ChemFET Array Noise Mitigation via Reference Pixel Segmentation
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Solution Overview
Problem
Large-scale ChemFET sensor arrays experience fluid potential noise due to parasitic capacitance charging and discharging, non-uniform voltage changes across the array, and contributions from fluid resistance, leakage resistance, and well capacitance, which adversely impact data quality by affecting sensor pixels proximal to reference pixels.
Innovation Solution
The implementation of systems and methods that mitigate fluid potential noise by reducing row-to-row voltage changes between reference and active pixels, using a stable reference electrode and sensing electrode to measure and adjust the voltage applied to reference pixels, thereby minimizing the impact of fluid potential noise on near-neighbor sensing pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large scale ChemFET sensor arrays are used to increase sensing capacity, then productivity is improved, but fluid potential noise increases due to parasitic capacitance charging and discharging
Solution Approach 1:
The sensor array is divided into multiple rows with reference pixels and active pixels separated into distinct groups. Reference pixels are positioned at specific locations (e.g., top and bottom rows) to serve as voltage reference points, while active pixels are arranged in intermediate rows for sensing. This segmentation isolates the reference voltage sources from the active sensing regions, reducing the coupling of fluid potential noise into the measurement signals and enabling larger array sizes without proportional increases in noise.
2Measurement precision
If more pixels are added to the sensor array to increase data quality, then measurement precision is improved, but fluid potential noise from row select switching increases
Solution Approach 1:
Reference pixels serve as intermediary elements between the row select switching circuitry and the active sensing pixels. These reference pixels are specifically designed to absorb and isolate the voltage transients generated during row switching, preventing direct coupling of these transients into the fluid and subsequent active pixel measurements. The reference pixels act as buffer elements that mediate the electrical disturbances, protecting the measurement integrity.
3Reliability
If reference pixels are positioned close to active pixels to reduce voltage changes, then reliability is improved, but coupling of row-to-row voltage changes into fluid increases
Solution Approach 1:
The sensor array employs non-uniform spatial distribution of pixel types, with reference pixels strategically positioned at specific locations (e.g., top and bottom rows) rather than uniformly distributed. This creates local regions with different functional qualities: reference regions for voltage stabilization and active regions for sensing. The localized placement of reference pixels optimizes their ability to reference against common-mode voltage changes while minimizing capacitive coupling to the fluid, as the reference pixels are positioned away from the central active sensing regions.
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 significantly reduces fluid potential noise, ensuring that active pixels remain within operational ranges, thereby improving data quality and reducing the number of out-of-range readings in sequencing and cell analysis runs.
Implementation Method 1
Changes in fluid potential during the progress of analysis using large scale ChemFET sensor arrays can be generated by the charging and discharging of parasitic capacitances in such sensor arrays
Data Source
AI summary
A manifestation of fluid potential noise is a periodic profile characterized by a periodic saw-tooth spike in a graph of average voltage across all columns of a sensor array as a function of time. This periodic profile is indicative of an adverse impact on the function of active sensor pixels that are proximal to reference pixels in sensor devices that include a large array of chemically-sensitive field effect transistor (ChemFET) sensors. Systems, devices, and methods are described that can mitigate the impact of reference pixels on fluid potential noise.