MASTER THESIS Biomimetic potential of sponge ... - IAP/TU Wien

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crack propagation (3). Thereby the crack continues to grow circumferentially in the silicalayer until it is energetically more favourable to break the organic layer (4). Subsequently a new crack initiates at a flaw in the next layer, or packet of layers (5) that travels similarly to the first crack, but also causes delamination (6). The last step consists in the iteration of steps 2-6 until, well before getting to the core of the spicule, a critical crack length leads to fast fracture. Thus the originally proposed mechanism is an oversimplification, especially since often individual layers of silica are observed to fracture as “packets” instead of sequentially. Still, during bending more energy is dissipated in spicules than in melt-processed glass fibres. Furthermore the authors found that spicules showed superior dampening characteristics compared to glass fibres. In general terms, the composite arrangement here conveys improved ductility, resilience and an increased capability to dissipate energy. Comparing fracture strength, strain-tofailure and fracture energy between spicules and massive glass rods demonstrates that the natural materials are several times more stable (cf. Figure 18) (Sarikaya et al., 2001) As most rigid biomaterials, sponge spicules possess a highly directional structure, which causes anisotropy. The dependence of mechanical properties on the direction of an applied force is therefore an important boundary condition to keep in mind. Spicules and optical fibres The preceding overview of the mechanical properties of basal spicules makes these spicules seem an appropriate role model for durable optical fibres. It is unlikely that basal spicules guide light in vivo and the waveguide properties are therefore almost certainly an accidental side-effect of a structure optimized to quite different ends (cf.Aizenberg et al., 2004). Nonetheless, the optical properties are remarkable (Voznesenskii et al., 2010) (Kulchin et al., 2011) and can compare to those of spicules whose light transmission properties serve a biological purpose (Müller et al., 2009a). Thus, the idea of using spicules as role model for telecommunications fibres is not a linear abstraction from one biological role model. Rather, better optical fibres should draw on basal spicules as their paradigm regarding mechanical properties and on skeletal spicules of demosponges that serve a biological purpose as light guides for their optical properties. 58
Since the optical properties happen to be similar in many basal and skeletal spicules, this distinction might be of theoretical and conceptual nature only. Figure 18: Differences in fracture strength between multi-layered layered spicules and simple glass fibres. (a) represents the untreated, fractured surface of a hexactinellid sponge spicule, while (b) shows the considerably less structured, untreated structure of a common glass fibre at ~10,000x magnification. (c) Qualitative comparison of energy dissipation during bending of different materials. The triangular curves represent the behaviour of b, while the dark grey curve demonstrates the residual strength of composites like sponge spicules. © by (Mayer, 2005) (for a and c) and (Militky et al., 2002) (for b) Instead of the benign failure mode of spicules (see above, (Koehl, 1982)) commercial communications fibres fail due to a single, catastrophic event (cf. Figure 18c). Spicules also 59
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Fachhochschule Kärnten Carinthia U
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Keywords biomimetics, biomimetics i
Page 8 and 9: einzigartige Prozess stellt nachhal
Page 10 and 11: Façade elements...................
Page 12 and 13: Figure 25: Daylight Guidance System
Page 14 and 15: Apart from this methodological dich
Page 16 and 17: That leaves us to talk of “silice
Page 18 and 19: Tissues, the next higher level of h
Page 20 and 21: shape of spicules, for most spicule
Page 22 and 23: and 24 basic types in Demospongiae
Page 24 and 25: Strikingly, the largest known natur
Page 26 and 27: spicules have swellings or hook-lik
Page 28 and 29: Figure 7 Spongial skeleton elements
Page 30 and 31: can be considered to start at order
Page 32 and 33: Figure 9: Levels of hierarchy in a
Page 34 and 35: would likely remain largely the sam
Page 36 and 37: Biomineralization “Biomineralizat
Page 38 and 39: properties (Lowenstam & Weiner, 198
Page 40 and 41: Figure 12 Array of diatoms. These u
Page 42 and 43: Spiculogenesis Overview Spiculogene
Page 44 and 45: their environment (Inagaki et al.,
Page 46 and 47: spicule is driven by intracellular
Page 48 and 49: Figure 14: Axial and appositional g
Page 50 and 51: Figure 15: Extracellular phase of s
Page 52 and 53: of rare earths (Zajec, 2010) or any
Page 54 and 55: of ways, e.g., their higher speed a
Page 56 and 57: precursor molecules is catalyzed an
Page 60 and 61: excel in flexibility due to their g
Page 62 and 63: single-mode waveguides can transmit
Page 64 and 65: Biomimetic potential of different b
Page 66 and 67: (iv) (v) crystallize the previously
Page 68 and 69: Brundtland Report, is “developmen
Page 70 and 71: Notwithstanding the problems involv
Page 72 and 73: Importantly, social jetlag is close
Page 74 and 75: For tropical and temperate regions,
Page 76 and 77: Figure 25: Daylight Guidance System
Page 78 and 79: the ground have been reported to be
Page 80 and 81: synthesis of these elements could i
Page 82 and 83: the availability of spicule-inspire
Page 84 and 85: This flexibility certainly would al
Page 86 and 87: Another application to increase the
Page 88 and 89: and comfort of natural light, espec
Page 90 and 91: Tensegrity: structural principle us
Page 92 and 93: Brien P, Lévi C, Sarà M, Tuzet O,
Page 94 and 95: Gebeshuber I, Crawford R (2006) Mic
Page 96 and 97: Latzelsperger F (2012) Biomimetics
Page 98 and 99: Ozin G, Hall N (2003) The photonic
Page 100 and 101: Smith B, Schäffer T, Viani M, Thom
Page 102: Wiens M, Bausen M, Natalio F, Link
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MASTER THESIS Biomimetic potential of sponge ... - IAP/TU Wien

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