Microfluidic Chip Stepped Channel for 3D Particle Focusing
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Solution Overview
Problem
Current impedance detection techniques face challenges in distinguishing between different particles, such as circulating tumor cells and blood cells, due to similar impedance signals, requiring additional cell labeling methods which increase costs and complexity.
Innovation Solution
A microfluidic chip design with a stepped structure at the junction of the sheath fluid channel and sample channel, combined with three-dimensional focusing, enhances particle focusing and impedance measurement by creating a pressure effect that brings particles closer to the detection electrode, allowing for more stable and effective discrimination using the resistance to capacitive reactance ratio (R/XC) analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional impedance detection is used to detect particles, then the detection process is simple, but the detection precision is low because particles of different types produce similar impedance signals
Solution Approach 1:
The patent transitions from conventional two-dimensional particle focusing (horizontal direction only) to three-dimensional focusing by adding vertical direction control through a stepped channel structure. The sheath fluid channel has a first section at a higher level and a second section at a lower level, creating vertical pressure gradients that focus particles both horizontally and vertically, enabling precise 3D positioning near the detection electrode
Solution Approach 2:
The sheath fluid channel is segmented into multiple sections with different heights (first section at higher level, second section at lower level), allowing independent control of fluid pressure in different vertical zones. This segmentation enables differentiated pressure application to achieve both horizontal and vertical particle focusing
2Measurement precision
If additional cell labeling methods are used to distinguish target particles, then the detection precision improves, but the device complexity and cost increase
Solution Approach 1:
The system uses the inherent physical and electrical properties of particles (size, shape, electrical characteristics) for differentiation without requiring external markers or labels. The 3D focused impedance detection naturally distinguishes particles based on their own characteristics, making the system self-sufficient and eliminating the need for additional labeling reagents or complex staining procedures
3Stability of the object's composition
If particles are only focused in the horizontal direction, then the device structure is simple, but the detection signal stability is poor due to uneven vertical particle distribution
Solution Approach 1:
The patent adds vertical dimension control to the particle focusing system through a stepped channel design. The sheath fluid channel transitions from a first section at a higher level to a second section at a lower level, creating vertical pressure gradients that actively focus particles in the vertical direction toward the detection electrode, achieving stable 3D positioning
Solution Approach 2:
The patent uses hydraulic pressure control through the stepped sheath fluid channel structure to achieve vertical particle focusing. The height difference between channel sections creates pressure differentials that drive particles vertically toward the detection electrode, complementing the horizontal focusing effect
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 more accurate and stable detection of target particles by improving signal consistency and sensitivity, effectively distinguishing between different types of cells without the need for additional markers, achieving high accuracy and reduced interference from non-target signals.
Implementation Method 1
when the sheath fluid enters the joint position, the sheath fluid will not only flow in the horizontal direction, but also move in the direction perpendicular to the surface of the chip. After converging with the sample channel, the sheath fluid would create a pressure both horizontally and vertically on the sample fluid flowing in the horizontal direction, producing an effect of three-dimensional focusing.
Implementation Method 2
detecting and counting of the particles based on the impeding and resisting effect of the particles on the measuring voltage or current
Implementation Method 3
using a sheath liquid to pack the target sample flow is able to focus the particle flow in the horizontal direction
Data Source
AI summary
A device and method for detecting particles by using electrical impedance measurement, in particular, relating to an improved electrical impedance measurement microfluidic chip and an improved particle detection method. The device comprises a sample injection part, a main channel (4) and an electrical impedance detection part. By means of said device and method, the present invention can accurately distinguish, detect and count different particles.