A Stanford University engineering team has built a radio the size of an ant that requires no batteries. The device gathers all the power it needs from the same electromagnetic waves that carry signals to its receiving antenna. Designed to compute, execute, and relay commands, the tiny wireless chip costs pennies to manufacture, making it cheap enough, they say, to become the missing link between the Internet and the connected smart gadgets envisioned in the “Internet of Things.”

The tiny radio-on-a-chip gathers all the power it needs from the same electromagnetic waves that carry signals to its receiving antenna. (Credit: Amin Arbabian)

"The next exponential growth in connectivity will be connecting objects together and giving us remote control through the web," said Amin Arbabian, an assistant professor of electrical engineering. Much of the infrastructure needed to enable us to control sensors and devices remotely already exists, the team states. The Internet can carry commands around the globe, and computers and smartphones can issue the commands. What's missing, they say, is a wireless controller cheap enough to so that it can be installed on any gadget anywhere.

"In the past when people thought about miniaturizing radios, they thought about it in terms of shrinking the size of the components," Arbabian said. But his approach to dramatically reducing size and cost entailed squeezing all the electronics found in a typical Bluetooth device down into a single, ant-sized silicon chip.

This approach to miniaturization would dramatically reduce power consumption, because a single chip draws much less power than conventional radios. However, to build a device this tiny, every function in the radio had to be reengineered. The antenna had to be small, one-tenth the size of a Wi-Fi antenna, and operate at 24 billion cycles per second. Standard transistors could not easily process signals that oscillate that fast. So the team had to improve basic circuit and electronic design.

The final design fits a receiving antenna that scavenges energy from incoming electromagnetic waves, a transmitting antenna to broadcast replies and relay signals over short distances, and a central processor to interpret and execute instructions—all on one chip.