Shielded Nanopore Amplifier Layout for Low-Noise Sensing
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Solution Overview
Problem
Nanopore applications face challenges in detecting molecules due to noise in ionic current measurements, primarily caused by parasitic capacitance between the sense and counter electrodes, which limits signal-to-noise ratio (SNR) and time resolution.
Innovation Solution
Incorporating a shield between the sense and counter electrodes, coupled to the amplifier's output, to mitigate parasitic capacitance by mirroring the sense electrode's potential, thereby reducing noise and improving SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard amplifier configuration is used without additional shielding, then the device complexity is low, but the signal-to-noise ratio deteriorates due to parasitic capacitance between electrodes
Solution Approach 1:
A shield electrode is introduced as an intermediary component between the sense electrode and counter electrode. This shield is coupled to the amplifier output and serves to mitigate the parasitic capacitance effect by providing an intermediate conductive structure that reduces the direct capacitive coupling between the sense and counter electrodes, thereby improving the signal-to-noise ratio without requiring fundamental changes to the amplifier architecture
Solution Approach 2:
The shield electrode is connected to the amplifier output, which maintains it at a potential that tracks the sense electrode potential. This equipotential arrangement minimizes the voltage difference between the shield and sense electrode, reducing the electric field and associated parasitic capacitance effects in the region between these electrodes
2Measurement precision
If the capacitance at the amplifier input is reduced, then the noise peaking is reduced and SNR improves, but the time resolution may be compromised due to the pole formation with output impedance
Solution Approach 1:
The shield electrode acts as an intermediary that reduces the effective parasitic capacitance seen by the amplifier input. By positioning the shield between the sense and counter electrodes and coupling it to the amplifier output, the structure reduces the capacitive loading on the amplifier input, thereby reducing noise peaking and improving SNR without significantly affecting the time resolution of the measurement system
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
The shield significantly reduces parasitic capacitance, enhancing the SNR and time resolution of nanopore measurements, allowing for more accurate detection of molecules.
Implementation Method 1
noise in the ionic current measurement limits the signal-to-noise ratio (SNR) and the effective time resolution of the detection. The noise is dependent on any capacitance present at the input to the amplifier that senses and amplifies the ionic current signal. For solid-state nanopores, the total capacitance includes the capacitance of the thin membrane in which the nanopore is fabricated, the capacitance of the wiring between the electrodes and the amplifier, and the characteristic capacitance of the amplifier at its input.
Implementation Method 2
A target molecule in an electrolyte solution can be driven through a nanopore (either biological or solid-state) by electrophoresis. A highly-focused external electric field applied transverse to and in the vicinity of the nanopore (e.g., by electrodes used to read or detect the molecule) acts on a relatively short segment of the negatively charged molecule and directs it through the hole in the nanopore.
Data Source
AI summary
Disclosed herein are systems and devices for detecting molecules. In some embodiments, a system for detecting molecules comprises an amplifier and a nanopore unit, wherein the nanopore unit comprises a nanopore, a sense electrode, a counter electrode, and a shield situated between the sense electrode and the counter electrode and coupled to an output of the amplifier. The shield may be recessed from a hole in the nanopore. A system or device may include an array of nanopore units that may share some components, such as a read amplifier, a digitizer, drive circuitry, control logic, and/or a multiplexer.