The best of the UK's cutting-edge science, engineering and technology are on display at London's Southbank Centre at the Royal Society summer science festival. Scientists and engineers from the Universities of Cambridge and Bristol are presenting some of their work on the development of, and science behind, novel "shape-shifting" structures at the Royal Society's Annual Summer Science Exhibition.
Conventional structures, such as buildings and bridges, do not visibly move, for solidity and safety. A structure that shifts shape radically alters in form to give new purpose to the structure. A popular example from the world of science fiction is a transformer: it is a high performance vehicle in one shape, in another, it is a fighting robot. Conventional (and real) examples abound in everyday life: from folding deck-chairs to pop-tents, from opening doors to deploying aircraft flaps, from flip-top 'phones to unfurling satellites; from inflating lungs to twisting DNA. For the last five years, Cambridge engineers have been developing novel structures that shift shape without using the standard articulating hinges seen in current examples: in research centres, these are known as "morphing" structures. These structures have no moving parts, have at least two distinctly different shapes, and are made from ordinary materials such as metals and plastic; colleagues in the Aerospace Department at Bristol University have been developing similar structures made from composite materials such as glass-fibre reinforced plastics.
"We do not need to modify the fundamental material behaviour in any way," according to Dr Keith Seffen of the Advanced Structures Group here at the Department of Engineering, "our structures perform as they do because we are pushing the limits of structures technology and not material technology. This difference is subtle but it is essentially this. The properties of a material are fixed by Nature - you can't really change how strong a metal is, for example. They can also strain by a limited amount, which restricts large changes in shape unless the material is permanently deformed, and this is not ideal for practical use. However, it is well known that conventional structures sometimes fail by a phenomenon known as buckling, in which regions of the structure undergo substantial geometrical changes without the material reaching its natural limits. Conventional structural design rightly treats buckling as anathema but it is difficult to predict and control. In our work, we've turned the buckling notion on its head. We are taming buckling so that the associated shift in shape is predictable, it serves a new purpose and structural integrity is not compromised - these principles underlie the science that we are rigorously developing in our labs."
The shape-shifting process is often dramatic and fast, which makes their structures exciting. At the exhibition, academics and research students will showcase handheld demonstrations for the visitors to observe and to play with, and will even reveal how to make some of them at home. Noteworthy examples include a shape-shifting helicopter blade, a land periscope, a mechanical Venus fly-trap, dimpled metallic skins, morphing loops, a mini solar sail, and flick-bracelets made from tape-measures, and more.
According to Dr Seffen, their exhibit will appeal to families with children, teachers, students, as well as boffins, academics and learned folk. "Come and have a play! We have divided our exhibit into three activities for visitors. You will first observe so-called deployable structures, which are compactly stored being unfurled into a new shape for a new job. The land periscope example is an extendible, single-piece tube with a controllable tip camera to give a bird's eye view of the exhibition hall. Second, visitors will be able to view mock-up versions of promising future technology, including a roll-up electronic display, showing how we might be using our computers or phones in the future, and dimpled metal sheets that pop-through to create shape-changing skins for advanced vehicles, which can modify the airflow around them. Third, we will present simple but fundamental structures at the heart of our research that highlight the principles of shape-shifting. These will include loops that fold and twist into smaller loops, textured sheets that jump from one shape to another and structures that are remarkably and unexpectedly floppy in certain directions, despite being very strong in other ways."
He adds: "our structures are exciting, fun and offer a glimpse of tomorrow's technology, today. Structural engineering is more than buildings and bridges: it's about aircraft, cars, satellites, electronics, gadgets - anything that is made that needs to be strong enough to endure within their working life. Shape-shifting structures add a new dimension to their performance, where the change in shape gives added benefit. Our research ethos is simple: pose interesting problems, extract the underlying principle, devise simple solutions. We, and the UK teams represented here, lead the world in the science of shape-shifters, and we're very delighted to be able to present our work to the general public."