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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.