MEMS-based circuits keep working despite irradiation


RESEARCHERS with the University of Utah have designed ultra-tough microscopic mechanical devices which keep working despite radioactive abuse.

According to the engineers, the devices can withstand intense radiation and heat, so they can be used in circuits which are exposed to radiation in space, damaged nuclear power plants or nuclear attack.

The researchers dipped the devices into the core of the University of Utah’s research reactor for two hours, and subjected them to intense ionising radiation, but they kept working. Simple circuits could also be built with the devices.

Ionising radiation can very quickly destroy modern electronic circuits, so robots navigating into nuclear disaster zones (such as Japan’s Fukushima nuclear power plants which were damaged in 2011) or used in space require heavy shielding. Even so, the radiation eventually destroys the electronics.

Electronic materials require a semiconducting channel to carry current, and the channel is controlled by charges. Radiation creates current inside the semiconductor channel, interfering with the control capability, resulting in signals getting lost.

The new devices are "logic gates" that perform logical operations such as "and" or "not" and are a type of device known as MEMS or micro-electro-mechanical systems. Each gate takes the place of six to 14 switches made of conventional silicon electronics.

These MEMS logic gates lack semiconducting channels. Electrical charges act as switches to make electrodes move to touch each other.

However, MEMS are 1000 slower than silicon electronics and less reliable due to moving parts. The breakthrough is the use of one MEMS device as a logic gate, instead of using separate MEMS switches. The researchers also came up with a technique to form very narrow gaps between the bridges in the logic gates, allowing the devices to be activated with very small voltages.

The researchers say that with circuits that continue working despite ionising radiation, it is possible to provide continuous computational power for critical defense infrastructures.

The research was conducted by Tabib-Azar, University of Utah electrical engineering doctoral student Faisal Chowdhury and computer engineer Daniel Saab at Case Western Reserve University in Cleveland.

The next stage for the researchers is to build a small computer using the logic gates and circuits.