Nixe: Bioinspired Sustainable and Water-repellent Textile Coating

The Problem

PFAs, per- and polyfluorinated chemical compounds, were first used with the invention of Teflon in 1938 and by now are found in the blood of 97% of Americans. They pose risks to human reproductive and immune health, and are strongly suspected to cause cancer, developmental defects, and other health problems. As “forever chemicals,” they are passed through entire ecosystems and along food chains. PFAs are ingredients in a large variety of everyday products, including nonstick cookware, personal care products, stain-resistant furniture and carpet coatings, cleaning supplies, and many others. Strikingly, their use in water-resistant textile coatings alone amounts to 50% of their total global use. However, it has been challenging to design an alternative, environmentally responsible, durable water repellent that does not compromise fabric functionality, but that could help reduce the quantity of and dependency on PFAs.

Our Solution

Researchers at the Wyss Institute for Biologically Inspired Engineering and Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and their collaborators, have developed Nixe, a PFAS-free nanostructured silica-based coating for use on and within textile substrates. The Nixe coating imparts significant water repellency, but does not impact fabric functionalities, such as breathability, durability, and flexibility, by capitalizing on the promising research of bioinspired (“lotus leaf effect”) bumpy surfaces that combine micro- and nanostructured surface topography with hydrophobic surface chemistry to trap air at the liquid-substrate interface. This lotus leaf-like topography enables strong and stable binding to fabric surfaces and provides advanced chemical functionalization and design opportunities. 

Product Journey

Nixe was developed in a multidisciplinary effort by Wyss Research Fellow Caroline Dignes and other members of Joanna Aizenberg’s group at the Wyss and SEAS in collaboration with Thomas Schroeder at the Department of Textile Engineering, Chemistry, and Science at North Carolina State University. The team’s aim was to engineer a super-hydrophobic water-repellent coating that retains the hand feel, visual appearance, fabric drape, and flexibility of textiles to eventually help supplant PFAs coatings on textiles and eventually also other flexible surfaces. All existing solutions for PFA-free polymer coatings fell short of the performance expectations created by PFAs. The Nixe project led them to a novel coating in which two sizes of silica NPs are irreversibly attached to the fabric surface to recreate the bumpiness of the lotus leaf. This particular topology, combined with specific surface chemistry, enabled them to create a breathable interface between fabric and water, offering a next-generation PFAs-free water-repellent solution.

The team designed and optimized their fabrication method as a low-cost process that, in principle, is scalable and consumes dramatically less water than the coating processes used in the fashion and other industries, thereby reducing the impact of textile manufacturing on water and climate – currently, processing a kilogram of fiber requires 100 to 150 liters of water. Nixe’s process re-uses the same solutions required for its layered fabrication in a closed-loop, water-free system and applies refined textile exposure conditions in each of the solutions. This allows the coating of multiple fabric batches without any loss in efficiency. In proof-of-concept studies, the team demonstrated the performance and integrity of Nixe-coated fabrics through rigorous functional testing and dozens of wash cycles and found them to be on par with PFA-coated fabrics.

Due to its outsized potential, Nixe has been supported as a 2024/2025 Wyss Validation Project with special funding and business development expertise. It also received an award from the Director’s Fund established by the Wyss’ Collaborative Fund Venture Alliance. The team is looking for additional funding, collaboration, and licensing opportunities to commercialize their technology.