Microfluidic Passive Valve with Ultra-Low Threshold Pressure for High-Throughput Liquid Delivery

Abstract

The microvalve for accurate flow control under low fluidic pressure is vital in cost-effective and miniaturized microfluidic devices. This paper proposes a novel microfluidic passive valve comprising of a liquid chamber, an elastic membrane, and an ellipsoidal control chamber, which actualizes a high flow rate control under an ultra-low threshold pressure. A prototype of the microvalve was fabricated by 3D printing and UV laser-cutting technologies and was tested under static and time-dependent pressure conditions. The prototype microvalve showed a nearly constant flow rate of 4.03 mL/min, with a variation of ~4.22% under the inlet liquid pressures varied from 6 kPa to 12 kPa. In addition, the microvalve could stabilize the flow rate of liquid under the time-varying sinusoidal pressures or the square wave pressures. To validate the functionality of the microvalve, the prototype microvalve was applied in a gas-driven flow system which employed an air blower or human mouth blowing as the low-cost gas source. The microvalve was demonstrated to successfully regulate the steady flow delivery in the system under the low driving pressures produced by the above gas sources. We believe that this new microfluidic passive valve will be suitable for controlling fluid flow in portable microfluidic devices or systems of wider applications.

Fluid-Structure Interaction Analysis on Membrane Behavior of a Microfluidic Passive Valve

“…The parameters of the MPV are consistent with Zhang et al [ 24 ]. The diameter of the liquid chamber is 1500 μm.…”

“…At this time, the flow resistance in the MPV tends to be infinite, and the flow rate is close to zero. The material and structure of the membrane in this paper are different from the literature [ 24 ]. In the numerical calculation process, when the inlet pressure reaches about 4 kPa, the flow rate has stabilized, achieving the purpose of a high flow rate control under ultra-low threshold pressure.…”

“…The microvalve structure consists of a cover, seal layer, membrane, and bottom. The internal flow channel is divided into three parts: a liquid chamber, microholes and control chamber, as shown in Figure 1 c. The flow regulation performance of the microvalve is achieved by the deformation of the membrane under the action of the fluid pressure, as shown in Figure 1 d. Zhang et al [ 24 ] have verified the flow regulation performance of the microfluidic passive valve experimentally.…”

“…The flow rate in the MPV proposed by Zhang et al [ 24 ] can be estimated as: where P refers to the initial inlet pressure; Δ P refers to the pressure gradient; R f refers to the initial flow resistance of the valve; Δ R f refers to the resistance increment. It can be found from Equation (9) that, when the inlet pressures increase Δ P , the resistance caused by the deformation of the membrane increases Δ R f .…”

“…The membrane deformation and pressure drop of the microfluidic device were tested through experiments and FSI analysis. Zhang et al [ 24 ] fabricated a microfluidic passive valve that can achieve the constant flow rate at a lower threshold pressure, i.e., the constant flow rate of the microvalve was 4.03 mL/min when the threshold pressure reached 6 kPa. This microvalve has a lower threshold pressure and better regulation performance of flow rate than the previously reported passive microvalves.…”