In-Liquid Potential Measurement via High-Frequency AC
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Solution Overview
Problem
Conventional potential measurement techniques using atomic force microscopes are ineffective in measuring surface potentials in liquids due to ion reallocation, osmotic pressure, and electrochemical reactions, which lead to inaccurate and unreliable results.
Innovation Solution
An in-liquid potential measurement device employing an AC source with a frequency of 10 kHz or higher to suppress electrochemical reactions and ion reallocation, combined with a signal detection unit that measures specific frequency components to detect surface potentials, and a potential calculation unit to calculate the surface potential based on these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional potential measurement techniques (KPFM/SMM) are used in liquids, then surface potential measurement is attempted, but electrochemical reactions and ion reallocation occur causing measurement failure
Solution Approach 1:
The patent applies periodic AC voltage at high frequency (10 kHz or higher) between the probe and sample to induce periodic electrostatic force that can be detected. This periodic action allows measurement of surface potential without DC bias, thereby preventing electrochemical reactions and ion reallocation that would occur with conventional DC-based methods in liquid environments
Solution Approach 2:
The patent changes the frequency parameter of the applied voltage to 10 kHz or higher, which is sufficiently high to suppress electrochemical reactions and ion reallocation in liquid while still allowing detection of the electrostatic force signal. This parameter change transforms the measurement conditions to be compatible with liquid environments
2Measurement precision
If high frequency AC voltage (10 kHz or higher) is applied to suppress electrochemical reactions, then measurement accuracy improves, but signal detection complexity increases
Solution Approach 1:
The patent employs feedback control to maintain constant oscillation amplitude of the probe by adjusting the oscillation driving force based on detected amplitude variations. This feedback mechanism compensates for disturbances caused by electrostatic force, enabling accurate surface potential measurement despite the complexity of high-frequency signal detection in liquid
3Measurement precision
If probe oscillation is used to detect electrostatic force, then surface potential can be measured, but oscillation amplitude changes due to electrostatic force must be precisely controlled
Solution Approach 1:
The patent uses feedback control where the oscillation amplitude is detected and compared with a reference value, and the oscillation driving force is adjusted based on the amplitude difference to maintain constant oscillation amplitude. This automatically compensates for the influence of electrostatic force, simplifying the measurement process while maintaining high precision
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 accurate measurement of surface potentials in liquids by suppressing electrochemical reactions and improving signal-to-noise ratio, thereby enhancing measurement accuracy and reliability.
Implementation Method 1
an AC source that applies an AC voltage between the electrode and the sample; where a frequency of the AC voltage applied by the AC source is 10 kHz or higher
Implementation Method 2
employing an AC source with a frequency of 10 kHz or higher to suppress electrochemical reactions and ion reallocation
Implementation Method 3
a signal detection unit that measures specific frequency components to detect surface potentials
Data Source
AI summary
To measure surface potentials in a liquid, the in-liquid potential measurement device according to the present invention includes: a cantilever having a probe at its free end; a displacement measurement unit that measures a voltage corresponding to a displacement of a tip of the cantilever; an AC source that applies an AC voltage between the probe and the sample; and a signal detection unit. A frequency of the AC voltage is 10 kHz or higher. The signal detection unit detects, from the voltage measured by the displacement measurement unit, an amplitude of a frequency component having the same frequency as that of the AC voltage, an amplitude of a frequency component having double frequency of that of the AC voltage, and a frequency component having the same phase as that of the frequency of the AC voltage.