Stanford
Microfluidics Laboratory

On-chip isotachophoresis: Fundamentals

In isotachophoresis (ITP), you apply an electric field along a channel that is pre-filled with two different ion solutions. One solution contains a high-mobility ion (the leading electrolyte or LE) and the second contains a low-mobility ion (the trailing electrolyte or TE). The difference in ion mobility causes an electric field gradient which translates through the channel and accumulates ions whose mobility is bracketed by those of the TE and LE. This wave is a self-sharpening, ion concentration shock wave.

Samples focused in isotachophoresis (ITP) as they pass through a taper in a channel

Bifurcation of an isotachophoresis (ITP) zone at an intersection

Isotachophoresis zone subjected to various pressure pulses (brief)

References

Ashwin Ramachandran and Juan G. Santiago. "Microfluidic Isotachophoresis: Theory and Applications" Chemical Reviews 122, no. 15 (2022): 12904-12976.

Alexandre S. Avaro, Yixiao Sun, Kaiying Jiang, Supreet S. Bahga, and Juan G. Santiago. "Web-Based Open-Source Tool for Isotachophoresis" Analytical Chemistry 93, no. 47 (2021): 15768-15774.

Giancarlo Garcia-Schwarz, Anita Rogacs, Supreet Bahga, and Juan G. Santiago (2012). "On-chip isotachophoresis for separation of ions and purification of nucleic acids" JoVE (Journal of Visualized Experiments), (61), e3890.