Graphite coating makes MEMS relays more reliable

Tiny relays can withstand higher temperatures and radiation
6th April 2018

Researchers from the University of Bristol have been working with chip company Microsemi to vastly improve the reliability of micromachined relays.

Bristol- and Caldicott- based Microsemi worked alongside UoB and the University of Southampton to coat the contacts of micromachined electromechanical (MEMS) relays in nanocrystalline layers of graphite, which can be used to build tiny mechanical switches a few microns in size.

“This is a breakthrough result that could pave the way for a new class of extremely energy-efficient electronic components for use in emerging applications such as autonomous sensor nodes in the Internet-of-Things,” said DrDinesh Pamunuwa, Reader in Microelectronics at Bristol.

“The relays can withstand temperatures over 225˚C and can easily absorb radiation doses that are two orders of magnitude higher than transistors are able to withstand,” he added. “The challenge has been to make them reliable, and these thin films of nanocrystalline graphite effectively act as a conducting solid lubricant, protecting the relay electrodes as they physically make and break contact millions of times.”

These tiny electromechanical relays have effectively zero leakage current and can operate at much higher temperatures and levels of radiation than solid-state transistors, opening up opportunities for use in smart electronic sensors and actuators that are extremely energy-efficient; their moving parts increase the need for long-term reliability.

The work demonstrates how films of nanocrystalline graphite that have a thickness of tens of nanometres protect the relay tips against degradation over millions of switching cycles and provides a reliable electrical contact.

The relays were designed by Dr Sunil Rana, a senior postdoctoral research associate at Bristol. The work was carried out as a collaboration between Bristol’s Microelectronics research group led by Dr Dinesh Pamunuwa, and Dr Harold Chong’s group at Southampton University, with Dr Jamie Reynolds and Dr Suan Hui Pu.

You can find out more about the work of the group at Bristol’s Department of Electrical and Electronic Engineering