Microtechnology: Miniature magnetic switches

Apr 14, 2011 By Lee Swee Heng
Two miniature magnetic switches on a US one-cent piece. Credit: 2010 IEEE

Transistors are commonly used in electronics as switches to turn an electrical current on or off. For applications that require a very large ratio between the on and off current, however, it is necessary to use mechanical ‘reed’ switches, in which magnetic fields physically move metallic wires (or reeds) towards and away from electrical contact points. As devices become more compact, these mechanical switches need to be miniaturized into small packages, without sacrificing performance.

Min Tang and co-workers at the A*STAR Institute of Microelectronics have now demonstrated a high-performance, ultra-compact version of the mechanical magnetic switch (pictured). Their device consists of a magnetic plate supported by two torsion bars, one on each side. The plate is made from a soft magnetic material of 80% nickel and 20% iron, and is patterned into long, narrow strips. When a magnet is brought close to the device, the strips align with the direction of the , tilting the plate down to establish electrical contact between two gold pads. When the magnetic field is released, the torsion bars tilt the plate back to its original position, breaking the electrical contact with the gold pads.

Tang and her co-workers maximized the response of the plate to the magnetic field by choosing appropriate lengths, widths and thicknesses for the strips. This allowed them to use a smaller magnet to actuate the device, which in turn reduced the overall size and power consumption of the switch. The researchers were able to reduce the required magnetic field to 4.8 milliteslas, or about half the field strength required in previous designs. Despite the modest magnetic field strength, they could repeatedly form a reliable electrical connection between the plate and electrical contacs with an on resistance as low as 0.5 ohms and a switching time of close to 2 milliseconds.

The fabrication requirements for this novel switch are particularly simple because the device consists of a single magnetic plate, whereas previous designs require two. This helps in achieving a small footprint of about four square millimeters. Importantly, the researchers demonstrated that the switch has excellent lifetime characteristics of 34 million switching cycles, and strong shock resistance of greater than 500 g. These characteristics make the switch suitable for a variety of personal electronics applications, including laptops, cellular phones and personal data assistants, as well as medical devices like hearing aids and pacemakers. The researchers’ next step is to develop a hermetically sealed package for the switch to support such applications.

Explore further: New ultrasound device may add in detecting risk for heart attack, stroke

More information: Tang, M. et al. A magnetostatic MEMS switch designed for portable applications. Journal of Microelectromechanical Systems 19, 1131–1139 (2010).

Provided by Agency for Science, Technology and Research (A*STAR)

5 /5 (2 votes)
add to favorites email to friend print save as pdf

Related Stories

Fridge magnet transformed

Mar 11, 2011

The ubiquitous and unremarkable magnet, BaFe12O19, is manufactured in large volumes, has the simplest crystal structure in its class, and is often seen on refrigerator doors—but it is set for an inte ...

World's tiniest mirror

Aug 10, 2010

Just as the path of photons of light can be directed by a mirror, atoms possessing a magnetic moment can be controlled using a magnetic mirror. Research reported in the Journal of Applied Physics investigates the feasibility of usi ...

Magnetic Sensor That Brooks No Interference

Jun 03, 2008

Sensors accurately register the slightest temperature fluctuations, the tiniest changes to a magnetic field, or barely perceptible air currents. In some cases, however, there are limits to their accuracy – ...

Powerful new way to control magnetism

Aug 23, 2010

A team of scientists at Rutgers University has found a material in which an electric field can control the overall magnetic properties of the material. If the magnetoelectric effect discovered by the Rutgers group can be ...

Research paper on magnetic control makes the top 10

Nov 30, 2010

A study of the electric field control of magnetism led by a Northeastern engineering professor was named one of the top 10 papers of the past decade by the prestigious journal Advanced Functional Materials.

Recommended for you

A smart prosthetic knee with in-vivo diagnoses

Apr 22, 2014

The task was to develop intelligent prosthetic joints that, via sensors, are capable of detecting early failure long before a patient suffers. EPFL researchers have taken up the challenge.

User comments : 0

More news stories

Facebook buys fitness app Moves

Facebook has bought the fitness app Moves, which helps users monitor daily physical activity and their calorie counts on a smartphone.

Genetic code of the deadly tsetse fly unraveled

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.

Ocean microbes display remarkable genetic diversity

The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live i ...