Characterization of a Shear Thinning Fluid System for Cardiovascular Medical Device Assessment

Mammalian blood is a non-Newtonian fluid that decreases in viscosity as the shear rate increases. This complex behavior of the fluid contributes heavily to the complex flow patterns that affect circulatory assist devices. In order to adequately verify these devices in an in vitro setting, a substitute fluid must be used that delivers a level of fidelity that makes the experimental results relevant. Traditional formulations have been based on natural products (e.g. Xanthan Gum) and have required large dilutions (e.g. PMMA). Both of these factors have made the use of these analogs unreliable and difficult to accurately construct, respectively. A new formulation is proposed that addresses the issues of solution reliability and robustness in construction. The formulation is comprised of silicon dioxide and polyalphaolefin. The former is a powder mix and the latter is a solution. The mixing quantities do not require analytical grade equipment to formulate the proper solution within an industry accepted range of error. The liquid system also exhibits a high level of clarity, which makes it compatible with imaging methods used to visualize the flow patterns of the fluid using particle image velocimetry (PIV). Presentation of the liquid system and rheological data will be delivered to support this study's conclusion that this solution is a more adequately suited blood analog for in vitro flow studies of the cardiovascular system.