Squid, plastic, printing and crude oil are words you don’t normally find in the same sentence, but in this case they are very apt.
Today’s story starts with the squid. Found across all over the world’s oceans, near the surface and at great depths, they are a source of protein and tall tales told by sailors through the ages.
Squid have ‘beaks’ which are made of one of nature’s toughest materials and ideal for catching and eating their prey.
Squid beaks are a mix of water, protein and a natural, plastic-like polymer called chitin. Chitin is the same stuff as in crab shells, scorpion stingers and beetle wings. It’s tougher than tooth enamel, but unlike teeth, it contains no minerals, just organic material.
The special design of squid beaks has already been looked at for use in the relation to attaching prosthetic limbs. Now, Penn State University are looking the squid’s ring teeth as inspiration for an alternative plastic that can be used in 3-D printing.
Most plastics are currently manufactured from fossil fuel sources like crude oil. Some high-end plastics are made from synthetic oils. Thermoplastics are polymer materials that can melt, be formed and then solidify as the same material without degrading materials properties.
The researchers, including Wayne Curtis, professor of chemical engineering at Penn State, have collected the genetic sequence for six squid collected around the world and looked at it for the protein complex molecule and tried synthesizing a variety of proteins from the complex, with the results published Advanced Functional Materials.
Penn State’s innovation can can be fabricated either as a thermoplastic, heated and extruded or molded, or the plastic can be dissolved in a simple solvent like acetic acid and used in film casting.
The material can also be used in 3D printing machines as the source material to create complicated geometric structures.
To manufacture the squid teeth molecule, the researchers used recombinant techniques.
They inserted the squid’s teeth protein genes into E. coli, so that this common, harmless bacteria could produce the plastic molecules as part of their normal activity and the thermoplastic was then removed from the media where the E. coli lived.
The thermoplastic created is semi-crystalline and can be rigid or soft. It has a very high tensile strength and is a wet adhesive; it will stick to things even if it is wet.
This thermoplastic protein has a variety of tunable properties, which can be adjusted to individual requirements of manufacturing. Because it is a protein, it can be used for medical or cosmetic applications.
As a more eco-friendly alternative to both synthetic and fossil fuel based plastics, this is a great piece of work with some very interesting applications.