editor's blog
Subscribe Now

A Move Towards a Magnetic MEMS Relay

Relays might seem amongst the most mundane of components, and yet even they are getting a miniaturization upgrade with the help of MEMS technology. Of course, you might reasonably ask, since reed relays are already mechanical devices, why not simply make them smaller? And there’s a very specific reason: The reed is encased in glass, and that glass is fused onto the leads, which have rhodium or ruthenium or iridium on the contacts. That fusing process is hot, and if you shrink the relay too much, that heat gets too near the contacts and the metal melts.

So you’re stuck with something bigger than you might want. Which suggests a MEMS alternative. And the obvious first approach would be electrostatic. Which, being the obvious first approach, has been tried. And, according to Coto, it was beset with issues, most notably stiction. In case you haven’t run into stiction, it’s a situation where, in this case, some sort of cantilever or see-saw structure gets stuck in a closed position due to low-level forces at the tip. An always-closed relay isn’t of much value. Evidently, a couple of companies have already gone out of business trying this.

So Coto is working its way towards a magnetically-actuated relay. Only they’re taking it one step at a time, starting with the switch only, which they call their Redrock switch. It’s a magnetically-actuated switch, so you essentially supply the magnet separately.

Where, you might wonder, might this be useful? They listed a few examples where you would not want an integrated actuator:

  • A brake fluid level sensor in a car: you float the magnet in the fluid and put several sensors along the fluid reservoir column so that, as the magnet floats down, you can get advance warning that the level is dropping. With a non-MEMS approach, the sensors in this “ladder” need to be far apart so they respond independently – meaning you need a deeper reservoir. By using MEMS, the whole assembly can be made smaller.
  • A switch inside some assembly where gases or liquids are flowing; you can actuate the switch from outside with a magnet.
  • A “capsule endoscope” is a small diagnostic “pill” that tours your insides, but it might be 18 months or so between the time it’s shipped from the factory until it’s actually used – you don’t want the battery to die during that time. So a magnet can be put in the enclosing box, keeping a switch open. Only when the box is opened and the magnet is no longer present will the unit turn on.

The unit is a surface-mount device formed by etching a ceramic substrate using X-ray lithography, seeding with a titanium seed layer, and then plating with nickel/iron. On a separate wafer, copper walls are grown; this “housing” is placed over the switch in a vacuum with a gold/gold seal that results in a perfectly hermetic enclosure.

The actual switch consists of two metal blocks and a cantilever that is attached to one and lies over the other. The two blocks are of opposite magnetic polarity and concentrate the magnetic flux in the gap between the cantilever tip and the block below it, bringing the cantilever tip into contact when actuated. The result is directional: you have to approach from the right angle with the magnet for it to work (or, at the very least, sensitivity is greatest from certain angles).

Why might directionality help? Well, consider the case of an insulin pump where there was a switch in the electronics and a magnet in the disposable insulin reservoir. Apparently there was a case where a stray magnetic field from an electric drill caused insulin to be injected at the wrong time. So the directionality provides a measure of selectivity, helping to make sure that the switch isn’t necessarily moved from any old magnetic field.

The next step is to integrate a magnet into a full-on relay. But apparently this isn’t trivial: you have to print a big enough magnet. They’re looking at proof-of-concept for this by the end of the year, with production a couple years out (assuming it works, of course).

You can find out more on their website.

Leave a Reply

featured blogs
Jan 17, 2022
Today's interview features Dajana Danilovic, an application engineer based near Munich, Germany. In this video, Dajana shares about her pathway to becoming an engineer, as well as the importance of... [[ Click on the title to access the full blog on the Cadence Community sit...
Jan 13, 2022
See what's behind the boom in AI applications and explore the advanced AI chip design tools and strategies enabling AI SoCs for HPC, healthcare, and more. The post The Ins and Outs of AI Chip Design appeared first on From Silicon To Software....
Jan 12, 2022
In addition to sporting a powerful processor and supporting Bluetooth wireless communications, Seeed's XIAO BLE Sense also boasts a microphone and a 6DOF IMU....

featured video

Synopsys & Samtec: Successful 112G PAM-4 System Interoperability

Sponsored by Synopsys

This Supercomputing Conference demo shows a seamless interoperability between Synopsys' DesignWare 112G Ethernet PHY IP and Samtec's NovaRay IO and cable assembly. The demo shows excellent performance, BER at 1e-08 and total insertion loss of 37dB. Synopsys and Samtec are enabling the industry with a complete 112G PAM-4 system, which is essential for high-performance computing.

Click here for more information about DesignWare Ethernet IP Solutions

featured paper

MAX22005 Universal Analog Input Enables Flexible Industrial Control Systems

Sponsored by Analog Devices

This application note provides information to help system engineers develop extremely precise, highly configurable, multi-channel industrial analog input front-ends by utilizing the MAX22005.

Click here to read more

featured chalk talk

NEUTRIK Fiber Optic Solutions

Sponsored by Mouser Electronics and Neutrik

The advantages and benefits of fiber optics are a mile long…but how can you design with them? How can you clean them? How do you repair them? Need a bit of a refresher? In this episode of Chalk Talk, Amelia Dalton chats with David Kuklinski from Neutrik about the OpticalCon advanced, OpticalCon LITE and Opticalcon DragonFly fiber optic solutions from Neutrik. They take a closer look at what benefits each of these solutions brings to the table, what kind of configurations are offered with each of these fiber optic solutions and what kind of performance you can expect when using them in your next design.

Click here for more information about Neutrik opticalCON® Fiber Optic Connector System