Pellicular Morphing Surfaces for Soft Robots

Soft structures in nature endow organisms across scales with the ability to drastically deform their bodies and exhibit complex behaviors while overcoming challenges in their environments. Inspired by microstructures found in the cell membranes of the Euglena family of microorganisms, which exhibit giant changes in shape during their characteristic euglenoid movement, this letter presents the design, fabrication, and characterization of bio-inspired deforming surfaces. The result is a surface of interconnected strips, that deforms in 2-D and 3-D due to simple shear between adjacent members. We fabricate flexible polymeric strips and demonstrate three different shapes arising out of the same actuation by imposing various constraints. We characterize the strips in terms of the force required to separate them and show that the bio-inspired cross section of these strips enables them to hold up to 8 N of force with a meagre 0.5 mm of material thickness, while still being flexible to deform. Further, the design of a soft robot module, with an actively deformable surface has been presented, which replicates the mechanism of shape change seen in the Euglena. This letter shows the potential for this new form of shape morphing surface in realizing bio-mimetic soft robots exhibiting large changes in shape.</p

NeatSkin:A Discrete Impedance Tomography Skin Sensor

In this paper we present NeatSkin, a novel artificial skin sensor based on electrical impedance tomography. The key feature is a discrete network of fluidic channels which is used to infer the location of touch. Change in resistance of the conductive fluid within these channels during deformation is used to construct sensitivity maps. We present a method to simulate touch using this unique network-based, low output dimensionality approach. The efficacy is demonstrated by fabricating a NeatSkin sensor. This paves the way for the development of more complex channel networks and a higher resolution soft skin sensor with potential applications in soft robotics, wearable devices and safe human-robot interaction.</p

Quantifying Dynamic Shapes in Soft Morphologies

Soft materials are driving the development of a new generation of robots that are intelligent, versatile, and adept at overcoming uncertainties in their everyday operation. The resulting soft robots are compliant and deform readily to change shape. In contrast to rigid-bodied robots, the shape of soft robots cannot be described easily. A numerical description is needed to enable the understanding of key features of shape and how they change as the soft body deforms. It can also quantify similarity between shapes. In this article, we use a method based on elliptic Fourier descriptors to describe soft deformable morphologies. We perform eigenshape analysis on the descriptors to extract key features that change during the motion of soft robots, showing the first analysis of this type on dynamic systems. We apply the method to both biological and soft robotic systems, which include the movement of a passive tentacle, the crawling movement of two species of caterpillar (Manduca sexta and Sphacelodes sp.), the motion of body segments in the M. sexta, and a comparison of the motion of a soft robot with that of a microorganism (euglenoid, Eutreptiella sp.). In the case of the tentacle, we show that the method captures differences in movement in varied media. In the caterpillars, the method illuminates a prominent feature of crawling, the extension of the terminal proleg. In the comparison between the robot and euglenoids, our method quantifies the similarity in shape to ∼85%. Furthermore, we present a possible method of extending the analysis to three-dimensional shapes.</p

Multi-directional crawling robot with soft actuators and electroadhesive grippers

This paper presents the design of a planar, low profile, multi-directional soft crawling robot. The robot combines soft electroactive polymer actuators with compliant electroadhesive feet. A theoretical model of a multi-sector dielectric elastomer actuator is presented. The relation between actuator stroke and blocking force is experimentally validated. Electrostatic adhesion is employed to provide traction between the feet of the robot and the crawling surface. Shear force is experimentally determined and forces up to 3N have been achieved with the current pad design. A 2D multi-directional gait is demonstrated with the robot prototype. Speeds up to 12mm/s (0.1 body-lengths/s) have been observed. The robot has the potential to move on a variety of surfaces and across gradients, a useful ability in scenarios involving exploration.</p

B:Ionic Glove: A Soft Smart Wearable Sensory Feedback Device for Upper Limb Robotic Prostheses

Upper limb robotic prosthetic devices currently lack adequate sensory feedback, contributing to a high rejection rate. Incorporating affective sensory feedback into these devices reduces phantom limb pain and increases control and acceptance. To address the lack of sensory feedback we present the B:Ionic glove, wearable over a robotic hand which contains sensing, computation and actuation on board. It uses shape memory alloy (SMA) actuators integrated into an armband to gently squeeze the user's arm when pressure is sensed in novel electro-fluidic fingertip sensors and decoded through soft matter logic. We found that a circular electro-fluidic sensor cavity generated the most sensitive fingertip sensor and considered a computational configuration to convey different information from robot to user. A user study was conducted to characterise the tactile interaction capabilities of the device. No significant difference was found between the skin sensitivity threshold of participants' lower and upper arm. They found it easier to distinguish stimulation locations than strengths. Finally, we demonstrate a proof-of-concept of the complete device, illustrating how it could be used to grip an object, solely from the affective tactile feedback provided by the B:Ionic glove. The B:Ionic glove is a step towards the integration of natural, soft sensory feedback into robotic prosthetic devices.</p

