Three water drops illuminating 20 LEDs

Harvesting energy in place has been considered a potential game-changing technology, especially for applications that require long-term, unattended operations of distributed devices, such as wireless sensors, wearable electronics, medical implants, etc. It could also have larger grid-scale potential. After years of researching, a group of University of Hawaiʻi at Mānoa engineers have made a breakthrough that paves the way for harvesting the abundantly available and, yet, extremely low-level, ambient energy, the holy grail for self-powered devices.

While abundant in the environment, ambient energy sources for mini electronic devices are often of a low-level, intermittent nature, making it an insurmountable challenge for scavenging. The researchers, led by David T. Ma, interim associate dean and professor in civil engineering in the College of Engineering, discovered a method to snowball any arbitrarily low level ambient energy to a useable level. UH has filed an international patent based on this invention.

This unprecedented exponential growth of harvested energy results from an intentionally introduced instability in a scavenger through repetitively switching the scavenger between two configurations. An energy scavenger is a device that harvesting energy from the environment. According to the article published in Communications Physics on March 22, 2018, the method is a generic one, applicable for energy conversion between different forms.

Ma’s group used mini electrical generator fabricated with droplet capacitors to harvest energy that enabled the necessary switching. Within a few cycles of reconfiguration, a generator with three water droplets could produce a voltage of 56V, enough to light up 20 LEDs. Although they demonstrated the idea using mini generators, the researchers believe it can be scaled up for large-scale applications and it holds potential for revolutionizing grid-level DC power supply systems.

Other team members included a PhD student J. Yu, and an undergraduate student intern E. Ma.