Nanofluidic rocking Brownian motors.

Area of Science:

• Nanotechnology
• Fluid dynamics
• Statistical mechanics

Background:

• Controlling nanoscale objects in fluids is difficult due to scaling limitations of interaction mechanisms.
• Electrostatic interactions and fluid dynamics present challenges at the nanoscale.

Purpose of the Study:

• To design and demonstrate a method for directed transport and sorting of nanoparticles in nanofluidic systems.
• To overcome the challenges of nanoscale object manipulation using engineered energy landscapes.

Main Methods:

• Designed nanofluidic slit geometry to create specific energy landscapes for nanoparticles.
• Utilized electrostatic interactions between like-charged nanoparticles and walls.
• Implemented a rocking Brownian motor by combining asymmetric potentials with an oscillating electric field.
• Investigated the motor's physics using 60-nanometer gold spheres with high spatiotemporal resolution.

Main Results:

• Achieved directed transport of nanoparticles by shaping energy landscapes and applying oscillating electric fields.
• Fabricated a nanofluidic sorting device capable of separating 60 nm and 100 nm gold nanoparticles.
• Demonstrated rapid separation of particles in opposing directions within seconds.
• Modeling indicated the device can separate particles with a radial difference as small as 1 nanometer.

Conclusions:

• Engineered energy landscapes and rocking Brownian motors offer effective control over nanoscale object transport.
• The developed nanofluidic device demonstrates high-efficiency size-based particle separation.
• This work provides a foundation for advanced nanofluidic devices in fields like diagnostics and materials science.