A new untethered and insect-sized aerial vehicle more than 25 times lighter than other radiofrequency-powered micro-sized vehicles

https://techxplore.com/news/2021-12-untethered-insect-sized-aerial-vehicle.html

"robot... based on a radiofrequency power receiver with a remarkable power-to-weight density of 4,900 W kg-1... highly efficient flapping actuation, which is achieved using high-power single-crystal piezoelectric material and a low-loss layout with two wings facing each other,.. This design enables a power-to-weight efficiency comparable to that of live insects.... a sub-gram circuit can receive and handle high power of over 1 W at a distance via an RF wave,... weighs only 1.8g"