External Resistors for Microfluidic Flow Balancing
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Solution Overview
Problem
Controlling and balancing fluid flow rates in microfluidic devices is challenging due to the difficulty in fabricating and calibrating internal microfluidic resistors, which are prone to variations, affecting the proportion of fluid flowing through pathways, and pressure-controlled flow rates are unpredictable.
Innovation Solution
A device with upstream and downstream resistors external to the microfluidic chip is used to control fluid flow, providing a network of resistances that override internal resistances, allowing for precise and predictable fluid flows by altering pressure differentials across pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If internal microfluidic resistors are used to control flow rates, then flow control is achieved, but manufacturing complexity and cost increase due to high fabrication accuracy requirements
Solution Approach 1:
The patent extracts the flow control function from the microfluidic chip itself by removing the internal microfluidic resistors and replacing them with external resistors connected to the chip's inlet and outlet ports. This separation allows the chip to be manufactured without complex internal resistor structures, significantly reducing fabrication complexity while maintaining flow control capability through external components.
Solution Approach 2:
The patent introduces external resistors as intermediary components that mediate between the pressure source and the microfluidic chip. These external resistors serve as the flow control elements, allowing precise flow rate adjustment without requiring complex internal structures within the chip. The external resistors act as a buffer that decouples the flow control function from the chip's manufacturing process.
2Reliability
If internal microfluidic resistors are fabricated with high accuracy, then flow rate control improves, but chip-to-chip and batch-to-batch variations must be minimized increasing manufacturing difficulty
Solution Approach 1:
By extracting the resistor components from the chip's internal structure and placing them externally, the patent eliminates the need for high-precision fabrication of resistors during chip manufacturing. The external resistors can be selected from standard components with known, consistent values, ensuring flow rate reliability without imposing stringent manufacturing requirements on the chip fabrication process.
Solution Approach 2:
The patent changes the location and implementation of the resistance parameter from internal microfluidic structures to external mechanical/electrical resistors. This parameter change allows the use of standard resistor components with well-defined resistance values, ensuring consistent flow rates across different chips and batches without requiring complex manufacturing control.
3Stability of the object's composition
If pressure controlled flow is used to achieve high flow stability, then flow stability improves, but flow rates remain unknown requiring accurate determination
Solution Approach 1:
The patent implements a feedback mechanism where the known resistance values of the external resistors are used to calculate and determine the actual flow rates through the system. By measuring the pressure differential across the known external resistors and applying Ohm's law analog for fluid flow, the system can accurately determine flow rates while maintaining stability through the controlled pressure differential.
Solution Approach 2:
The external resistors serve as intermediary elements that enable flow rate determination. Their known, fixed resistance values act as reference points that, when combined with pressure measurements, allow calculation of flow rates. This intermediary approach provides both flow stability through pressure control and flow rate knowledge through the relationship defined by the external resistors.
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
This solution enables precise control and balancing of fluid flows, reducing the impact of chip variability and manufacturing tolerances, allowing for reliable operation across various configurations, particularly effective in complex networks with multiple inlets and outlets, and suitable for biological and chemical synthesis.
Implementation Method 1
altering the pressure differential across the fluid pathway resulting in a modification of the flow rate of fluid through said pathway
Implementation Method 2
each upstream resistor is configured to provide a resistance at an upstream end of a fluid pathway
Data Source
AI summary
A device for controlling a fluid flow in an array of fluid pathways on a microfluidic chip is provided. The device comprising: two or more resistors provided upstream of the chip wherein each upstream resistor is configured to provide a resistance at an upstream end of a fluid pathway;two or more resistors provided downstream of the chip wherein each downstream resistor is configured to provide a resistance at a downstream end of a fluid pathway,wherein the values of the resistances are selected in order to control a proportion of fluid that flows through each fluid pathway.