New “Cat-Eye” Design Simplifies Fabrication, Control, and Operation of Very Tiny Motors

Achievement date: 

Researchers at the NSF-funded Nanosystems Engineering Research Center (NERC) for Translational Applications of Nanoscale Multiferroic Systems (TANMS), headquartered at UCLA, are developing new technologies to enable very tiny electromagnetic motors. This new “cat-eye” design simplifies motor fabrication, control, and operation by building on a prior revolutionary breakthrough, which showed that enormous efficiency improvements are possible by using a voltage-based system (i.e., relative absence of electric current) to control magnetization in a structure referred to as multiferroic—that is, having two or more properties, such as ferroelectricity and ferromagnetism. 


Tiny motors like those being developed could advance a wide range of medical applications (e.g., drug delivery, blood-clot treatment, etc.); more immediate applications also include next-generation lab-on-a- chip technologies, such as cell sorting. It is exciting to recognize that one day such advances might propel a submarine the size of a red blood cell through the human circulatory system. With respect to the “cat-eye” design itself (see figure), this discovery has moved the TANMS team toward a more useful operating structure to continue the 2015 demonstration of manipulating small magnetic particles that can be used to drive rotor-based systems. For example, using the new “cat-eye” design, a motor can be rotated 360° with a single oscillating voltage input; in contrast, prior motor designs required multiple voltage inputs. The discovery of “cat eye” is a critical step toward future demonstration of a fully functioning motor testbed with micron dimensions  (one millionth of a meter).  


To create a micron-scale multiferroic motor system, a simple magnetic stator is needed to control 360° magnetization rotation. The emphasis on simplicity is important because significant architecture complications occur at dimensions below the size of a red blood cell. The “cat-eye” shaped ring structure discovered by the TANMS researchers solves this problem using a basic two-terminal design with a single input.

The voltage-controlled magnetic ring associated with the “cat-eye” design has provided a novel demonstration of a magnetic ring structure capable of producing 180° deterministic magnetization rotation in response to a voltage. Simply oscillating the voltage again produces another 180° deterministic magnetization rotation, thus generating a full 360° deterministic magnetization rotation. One might view this “cat-eye” geometry process as a magnetic “ratchet” similar to the ratchet wrenches commonly in use today.    

The “cat-eye” geometric shape is based on magnetic energy wells and their relative locations, using a parameter called “magnetic shape anisotropy.” By selecting a pseudo-circular geometry with energy-well barriers within 90°, the shape produced has geometric similarities to a cat’s eye. The geometry has a circular exterior and a slit-shaped interior.