Euglenoid-inspired Giant Shape Change for Highly Deformable Soft Robots

Nature has exploited softness and compliance in many different forms, from large cephalopods to microbial bacteria and algae. In all these cases, large body deformations are used for both object manipulation and locomotion. The great potential of soft robotics is to capture and replicate these capabilities in controllable robotic form. This letter presents the design of a bioinspired actuator capable of achieving a large volumetric change. Inspired by the changes in body shape seen in the euglena Eutreptiella spirogyra during its characteristic locomotion, a novel soft pneumatic actuator has been designed that exploits the hyperelastic properties of elastomers. We call this the hyperelastic bellows (HEB) actuator. The result is a structure that works under both positive and negative pressure to achieve euglenoid-like multimodal actuation. Axial expansion of 450% and a radial expansion of 80% have been observed, along with a volumetric change of 300 times. Furthermore, the design of a segmented robot with multiple chambers is presented, which demonstrates several of the characteristic shapes adopted by the euglenoid in its locomotion cycle. This letter shows the potential of this new soft actuation mechanism to realise biomimetic soft robotics with giant shape changes.</p

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

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

Tiled Auxetic Cylinders for Soft Robots

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.</p

Euglenoid-Inspired Giant Shape Change for Highly Deformable Soft Robots

Nature has exploited softness and compliance in many different forms, from large cephalopods to microbial bacteria and algae. In all these cases, large body deformations are used for both object manipulation and locomotion. The great potential of soft robotics is to capture and replicate these capabilities in controllable robotic form. This letter presents the design of a bioinspired actuator capable of achieving a large volumetric change. Inspired by the changes in body shape seen in the euglena Eutreptiella spirogyra during its characteristic locomotion, a novel soft pneumatic actuator has been designed that exploits the hyperelastic properties of elastomers. We call this the hyperelastic bellows (HEB) actuator. The result is a structure that works under both positive and negative pressure to achieve euglenoid-like multimodal actuation. Axial expansion of 450% and a radial expansion of 80% have been observed, along with a volumetric change of 300 times. Furthermore, the design of a segmented robot with multiple chambers is presented, which demonstrates several of the characteristic shapes adopted by the euglenoid in its locomotion cycle. This letter shows the potential of this new soft actuation mechanism to realise biomimetic soft robotics with giant shape changes.</p

Reports to the President

A compilation of annual reports for the 1986-1987 academic year, including a report from the President of the Massachusetts Institute of Technology, as well as reports from the academic and administrative units of the Institute. The reports outline the year's goals, accomplishments, honors and awards, and future plans