The recent discovery of fuel-free propulsion of nanomotors using low power ultrasonic energy has provided a new avenue for exploring the biomedical applications of nanomotors. The ability to remotely control and steer nanomotors towards targets of interest such as cells and tissues is important in these applications. In this work, we demonstrate the magnetic steering of acoustically propelled motors in a biologically compatible phosphate buffer.Steering was accomplished by the incorporation of a thin magnetic nickel stripe within the electrochemically grown metallic rods. The metal rods were grown to be 350nm in diameter and 4.5 �m in length. The metal rods were propelled using ultrasound in the MHz range (see Wang et al., ACS Nano 2012, 6, 6122) and an external magnetic field was used to define the motor's path. In the acoustic field, metallic nanorods with 70-80 nm thick magnetic stripes exhibited the same behavior as non-magnetic rods, including pattern formation into concentric circles, alignment into spinning chains and autonomous axial movement, as their non-magnetic counterparts, but they were also responsive to an externally applied magnetic 150-300 Gauss in strength. Magnetic fields can disrupt pattern formation, while autonomously moving wires and their paths become oriented as evidenced by the decrease in their rotational diffusion coefficient. Coordinated movement of multiple motors and in vitro targeting of motors towards HeLa cells with micron-level precision was achieved.

In vitro steering and cell targeting of ultrasonically propelled nanomotors in a biologically compatible fluid using magnetic fields

246th National Meeting (2013)

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