Reconfigurable paramagnetic microswimmers: Brownian motion affects non-reciprocal actuation

Area of Science:

• Physics
• Engineering
• Materials Science

Background:

• Microscale swimmers face significant viscous drag at low Reynolds numbers, necessitating non-reciprocal motion for propulsion.
• Purcell's three-component model highlights the principles of microscale locomotion via non-reciprocal deformation.

Purpose of the Study:

• To design and demonstrate a simple, controllable microswimmer using readily available components.
• To investigate the influence of magnetic fields on microswimmer dynamics and locomotion.
• To explore the effects of Brownian motion on both reciprocal and non-reciprocal microswimmers.

Main Methods:

• Constructed a microswimmer from two rigid paramagnetic particles of different sizes.
• Utilized an eccentric magnetic field to induce non-reciprocal body motion and directional swimming.
• Investigated multibody microswimmers with additional components for cooperative motion.
• Analyzed the impact of stochastic thermal forces (Brownian motion) on swimmer dynamics and speed.

Main Results:

• Achieved controllable, directed locomotion of the microswimmer using magnetic fields.
• Demonstrated cooperative translation in multibody configurations.
• Observed fragmentation of multibody swimmers due to thermal forces, altering locomotion.
• Confirmed that Brownian motion affects both reciprocal and non-reciprocal microswimmers.

Conclusions:

• The paramagnetic particle microswimmer offers a simple yet effective platform for controlled microscale locomotion.
• Novel time-varying magnetic fields can direct the motion of active microscale systems.
• Brownian motion plays a crucial role in the locomotion dynamics of microswimmers, irrespective of their reciprocal or non-reciprocal nature.