Inspired by a desire to help healthcare providers, first responders, and other emergency personnel be better protected, researchers at PNNL developed a groundbreaking, superhydrophobic material that repels liquids and could be applied to personal protective equipment (PPE)—such as gloves, face shields, shoes, and protective suits—in the manufacturing process. Called ElastiDry Protective Coating, the advancement would prevent liquids containing bacterial, viral, and other dangerous contaminants from “sticking” to PPE. The coating’s elasticity contributes to improved durability. Remarkably, the material has even greater liquid repellency as it is stretched and deformed, a novel quality not present in conventional superhydrophobic materials.
Researchers have for years been aware of the value of superhydrophobic materials, working to improve the products that are currently in the marketplace. Previous attempts at making these synthetic materials have fallen short for many applications, because the advanced material lacks durability. Traditional superhydrophobic materials are especially vulnerable in pliable materials, on which performance and durability suffer from deformation in the material. ElastiDry was designed to overcome these limitations. A key feature of the material is its ability to transform its surface microstructure as it is deformed by stretching or abrasion.
ElastiDry’s surface has a very fine texture that holds water off the coating like a circus performer lying on a bed of nails. In the ElastiDry coating, this unique behavior occurs whether the synthetic material is at ease or being stretched. In fact, the material’s qualities are enhanced, not diminished when stretched. Under that stress condition, the coating maintains its superhydrophobic behavior even as the underlying latex or nitrile are stretched to their limits. Liquid droplets that land on these materials don''t spread out over the surface; instead the liquid rolls up into droplets that slide effortlessly off the surface.
Applications and Industries
The inexpensive and non-toxic elements of ElastiDry allow for the broadest range of potential application areas—from healthcare to the food industry to national security. Furthermore, it is highly compatible with many existing manufacturing processes, meaning it can easily be integrated into what is already industrially available for high-impact products, such as:
- PPE for healthcare workers and first responders
- Military gear
- Flexible tubing
- Food processing
- Industrial manufacturing
Durability distinguishes ElastiDry from other superhydrophobic synthetic materials. In other materials, light abrasion or deformation of the surface breaks the fragile structure that confers water-repellent behavior. In fact, this delicate, fine structure represents one of the largest hurdles to commercializing superhydrophobic coatings. In contrast to these other materials, ElastiDry was designed to start with a uniform nanotextured surface that is intended to break apart into micro-sized surface agglomerates during stretching or abrasion. Transition from the uniform coating to a multi-scale hierarchical structure (when stretched) leads to an increase in water repellency, as measured by water contact angle. Remarkably, in lab testing, the ElastiDry stretchable coating maintained superhydrophobic behavior even as the underlying polymers ripped or tore due to excessive abrasion and without suffering material failure or becoming fragile, like traditional superhydrophobic materials would.
ElastiDry can be a composite mix of stretchable polymer substrate (e.g., natural rubber latex) and a very fine engineered form of glass known as nanosilica fibers. The nanosilica forms a surface layer that breaks apart into small, island-like structures when expanded. The material can be spray-coated onto a large variety of surfaces. The materials used to make ElastiDry are non-toxic and inexpensive. Additionally, the process to make the coating is simple enough to be applied even to disposable items.