  Rapid and versatile object manipulation in air is an open challenge. An
energy-efficient and adaptive soft gripper combined with an agile aerial
vehicle could revolutionize aerial robotic manipulation in areas such as
warehousing. This paper presents a bio-inspired gripper powered by
hydraulically amplified electrostatic actuators mounted to a quadcopter that
can interact safely and naturally with its environment. Our gripping concept is
motivated by an eagle's foot. Our custom multi-actuator concept is inspired by
a scorpion tail design (consisting of a base electrode with pouches stacked
adjacently) and spider-inspired joints (classic pouch motors with a flexible
hinge layer). A hybrid of these two designs realizes a higher force output
under moderate deflections of up to 25{\deg} compared to single-hinge concepts.
In addition, sandwiching the hinge layer improves the robustness of the
gripper. For the first time, we show that soft manipulation in air is possible
using electrostatic actuation. This study demonstrates the potential of
untethered hydraulically amplified actuators in aerial robotic manipulation.
Our proof of concept opens up the use of hydraulic electrostatic actuators in
mobile aerial systems.
