It was incredible the first time the system kicked in and healed itself. It felt like we were witnessing the next step in the evolution of integrated circuits," says Ali Hajimiri, professor of electrical engineering at Caltech. "We had literally just blasted half the amplifier and vaporized many of its components, such as transistors, and it was able to recover to nearly its ideal performance."
Imagine if the chips in your phone or computer could fix themselves almost instantly from problems such as battery power loss and transistor failure.
It might sound like the stuff of science fiction, but a team of engineers at the California Institute of Technology (Caltech), for the first time ever, has developed just such self-healing integrated chips. The team demonstrated this self-healing capability in tiny power amplifiers. The amplifiers are so small that 76 of the chips—including everything they need to self-heal—could fit on a single penny.
In perhaps the most dramatic of their experiments, the team destroyed various parts of their chips by zapping them multiple times with a high-power laser, and then observed as the chips automatically developed a work-around in less than a second.
Until now, even a single fault has often rendered an integrated-circuit chip completely useless. The engineers wanted to give integrated-circuit chips a healing ability akin to that of our own immune system—something capable of detecting and quickly responding to any number of possible assaults in order to keep the larger system working optimally.
The power amplifier they devised employs a multitude of robust, on-chip sensors that monitor temperature, current, voltage, and power. The information from those sensors feeds into a custom-made application-specific integrated-circuit (ASIC) unit on the same chip, a central processor that acts as the “brain” of the system. The brain analyzes the amplifier’s overall performance and determines if it needs to adjust any of the system’s actuators—the changeable parts of the chip.
Interestingly, the chip’s brain does not operate based on algorithms that know how to respond to every possible scenario. Instead, it draws conclusions based on the aggregate response of the sensors.
“You tell the chip the results you want and let it figure out how to produce those results,” says Steven Bowers, a graduate student in Hajimiri’s lab and lead author of the new paper. “The challenge is that there are more than 100,000 transistors on each chip. We don’t know all of the different things that might go wrong, and we don’t need to.
World of possibilities: The team chose to demonstrate this self-healing capability first in a power amplifier for millimeter-wave frequencies. Such high-frequency integrated chips are at the cutting edge of research and are useful for next-generation communications, imaging, sensing, and radar applications.
By showing that the self-healing capability works well in such an advanced system, the researchers hope to show that the self-healing approach can be extended to virtually any other electronic system.
“Bringing this type of electronic immune system to integrated-circuit chips opens up a world of possibilities,” says Hajimiri. “It is truly a shift in the way we view circuits and their ability to operate independently. They can now both diagnose and fix their own problems without any human intervention, moving one step closer to indestructible circuits.”
Via Dr. Stefan Gruenwald