Wedge Shaped Electrode for DNA Sequencing Nanogap Precision
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Solution Overview
Problem
Current DNA sequencing methods face challenges in fabricating nanochannels and nanoelectrodes with ultrasmall dimensions required for direct, low-cost, and high-throughput sequencing, particularly in achieving the precise nanogap sizes necessary for accurate transverse tunneling current measurements of individual nucleotides.
Innovation Solution
The development of a DNA sequencing device with nanoelectrodes featuring a wedge or tapered shape, fabricated using techniques such as directional deposition and reactive-ion etching, to create a nanogap of 0.3 nm to 2 nm between electrode members, enhancing the signal-to-noise ratio and improving the detection of individual nucleotides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication methods are used to create nanoelectrodes, then manufacturing simplicity is maintained, but manufacturing precision of nanogap dimensions deteriorates
Solution Approach 1:
The fabrication process is divided into distinct stages: initial electrode formation, resist coating, lithographic patterning, and precision trimming. Each stage addresses specific dimensional requirements, with the trimming stage specifically targeting nanogap precision to achieve the required 0.3-2 nm tolerance that cannot be obtained through conventional single-step fabrication methods.
Solution Approach 2:
The invention employs reactive ion etching with controlled parameters (gas composition, power, pressure, etch time) to precisely remove material and achieve the target nanogap dimensions. By adjusting these etching parameters, the process can selectively remove portions of the electrode to create the precise 0.3-2 nm gap required for accurate tunneling current measurements.
2Measurement precision
If larger electrode gap sizes are used, then device complexity is reduced, but measurement precision of tunneling current deteriorates
Solution Approach 1:
The invention uses asymmetric electrode geometries where one electrode has a planar surface and the opposing electrode has a tapered or wedge shape. This asymmetric configuration allows the electrodes to be positioned at precise angles relative to each other, enabling control of the nanogap dimension through the geometry of the tapered electrode rather than requiring symmetric positioning, thus achieving the required 0.3-2 nm gap for accurate measurements.
Solution Approach 2:
Instead of controlling the gap size solely through lateral positioning in one dimension, the invention introduces a dimensional approach where the tapered electrode geometry provides control through the angle and length of the taper. This transforms the gap control problem from a purely lateral positioning challenge to one that can be solved through geometric design in multiple dimensions.
3Measurement precision
If uniform electrode shapes are used, then manufacturing simplicity is maintained, but signal-to-noise ratio in detection deteriorates
Solution Approach 1:
The invention applies different geometric properties to different regions of the electrode structure. The tapered electrode features a varying cross-section along its length, with a wider base for mechanical support and a narrower tip region that creates the precise nanogap. This local variation in geometry optimizes the electric field distribution and tunneling current characteristics at the critical measurement region while maintaining overall structural integrity.
Solution Approach 2:
The tapered electrode incorporates curved surfaces rather than sharp edges, with a smoothly varying cross-sectional area along its length. This curvature provides several benefits: it facilitates material removal during fabrication, creates a more uniform electric field distribution, and reduces field concentration effects that could lead to noise or breakdown, thereby improving the signal-to-noise ratio.
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 improved signal-to-noise ratio and accuracy in DNA sequencing by reducing noise in the measured electronic signal, facilitating the determination of nucleotide sequences with enhanced throughput and reduced costs.
Implementation Method 1
depositing a conductive material on the resist layer and in the trench, the conductive material in the trench having a tapered profile
Implementation Method 2
patterning the resist layer to form a trench, may include using electron beam lithography for the patterning
Implementation Method 3
Lifting off the conductive material may include dissolving the conductive material in a solvent
Implementation Method 4
Trimming the first electrode member may include using reactive ion etching (RIE) or ion beam etching (IBE) to remove portions of the first electrode member
Implementation Method 5
detect a change in electronic signal as the DNA strand passes through the electrode gap
Data Source
AI summary
A DNA sequencing device, and related methods, include a nanochannel sized to receive a DNA strand, a first electrode member exposed within the nanochannel, and a second electrode member exposed within the nanochannel and spaced apart from the first electrode to form an electrode gap. The second electrode member has a wedge shaped profile, and the first and second electrode members are operable to detect a change in electronic signal as the DNA strand passes through the electrode gap.