Influence of fluid viscosity on elastocapillary coiling

A typical spider web is composed of many different types of silk, each designed for a specific

purpose. The capture thread is a soft, extensible silk thread decorated with sticky glue droplets

which adhere prey to the web. Elastocapillary interactions cause the silk thread to buckle and then

coil within the glue droplets as the thread is compressed. The surface tension of the droplets keep

the fiber taut. This means that the capture thread can be compressed far beyond the length at which

an uncoated fiber would begin to sag while remaining taut. It is hypothesized that this morphology

evolved to prevent the web from tangling with itself during wind loading or insect impact. We

expand upon previous studies by exploring the effects of droplet viscosity on the dynamic response

of the drop on fiber system. We test a model system composed of a polymer fiber and silicone oil

droplets and measure the sub micronewton tension in the thread during coiling using micropipette

force sensing.The results of this study will provide a deeper understanding of how spider webs

work and could be used to create solid-liquid hybrid metamaterials.