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Red Rock Application

Red Rock Application

Something as deceivingly simple as a MEMS magnetic reed switch can make a huge difference in the medical market via miniaturization thanks to MEMS manifacturing techniques.

Coto Technology Inc., announced at the Design West Conference the availability of its RedRock™ RS1-A-2515 MEMS-based magnetic reed switch. Based on its unique high aspect ratio, MEMS design and manufacturing processes, the switch provides all of the advantages of conventional magnetic reed switch technology, including zero power operation and high-power hot switching.


The RedRock MEMS switch represents the first use of High Aspect Ratio Microfabrication (HARM) to pro­duce a commercially available switch. HARM produces switch structures that generate contact closure forces many times greater than those exhibited by previous MEMS-based magnetic switches, enabling hot switch­ing up to several hundred milliwatts. Furthermore, the high retract forces developed in the switch when it opens alleviates any tendency for the switch to stick shut during hot switching or after long closure peri­ods, a problem that plagued earlier MEMS switch designs.


High Aspect Ratio Microfabrication (HARM)


Coto has managed to combine these features to the inherent benefits of MEMS-based design and manufacture, including item-to-item uniformity, robustness and small size by using wafer level packaging (WLP). The resulting solution meets the demanding requirements of applications in the medical, military, and industrial markets. The switch has a footprint of less than 2.4 mm2 (1.10 x 2.18 mm), is 1.10 mm high.


The switch exhibits all of the high performance characteristics inherent in classical reed switches, including closure sensitivity ranges from 5 to 25 millitesla, permitting operation up to 20mm using a small NdFeB magnet. This provides it with the ability to address a wide range of applications.


The switch has a release sensitivity of approximately 60% of the closure sensitivity. This high level of hysteresis minimizes the potential of sticking when the magnetic field is removed greatly adding to the switch’s reliability. The switch has a maximum switching voltage of 100 VDC with a switching current of 50mA DC or 35mA AC, RMS. The zero operating power is a critical advantage in power sensitive applications, particularly those operating with battery power.




Hearing aids


Hearing aid sizes are miniaturized by MEMS technology




Various types of behind-the-ear and in-canal hearing aids




Hearing aid PCB (center) with conventional reed switches (top & bottom) and RedRock microfabricated switch (left).


Capsule endoscopes


Capsule endoscopes are pill-sized devices that contain one or more video cameras and white LED “headlamps.” After a patient swallows the capsule, it takes pictures of the gastrointestinal tract and transmits them to an external mon­itoring system.



Typical capsule endoscope turned on and ready for ingestion


Insulin delivery control


Typically, a reed switch in the insulin pump body is triggered by a magnet attached to the reservoir. The reed switch may also detect when the insulin reservoir is running low. It is vitally important that this switching link works reliably, to ensure correct dosing or sound an alarm when the reservoir needs to be replaced. It’s also extremely important that the reed switch can’t be triggered by extraneous magnetic fields, for example from a cell phone speaker, to avoid false dosing or spurious low insulin level warnings. This is an ideal ap­plication for the RedRock switch, not just because of its small size and zero power requirement, but also its customizable magnetic sensitivity pattern.



Early insulin pump    Modern insulin pump



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