Surface Plasmon Resonance Imaging for Surface Impedance

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Solution Overview

Problem

Current detection methods for surface impedance and mass-to-charge ratio of molecules in liquid phase are limited by their inability to image entire electrode surfaces and require labeling, and they lack sensitivity and specificity for molecular identification.

Innovation Solution

A method utilizing surface plasmon resonance (SPR) imaging and potential modulation to image and quantify surface impedance and mass-to-charge ratios of molecules on electrodes, allowing for label-free monitoring of molecular binding processes and providing detailed charge and mass information through pH variation and microfluidic setups.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If conventional SPR imaging is used to detect molecular binding, then molecular coverage information is obtained, but surface impedance information and charge information are not provided

Engineering Contradiction:

Improvesurface impedance informationVSAvoiddetection system complexity

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The patent combines conventional SPR imaging with electrochemical impedance spectroscopy by integrating a modulated potential application system with the SPR optical detection system. This merging allows simultaneous acquisition of both optical (molecular coverage) and electrical (surface impedance) signals from the same sensor surface, eliminating the need for separate measurement systems and providing comprehensive molecular information including charge characteristics.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sensor surface serves multiple functions: it acts as both the optical sensing element for SPR detection and the electrochemical working electrode for impedance measurement. This multi-functional design enables a single sensor to provide molecular coverage, surface impedance, and charge information, replacing the need for multiple specialized sensors.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If mass spectroscopy is used to detect mass to charge ratio, then molecular identification is achieved, but it does not work in solution phase and requires miniaturization

Engineering Contradiction:

Improvemass to charge ratio detectionVSAvoidsolution phase applicability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical/gas-phase ionization and mass analysis system of mass spectroscopy with an electrochemical-optical system that operates directly in liquid phase. By applying modulated potential to the sensor surface and detecting the resulting SPR signal modulations, the system determines mass to charge ratios of molecules in solution without requiring vacuum conditions or complex miniaturized MS instrumentation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If atomic force microscopy is used to probe local capacitance, then local impedance information is obtained, but it is slow and complicated for routine analysis

Engineering Contradiction:

Improvelocal capacitance measurementVSAvoidanalysis speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent extracts the impedance measurement function from slow, sequential scanning probe methods and integrates it into a rapid optical detection system. By using SPR imaging with modulated potential, the system simultaneously measures local impedance across the entire sensor surface in parallel, achieving high spatial resolution and fast data acquisition suitable for routine analysis and real-time monitoring.

Inventive Principle:

Principle #2Taking out (Extraction)

4Loss of information

If conventional SPR imaging is used, then molecular binding is detected, but charge information and identity of target molecules are not provided

Engineering Contradiction:

Improvemolecular charge and identity informationVSAvoidsignal transduction sensitivity

Core Design Contradiction:

Loss of informationVSMeasurement precision

Solution Approach 1:

The system uses feedback from the modulated SPR signal to extract both amplitude (related to molecular coverage) and phase (related to surface impedance and charge) information. By analyzing the phase response of the SPR signal to modulated potential, the system obtains charge information that provides molecular identity, creating a feedback mechanism that enhances detection specificity without sacrificing sensitivity.

Inventive Principle:

Principle #23Feedback

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 real-time imaging of surface impedance and determination of mass-to-charge ratios with high sensitivity and specificity, enhancing molecular identification and understanding of molecular functions on biosensors and biochips.

Implementation Method 1

At an appropriate incident angle (called resonance angle), light excites collective oscillations of conduction electrons in the metal film, known as surface plasmons, which causes a sharp decrease in the reflection of light.

Methodology Applied

Scientific EffectSurface plasmon resonance: Resonance