Dynamic Rheological Properties of Field Responsive Nanomaterials for Application in Transtibial Prosthesis

STFs (shear thickening fluids) are non-Newtonian fluids that display increases in viscosity at high rates of shear. This unique behavior of STFs can be utilized in various types of protective gear applications. Ultimately, the goal of this project is to design and implement an STF device into a transtibial prosthetic. Those who wear transtibial prosthesis are prone to degenerative joint disease due to elevated loading in the intact extremity of the leg. An STF damper located in the ankle of the prosthetic will absorb gait stresses and protect the intact extremity.  

With this goal in mind, the current work seeks to understand the mechanism behind shear thickening and shear thinning at the microstructure level, characterize the STF through steady state and dynamic rheology, and to investigate the dynamic response of the STF to time-scale dependent deformations. These objectives were accomplished through conducting steady state sweeps, amplitude sweeps, frequency sweeps, and large amplitude oscillatory shear experiments to characterize the sample. The experiments probed the STF response to both constant and dynamic deformations, and allowed for a greater understanding of the material as well as an evaluation of STF effectiveness in a transtibial prosthetic.

The experimental results provided further evidence for the hydrocluster mechanism of shear thickening as well as confirming that the mechanism was universal across all compositions. Furthermore, the STF was shown to increase in both energy dissipation and elasticity with an increase in oscillatory strain. This unique property motivates for further research into the damper capabilities of STFs.