In particular, small soft robots at millimeter scale are of practical interest as they can be designed as a combination of miniature actuators simply driven by pneumatic pressure. They are also well suited for navigation in confined areas and manipulation of small objects. However, scaling down soft pneumatic robots to millimeters results in finer features that are reduced by more than one order of magnitude. The design complexity of such robots demands great delicacy when they are fabricated with traditional processes such as molding and soft lithography. Although emerging 3D printing technologies like digital light processing (DLP) offer high theoretical resolutions, dealing with microscale voids and channels without causing clogging has still been challenging.

Spider silk, already known as one of the strongest materials for its weight, turns out to have another unusual property that might lead to new kinds of artificial muscles or robotic actuators, researchers have found. A team from MIT and Huazhong University of Science and Technology has showed that spider silk could contract and twist in humidity that can be used to make artificial muscle or robotic actuators. The demonstrated that slender spider fibers could suddenly shrink in response to changes in moisture, hence portraying a strong torsional force, a process known as'supercontraction'. The team suspended a weight from the spider silk to make a type of pendulum. They then enclosed it in a chamber where they could control the relative humidity inside.

Inspired by our bodies' sensory capabilities, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering have developed a platform for creating soft robots with embedded sensors that can sense movement, pressure, touch, and even temperature. The research is published in Advanced Materials. "Our research represents a foundational advance in soft robotics," said Ryan Truby, first author of the paper and recent Ph.D. graduate at SEAS. "Our manufacturing platform enables complex sensing motifs to be easily integrated into soft robotic systems." Integrating sensors within soft robots has been difficult in part because most sensors, such as those used in traditional electronics, are rigid. To address this challenge, the researchers developed an organic ionic liquid-based conductive ink that can be 3D printed within the soft elastomer matrices that comprise most soft robots.