We show that the plastic deformation of snow under uniaxial compression is characterized by complex spatio-temporal strain localization phenomena. Deformation is characterized by repeated nucleation and propagation of compaction bands. Compaction bands are also observed during the very first stage of compression of solid foams where a single band moves across the sample at approximately constant stress. However, snow differs from these materials as repeated nucleation and propagation of bands occurs throughout the subsequent hardening stage until the end of the deformation experiment. Band nucleation and/or reflection of bands at the sample boundaries are accompanied by stress drops which punctuate the stress strain curve. A constitutive model is proposed which quantitatively reproduces all features of this oscillatory deformation mode. To this end, a well-established compressive plasticity framework for solid foams is generalized to account for shear softening behavior, time dependence of microstructure ('rapid sintering') and non-locality of damage processes in snow. arXiv:1501.02184v1 [cond-mat.soft]

In this study, we present a modular worm-like robot, which utilizes voice coils as a new paradigm in soft robot actuation. Drive electronics are incorporated into the actuators, providing a significant improvement in self-sufficiency when compared with existing soft robot actuation modes such as pneumatics or hydraulics. The body plan of this robot is inspired by the phylum Annelida and consists of three-dimensional printed voice coil actuators, which are connected by flexible silicone membranes. Each electromagnetic actuator engages with its neighbor to compress or extend the membrane of each segment, and the sequence in which they are actuated results in an earthworm-inspired peristaltic motion. We find that a minimum of three segments is required for locomotion, but due to our modular design, robots of any length can be quickly and easily assembled. In addition to actuation, voice coils provide audio input and output capabilities. We demonstrate transmission of data between segments by high-frequency carrier waves and, using a similar mechanism, we note that the passing of power between coupled coils in neighboring modules—or from an external power source—is also possible. Voice coils are a convenient multifunctional alternative to existing soft robot actuators. Their self-contained nature and ability to communicate with each other are ideal for modular robotics, and the additional functionality of sound input/output and power transfer will become increasingly useful as soft robots begin the transition from early proof-of-concept systems toward fully functional and highly integrated robotic systems.

Soft robotic systems present a variety of new opportunities for solving complex problems. The use of soft robotic grippers, for example, can simplify the complexity in tasks such as the grasping of irregular and delicate objects. Adoption of soft robotics by the informatics community and industry, however, has been slow and this is, in-part, due to the amount of hardware and software that must be developed from scratch for each use of soft system components. In this paper, we detail the design, fabrication, and validation of an open-source framework that we designed to lower the barrier to entry for integrating soft robotic subsystems. This framework is built on the robot operating system (ROS), and we use it to demonstrate a modular, soft-hard hybrid system, which is capable of completing pick and place tasks. By lowering this barrier to entry through our open sourced hardware and software, we hope that system designers and Informatics researchers will find it easy to integrate soft components into their existing ROS-enabled robotic systems.

What are the potential benefits and problems?

No abstract