Bio-inspired, Flexible Structures and Materials - Biotechnologies and Biomimetics for Civil Engineering - page 271

initially straight or planar configuration. The category of elastic-kinetic structures
takes this form-defining approach one step further by considering that the
deformation process can also be reversible thus allowing the creation of adaptive
systems and compliant mechanisms (Lienhard et al. 2010 ; Schleicher et al.
2011 ).
An initial review by Lienhard et al. ( 2013a , b ) on bending-active structures has
shown how these systems face two major challenges in the design process: Firstly,
since bending-active structures are not based on known typologies, the central
question is about the form and functional inspiration. Secondly, there is the dif-
ficulty of predicting the system's geometrical shape or structural performance
without immediately consulting advanced digital simulations or physical tests.
Recent studies suggest that biomimetic abstraction processes can provide
helpful scientific methods that may be used for the design of elastic systems
entirely born out of a process based on material behaviour rather than typology
based model thinking. (Knippers and Speck 2012 ; Knippers 2013 ). This trend is
also supported by computational developments, which enable the simulation of
nonlinear behaviour in large elastic deformations. In fact, today, the engineering of
a structure is increasingly becoming an essential part in modern design processes
and is no longer a downstream proof calculation that comes into play when the
decisions about shape and form have already been made.
A constructional design approach based on flexibility rather than on stiff
members and movable joints however has not yet established itself. In terms of
today's building industry there is uncharted ground, in which experience and
expertise is lacking and role models are scarce. Interestingly, however, soft and
flexible structures are rampant in Nature and indicate the promising potential of
this construction principle. It is therefore reasonable to combine research on
flexible structures and materials with the topic of biomimetics; with the goal of
understanding flexible structures in biology and to transferring, scale-up, and
implement their underlying principles into bio-inspired technical devices and
structures.
So far, however, most bio-inspired technical structures consider applications
either purely theoretically and/or include very simple models on laboratory scale
(Marder and Papanicolaou 2006 ; Kobayashi et al. 2000 ; Liang and Mahadevan
2009 ; de Focatiis and Guest 2002 ; Jenkins 2005 ). Even the most well known
elastic kinetic structures, namely deployable space structures like foldable solar
panels and retractable satellite antennas (Miura 1993 ; Furuya and Satou 2008 ),
which are often discussed in relation to biologically inspired folding and unfolding
techniques, are inspired by traditional Japanese folding techniques (e.g. Origami)
rather than actual studies of flexible structures in plants and animals.
Only recently, some projects like the patented Fin Ray Effect (Patent: Leif
Kniese 2012 ) or the Flectofin (Patent: Knippers et al. 2011a , b ) have attracted
attention and open up the potential for a successful implementation of bio-inspired
flexible structures and materials.