SEM images of the hybrid soft pop-up actuators. The image has been colored in post processing to differentiate between the soft (in yellow) and the rigid structure (in blue) (Credit: Wyss Institute at Harvard University)

Researchers have developed a hybrid rigid-soft robotic arm for endoscopes with integrated sensing, flexibility, and multiple degrees of freedom. This arm — built using a manufacturing paradigm based on pop-up fabrication and soft lithography — lies flat on an endoscope until it arrives at the desired spot, then pops up to assist in surgical procedures.

Soft robots are promising for surgical applications because they can match the stiffness of the body, meaning they won’t accidentally puncture or tear tissue. However, at small scales, soft materials cannot generate enough force to perform surgical tasks.

Inspired by biology, the team developed a hybrid model that uses a rigid skeleton surrounded by soft materials. The system’s soft actuators are powered by water. They are connected to the rigid components with an irreversible chemical bond, without the need of any adhesive.

The team demonstrated the integration of simple capacitive sensing that can be used to measure forces applied to the tissue and to give the surgeon a sense of where the arm is and how it’s moving. The fabrication method allows for bulk manufacturing, which is important for medical devices, and enables increased levels of complexity for more sensing or actuation. Furthermore, all materials used are biocompatible.