Summer Exhibition — The Science of Shape-Shifting Structures
This year, the Royal Society, the UK’s academy of science celebrated its 350th anniversary by hosting an exhibition at the Royal Festival Hall. Leading researchers and scientists across the country were invited to showcase their work in London. Collaborating with Bristol University, the Advanced Structures Group from the University of Cambridge exhibited their work on the science of shape shifting structures.
The Advanced Structures Group lead by Drs Keith Seffen and Simon Guest, aims to use conventional materials in a smart way to create novel structures. The principle goal in the study of shape shifting structures is to manipulate how many states of stability a system has and make them interchangeable. To achieve this, it is necessary to define a mechanism by which the transformation takes place, and ensure it happens elastically. Pushing the material beyond its elastic limit into plasticity would fatigue the mechanism thereby causing damage. All items on display embodied these key concepts but the pieces below generated particular public interest.
Roll-up electronic display device:
The roll-up screen prototype uses a bistable corrugated sheet as the structural support for a flexible display device. “Breaking” the corrugated pattern at one end induces stresses within the structure that cause the system to morph elastically from its flat state to the coiled form. Depending on the profile of the corrugated pattern, the structure may also be stable in the transitional state. Earlier this year, Sony unveiled the first rollable OLED display approximately 4.1 inches in width.
Similar in geometry to a carpenter’s tape, the rolatube is also a bistable structure; the bistability is due to the non-isotropic material properties, while internal damping means the transition state can also be stable. The tube on display was made from uni-directional layers of glass fibre orientated at 45° to one another in a polypropylene matrix. Applications for the rolatube are vast. Generally speaking, it can serve as a replacement for any extension mechanism (e.g. deployable pipes) where great extensions in length are required.
Bistability is a phenomena also exhibited by nature. The venus fly-trap for example, is the fastest moving plant and it uses snap-buckling instability to rapidly close its leaves on alighted insects. The leaves close under a small change in internal fluid pressure, and gradually open as the pressure is relieved. The closure trap is initiated by the mechanical stimulation of the trigger hairs which instigate this change in fluid pressure.
Multi-stable dimpled sheets:
The dimples on this sheet are bistable — either popped in or out however, when arranged in a particular manner, they give that sheet the property of being multi-stable. One area of research and development is using these sheets as adaptive skins for aircraft.
These exhibits and plenty more were on display from the Advanced Structures Group this summer. To find out more about the group or their research, please visit them on: www-g.eng.cam.ac.uk/advancedstructures.
Miss Tafara Estelle Makuni