Silk in Tomorrow’s High Technology Applications – Dr Chris Holland – 6th June 2016

Many of our members (not all, one should add) associated silk with parachutes, dressing gowns and lingerie, but no more after this fascinating talk by Chris Holland of the Materials Science and Engineering Department at the University of Sheffield.

Silk is the oldest commercial fibre and has been produced industrially for over four thousand years through the domestication of the Chinese silkworm. Silks are a group of structural proteins spun into fibres for use outside the body that have evolved independently in spiders, silkworms, ants and bees. This very fact was surprising to our members as I am sure all assumed silk only came from silkworms feasting on mulberry leaves. Indeed, spiders can make up to 7 different types of silk as they weave their intricate webs.

Chris Holland’s work focuses mainly on the rheology of silks which is the study of the flow and deformation of the material. Silk is stored as a liquid-like gel inside the spinning glands of the spider, silkworm, bees etc. However, by pulling the gel through spinning glands of the animal it turns into a solid fibre because of the energy generated. Chris demonstrated through a film clip which showed the forced pulling of silk from spiders and silkworms. Both the pulling speed and the environment affects the properties of the resulting silk – the slower the silk is pulled the more stretchy it is.

Tensile testing equipment is common in engineering laboratories, yet we were surprised to see a film clip of silk undergoing tensile testing. Silk is stronger than steel weight for weight. Spider silk is strong and stretchy whereas glass fibres may be strong but not stretchy. Silks are a thousand times easier to spin than other materials, including common plastics. All very conclusive facts demonstrating that silk is such a versatile strong and flexible material .

Silk has many applications and is used in the medical device called ‘surgical suture’ which is used to hold body tissues together after injury or surgery, involving a needle with attached length of thread. Other applications involve orthopaedic implants, treatments of knee cartilage, replacement corneas, vascular and nerve repairs, bio-medical devices, fibre optics. The applications to the medical world seem endless.

A most interesting talk on a subject that most of our members had never given a second thought presented by Dr Chris Holland whose knowledge and enthusiasm shone through.