Nowadays, rapid robot prototyping is a desired
capability of any robotics laboratory. Combining the speed of
3D plastic printing and the use of custom Open Source electronic
hardware/software solutions, our laboratory successfully
developed and used tools related to variable impedance robot
technology. This paper describes how we capitalized the design
and use of one kind of variable stiffness actuators as a modular
tool to prototype and test in a quick fashion several robot
capabilities. The extension of such a modular tool for rapid
prototyping allowed us to use it in several applications and
scenarios, including the educational setting, aiming to speed up
the gap between theory and practice in robotics. The complete
palette of developments of our laboratory in hardware/software
as well as some robotic systems applications shown here, are
open source and contribute to the Natural Motion Initiative