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Direct observation of confinement-induced diffusophoresis
Saeid Movahed1, Zubair Azad1, Saroj Dangi1
1Department of Physics, North Carolina State University, Raleigh, NC 27695, United States of America.
Nanotechnology
|July 14, 2019
Summary
Ionic strength gradients in nanofluidic devices drive macromolecule drift even at equilibrium. This intrinsic force, observed in DNA motion, is driven by diffusophoresis, not external forces.
Area of Science:
- Physics
- Chemistry
- Biotechnology
Background:
- Nanofluidic devices approach Debye length scales, influencing ion and biomolecule behavior.
- Conventional nanofluidics rely on external forces for concentration polarization.
- Intrinsic ionic strength gradients exist in nanofluidic systems.
Purpose of the Study:
- To investigate macromolecule drift driven by intrinsic ionic strength gradients in nanofluidic devices.
- To demonstrate that external driving forces are not necessary for macromolecule migration.
- To identify the primary mechanism behind equilibrium-driven macromolecule motion.
Main Methods:
- Confining long DNA molecules in 100x100 nm2 nanochannels connected to microfluidic reservoirs.
- Observing DNA motion under equilibrium conditions without external driving forces.
- Employing numerical models to analyze ionic strength gradients and molecular drift.
Main Results:
- Macromolecules (DNA) exhibited migration towards the nano-micro interface at low ionic strengths.
- DNA molecules showed purely diffusive motion in high ionic strength solutions.
- Numerical simulations confirmed that equilibrium ionic strength gradients drive the observed drift.
Conclusions:
- Intrinsic ionic strength gradients in nanofluidic devices induce macromolecule drift via diffusophoresis.
- This equilibrium-driven drift is a fundamental property of nanofluidic systems.
- Understanding this phenomenon is crucial for designing advanced nanofluidic applications.
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