Paper Number
BA1 

Session
Biorheology & Active Fluids

Title
Network formation in an infinite sea of water: Concentration-dependent rheology of hagfish defense gel

Presentation Date and Time
February 13, 2017 (Monday) 10:00

Track / Room
Track 2 / Audubon A

Authors (Click on name to view author profile)

1. Chaudhary, Gaurav (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)
2. Fudge, Douglas S. (Chapman University, Schmid College of Science and Technology)
3. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Gaurav Chaudhary¹, Douglas S. Fudge², and Randy H. Ewoldt^1
1Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; ²Schmid College of Science and Technology, Chapman University, Orange, CA 92866

Speaker / Presenter 
Chaudhary, Gaurav

Text of Abstract
Hagfish make a unique material with remarkable properties. When provoked or attacked, the animal releases a small volume of biopolymer/biofilament material that unfolds, assembles, and expands in water by a factor of 10,000. The resulting gel is cohesive, forming a clogging network used for defense. The successful use of the defense gel is ever the more remarkable considering that hagfish cannot control the concentration of the resulting gel directly; they simply exude a concentrated material into an "infinite" sea of water. This raises questions about the robustness of gel formation and properties across a range of concentrations. In this work, we study the concentration dependent rheology of hagfish defense gel. We observe that viscoelastic properties are linearly dependent on concentration, over the range explored. Moreover, this ultra-soft material (G~0.02 Pa) has a power-law viscoelastic response in creep (fit by a fractional Kelvin-Voigt model), persistent at all concentrations with nearly constant fractal dimension, indicating a robust self-similarity in its structure. Oscillatory shear experiments are consistent with the creep tests. The linear dependence of elastic modulus on concentration is similar to that of affine stretch-dominated networks with high crosslink density. Notably, this is different from many other biopolymers networks which show a stronger dependence on concentration. Thus, hagfish defense gel seems distinctly suited to assemble in an un-controlled "infinite" sea of water.