Electroosmotic Self-Propelled Microswimmer with Magnetic Steering

Microswimmers have significant potential for medical applications such as long-term on-demand medication, painless microscale surgery, and so on. The outstanding challenge is to realize power supply, propulsion, and steering mechanisms suitable for operations within the human body and microscale fluids. We propose the microswimmer composed of a self-propulsive disk- shaped module with multiple channels using biofuel cell (BFC) and electroosmotic propulsion (EOP) and a magnetic rod using mag- netic steering (MS). The BFC produces an open-circuit potential (OCP) between a bioanode and a biocathode by redox reactions. The EOP generates a self-propulsive velocity due to counteracting forces of electroosmotic flows produced by the OCP in the channels arranged between the electrodes. The MS works by aligning the magnetic rod in a controlled magnetic field direction. The pro- totype was designed and fabricated using an insulating polymer layer, two conductive layers incorporating silver nanoparticles with anodic/cathodic enzymes, and a magnetic layer containing magnetic nanoparticles. The fast self-propulsion of continuously rotating 30 μm prototypes by the steering in a glucose solution was demonstrated as expected theoretically. This concept has the potential to be used as microrobots for future medical applications such as a pulling mechanism to assist in guidewire insertion or agents delivering drugs.