A handful of sea shells from a trip to the beach can be an everlasting connection to the sea or a beautiful display of art but it can also be the source of a bioplastic revolution. A research team at Harvard's Wyss Institute, led by postdoctoral fellow Javier Fernandez, PhD, and founding director Don Ingber, MD, PhD, has developed a fully degradable bioplastic from chitosan, which is a form of chitin. Chitin is a natural polymer found in shrimp shells and is the second most abundant organic material on earth.
Though Fernandez and Ingber based their research on shrimp cells this is not the only source of chitin, which can be found throughout the natural world in fungus, insects, mollusks and many other places. The bioplastic can be used to manufacture everyday objects and once used it can be safely returned to nature where it breaks down within two weeks and releases nutrients to aid plant growth.
We speak to researcher Javier Fernandez about chitosan bioplastic, how easy is could be to manufacture and what makes it different to other types of bioplastic.
Stephanie Phillips: What is Chitosan and what part does it play in your bioplastic?
Javier Fernandez: Chitosan is a natural component. It's a derivative of chitin; the second most abundant polymer on earth. This polymer is very similar to cellulose. It's like the cellulose of the animals more or less. This is basically like around nature in very hard structures. Shrimp cells are a good example but also mollusk cells are also made of this component.
We use it because it's a natural polymer with mechanical like properties. Even if the natural point of this polymer is to make structures, the use [of the polymer] these days is as fertiliser or cosmetics, things like that, they are not related to the mechanical properties. This is why this research is different because we basically look for the way that nature uses that polymer and replicate that way of manufacturing with it in an artificial system. What we are able to do is also reproduce those very good mechanical properties that are in nature.
SP: Is there a name for the new bioplastic?
JF: We have two versions of this polymer. We started with a very experimental, theoretical research that was trying to demonstrate that if you take a natural polymer and then you reproduce the design molecularised scale of that polymer in nature you can achieve mechanical properties that are completely out of the scale with what we do with synthetic polymers. You are interested in the chemistry of the polymer but you are not interested in the molecular designs and in nature it is completely the opposite.
Molecular design is more important than the chemistry. So we did the polymer and then there was a mix between protein and chitin and we called it shrilk because basically the protein was coming from silk and the polysaccharide, chitin, was coming from shrimp cells.
We have similar projects and fabrications of this polymer in medical engineering. The thing is that polymer is really difficult and expensive to manufacture. Then we decided to try to move all of our research to a cheaper and easier way to manufacture and that is why we started working with chitin. The next study is basically a study of the molecular arrangement of chitin, pure chitin without protein to try to reproduce them in artificial systems and the data will be published. It was about how to use pure chitin instead of this combination of chitin and protein. The good thing is now the polymer is using chitin and it's cheap and is easier to manufacture. On the other hand it is weaker than the original one.
SP: How cost effective and easy to manufacture is it?
JF: Right now without taking into account all the energy for manufacturing until we scale up to industrial levels we cannot know that. One advantage of our fabrication is that we don't need higher temperatures.
We use the same principles we use in nature, [we] do everything in a water-based environment and also work with self assembly to let the molecules get in their natural conformation. That will be cheaper but then on the other hand the polymer by itself is around twice to three times the cost of commodity plastic. We expect these costs to drop as soon as you have a higher demand because these days most of the polymer is being discarded but again this is a process that will move forward with time.
SP: What makes this bioplastic different to other types of bioplastic?
JF: For other types of bioplastic, or in general, what you do is take a carbon source and then you make a polymer, similar to the polymers that we use for manufacturing these days. You don't use the original natural polymer. You use the polymer as a source for the fabricator hydrocarbon.
In this case we don't do any modification of the polymer. We take it as it is in nature and then we play with methods of fabrication and then the control of moleculised scale to get the strength. It's not just transforming it into something that you know how to work with. It's working with the natural component.
The advantage of that is then the polymer is not only produced in several instances in nature but is also absorbed very fast in different environments so you don't need specific kind of microorganisms or conditions to degrade it or compost it.
SP: What types of objects could be manufactured using this bioplastic?
JF: We made several objects just to try the boundaries of the technique. We make the plastic caps, the cartons and the chess pieces that are all over the place. We also fabricated several different geometries, like spheres, pyramids, cubes; that's the kind of thing that we can do.
SP: How durable is the bioplastic?
JF: The feeling of when you have one in your hand and the mechanical properties are similar to regular plastic cup like the ones used today and also the mechanical properties are in the same range in terms of strength and in terms of thickness.
SP: Do you think the new bioplastic could the solution to many industries need for sustainable materials?
JF: We are now talking to several companies. There is a great interest from both sides from people who actually have all these leftovers that are rich in chitin; from people who are growing insects to people who are growing mushrooms to people who are processing squid. All of these people have leftovers that have a high content in chitin that these days for them is waste and also ... they need to dispose of it in a proper way.
What we are doing is taking all this waste and forming something with value. All these people have an interest in the technology and the other people we are selling it to are the people who manufacture with plastics like the plastic manufacturing industry.
There are people that are so used to using conventional polymers that they cannot get rid of them from their technologies but what they want to do is to use it as the minimal of this kind of polymer and substitute most of it with our polymer. That means that if you were creating plastic bags or sheets the bulk of the polymer, 95% of the polymer, will be our material and the last two layers are where you can actually do thermo-processing or put colours or put graphics on it so that will be the one that is like a common polymer.