A soft robot fish swims independently in three dimensions and enables studies of aquatic life in natural coral reef habitats.

Giving a hand to metamaterials: Auxetic materials expand in an unusual way: perpendicular to the direction in which they are stretched. Lipton et al. engineered a type of auxetic material that also has handedness. When this material is sheared, it twists either to the right or the left. By tiling the underlying patterns onto spheres and cylinders, rigid or compliant structures can be made. Linear and 4-degree-of-freedom actuators can thus be made from hollow tubes, which could be valuable for a variety of engineering and medical applications. Science , this issue p. 632

This paper introduces a novel technique for fabricating functional robots using 3D printers. Simultaneously depositing photopolymers and a non-curing liquid allows complex, pre-filled fluidic channels to be fabricated. This new printing capability enables complex hydraulically actuated robots and robotic components to be automatically built, with no assembly required. The technique is showcased by printing linear bellows actuators, gear pumps, soft grippers and a hexapod robot, using a commercially-available 3D printer. We detail the steps required to modify the printer and describe the design constraints imposed by this new fabrication approach.

Soft robotics offers a range of attractive features relative to traditional rigid robots, including rapid customization, inherently safer human-robot interactions, and continuous passive dynamics that enable morphological computation. Here we present an actuator with an integrated print-in-place strain sensor which is produced entirely via multi-material additive manufacturing and requires no post processing or manual fabrication steps. One natural application of this technology is the end effector of robotic arms; incorporating deformable actuators into a gripping mechanism allows for the safe integration of robotic assistance in human-occupied settings. While numerous soft robot actuators have been implemented without feedback, force sensing and proprioception are valuable signals to leverage in extending the capabilities of these systems. Prior approaches to integrating sensors into soft robot components have relied on manual processes, or specialized fabrication tools. Our work shows a novel method for automatically manufacturing soft pneumatically-driven actuators with embedded sensors through readily available 3D printing tools with no human fabrication required. Automatically manufacturing these sensor-actuator systems enables more complex, capable, and integrate-able designs, because the labor of assembly is eliminated; actuator-sensor designs that would be tedious or impossible become tractable with our approach.

Negative density-dependence is generally studied within a single trophic level, thereby neglecting its effect on higher trophic levels. The ‘functional response’ couples a predator's intake rate to prey density. Most widespread is a type II functional response, where intake rate increases asymptotically with prey density; this predicts the highest predator densities at the highest prey densities. In one of the most stringent tests of this generality to date, we measured density and quality of bivalve prey (edible cocklesCerastoderma edule) across 50 km² of mudflat, and simultaneously, with a novel time-of-arrival methodology, tracked their avian predators (red knotsCalidris canutus). Because of negative density-dependence in the individual quality of cockles, the predicted energy intake rates of red knots declined at high prey densities (a type IV, rather than a type II functional response). Resource-selection modelling revealed that red knots indeed selected areas of intermediate cockle densities where energy intake rates were maximized given their phenotype-specific digestive constraints (as indicated by gizzard mass). Because negative density-dependence is common, we question the current consensus and suggest that predators commonly maximize their energy intake rates at intermediate prey densities. Prey density alone may thus poorly predict intake rates, carrying capacity and spatial distributions of predators.