Dexterous textile manipulation using electroadhesive fingers

Handling of fabric is a crucial step in the manufacturing of garments. This task is typically performed by trained workers who manipulate one sheet at a time, thus introducing a bottleneck in the automation of the textile industry. This paper seeks to address the challenge of picking fabric up by proposing a new method of achieving ply-separation. Our approach relies on a finger-tip sized (2 cm ) electroadhesive skin to lift fabric up. A pinch-type grasp is then used to securely hold the separated sheet of fabric, enabling easy manipulation thereafter. The ability to successfully pick up and manipulate a variety of commercial fabrics with diverse materials, shapes, sizes and textures is demonstrated. The ability to handle fabrics 100s of times larger than the electroadhesive skin is unique to our approach. Additionally, we demonstrate the manipulation of non-flat fabrics, a challenge that has not been previously addressed by electroadhesive approaches. We believe that this method introduces a smarter way of handling flexible and limp materials, showing great potential towards automation of garment manufacturing.</p

EuMoBot : Replicating euglenoid movement in a soft robot

Swimming is employed as a form of locomotion by many organisms in nature across a wide range of scales. Varied strategies of shape change are employed to achieve fluidic propulsion at different scales due to changes in hydrodynamics. In the case of microorganisms, the small mass, low Reynolds number and dominance of viscous forces in the medium, requires a change in shape that is non-invariant under time reversal to achieve movement. The Euglena family of unicellular flagellates evolved a characteristic type of locomotion called euglenoid movement to overcome this challenge, wherein the body undergoes a giant change in shape. It is believed that these large deformations enable the organism to move through viscous fluids and tiny spaces. The ability to drastically change the shape of the body is particularly attractive in robots designed to move through constrained spaces and cluttered environments such as through the human body for invasive medical procedures or through collapsed rubble in search of survivors. Inspired by the euglenoids, we present the design of EuMoBot, a multi-segment soft robot that replicates large body deformations to achieve locomotion. Two robots have been fabricated at different sizes operating with a constant internal volume, which exploit hyperelasticity of fluid-filled elastomeric chambers to replicate the motion of euglenoids. The smaller robot moves at a speed of 1=5 body lengths per cycle (20 mm min 21 or 2.2 cycles min 21 ) while the larger one attains a speed of 1=10 body lengths per cycle (4.5 mm min 21 or 0.4 cycles min 21 ). We show the potential for biomimetic soft robots employing shape change to both replicate biological motion and act as a tool for studying it. In addition, we present a quantitative method based on elliptic Fourier descriptors to characterize and compare the shape of the robot with that of its biological counterpart. Our results show a similarity in shape of 85% and indicate that this method can be applied to understand the evolution of shape in other nonlinear, dynamic soft robots where a model for the shape does not exist.</p

Euglenoid Movement and Novel Mechanisms for Soft Robots

Organisms in nature utilise giant changes in body shape to perform everyday functions such as locomotion, object manipulation and feeding. These changes are observed across diverse scales and enable organisms to overcome challenges in their environment. This thesis focuses on the Euglena family of micro-organisms that display a unique manner of locomotion called euglenoid movement in which the cell undergoes a large change in shape. Novel mechanisms for highly deformable soft robots, inspired by this interesting behaviour are presented.To numerically describe the shapes observed in euglenoids and the key features that change during locomotion, a mathematical method based on elliptic Fourier transforms is presented. This is a boundary-based, model free approach to quantify dynamic shapes of soft-bodied organisms and robots. In addition, it allows the comparison of shapes between two entities by providing a measure of similarity.Two approaches to replicating the shape changing behaviour of the euglenoids were explored and are presented in this thesis. In the first approach, a novel soft pneumatic actuator called the hyper-elastic bellows (HEB) actuator is presented, which achieves 450% axial expansion, 80% radial expansion and up to 300 times change in volume. This actuator is then used in the design of soft robots capable of swimming autonomously in a manner that is hydrodynamically similar to that of the euglenoids. A similarity in shape of 85% is demonstrated.In the second approach, the microscopic mechanism of pellicular sliding seen in euglenoids was replicated at a macro scale. The surface of the cell is covered in strips of protein, the relative sliding of which enables the organism to drastically alter its shape. Mimicking this structure, the design, fabrication and characterisation of morphing surfaces is presented which consist of flexible polymeric strips. These are used in the construction of a soft robotic module with an actively deforming surface.This thesis demonstrates that behaviours seen in microscopic organisms can be replicated at larger scales in a robotic system to achieve functional advantages

Pellicular Morphing Surfaces for Soft Robots

Soft structures in nature endow organisms across scales with the ability to drastically deform their bodies and exhibit complex behaviors while overcoming challenges in their environments. Inspired by microstructures found in the cell membranes of the Euglena family of microorganisms, which exhibit giant changes in shape during their characteristic euglenoid movement, this letter presents the design, fabrication, and characterization of bio-inspired deforming surfaces. The result is a surface of interconnected strips, that deforms in 2-D and 3-D due to simple shear between adjacent members. We fabricate flexible polymeric strips and demonstrate three different shapes arising out of the same actuation by imposing various constraints. We characterize the strips in terms of the force required to separate them and show that the bio-inspired cross section of these strips enables them to hold up to 8 N of force with a meagre 0.5 mm of material thickness, while still being flexible to deform. Further, the design of a soft robot module, with an actively deformable surface has been presented, which replicates the mechanism of shape change seen in the Euglena. This letter shows the potential for this new form of shape morphing surface in realizing bio-mimetic soft robots exhibiting large changes in shape.</p