Engineering nanoscale surface features to sustain microparticle rolling in flow.

Area of Science:

• Microfluidics and Nanotechnology
• Biomimetic Engineering

Background:

• Microfluidic channel walls are engineered with nanoscopic features to control fluid transport, particle behavior, and chemical reactions.
• Cellular processes like cell rolling, mediated by selectins, offer a biological paradigm for dynamic particle adhesion and transport.

Purpose of the Study:

• To develop an engineered platform for sustained microparticle rolling on synthetic channel surfaces.
• To investigate the influence of nanoscale surface features and processing parameters on microparticle rolling dynamics.
• To establish design principles for size-selective particle manipulation in microfluidic systems.

Main Methods:

• Incorporation of discrete, synthetic, nanoscale attractive features onto electrostatically repulsive flow channel surfaces.
• Systematic variation of surface feature loading, processing parameters, and feature spacing (tens of nanometers).
• Analysis of microparticle rolling velocity, travel distance, and transitions between rolling, free motion, and arrest states.

Main Results:

• Demonstrated sustained microparticle rolling using weakly adhesive nanoscale features on nonadhesive surfaces.
• Identified dependencies of rolling velocity and travel distance on flow conditions and surface design.
• Characterized a state space of surface and processing variables dictating particle motion regimes.
• Achieved size-selective particle manipulation by optimizing parameters like surface length scales, particle size, and flow rates.

Conclusions:

• Engineered nanoscale surface features can effectively sustain microparticle rolling, mimicking biological cell adhesion mechanisms.
• Systematic control over surface design and processing enables predictable manipulation of microparticle dynamics.
• The developed platform offers potential for size-selective particle sorting and targeted delivery in microfluidic devices.