Design and Fabrication of Pneumatically Actuated Valveless Pumps

In this study, a valveless pump was successfully designed and fabricated for the purpose of medium transportation. Different from traditional pumps, the newly designed pump utilizes an actuated or a deflected membrane, and it serves as the function of a check valve at the same time. For achieving the valveless property, an inlet or outlet port positioned in an upper- or lower-layer thin membrane was designed to be connected to an entrance or exit channel. Theoretical analysis and numerical simulation were conducted simultaneously to investigate the large deformation characteristics of the membranes and to determine the proper location of the inlet or outlet port on the proposed pump. Then, the valveless pump was fabricated on the basis of the proposed design. In the experiment, the maximum flow rate of the proposed pump exceeded 12.47 mL/min at a driving frequency of 5.0 Hz and driving pressure of 68.95 kPa.

Output of a valveless Liebau pump with biologically relevant vessel properties and compression frequencies

Liebau pump is a tubular, non-peristaltic, pulsatile pump capable of creating unidirectional flow in the absence of valves. It requires asymmetrical positioning of the pincher relative to the attachment sites of its elastic segment to the rest of the circuit. Biological feasibility of such valveless pumps remains a hotly debated topic. To test the feasibility of the Liebau-based pumping in vessels with biologically relevant properties we quantified the output of Liebau pumps with their compliant segments made of a silicone rubber that mimicked the Young modulus of soft tissues. The lengths, the inner diameters, thicknesses of the tested compliant segments ranged from 1 to 5 cm, 3 to 8 mm and 0.3 to 1 mm, respectively. The compliant segment of the setup was compressed at 0.5–2.5 Hz frequencies using a 3.5-mm-wide rectangular piston. A nearest-neighbor tracking algorithm was used to track movements of 0.5-mm carbon particles within the system. The viscosity of the aqueous solution was varied by increased percentage of glycerin. Measurements yielded quantitative relationships between viscosity, frequency of compression and the net flowrate. The use of the Liebau principle of valveless pumping in conjunction with physiologically sized vessel and contraction frequencies yields flowrates comparable to peristaltic pumps of the same dimensions. We conclude that the data confirm physiological feasibility of Liebau-based pumping and warrant further testing of its mechanism using excised biological conduits or tissue engineered components. Such biomimetic pumps can serve as energy-efficient flow generators in microdevices or to study the function of embryonic heart during its normal development or in diseased states.

Comprehensive Investigation of Diffuser/Nozzle Element at Low Reynolds Number Aimed at Valveless Pump Design

The performance of diffuser/nozzle element in valveless pumps depends upon a number of geometrical and operational parameters. In this study, the characteristics of low Reynolds number (Re < 100) flow through conical and planar diffuser/nozzle elements with varying half-angle and area ratio (AR) were investigated with simulations and experiments. The optimal half-angle, at which maximum diffuser efficiency occurs, was found to decrease with Reynolds number for both conical and planar elements. Therefore, the results provide a selection criterion for a diffuser/nozzle pair in a valveless micropump design, where no such criterion is available so far.

Investigation of the Flow in Valveless Pumps

An investigation of flow in valveless micropumps is presented. Numerical simulations are done using ANSYS. It is found that both laminar flow and turbulence phenomena would occurs in the diffuser/nozzle element. And SST (shear stress transport) turbulence model is chosen to be the most appropriate turbulence model,The simulations show when the opening angel gets bigger, the flow in the micropump, especially in the diffuser/nozzle becomes unsteady. When separation flow of fluid appears, pressure loss coefficient decreases rapidly.