  Due to their ability to move without sliding relative to their environment,
soft growing robots are attractive for deploying distributed sensor networks in
confined spaces. Sensing of the state of such robots would also add to their
capabilities as human-safe, adaptable manipulators. However, incorporation of
distributed sensors onto soft growing robots is challenging because it requires
an interface between stiff and soft materials, and the sensor network needs to
undergo significant strain. In this work, we present a method for adding
sensors to soft growing robots that uses flexible printed circuit boards with
self-contained units of microcontrollers and sensors encased in a laminate
armor that protects them from unsafe curvatures. We demonstrate the ability of
this system to relay directional temperature and humidity information in
hard-to-access spaces. We also demonstrate and characterize a method for
sensing the growing robot shape using inertial measurement units deployed along
its length, and develop a mathematical model to predict its accuracy. This work
advances the capabilities of soft growing robots, as well as the field of soft
robot sensing.
