TANMS ERC Makes Progress Towards Creating the Worlds Most Powerful Nanoscale Motor

Post date: Jul 14, 2014 5:55:27 PM

People interact everyday with electromagnetic motors, such as the ones that role up your car window or make your cell phone vibrate, that have power densities between 0.1 and 1 kW/kg. These devices are so widespread that it is easy to forget they are virtually everywhere.  While these conventional motors have large power outputs, as size decreases (to the fruit fly size or smaller) the power per unit mass degrades to the point the motor becomes relatively useless.  The TANMS nanomotor systems team is investigating multiferroic structures (e.g., ring shaped magnets) possessing special magnetic domain properties, enabling rotation of magnetization with very low energy dissipation and very fast reorientation times. This advanced high-speed, low energy dissipation operation overcomes the problems associated with conventional electromagnetic motors. Understanding deterministic magnetic control (i.e., placing the magnetization exactly where you want it) in these multiferroic structures could one day enable high speed control of magnetic nanomotors providing much higher power density than any other motor of similar size (~1-1000 kW/kg).  The envisioned nanomotor provides a much greater power density than currently possible with existing nanomotors (~0.001kW/kg) in this size regime, thereby enabling a wide range of applications from flow control on aircraft to implantable artificial kidneys.


The ultimate goal of this work is to create a new nanoscale electromagnetic motor using the scaling advantages provided by multiferroics. Conventional electromagnetic motors cannot be miniaturized because the current density in small wires leads to excessive heating. Multiferroics addresses this problem by using electric fields (as opposed to electric currents) to control magnetization, an approach that works better as devices are miniaturized.

The first step in developing a high power nanoscale motor is to understand the behavior of magnetization changes in the small scale. Understanding this behavior leads to deterministically controlling the magnetization state in the nanoscale multiferroic structure. The one problem with deterministic control of strain-mediated multiferroics is the stochastic (coin flip) process produced when applying an electric field induced strain to rotate the magnetization state. That is, the magnetization can statistically rotate the magnetization either +90 degree of -90 degrees (non-deterministic) rather than consistently only in one direction (deterministic). The research community has expressed concern that a strain-mediated process could not be deterministically controlled [1,2], a feature experimentally and analytically contradicted with this highlight (i.e. you CAN deterministically control magnetization with strain mediated approach if designed appropriately).