Diamagnetic repulsion--a versatile tool for label-free particle handling in microfluidic devices

Area of Science:

• Biophysics
• Microfluidics
• Materials Science

Background:

• Diamagnetic repulsion utilizes the force exerted on diamagnetic materials by magnetic fields.
• This effect is significantly amplified by suspending diamagnetic objects in paramagnetic solutions, such as manganese(II) ions (Mn2+).

Purpose of the Study:

• To explore and demonstrate the utility of diamagnetic repulsion for selective microparticle manipulation within microfluidic systems.
• To showcase applications in particle trapping, focusing, and separation for bioanalytical purposes.

Main Methods:

• Utilizing magnetic field gradients to induce diamagnetic repulsion for particle manipulation.
• Arranging magnets to trap particles for assays and modifying fields for particle focusing.
• Employing diamagnetophoresis for continuous flow separation of particles based on size.

Main Results:

• Successful trapping of functionalized polystyrene particles for simultaneous assays using minimal reagent volumes (22 nL).
• Achieved rapid particle focusing into a central stream at high flow rates (650 µm/s) for pre-concentration.
• Demonstrated complete separation of 5 µm and 10 µm polystyrene particles via diamagnetophoresis at low flow rates (20 µL/h).

Conclusions:

• Diamagnetic repulsion provides a versatile, label-free method for manipulating microparticles and potentially cells in microfluidics.
• This technique holds significant promise for various bioanalytical applications, including assays and particle separation.
• The demonstrated methods offer simple, efficient, and reagent-sparing solutions for microfluidic particle handling.