Micro- and Nanofluidic pH Sensors Based on Electrodiffusioosmosis

Area of Science:

• Nanoscale science and technology
• Electrochemistry
• Analytical chemistry

Background:

• Micro- and nanofluidic devices utilize large surface-to-volume ratios for nanoscale ion transport.
• Ionic current analysis is crucial for characterizing ions, molecules, nanoparticles, and biological cells.
• Ionic current rectification (ICR) arises from differential cation and anion transport in nanochannels.

Purpose of the Study:

• To induce and utilize electrodiffusioosmosis for pH analysis.
• To quantitatively evaluate proton concentration in nanochannels.
• To improve the stability and accuracy of pH measurements using micro- and nanochannels.

Main Methods:

• Induction of electrodiffusioosmosis via proton concentration differences in nanochannels.
• Quantitative evaluation of proton concentration using galvanostatic current (3 nA) and ICR.
• Development and testing of three micro- and nanochannel designs for improved current-voltage characteristics.
• Assessment of polyethylene glycol-filled nanochannels for enhanced performance.

Main Results:

• Successful quantitative evaluation of proton concentration from pH 1.68 to 10.01 with a slope of 243 mV/pH.
• Improved stability and measurement accuracy of current-voltage characteristics using novel micro- and nanochannel designs.
• Enhanced impedance and ICR ratio observed in nanochannels filled with polyethylene glycol.

Conclusions:

• The developed ICR method provides accurate pH analysis in nanochannels.
• The proposed micro- and nanochannel designs enhance measurement reliability.
• The principle is adaptable for analyzing various ion types in micro- and nanofluidic systems.