Oriented suspension mechanics with application to improving flow linear dichroism spectroscopy

Area of Science:

• Biophysics
• Fluid Dynamics
• Synthetic Biotechnology

Background:

• Flow linear dichroism (FLD) is a biophysical technique using shear-induced particle alignment.
• Optimizing FLD sensitivity is crucial for applications like waterborne pathogen detection.

Purpose of the Study:

• Develop a model for pressure-driven channel flow and particle orientation dynamics.
• Optimize FLD signal for a hand-held synthetic biotechnology prototype.

Main Methods:

• Coupled Fokker-Planck and narrow channel flow equations.
• Modeled steady and oscillating flow of microscopic fiber suspensions.
• Estimated linear dichroism signal considering biaxial orientation.

Main Results:

• Increased channel depth significantly improves FLD signal compared to width.
• Maximized alignment achieved with 2 mm channel depth and 5×10⁴ Pa m⁻¹ pressure gradient.
• Oscillating flow provides comparable alignment to steady flow at optimal frequencies.

Conclusions:

• Channel geometry, particularly depth, is key to enhancing FLD sensitivity.
• Oscillating flow offers practical advantages for small sample analysis.
• The model supports the development of sensitive, portable pathogen detection devices.