New Material Shrilk Might Rival Plastic

Here is a case of Biomimicry at its best.

For those wanting replacements for non-biodegradable and fossil fuel-dependent plastic, Harvard University’s Wyss Institute for Biologically Inspired Engineering has announced a new material for that is cheap to produce, biodegradable, and biocompatible. Its creators call it “Shrilk,” saying the unique structure of arthropod cuticle inspired the material discovery.

It might even be possible the material has the potential to replace plastics in consumer products and could also be used safely in a variety of medical applications, such as suturing wounds or serving as scaffolding for tissue regeneration.

Shrilk has the strength, toughness and laminar design of arthropod cuticle. Wyss Institute postdoctoral fellow, Javier Fernandez and Wyss Institute Founding Director Donald Ingber engineered a thin, clear film that has the same composition and structure as said cuticle.

According to the press announcement, “Natural insect cuticle, such as that found in the rigid exoskeleton of a housefly or grasshopper, is uniquely suited to the challenge of providing protection without adding weight or bulk. As such, it can deflect external chemical and physical strains without damaging the insect’s internal components, while providing structure for the insect’s muscles and wings. It is so light that it doesn’t inhibit flight and so thin that it allows flexibility. Also remarkable is its ability to vary its properties, from rigid along the insect’s body segments and wings to elastic along its limb joints.”

Arthropods have an outer skeleton made up of a composite material called cuticle that consists of layers of a polysaccharide polymer called chitin and protein organized in a laminar, plywood-like structure. In its unmodified form, which can be seen in the body wall of a caterpillar, chitin is translucent, pliable, resilient and quite tough, but arthropods are able to modify its properties to make it tough and rigid, as seen in the body wall of a beetle, or to make it elastic, as seen in arthropod limb joints.

“When we talk about the Wyss Institute’s mission to create bioinspired materials and products, Shrilk is an example of what we have in mind,” said Ingber. “It has the potential to be both a solution to some of today’s most critical environmental problems and a stepping stone toward significant medical advances.”

Shrilk is composed of fibroin protein from silk and from chitin. The material is similar in strength and toughness to aluminum alloys, but is only half the weight. Since chitin can be extracted from discarded shrimp shells it can be produced at very low cost. It is also biodegradable and can be molded into complex shapes. By controlling the water content in the fabrication process, the researchers were also able to vary the stiffness of the material, ranging from elastic to rigid.

Wyss researchers say that these attributes make Shrilk suitable for a wide range of applications, including providing a cheap, environmentally safe alternative to plastic, and for making garbage bags, packaging, and diapers that degrade quickly. Since it is also biocompatible and strong, it could also be used to suture wounds that bear high loads, such as hernia repair, or as a scaffold for tissue regeneration.

Photo: Harvard.edu