Abstract
Many living beings show the ability and necessity to develop invertible, tubular structures to enable additional functions temporarily. The biological archetypes always demonstrate a high change of volume of the structure between an inactive and active state. This makes the principle interesting for many technical applications, where a certain geometry or an additional volume has to be generated situationally for a task and can only be accepted temporarily, for example, in minimally invasive robotics. A possibility was sought to transfer the archetype into the technical context and to evaluate geometric-constructive dependencies based on an inversion of the structure. The result is a practicable design for repeatedly invertible net structures, which can be used for products with temporary additional functions and volumes.
Highlights
Depending on the situation, numerous technical structures need a certain geometry or additional volume to fulfill a specific task
The variation in the number of support structures showed that they have a great influence on the shape accuracy, which was expected–the higher the number, the better the shape accuracy
A design, improvement and process strategy are presented that enable the additive manufacturing production of tubular net structures that can be repeatedly everted without damage
Summary
Numerous technical structures need a certain geometry or additional volume to fulfill a specific task. Medical applications in minimally invasive surgery benefit from endoscopes that are designed with necessary high volume-change rate between active and inactive state, when not in use. Flexible tubular structures that evert from inside to outside, and simultaneously elongate at the top, fulfill the demands in volume change rate. Several examples for the everting of tubular body parts exist in nature: caterpillars of myrmecophilous Lycaenidae hold tentacle organs, pulling out if needed to expel nutritious secretions, which decrease ant aggressiveness [1]. Nemerteans can evert their proboscis when catching and eating their prey [2]. Apple snails (Pomacea) possess both gills and lungs; while submerging under water they are enabled to respire beneath due to the so-called siphon—a tube pushed by muscular activity from the mantle and connecting the pulmonary sac with air above the water surface [3]
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