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.