Ex vivo rheology of spider silk

Abstract

SUMMARY We investigate the rheological properties of microliter quantities of the spinning material extracted ex vivo from the major ampullate gland of a Nephila clavipes spider using two new micro-rheometric devices. A sliding plate micro-rheometer is employed to measure the steady-state shear viscosity of ∼1 μl samples of silk dope from individual biological specimens. The steady shear viscosity of the spinning solution is found to be highly shear-thinning, with a power-law index consistent with values expected for liquid crystalline solutions. Calculations show that the viscosity of the fluid decreases 10-fold as it flows through the narrow spinning canals of the spider. By contrast, measurements in a microcapillary extensional rheometer show that the transient extensional viscosity (i.e. the viscoelastic resistance to stretching) of the spinning fluid increases more than 100-fold during the spinning process. Quantifying the properties of native spinning solutions provides new guidance for adjusting the spinning processes of synthetic or genetically engineered silks to match those of the spider.

The role of interfacial viscoelasticity in the stabilization of an electrospun jet

“…7 probes only the linear response of the interface. The thinning dynamics of the filament during the electrospinning process is likely to induce also non-linear deformation and strain hardening of the interface [45,46]. The dynamic interfacial viscosity S η′ would then be lower than the actual interfacial viscosity σ η .…”

Editorial

“…Researchers are engaged in developing bioinspired and biomimetic systems -from the mundane to the elegant. The examples are numerous and the possibilities are endless: biomimicked spider silk formulations (Porter and Vollrath, 2009;Kojic et al, 2006); biomimetic glue (Ball, 2010) and adhesives (Geim et al, 2003); antirefl ective and light-trapping biomimetic optical and communication devices (Parker and Townley, 2007;Parker et al, 2003); biomimetic materials chemistry (Aizenberg, 2004) The current and the future technological signifi cance of this focussed approach is immense and far reaching in many diverse biosystems and biomimicked applications. Underpinned by fundamental science and engineering, typical areas of research interests are outlined in the scope of the journal (http://www.…”

Spider silk as a blueprint for greener materials: a review

“…164,166,168 Liquid crystallinity is thought to promote the spinnability of the dope despite its high protein concentration. Liquid crystallinity indeed provides the dope with non-Newtonian rheological characteristics, including a high shear-thinning capacity (a decrease of the viscosity with increasing shear rate), 143,151 thus making drawing more energy-efficient and promoting orientational ordering. 6,151,164 The native silk dope of B. mori consistently exhibits shear thinning in oscillatory rheological experiments.…”

“…Liquid crystallinity indeed provides the dope with non-Newtonian rheological characteristics, including a high shear-thinning capacity (a decrease of the viscosity with increasing shear rate), 143,151 thus making drawing more energy-efficient and promoting orientational ordering. 6,151,164 The native silk dope of B. mori consistently exhibits shear thinning in oscillatory rheological experiments. [169][170][171] The spinning dope also displays shear thickening 143 and strain-hardening during extensional rheology experiments performed with a capillary break-up micro-rheometer, so that the apparent extensional viscosity diverges at large strains and, ultimately, the viscoelastic dope solution dries to form a solid fiber with a finite and uniform diameter.…”

“…[169][170][171] The spinning dope also displays shear thickening 143 and strain-hardening during extensional rheology experiments performed with a capillary break-up micro-rheometer, so that the apparent extensional viscosity diverges at large strains and, ultimately, the viscoelastic dope solution dries to form a solid fiber with a finite and uniform diameter. 151 This strain hardening, due to the combined action of molecular alignment and water evaporation, is thought to contribute to the stabilization of the spinline and the inhibition of capillary break-up of the fiber during extensional flow. 151 Interestingly, B. mori and spider MA spinning dope exhibit similar shear-stress rheological behavior and seem to behave like polymer melts.…”