Bio-inspired, Flexible Structures and Materials - Biotechnologies and Biomimetics for Civil Engineering - page 284

Fig. 12.6 The trap leaves of Aldrovanda vesiculosa in open and closed configurations

bending of the midrib leads to an instant closure of the trap lobes. From a
mechanical perspective, this rapid motion results from a controlled sequence of
multiple interconnected deformations. At first, the midrib starts to bend, driven by
hydraulic actuation. This causes bending of the central portion, which transmits the
deformation further and triggers an out-of-plane bending of the adjacent softer
lobes. Similar to the Flectofin , the mechanism is actuated by an externally
induced support displacement. This translation movement causes bending in the
centre surface and triggers the flapping motion of the lobes (Fig. 12.7 ,
left)(Schleicher et al. ( 2010 ). Typically, for curved-line folding, this principle
couples convex and concave surface bending, which increases in curvature as the
folding proceeds. Due to the orientation of the curved-line fold, however, the lobes
can rotate in the opposite direction of the Flectofin and thus can be understood as
an inverse mechanism to it. Turning the curvature around and applying it to the
line between the Flectofin fin and its backbone will consequentially force it into
an outward bending motion (Fig. 12.7 , right).
This Double Flectofin is a further development of the initially proposed façade
component, which has an increased shading efficiency and higher wind stability,
shown in Fig. 12.8 .

12.4.1.3 Architectural Application

A significant expansion for possible future applications is provided by the fact that
the system functions without a straight turning axis. The geometrical flexibility of
these bio-inspired compliant mechanisms renders the unique possibility to enter,
for instance, the neglected market niche of shading double curved façades.
Compared to traditional sun protections (e.g. blinds and louvers) whose mechanics
are designed for planar and standardised facades, elastic-kinetic structures like the
Flectofin preserve their functionality even when distorted or scaled. In particular