Rheological Behavior of Shear Thickening Fluids and Its Potential Application in Soft Wearable Robotic

Abstract

We are now conducting a research on a kind of smart materials of shear thickening fluids (STFs), which show great potential in in our soft wearable robotic. A soft robotic knee brace which can provide torque in knee-joints to physically support elderly people has been developed by our team. In order to make the assistive robotic more soft, safe and effective, we do many attempts by making use of the STFs to optimize the robotic. STFs are dense colloidal suspensions exhibiting an abrupt increase in viscosity with increasing shear rate, the special property of STF is that the rheological behavior is reversible, which maybe make it a good choice to apply as a variable stiffness actuator, because it can act as an impact force at the moment it becomes solid-like state and return to soft state when at rest.
By widely studying about the mechanism and features of STFs, we are going to design a STF-based twisted string actuation, which is characterized by impregnating the shear thickening fluids into Kevlar strings. The strings are attached to a rotative electrical motor and twisted on one end, whereas on the other end the strings are connected to a slide. The basic drive mechanism is that the impact force will be generated on the slide when twist the STF/ Kevlar strings at high shear rates as the viscosity of STFs will increase suddenly. In our future work, we will do various attempts like single STF/ Kevlar string twisted, multiple STF/ Kevlar strings intertwined, etc. at different rotational speeds to verify the shear thickening effect, mathematical model and experimental validation of the STF-based strings will both be conducted, and eventually make STF/ Kevlar an effective actuator applying in soft wearable robots.