The day when mobile phones, laptops, and other gadgets won’t need their batteries anymore is near. Scientists created a new technology that could convert WiFi signals to electricity that could power electronics.
The new device called ‘rectenna’ could tap into nearby WiFi signals or other AC electromagnetic waves and supply power to electronics in a large area. Additionally, it is made from flexible and inexpensive materials which can easily be fabricated.
The Science Behind the ‘Rectenna’
In a paper published in the journal Nature, researchers at the Massachusetts Institute of Technology described how the rectennas work. It uses a flexible radio-frequency (RF) antenna which captures electromagnetic waves, including WiFi signals.
So where did the “rec-“ came from? To convert AC signal to electricity, the rectenna relies on a component known as a “rectifier,” which are typically made of either silicon or gallium arsenide. However, they are not flexible. And although they are not too expensive, they are inefficient in large areas.
The researchers created a novel two-dimensional semiconductor device made from molybdenum disulfide (MoS2). The device is just about three atoms thick, making it one of the world’s thinnest semiconductors.
“By engineering MoS2 into a 2-D semiconducting-metallic phase junction, we built an atomically thin, ultrafast Schottky diode that simultaneously minimizes the series resistance and parasitic capacitance,” said Xu Zhang, first author of the study. Parasitic capacitance is the condition in which certain materials store some electrical charge in electronics, slowing down the circuit. This is very common in all electronic devices
The antenna is connected to the semiconductor. As the AC signal travels to in it, it is converted into DC electricity which could be used to provide power to electronic circuits or recharge batteries. This way the rectenna could passively gather and transform the omnipresent Wi-Fi signals into much useful DC power.
Powering the ‘Electronic Systems of the Future’
After several experiments, the researchers found that when the device is exposed to Wi-Fi signals with typical power levels, which is around 150 microwatts, it can produce about 40 microwatts of power. This is enough to support a simple mobile display or silicon chips.
The innovation would be useful in supplying power to flexible and miniature electronics and wearables, which are too small for bulky and weighty batteries. It can also be used to certain medical devices, such as those which are implanted inside the body like a pacemaker. If these implantable medical devices leak lithium inside the body, it would be a great danger to patients.
The researchers also highlighted that the rectenna can be useful to future technological advances. Tomás Palacios co-author of the study and director of the MIT/MTL Center for Graphene Devices and 2D Systems in the Microsystems Technology Laboratories explained:
“What if we could develop electronic systems that we wrap around a bridge or cover an entire highway, or the walls of our office and bring electronic intelligence to everything around us? How do you provide energy for those electronics? We have come up with a new way to power the electronics systems of the future — by harvesting Wi-Fi energy in a way that’s easily integrated into large areas — to bring intelligence to every object around us.”