Microfluidic Buffer Exchange via Interfacial Focusing Flows
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Solution Overview
Problem
Existing methods for biological sample preparation, such as centrifugation, are time-consuming, costly, and can cause cell viability issues and selection bias, especially when dealing with heterogeneous samples.
Innovation Solution
The use of a microfluidic structure that applies interfacial focusing flows to establish a central region within a main channel, promoting ion diffusion and inhibiting cell dispersion, allowing for efficient buffer exchange and electrical separation of target cells without centrifugation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If centrifugation is used for sample preparation, then cell separation can be achieved, but cell viability decreases and selection bias is introduced
Solution Approach 1:
The patent replaces the mechanical centrifugal separation system with an electrical field-based separation system. Specifically, dielectrophoresis (DEP) and impedance-based methods are used to separate cells based on their electrical properties rather than density or size, eliminating the need for centrifugation and its associated harm to cell viability while maintaining separation efficiency
Solution Approach 2:
The patent changes the separation parameter from mechanical (centrifugal force) to electrical (dielectric properties and impedance). By applying spatially non-uniform electric fields, cells are separated based on their dielectric constants and impedance characteristics, which preserves cell viability while achieving effective separation of heterogeneous cell populations
2Loss of time
If buffer exchange is performed outside the microfluidic chip, then buffer replacement can be achieved, but cell dispersion occurs and sample preparation time increases
Solution Approach 1:
The patent merges the buffer exchange operation with the microfluidic separation and measurement operations into a single integrated chip system. The buffer exchange occurs in-line within the microfluidic channels, eliminating the need for separate external buffer replacement steps and preventing cell dispersion that would occur during external handling
Solution Approach 2:
The patent uses a buffer exchange mechanism where a first buffer is replaced with a second buffer through controlled flow within the microfluidic chip. This intermediary buffer exchange process occurs in-line and is controlled by the microfluidic system, ensuring uniform cell distribution and preventing the dispersion that would occur with external buffer replacement methods
3Ease of operation
If conventional sample preparation methods are used, then bulk processing can be achieved, but device complexity and operational cost increase
Solution Approach 1:
The patent designs a universal microfluidic chip platform that performs multiple functions: buffer exchange, dielectrophoretic separation, impedance measurement, and cell analysis. This multi-functional integrated system replaces multiple separate conventional devices and operations, simplifying the overall process while reducing device complexity and operational costs
Solution Approach 2:
The microfluidic chip is designed to perform sample preparation and separation operations autonomously without requiring complex external equipment or manual intervention. The chip integrates pumps, channels, electrodes, and detection elements that work together in a self-contained system, making the operation simpler and more accessible
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 approach enables efficient on-chip sample preparation and separation of target cells by maintaining cell viability and reducing selection bias, while also facilitating downstream biological separation and measurement tasks.
Implementation Method 1
promoting ion diffusion between the first buffer and the second buffer
Implementation Method 2
a velocity gradient established at the boundary can help inhibit dispersion of the target cells away from the central region
Implementation Method 3
The velocity gradient can help suppress or inhibit bulk convection between the first buffer and the second buffer during ion diffusion in the channel of the microfluidic structure
Implementation Method 4
Dielectrophoresis (DEP) is an electrokinetic phenomenon by which particles suspended in a dielectric medium are subjected to a force when exposed to a spatially non-uniform electric field
Implementation Method 5
performing electrical measurement or electrical separation of the central region of target cells using at least one of electrophoresis, dielectrophoresis, electrochemical measurement, or impedance measurement of cells or media
Implementation Method 6
performing electrical measurement or electrical separation of the central region of target cells using at least one of electrophoresis, dielectrophoresis, electrochemical measurement, or impedance measurement of cells or media
Data Source
AI summary
A method can include receiving a biological sample including the target cells, e.g., at an inlet of a microfluidic structure. This can involve flowing the target cells, e.g., suspended in a first buffer, at a first flow rate within a main channel of the microfluidic structure. At least one focusing flow can be applied to the biological sample, using a second buffer at a second flow rate, to help establish a boundary defining a central region or streamline. The central region can contain the target cells within the main channel and promote ion diffusion between the first and second buffers.