Differential ISFET pH Control for Fast Low-Dilution Adjustment
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Solution Overview
Problem
Current pH control methods are time-consuming, prone to error, and induce significant dilution, especially when controlling multiple conditions in parallel or in small sample volumes, and they often face issues like 'cross-talk' or 'bleed-over' in high-density arrays.
Innovation Solution
A closed-loop system using a feedback electrode set with a working electrode, counter electrode, reference electrode, and ion-sensitive field-effect transistors (ISFETs) that apply controlled current or voltage to achieve precise pH control with minimal dilution, utilizing differential voltage measurements to maintain target pH values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional pH control methods (buffer exchange or adding acid/base) are used, then pH can be changed, but the process is time-consuming and induces significant dilution
Solution Approach 1:
The patent replaces mechanical/manual pH control methods (buffer exchange, adding acid/base) with an electronic control system using field-effect transistors that apply electrical signals to modulate pH, eliminating the need for physical addition of reagents and thereby preventing dilution while reducing time
Solution Approach 2:
The patent changes the physical state or form of pH control from chemical addition to electrical field application, where voltage or current parameters are adjusted to control pH dynamically without altering the sample volume or composition through dilution
2Productivity
If an array of electrodes is used to locally control microenvironment, then parallel pH control is achieved, but cross-talk or bleed-over between sites occurs
Solution Approach 1:
The patent divides the control system into independently addressable field-effect transistor units, each controlling its own local microenvironment through separate gate electrodes, allowing parallel operation without cross-talk between adjacent control sites
Solution Approach 2:
The patent applies local electrical fields through individually controlled electrodes to create distinct microenvironments at each site, ensuring that pH control at one location does not affect neighboring locations, thereby eliminating cross-talk while maintaining high-density array configuration
3Productivity
If higher voltage or current is applied to overcome buffering capacity, then electrochemical reaction rate increases, but side reactions involving other components occur
Solution Approach 1:
The patent implements feedback control by monitoring pH at each electrode site and adjusting the applied voltage or current in real-time to maintain precise pH control, preventing excessive voltage application that would cause side reactions while ensuring sufficient reaction rate
Solution Approach 2:
The patent dynamically adjusts electrical parameters (voltage, current) based on measured pH values to optimize the electrochemical reaction rate without exceeding thresholds that would trigger unwanted side reactions, thereby achieving high productivity with minimal harmful effects
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
Enables rapid, precise, and flexible pH control with minimal dilution and reduced 'cross-talk' between electrodes, allowing for accurate and efficient pH modulation in high-density arrays.
Implementation Method 1
a first ion-sensitive field-effect transistor (ISFET) and a second ISFET
Data Source
AI summary
Closed-loop systems and methods for controlling pH. The system includes a working electrode, a counter electrode, a reference electrode, a first ion-sensitive field-effect transistor (ISFET), a second ISFET, and an electronic controller. The working electrode, the counter electrode, the reference electrode, and a first sensing terminal of the first ISFET are immersible in an active solution. A second sensing terminal of the second ISFET is immersible in a reference solution. The electronic controller is configured to apply a first amount of current or voltage to the working electrode and determine a differential voltage between the first ISFET and the second ISFET. The electronic controller is also configured to set a second amount of current or voltage to reduce a difference between the differential voltage and a target voltage. The electronic controller is further configured to apply the second amount of current or voltage to the working electrode.