Design for Shape Morphing

Tying a Robot in a Knot: Inverse Shape Design of Soft Growing Robots

As soft, continuum robots see increasing areas of application, many scenarios have arisen where it is necessary to consider the geometric shape of the robot, including manipulation, navigation, and interaction with human users. However, many previous control and design methods for continuum robots have focused on the movement of the tip, only tangentially referencing the shape control of the robot. In this presentation, I will discuss one design method we have implemented on soft growing continuum robots (vine robots) which uses generalizable geometry-based kinematics for the forward kinematic modeling and uses optimization techniques to close the loop and allow inverse design to match target shapes. I’ll present the full design and manufacturing pipeline, as well as alternative curve representation strategies that can aid in optimizing for the target shape.

The Simplest Ever 4D Printing: A Route Towards Inverse Design of Complex and Programmable Shape Morphing

4D printing is an emerging technology that provides a prototypical route for self-shaping growth, assembly, and actuation of 3D matters. Central to its challenge is how to precisely control the spatial distribution of the ‘extra-dimensional’ mechanical responses (i.e., strain) of 3D-printed structures. However, most existing approaches have been limited to translating the shape information of 3D matters, which is generally represented by a continuous form, into only a few discrete levels of strain and their spatial distributions. In this talk, I will present a facile 4D printing strategy that enables continuous strain programming along with arbitrary printing paths. Such continuity of strain programming aids in the precise translation between shape information, strain, and printing parameters, mediated by mathematical function representation. Using this framework, we program and inversely design the morphing of simple beams into the shape represented by arbitrary function forms, including polynomial, exponential, trigonometric, and their composites, and further attempt to generalize to arbitrary complex 3D surfaces.

Origami Balloons: Enhancing the Functionality of Inflatable Structures through Multistability

From stadium covers to solar sails, we rely on deployability for the design of large-scale structures that can quickly compress to a fraction of their size. Historically, two main strategies have been pursued to design deployable structures. The first and most common approach involves mechanisms comprising interconnected bar elements, which can synchronously expand and retract, occasionally locking in place through bistable elements. The second strategy instead, makes use of inflatable membranes that morph into target shapes by means of a single pressure input. Neither strategy however, can be readily used to provide an enclosed domain able to lock in place after deployment: the integration of protective covering in linkage-based systems is challenging and pneumatic systems require a constant applied pressure to keep their expanded shape. Here, we draw inspiration from origami, the Japanese art of paper folding, to design rigid-walled deployable structures that are multistable and inflatable. Guided by geometric analyses and experiments, we create a library of bistable origami shapes that can be deployed through a single fluidic pressure input. We then combine these units to build functional structures at the meter-scale, such as arches and emergency shelters, providing a direct pathway for a new generation of large-scale inflatable structures that lock in place after deployment and provide a robust enclosure through their stiff faces.

Incompatible Elasticity as a Route to Shape-morphing Inflatables

Shape-morphing structures are at the core of future applications in aeronautics, minimally invasive surgery and smart materials. In this talk, I will present two strategies consisting in programming slender morphing inflatable structures. The first strategy consists in manufacturing elastomeric plates embedding a network of channels, which expand when inflated mainly perpendicular to their local orientation, similarly to simple elastic tubes, whereas the second strategy consists in two superimposed inextensible thin sheets, sealed together along a specific line network which contract on inflation. Playing with both the orientation and density of channels, the direction and intensity of the in-plane homogenized “growth” may be programmed, in general incompatible with a flat geometry. The structure spontaneously buckles and adopts a shape, which minimizes its elastic energy. Using the framework of incompatible geometry, we program the morphing of such stiff inflatable structures and investigate their mechanics.