(NAST-625): Self Assembly of Nanostructures

By:Sudama Chaurasiya

M. Tech IInd Sem. (NAST) “Center for Nanoscience and Technology”

PONDICHERRY UNIVERSITY

BIO-INSPIRED APPROACH FOR COMPLEX SUPERSTRUCTURES

CONTENTS

• Introduction• What is Bio-Inspired Designing. • Typical biological materials with function integration.• Examples of biological materials bioinspired structures• Approaches/Methods to create superstructures.• Conclusion• References

INTRODUCTION Learning from nature has long been a source of bio-inspiration for human beings.

Multiscale structures of biological materials exhibit inherent multifunctional integration. This special biological solution provides some inspiration for scientists and engineers to design multifunctional artificial materials with multiscale structures.

SOME INSPIRATIONS WHICH ARE PRESENT AT VERY SMALL SCALE (at nm, i.e. 10-9 m)

BIO-INSPIRATIONS FOR COMPLEX SUPERSTRUCTURES

DIRECTIONAL ADHESION

SUPER-HYDROPHOBICITY

SELF CLEANING

ANTI REFLECTION

STRUCTURAL COLOR

WATER COLLECTION

WHAT IS BIO INSPIRED DESIGN?

• Bio inspired design is studying the structure and function of biological systems as models and designing or engineering the new materials and machines.

• It is widely regarded as being synonymous with biomimicry, biomimesis, biognosis and similar to biomimetics.

• The term biomimetics is derived from the Greek word bios, “life” and the suffix mimetic, “having an aptitude for mimicry”.

• Multiscale structures of biological materials exhibit inherent multifunctional integration and bio inspired design uses these properties.

TYPICAL BIOLOGICAL MATERIALS WITH FUNCTION INTEGRATION

TYPICAL BIOLOGICAL MATERIALS WITH FUNCTION INTEGRATION

EXAMPLES OF BIOLOGICAL MATERIALS BIOINSPIRED STRUCTURES

Fig. (a) Water droplets roll easily across the lotus leaf surface and pick up dirt particles, demonstrating the self-cleaning effect. (b) Low magnification scanning electron microscopy (SEM) image of the lotus leaf surface, showing the micropapillae in a random distribution. (c) SEM image of a single papilla, exhibiting cilium-like nanostructures superimposed on top of the micrometerscale papillae. (d) Atomic force microscopy (AFM) height image of an isotactic polypropylene coating obtained from a solution in p-xylene on a glass slide.(e) SEM images of superhydrophobic polystyrene films with special microsphere/nanofiber composite structures prepared via the EHD method. (f) SEM image of the biomimic surface with hemispheres/Ag nanoparticles composite arrays.

LOTUS LEAVES (SUPERHYDROPHOBICITY):

Contact angle plays major role in superhydrophobisity which is necessary for self cleaning.Various coating mechanism of nano porous materials can produce superhydrophobic surfaces on glass or metal sustrate.Electrohydrodynamics (EHD) technique is a versatile and effective method.

Contact angle on lotus leaf surface

Fig. (a) Cross-sectional SEM image of micropearl arrays with height variations 1.75 m/2 m. (b) Photo of a water droplet on modified micropearl arrays. measured contact angles enhanced by fluoroalkysilane modification. (c) SEM image of natural rice leaf.(d)Photos of a water droplet on the rice leaf along both directions and the contact angle measurement showing that the designed anisotropy.

RICE LEAVES: Having both both super -hydrophobicity and aniso -tropic wettability.To mimic the anisotropic wetting function of rice leaves, a rice-like aligned CNT film has been prepared by controlling the surface deposition of the catalyst, and a similar aniso -tropic wetting phenomenon has been Observed.

BUTTERFLY WINGS (IRIDESCENCE):

Fig. (a) Morpho didius. SEM images of (b) an oblique view and (c) a cross-section of a ground scale of the butterfly Morpho didius

Colors in nature are created by pigmentation, structural color (iridescence), or a combination of both. Results from the interaction of light with highly precise and sophisticated architectures, which has many characteristics that are not accessible using pigmentation.

Fig. (a) An optical microscope image of the alumina coated butterfly wing scales, of which the color changed from original blue to pink. (b) A low-magnification SEM image of the alumina replicas of butterfly wing scales on silicon substrate after the butterfly template was completely removed. (c) The energy dispersive X-ray spectrum of the alumina replica. (d) A higher magnification SEM image of an alumina replicated scale, where the replica exhibits exactly the same fine structures. (e) SEM image of two broken rib tips on an alumina replica.

SPIDER SILKS (MECHANICAL PROPERTIES AND WATER COLLECTION CAPABILITY):

Artificial dragline spider silk has been fabricated by spinning soluble recombinant dragline silk proteins (ADF-3; 60 kDa) produced in mammalian cells under modest shear and coagulation conditions. Single-walled carbon nanotubes (SWNTs)-PVA composite fibers has been fabricated by spinning method , which are tougher than spider silk and any other natural or synthetic organic fiber reported previously. Fibers possess periodic spindle-knots made of random nanofibrils separated by joints made of aligned nanofibrils. Artificial fibers that mimic the structural features of wet-rebuilt spider silk and exhibit the directional water-collecting ability.

Fig. (a) Moth compound eyes. (b) SEM image of an anti-reflective surface from the eye of a moth. (c) Cross-sectional view SEM image of bio-inspired silicon hollow-tip arrays and optical image of the water droplet profile on the array surface. Close-up of anti-fogging after exposure to water aerosol. (d) SEM image of artificial compound-eye analogues and a spherical water droplet on its surface.

MOTH COMPOUND EYES (ANTI-REFLECTIVE AND ANTI-FOGGING)

Gecko foot (Reversible adhesive, superhydrophobicity, and self-cleaning)

water strider leg(Superhydrophobicity)

Nacreous layer of the abalone shell (Mechanical strength and

structural color)

PAH-SPEEK/PAA: poly(allylamine hydrochloride) (PAH)-sulfonated poly(ether ether ketone) (SPEEK)/poly(acrylic acid) (PAA); PDMS: polydimethylsiloxane; PUA: Polyurethane acrylate; Upy: 2-ureido-4[1H]-pyrimidone.

MATERIALS AND METHODS/APPROACHES TO CREATE SUPERSTRUCTURES.

CONCLUSION In the last few decades, inspired by natural material, a great number of multifunctional materials have been fabricated. Although various properties of biological materials have been found in the last few years, some other properties may be hidden in the multiscale structures of natural materials and remain unravelled. Most of current work has still focused on the biomimetic synthesis of multiscale structures inspired by one biological materials. The increasing collaboration work would also be useful for the improved understanding of multiscale design laws, clarification of structure-multifunction relationship, extraction of useful engineering principles, and adaptation of models for practical applications.

REFERENCES

1. “Bio-inspired design of multiscale structures for function integration” by Kesong Liua, Lei Jianga Elsevier Nano Today (2011) 6, (155—175)

2. http://en.wikipedia.org/wiki/Biomimetics3. “Bio-inspired fabrication of antireflection nanostructures by replicating fly eyes” by

Jingyun Huang, XudongWang and Zhong LinWang IOP Nanotechnology 19 (2008) 025602 (6pp)

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