Poiseuille Flow? Not in Nanochannels

This video explores how fluid transport inside nanometer-scale channels fundamentally defies classical fluid dynamics, revealing new physics that only emerges when confinement reaches molecular dimensions. At the nanoscale, long-trusted assumptions behind Poiseuille’s law collapse: fluids slip instead of sticking to walls, viscosity becomes position-dependent, electrostatic forces dominate hydrodynamics, and individual molecules matter. Nanofluidics is therefore not a small correction to microfluidics — it is a qualitatively different transport regime. You will see why a 10-nm channel cannot be treated as a continuous fluid, how electric double layers reshape flow profiles, and how nanochannels begin to behave more like ionic devices than pipes. The lecture connects these effects to powerful real-world technologies, from DNA sequencing and desalination to energy harvesting, showing how breaking Poiseuille flow unlocks entirely new functionality.

What you will learn:
Why Poiseuille’s law fails at the nanoscale
Which classical assumptions break down in nanochannels
How molecular layering destroys the continuum hypothesis
Why the no-slip boundary condition fails and slip flow emerges
How viscosity increases near channel walls
What the electric double layer is and why Debye length matters
How overlapping double layers create plug-like flow
Why nanochannels become ion-selective
How conical nanopores act as ionic diodes
What concentration polarization is and how it is used
How the Knudsen number quantifies breakdown of continuum theory
Why molecular dynamics simulations become necessary
How nanopores enable single-molecule DNA sequencing
Why carbon nanotube membranes enable ultrafast desalination
How salinity gradients can be converted into electricity
Which theoretical frameworks replace classical hydrodynamics
How experiments validate nanofluidic theory
Why optimal channel size exists for performance
What future nanofluidic technologies may enable

Timestamps:
00:00 — Introduction to nanofluidics
00:38 — Failure of classical fluid assumptions
01:15 — Molecular scale of nanochannels
02:16 — Breakdown of no-slip boundary condition
03:50 — Spatially varying viscosity
04:29 — Electric double layer and Debye length
05:35 — Double layer overlap and electroosmosis
07:07 — Ion selectivity in nanochannels
07:51 — Ion current rectification
09:16 — Concentration polarization
09:53 — Knudsen number and regime breakdown
10:46 — Molecular dynamics simulations
11:25 — DNA sequencing with nanopores
12:00 — Nanoporous desalination membranes
12:34 — Blue energy from salinity gradients
13:09 — Theoretical frameworks beyond Poiseuille flow
14:25 — Experimental verification techniques
15:09 — Scaling laws and optimal design
15:55 — Future directions in nanofluidics

#Nanofluidics #PoiseuilleFlow #Microfluidics #NanoscalePhysics #LabOnAChip #IonTransport #DNASequencing #Desalination