Photocatalytic Magnetic Microgyroscopes with Activity-Tunable Precessional Dynamics.

Area of Science:

• Physics, Soft Matter
• Chemical Engineering
• Biomedical Engineering

Background:

• Magnetic nano/microrotors are passive elements used in fluid mixing, drug delivery, and biomedicine.
• These micro-rotors are typically confined to a plane and driven by external rotating magnetic fields.

Purpose of the Study:

• To create an active magnetic microgyroscope driven by both a photoactivated catalytic reaction and a rotating magnetic field.
• To investigate the uplift dynamics and the contribution of phoretic and osmotic forces to gravitational torque.
• To demonstrate hysteresis loops in uplift dynamics by modulating magnetic field amplitude.

Main Methods:

• Experimental investigation of microgyroscope dynamics under combined magnetic and light-induced catalytic driving.
• Theoretical modeling to analyze the interplay of phoretic, osmotic, magnetic, and viscous forces.
• Precise measurement of gravitational torque contributions and observation of uplift dynamics.

Main Results:

• The active microgyroscope exhibits self-propulsion due to light-induced hydrogen peroxide decomposition.
• Phoretic and osmotic forces cooperatively increase effective gravitational torque, counteracting magnetic and viscous torques.
• Modulating magnetic field amplitude successfully induces hysteresis loops in the uplift dynamics.

Conclusions:

• The developed active microgyroscope offers new possibilities for controlled motion and manipulation at the microscale.
• Understanding the interplay of different forces is crucial for designing and controlling active micro-machines.
• The observed hysteresis opens avenues for novel applications in micro-actuation and sensing.