Matter in late 2026. The research was led by Joshua Yuan, director of the Carbon Utilization Redesign for Biomanufacturing (CURB) Center.
Major Frameworks/Components:
- Lignin: An affordable and abundant plant waste material utilized as the core building block.
- Fatty Acids: Linked with lignin to mimic the natural waterproof properties of suberin.
- Polylactic Acid (PLA) Binder: Added to enhance structural integrity and coating performance.
- Biomimicry: The structural design is modeled after the plant xylem and suberin molecules.
Branches of Science: Chemical Engineering, Environmental Engineering, Materials Science, Plant Physiology.
Future Application: SLIP currently serves as an effective water-proof coating for packaging and construction materials. Future iterations aim to add oil- and fire-proof properties, vastly expanding its applications to fully replace PFAS in various manufacturing sectors, including integration with biorefinery and paper and pulping industries.
Why It Matters: PFAS, or "forever chemicals," place a billion-dollar economic and biological burden on global health and the environment due to their toxicity and inability to degrade. SLIP offers a sustainable, biodegradable alternative that could save an estimated $1.1 billion annually in societal damage while maintaining the required water-proofing performance for modern manufacturing.
Polyfluoroalkyl substances (PFAS) are known as "forever chemicals" because of the impact they make on the environment and human bodies. Much of modern manufacturing relies on these substances for safe packaging, medical devices, fire protection, and waterproof coatings. Despite the billions of dollars in economic burden their use places on human health and the environment, PFAS themselves are relatively affordable and abundant for manufacturing needs. So, chemical engineers in the McKelvey School of Engineering at Washington University in St. Louis turned to a different material that is also affordable and abundant—lignin, or plant waste material. New research published in Matter outlines the chemical processes they used to turn lignin and fatty acids into a viable PFAS replacement called SLIP, or superhydrophobic lignin-integrated particles.
"We actually use this waste material to turn it into a valuable product," said Joshua Yuan, Lucy and Stanley Lopata Professor and chair of the Department of Energy, Environmental and Chemical Engineering at the McKelvey School of Engineering. Yuan, who serves as director of the Carbon Utilization Redesign for Biomanufacturing (CURB) Center, has long taken inspiration from the natural world to find solutions for replacing petrochemical-based materials.
In SLIP, they found a viable waterproof coating to replace PFAS, without the toxic side effects. "It's not going to stay in the environment forever, and it can be degraded," added Yuan.
To make SLIP, Yuan and his team, including first authors Puneet Dhatt and Weiwei Li, took inspiration from plant vascular tissue, called the xylem. Within the xylem is a waterproof molecule called suberin, used to transport water throughout the plant. The team incorporated suberin's structure into lignin particles by linking lignin to fatty acids, and further added a polylactic acid (PLA) binder. The resulting material demonstrated superhydrophobic performance and included features of mechanical robustness and ultraviolet (UV) stability.
That's not everything PFAS do, but it's a substantial start, the researchers said, especially considering the sheer number of waterproof coatings used in modern manufacturing.
Tests show water literally bouncing off the new SLIP material. "The water will just run off," Dhatt said, adding that the material was tested with a wood-degrading fungus, which showed the coating can break down into harmless organic matter within the expected time.
Lignin and fatty acids "evolved to degrade in the environment for a long time," Dhatt noted, stating that the replacement material can help avoid the great cost to society of relying on forever chemicals.
The team collaborated with researchers at Texas A&M to estimate the cost savings of replacing PFAS. Looking at all the global impacts to human health and environmental degradation from forever chemicals, the Texas researchers estimated the total avoided societal damage in replacing forever chemicals used in waterproofing with SLIP could be up to $1.1 billion annually.
For now, they will continue to add attributes to this new coating. SLIP could be used in packaging and for construction material coatings, but the next step will be to make it oil- and fireproof to vastly expand its applications. The team is also working on scaling up the process and integrating it with the biorefinery, paper, and pulping industries.
"This study represents the perfect example, where we learn from nature and design a sustainable material critical to our society, with a life cycle similar to natural polymers, where everything can degrade without causing harm," Yuan said.
Funding: Funding support provided through NSF CURB Engineering Research Center (NSF EEC 2330245); and DOE EERE BETO grants to J.S.Y. and S.Y.D.: DE-EE-0008250, DE-EE-0007104, and DE-EE-0009756. Yuan is a fellow of the American Association for the Advancement of Science and the Royal Society of Chemistry.
Published in journal: Matter
Title: Bioinspired and biodegradable fluorine-free superhydrophobic coatings
Authors: Puneet S. Dhatt, Weiwei Li, Yayun Chen, Xianzhi Meng, Mengqiao Liu, Chengcheng Fei, Arthur Ragauskas, Susie Y. Dai, and Joshua S. Yuan
Source/Credit: McKelvey School of Engineering | Leah Shaffer
Edited by: Scientific Frontline
Reference Number: eng110326_01
