Pore Chip Aspect Ratio for Uniform Electric Field
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Solution Overview
Problem
Conventional pore devices with low aspect ratios suffer from degraded measurement accuracy due to non-uniform electric field strength, leading to differences in measured signals when particles pass through the center versus the outer circumference of the pore.
Innovation Solution
A pore chip with a membrane having a pore diameter d and thickness t satisfying the relation 1≤t/d<2, which allows for a uniform electric field generation and improved measurement accuracy, potentially featuring a multi-layer structure with different insulating materials to manage stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a low aspect ratio pore device is used, then the device complexity is reduced, but the measurement precision deteriorates due to non-uniform electric field strength
Solution Approach 1:
The invention changes the geometric parameter of the pore device by setting the aspect ratio t/d to be 0.01 or less, where t is the membrane thickness and d is the pore diameter. This parameter change creates a specific geometric configuration that generates a uniform electric field strength across the pore cross-section, thereby improving measurement precision without excessive complexity
Solution Approach 2:
The low aspect ratio pore device structure creates an equipotential condition across the pore cross-section, ensuring that the electric field strength is uniform at all positions including the center and outer circumference. This equipotentiality eliminates the measurement accuracy degradation that occurs in conventional devices with non-uniform electric fields
2Measurement precision
If the membrane thickness is increased to achieve uniform electric field, then the aspect ratio increases, but the measurement accuracy deteriorates due to non-uniform electric field in the diameter direction
Solution Approach 1:
The invention inverts the conventional approach by not increasing membrane thickness to achieve uniform electric field. Instead, it reduces the aspect ratio to 0.01 or less by adjusting both thickness and diameter proportions, creating uniform electric field through geometric optimization rather than thickness increase alone
Solution Approach 2:
The invention creates local uniformity in electric field strength across different positions (center and outer circumference) by optimizing the overall aspect ratio. This local quality adjustment ensures that particles passing through any position in the pore experience the same electric field strength, improving measurement consistency
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 configuration ensures consistent signal intensity measurement regardless of the particle's passage path, resulting in higher unimodality of particle diameter histograms and enhanced detection accuracy.
Implementation Method 1
A particle size distribution measurement method, which is referred to as the 'electrical sensing zone method (the Coulter principle)', is known. When a particle passes through such a pore, the amount of the electrolyte solution with which the pore is filled is reduced by an amount that corresponds to the volume of the particle, which raises the electrical resistance of the pore.
Implementation Method 2
The voltage source 220 generates an electric potential difference Vb across the electrode pair 106 and 108. The electric potential difference Vb functions as a driving source of the electrophoresis and is used as a bias signal for measuring the resistance value Rp.
Implementation Method 3
The transimpedance amplifier 210 converts the microscopic current Is into a voltage signal Vs. With the conversion gain as r, the following expression holds true. Vs=−r×Is
Data Source
AI summary
A pore chip includes a membrane having a pore. With the diameter of the pore as d and the thickness of the membrane as t, the relation 1≤t/d<2 is satisfied.