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Magnetic Paper can Make Tiny Motors and Robots

Breakthrough:
Magnetized paper with a host of potential applications from miniature speakers to tiny robots crawling through blood vessels.

Business:
Professor Babak Ziaie, Purdue University

The Story:
Magnetic Paper can Make Tiny Motors and Robots

Magnetic ferropaper is a revolutionary type of material that is the creation of scientists from Purdue University. The substance is made by impregnating paper with a mixture of mineral oils and magnetic nanoparticles of iron oxide. As a result the paper substrate’s motion and shape can be controlled in a magnetic field.

Paper: The Ideal Substrate

Paper is a porous material that soaks up the magnetic mixture, and according to researchers all types of paper can be used, but newspaper and soft tissue paper are the best.

The ferropaper is then coated with parylene C, a biocompatible plastic film that makes it water resistant and prevents the mixture from evaporating. It also improves some of the paper’s mechanical properties such as stiffness and elasticity.

Mini Magnetic Actuators

During the course of their research the scientists experimented with a number of shapes and structures to see how they behaved in a magnetic field. The aim was to come up with an mm-scale magnetic actuator. One of the simplest structures they created was a cantilever, a beam supported at one end that could be moved by applying a magnetic field.

“Cantilever actuators are very common, but usually they are made from silicon, which is expensive and requires special clean room facilities to manufacture," said Babak Ziaie, a professor of electrical and computer engineering and biomedical engineering at Purdue. "So using the ferropaper could be a very inexpensive, simple alternative. This is like 100 times cheaper than the silicon devices now available.”

The scientists envisage a number of applications for their wonder material including low-cost ways of making:

• miniature speakers
• motors for tiny robots that could explore the human circulatory system
• tiny motors for surgical instruments
• tiny tweezers to study cells and sub-cellular structures

Magnetic actuators are ubiquitous in the macro-domain but according to Purdue scientists they do not scale well in the mm-scale. In this domain they offer a number of attractive features, but manufacturing them is expensive and unwieldy.

The technology developed by Purdue scientists does not require any expensive specialized laboratory equipment. The nanoparticles are about 1/10,000th the width of human hair, and although larger particles can be used, nanoparticles are easier and cheaper to manufacture.

“It is very inexpensive to make. You put a droplet on a piece of paper, and that is your actuator, or motor,” Ziaie said.

The ferropaper concept is being presented at conferences and in papers, and research to refine the technology still further is ongoing.

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