The "Liebau pump" is a seemingly simple pump, composed solely of sections of flexible tubing with differing wall elasticities, that is capable of producing unidirectional fluid flow without the use of any valves, from a very simple contractile motion. The Liebau mechanism may be at play in the embrionc heart, which is also a simple tube that can create unidirectional flow from a contractile motion without using valves. Better understanding of the Liebau mechanism presents an opportunity to improve current modeling of embryonic heart flow dynamics. There is very limited data on the velocity field inside of an operating Liebau Pump. Such data could lead to a better understanding of the mechanisms of Liebau pumping, and if those mechanisms in fact play a role in the embrionic heart. This work describes the design and construction of a refractive index matched particle image velocimetry (RIM-PIV) compatible Liebau pump. RIM-PIV is then used to visualize and measure the flow in the operating pump. RIM-PIV requires that both the fluid and solid tubing have a matched refractive index; a water-glycerin mixture and PDMS were chosen for the fluid and tubing, respectively. The PDMS is only available in its raw liquid form, so the required tubing had to be manufactured by casting. Since Liebau pumps work by having the tubing rhythmically compressed, a cam based compression mechanism was designed to controlably "drive" the pump (i.e. compress the tubing.
Prior research indicating the Liebau pumping model to be an improvement for embryonic heart flow dynamics. Current theory suggests the embryonic heart follows a peristaltic model. However, peristaltic pumps differ from embryonic hearts in several regards: peak flow velocity depends on compression speed of the walls, there is a linear relationship between compression wave frequency and flow rate, and the compression location moves length wise down the deformable tube. These these features are not always observed in embryonic hearts. Liebau pumps demonstrate a nonlinear relationship between wall compression frequency and flow velocity, as well as possess only a single active compression site. These findings indicate the possibility of an improved model for embryonic heart flow dynamics based on the Liebau model.