Optothermal molecule trapping by opposing fluid flow with thermophoretic drift

Area of Science:

• Physical Chemistry
• Biophysics
• Microfluidics

Background:

• Thermophoresis describes molecule movement along temperature gradients, typically towards colder regions.
• Microfluidic systems offer controlled environments for studying molecular transport phenomena.
• Understanding combined fluid and thermal forces is crucial for molecular manipulation.

Purpose of the Study:

• To investigate the superposition of fluid flow and thermophoresis on molecule transport.
• To quantify DNA molecule accumulation under opposing flow conditions in microfluidics.
• To explore the application of engineered temperature fields for molecular confinement.

Main Methods:

• Utilized microfluidic devices to create controlled temperature gradients and fluid flows.
• Employed fluorescence microscopy for real-time imaging and quantification of DNA molecule distribution.
• Developed and applied both 3D and 1D analytical models to describe experimental observations.

Main Results:

• Achieved a 16-fold accumulation of DNA molecules in regions where thermophoresis and fluid flow oppose each other.
• Observed slower trapping kinetics than theoretically predicted for an 800-fold accumulation.
• Demonstrated the confinement of short DNA fragments into a 10 micrometer spot using a radially converging temperature field.

Conclusions:

• The interplay between thermophoresis and fluid flow enables significant molecular trapping and accumulation.
• Analytical models accurately describe the observed phenomena, validating the experimental approach.
• Engineered temperature fields present a viable method for precise spatial control and concentration of DNA molecules.