Biomedical Engineering Reference
In-Depth Information
19.4
BIO-INSPIRED MATERIALS FOR BIOMIMETIC ACTION — CONCLUSIONS
Plants are adaptive machines that have developed and perfected their structures over millions of
years of evolution in constantly changing and increasingly complex environments. With their
autonomous and locally controlled responses plant movements do not require remote control
through a central nervous system or computer. Life originated in water and nastic structures as
well as their motors are optimized to use the potentialities of this unique solvent. In addition to
ATP-dependent molecular motors, contracting or inflating molecules, such as the P-protein of the
phloem conduits, we presented here three types of hydration motors (osmotic, colloidal, and
fibrous) that figure as the major workhorses for nastic plant movements. Most plant movements
and growth are driven by osmotic motors, and several examples illustrate how the isometric,
internal cell pressure is transmitted into anisometric movement patterns. Colloid motors are
known to be used by plants to overcome the formidable resistance of multilayered seed shells to
start germination. Fibrous motors are known to be involved in the opening of seed containers.
A striking particularity of nastic structures is an efficient and inconspicuous design that integrates
two or more functions (like motor and valve or sensor, motor and lever) in one smoothly operating
unit. The knowledge gained from studying nastic structures is key input for designing human-made
adaptive structures and smart materials and includes novel and increasingly complex multifunctional
materials like fiber-reinforced bio-composites, pressure-sensing, humidity-sensing, sugar (or other
chemical)-sensing fiber-reinforced hydrogels, nastic-inspired combinations of actuators, and force-
guiding structures like matrixes with pressurized body inclusions, as well as arrayed actuators
combining memory shape alloys, photomechanical films, electro-active polymers, and sensing
hydrogels in one multifunctional unit. Even the most modest, selective presentation of such bio-
inspired materials and designs is far beyond the scope of this chapter but good examples can be
found in some chapters of this topic and other publications as well (e.g., Taya, 2003). In the past, some
passive plant structures have served as the basis for a few successful phytomimetic designs of
buildings (Paxton's Crystal Palace in London following rib construction of floating leaves from
Victoria amazonica
), attachments [VELCRO fastener after burdock or
Arctium
seed pods (Paturi,
1976; Benyus, 1997; Vincent, 1997; Vogel, 1998)], and airplanes [wings of glider and motor planes
with extremely reduced stalling features were designed after
Zanonia
seeds (Etrich, 1915)]. The next
generation of phytomimetic designs is more likely to be inspired by active plant structures like
those reviewed here. Powerful and energy-efficient, auto-sensing and autonomously adjusting,
multifunctional, exhaust-free and silent actuators, tools, motors, as well as new materials from
leak-free storage of liquids to the silent demolition of buildings, can be based on the integrated
workings of nastic structures. By reviewing the major guiding principles and selected examples of
natural nastic structures, this chapter is meant to inspire, stimulate, and broaden their current and
future technical application.
REFERENCES
Alexander RM (1992)
Exploring Biomechanics: Animals in Motion
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York.
Asada T, Collings D (1997) Molecular motors in higher plants.
Trends in Plant Science
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Aylor DE, Parlange J-Y, Krikorian AD (1973) Stomatal mechanics.
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Benyus JM (1997)
Biomimicry — Innovation Inspired by Nature
. William Morrow and Company, New York.
Brauner L, Bukatsch F (1980)
Das kleine pflanzenphysiologische Praktikum
. Gustav Fischer Verlag, Jena.
Brett C, Waldron K (1996)
Physiology and Biochemistry of Plant Cell Walls.
Chapman & Hall, London.
Cleland RE, Virk SS, Taylor D, Bjorkman T (1990) Calcium, cell walls and growth. In
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Growth and Development
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