Jie Wu, an engineering graduate student, was studying a type of striking white beetle found in Southeast Asia and attempting to figure out how to mimic its brilliant color when an unexpected discovery upended the experiment.
Jie and I had been hoping to identify naturally occurring whitening pigments that could be used in paper and paints. The beetle’s white exoskeleton is made from a compound called chitin, which is a type of carbohydrate – one that is also commonly found in crab and lobster shells.
First, Jie extracted chitin nanofibers from crab shells obtained from food waste that are chemically the same as those found in the white beetles. But instead of creating a white material as intended, Jie produced dense, transparent films. The nanofibers more readily assembled in tightly packed films than in the porous structures Jie desired.
An attempt to mimic the striking white color of Cyphochilus beetles led researchers to a unique discovery.
Olimpia1lli/Wikimedia Commons, CC BY-NC-ND
On a whim, Jie measured the rate at which oxygen passed through the film. The result was astonishing: The barrier allowed less oxygen through than many existing packaging plastics.
That serendipitous finding in 2014 shifted my team of engineering students’ focus from color to packaging. We asked whether natural materials could rival the performance of common plastics. In the years since, our team has used this discovery to create biodegradable films that offer a more sustainable and effective alternative to plastic packaging.
Challenges of plastic packaging
Plastic packaging is commonly used to protect food, pharmaceuticals and personal care products. These plastics keep out moisture and oxygen from the air, so products stay fresh and safe.
Most packaging has several layers that work together to keep air out, but these layers hinder reuse and recycling efforts. As a result, most of this plastic barrier packaging is discarded to landfills as single-use materials.
Many researchers have sought alternatives that are renewable, biodegradable or recyclable, yet just as effective. At Georgia Tech, my team of students and post-docs has spent more than a decade tackling this problem. This journey began with that beetle.
Building a better barrier
Chitin is widely available in food waste and mushrooms, and it is used in products such as water filters and wound dressing. However, our early attempts to scale up the film technology based on the beetle-inspired experiment failed.
In 2018, the team made an important leap forward by using spray coating to create layers of chitin and cellulose nanomaterials. Cellulose, like chitin, is a carbohydrate polymer – a chain of repeating carbohydrate units – and it is obtained from plants. These abundant natural materials have opposite electric charges, which led to better barrier performance when we combined them than either material alone.
In this approach, the…
