Soft robots have the potential to diminish the need for humans to venture into unsuitable environments or work in extreme conditions. While their soft nature gives them the advantage of being adaptable to changing environments, their control can be challenging because of the compliance that makes them effective. In this paper we present RUBIC: the Rolling, Untethered, Ballooning, Intelligent Cube, that overcomes some of the difficulties of 2D control by constraining motion to a discretised Cartesian space. RUBIC's method of locomotion is by rolling from one face of the cube to another, in any one of four directions. This motion causes it to move within a 2D grid structure, the dimensions of which are defined by the cube's characteristic length. When in its resting position RUBIC is inherently stable and forms a safe platform for tasks including taking measurements and soil samples, for localization and ad hoc network infrastructure, and as the foundation for larger robots and structures. We present the design of RUBIC's body, the four pneumatic ballooning actuators per face that generate its unique gait, and the control systems for locomotion and obstacle climbing. We consider constraints imposed by the design and fabrication methods including physical dimension and weight, material properties and control fidelity. An alternative locomotion scheme is proposed to improve the speed and linearity which also increases the distance traveled per roll. RUBIC travels with a mean locomotion accuracy of 4.58 • deviation and successfully traverses steps up to 35% of its own height. The discretisation of a soft robotics workspace, as demonstrated by RUBIC, has advantages for safe and predictable locomotion and has applications in both structured and hazardous environments.

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Currently, the majority of wearable robotic haptic feedback devices rely on vibrations for relaying sensory information to the user. While this can be very effective, vibration as a physical stimulation is limited in modality and is uncommon in the natural world. In many cases, for human-robot and humanhuman interaction, a more natural, affective tactile interaction is needed to provide comfortable and varied stimuli. In this work we present the Super-Cutaneous Wearable Electrical Empathic Stimulator (SCWEES), a tactile device that gently stretches and squeezes the surface of the skin. Our hypothesis is that this device can create a pleasant, unobtrusive sensation that can be used to mediate social interactions or to deliver subtle alerts. We describe the design of the SCWEES, a lightweight 3D-printed semi-flexible structure that attaches to the skin at two points and actuates via two shape-memory alloy coil actuators. We evaluate the SCWEES through a range of human interaction experiments: stimulation strength and pleasantness, contraction and extension, and the conveyance of non-disruptive notifications. Quantitative and qualitative results show that the SCWEES generates a pleasant sensation, can convey useful information in humanmachine interactions, and delivers affective stimulation that is less disruptive than conventional vibratory tactile stimulation when the user is engaged in a task.

Mediated social touch has the potential to enhance our interactions with machines and with each other. We present three wearable tactile devices that generate affective haptic sensations via three localised skin stretching modalities; pinching, squeezing, and twisting. The Pinch device is adhered to the skin of the forearm, generating pinching sensations in three locations. The Squeeze and Twist devices are wristbands that elicit squeezing and twisting sensations on the skin of the wrist. All of these devices are powered by shape memory alloy actuators, enabling them to be quiet, lightweight and discreet wearable interfaces, unlike their vibrotactile or servo-motor driven counterparts. We investigate the potential for these devices to be used in mediated social touch interactions by conducting preliminary psychometric tests measuring affective response. The Pinch device and Squeeze wristband were found to simulate positive affective touch sensations, particularly in comparison to vibrotactile stimuli.

Compliant structures allow robots to overcome environmental challenges by deforming and conforming their bodies. In this paper, we investigate auxetic structures as a means of achieving this compliance for soft robots. Taking a tiling based approach, we fabricate 3D printed cylindrical auxetic structures to create tiled auxetic cylinders (TACs). We characterise the relative stiffness of the structures and show that variation in behaviour can be achieved by modifying the geometry within the same tiling family. In addition, we analysed the equivalent Poisson's ratio and found the range between the investigated designs to span from -0.33 to -2. Furthermore, we demonstrate a conceptual application in the design of a soft robot using the auxetic cylinders. We show that these structures can reactively change in shape, thereby reducing the complexity of control, with potential applications in confined spaces such as the human body, or for exploration through unpredictable terrain.