Nanopore Formation via Cyclic Voltage and Current Threshold Control
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Solution Overview
Problem
The existing methods for forming nanopores in semiconductor substrates face challenges such as varying defect levels and currents, leading to inconsistent pore sizes, increased signal processing requirements, and difficulties in forming small nanopores with precise diameters, which complicates DNA sequencing and increases costs and complexity in parallelized systems.
Innovation Solution
A method involving sequential voltage applications with a low voltage to minimize defect-related currents, allowing for precise measurement and control of nanopore formation, using a control circuit to manage voltage and current thresholds, and a memory unit to store relations between pore sizes and current values, enabling uniform cutoff current values across membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high voltage is continuously applied to form nanopores, then nanopore formation is achieved, but the current varies due to defect levels leading to inconsistent pore sizes
Solution Approach 1:
The patent applies periodic voltage pulses instead of continuous voltage to form nanopores. The voltage is applied in multiple cycles, with each cycle consisting of a voltage application period followed by a measurement period. This periodic action allows the system to measure the current at specific intervals and stop the voltage application when the current reaches a threshold, thereby achieving consistent nanopore diameters despite variations in defect levels.
Solution Approach 2:
The patent implements a feedback mechanism where the current is continuously monitored during nanopore formation. When the current reaches a predetermined threshold value, the voltage application is automatically stopped. This feedback control ensures that nanopores with consistent diameters are formed across different membranes, compensating for variations in defect levels and current characteristics.
2Manufacturing precision
If TEM apparatus is used to form nanopores, then precise nanopore formation is achieved, but processing time increases due to vacuuming and stabilization
Solution Approach 1:
The patent replaces the complex mechanical vacuum system of TEM apparatus with a simpler electrical field-based nanopore formation method. By applying voltage directly to the membrane in an aqueous environment, the system eliminates the need for vacuuming and stabilization procedures, thereby maintaining nanopore formation precision while significantly improving throughput and productivity.
3Measurement precision
If signal processing is enhanced to handle varying currents, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent performs preliminary characterization of the current-defect level relationship before actual nanopore formation. By establishing this relationship in advance and using it to set appropriate current thresholds, the system achieves accurate nanopore diameter control without requiring complex real-time signal processing algorithms during the formation process.
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 simplifies and cost-reduces nanopore formation, achieves precise control over pore diameters, and reduces signal processing complexity, enabling accurate and efficient DNA sequencing by minimizing defect-related currents and allowing uniform cutoff current values.
Implementation Method 1
When a high voltage is applied between both electrodes, charges break bonds in the film, and therefore the number of defect levels rapidly increases. The leakage current IPF that passes through the membrane increases accordingly.
Implementation Method 2
charges having ions are conducted through the SiN membrane as a current that passes through the SiN membrane owing to the tunnel effect
Implementation Method 3
a current that is conducted through the SiN membrane via defect levels in the SiN membrane (these two types of currents that pass through a membrane are referred to as a tunnel current and a Pool-Frenkel current respectively)
Implementation Method 4
a power supply for applying a voltage between the first electrode and the second electrode
Implementation Method 5
a measurement unit for measuring a value of a current obtained by applying the voltage
Data Source
AI summary
A pore forming method in which a pore is formed in such a way that a first voltage is applied between electrodes that are disposed with a film in an electrolytic solution therebetween; a second voltage, which is lower than the first voltage, is applied between the electrodes; a current that flows between the electrodes owing to the application of the second voltage is measured; it is judged whether a value of a current is equal to or larger than a predefined threshold; and if the value of the current is smaller than the threshold, the above sequence is repeated until a pore is formed. In this case, the second voltage is a voltage that makes the value (IPF) of the current flowing through the film practically 0. With the use of the above method, a nanopore is formed in the film simply, easily, and accurately.