Diffusion-Blocking Check Valve for Ultra-Low Flow Sealing
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Solution Overview
Problem
Traditional check valves fail to seal at ultra-low flow rates due to low-Reynolds laminar and Stokes flow, leading to leakage and poor pumping efficiency, with no micro-scale options available for diffusion blocking, especially for slow actuators like phase change materials.
Innovation Solution
A closed diffusion-blocking one-way check valve design featuring a membrane with intrinsically stressed biasing elements, tethers, and a spacer layer, which forces the valve seat into a closed position without requiring backpressure, using silicon-on-silicon sealing surfaces and controlled thin film stress to ensure leak-free operation at high backpressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional check valves are used, then they can operate at normal flow rates, but they fail to seal at ultra-low flow rates due to low-Reynolds laminar and Stokes flow
Solution Approach 1:
The patent changes the sealing mechanism parameter from backpressure-dependent (traditional) to biasing-element-dependent (invention). The biasing element applies a predetermined force to maintain the closed position regardless of flow rate, enabling reliable sealing at ultra-low flow rates where traditional backpressure-based valves fail.
Solution Approach 2:
The patent replaces the traditional spring-based mechanical biasing system with a microfabricated biasing element integrated into the valve structure. This substitution enables the valve to function at micro-scale dimensions while maintaining the ability to counteract low-Reynolds laminar flow and Stokes flow effects.
2Reliability
If spring-loaded valves are used to prevent leakage at ultra-low flow rates, then sealing improves, but the overall assembly becomes too large for micro-scale applications
Solution Approach 1:
The patent nests the biasing element within the valve body structure, integrating it into the membrane assembly rather than using an external spring. The biasing element is positioned between the membrane and the valve seat, allowing the force-generating component to be contained within the compact valve architecture, achieving leak-free operation at micro-scale dimensions.
Solution Approach 2:
The patent uses a flexible membrane as the valve closure element, which is biased by the integrated biasing element. The membrane's flexibility allows it to conform to the valve seat for sealing, while the thin-film construction keeps the overall valve size small, suitable for micro-scale applications.
3Device complexity
If no biasing element is used, then the valve structure remains simple, but the valve cannot block diffusion-mediated transport at ultra-low flow rates
Solution Approach 1:
The biasing element is designed to automatically maintain the valve in the closed position without requiring external control or additional components. The predetermined biasing force self-adjusts to counteract diffusion-mediated transport and low-Reynolds flow effects, providing reliable diffusion blocking while keeping the valve structure relatively simple.
4Reliability
If high backpressure is required to generate a seal, then the valve can seal at normal flow rates, but it fails to seal at ultra-low flow rates where backpressure is insufficient
Solution Approach 1:
The biasing element applies a predetermined closing force to the membrane before flow occurs, pre-positioning the valve in the closed state. This preliminary action eliminates the need to rely on backpressure generation during flow, enabling sealing at ultra-low flow rates where backpressure would otherwise be insufficient to overcome diffusion-mediated transport.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides effective one-way check-valve operation at high backpressures up to 4 MPa without leakage, allowing for diffusion blocking and flow rectification in ultra-low flow regimes, with tunable opening pressures and reduced leak rates, suitable for microfluidic and implantable applications.
Implementation Method 1
an intrinsically stressed biasing element disposed on a side of the flap opposite the valve seat contacting area... wherein the biasing element forces the valve seat contacting area of the flap against the valve seat of the handle
Implementation Method 2
using silicon-on-silicon sealing surfaces and controlled thin film stress to ensure leak-free operation at high backpressures
Data Source
AI summary
A closed leak-free, diffusion-blocking one-way check valve is composed of a substrate having a flow passage through the substrate, the flow passage has a sealing surface between the substrate and a membrane preventing flow through the flow passage. A thin film having internal stress is disposed on the membrane which induces deformation of the membrane biasing the membrane resulting in the sealing surface in a closed orientation. A method for fabrication and pump utilizing the check valve are disclosed.