Bio-inspired Metamaterials - University of New...

Bio-inspired Metamaterials

Simon ButlerSupervisor: Prof. Rebecca Seviour

2/06/2017

01/06/2017 Simon Butler - University of Huddersfield 1

What is a metamaterial?


• Defined by the meta atom and its position in the lattice

• Defined by the atom and its position within the lattice

Conventional material Meta material

• It is important to note: Both materials are smaller than the wavelength of interest. This makes them HOMOGENLOUS. The individual units are indistinguishable from the greater structure as a whole.

Convention against Meta: A contrast comparison

• Plane Wave HFSS simulations of infinite sheet.

• Determined S11 S21

• Material Properties determined via a Nicholson-Ross-Weir approach


EM Simulations

70 nm unit cell

50nm major radius10nm minor radius 25% circumference split

Wave propagation


Equations

Smith DR, Schultz S, Markos P, Soukoulis CM (2002) Determination of effective permittivityand permeability of metamaterials from reflection and transmission coefficients. Phys Rev B65:195104

Transmission

Reflection

Transmission

Reflection


Extracted EM parameters

Imaginary

Imaginary

Real

Real

Permittivity

Permeability

01/06/2017 Simon Butler - University of Huddersfield6

EM Simulations

125 nm unit cell

100nm major radius10nm minor radius 25% circumference split

Wave propagation

Transmission

Reflection

Transmission

Reflection

7

Extracted EM parameters

Imaginary

Imaginary

Real

RealPermittivity

Permeability


Technique Resolution Cost Limitations Throughput

Optical lithography 15nm $30 million2D,

HighPhotosensitive material

Laser interference lithography 20nm $50,000

2D,

Photosensitive material,

Limits in design

High

Electron beam/Focused Ion Beam lithography 4nm $2000000 2D, Photosensitive material Low

Scanning Tunnelling Microscopy Atomic $30,000 to $50,000

Conductive material, V low

throughput/construction in parallel not possible

due to topological differences on the atomic scale

V. Low

Atomic Force Microscopy Atomic $30,000 to $50,000

V low throughput/construction in parallel not

possible due to topological differences on the

atomic scale

V. Low

Molecular Beam Epitaxy 45nm £150,000Crystalline structures greatly limit design

flexibility, low resolutionHigh

Liquid Phase Epitaxy 50nm £150,000Crystalline structures greatly limit design

flexibility, low resolutionHigh

DNA Origami ~5nm ~£800 Functionalisation. Aggregation. V. High

Conventional fabrication techniques

• Biological has been fabricating EM systems for billions of years.

• DNA has the potential to rapidly produce, in a high throughput manner, nanoscale geometries.


EM materials in nature


• Origami refers to folding paper into a fixed final structure.

Brown paper Turns into Science Fox

• DNA origami refers to folding DNA into a fixed final structure.

Scaffold and staples

Turns into

Folded DNA construct

DNA origami - Principals

• Technically in the terms defined earlier this lattice structure as oppose to the functional unit.

• The meta atom will be a single split ring of gold going around the perimeter of the sphere.

• It has a major radius of ~21nm and consists of 7249 base pairs arranged in a 24 layered helices.


Structure considered


• Evolution of genetic code requires strict (Or at least very high levels) of conservation during replication.

• The 4 bases will always bind in the predictable A to T C to G.

• Due to the weak hydrogen bonds which stabilise the DNA helix, when heated it will separate, when the temperature is lowered bases in proximity will anneal to their specific Watson Crick partners.

DNA origami - Mechanics

• Individual helices are created and joined by junctions.

• Once complete a sequence is applied to the continuous scaffold.

• Output sequences are then provided for all staples.


caDNAno - Introduction

100 nanometer line

Castro CE, Kilchherr F, Kim D, Shiao EL, Wauer T, Wortmann P, Bathe M and Dietz H (2011) A primer to scaffolded DNA origami. Nature Methods, 8(3):221-9

• The first design was a single split ring the curvature of the split ring was created by joining 6 separate helices.

• DNA has a helical pitch of 10.5 bases per 360 degree.

• If insertion or deletion events break this rule it will create torsion in the helices. This effect was facilitated to create a C from varying lengths of DNA.


DNA origami design - caDNAno

• Examples of structures which benefit from simulation include structures which do not rely on general distribution and symmetry in their final design.

• The first design: A single free floating split ring is highlighted above. Further lattice components in this project will always be simulated in this manner pre fabrication.


Cando

• The second (and current) design is a sphere comprising of 24 helices.

• Unlike the first design there is no, or to be precise very little, tension between helices.

• The curvature is facilitated by a carefully measured ratio of sequence lengths each representing a latitudinal line 1/24th of the way down the sphere.


DNA origami design - caDNAno

Site specific

• As discussed, technically, the DNA origami units are not the functional units themselves but a lattice which provides structure.

• 2 Strategy types are available for functionalisation – Global and site specific.


Functionalisation

Site specific strategy Global aggregation strategy

Kuzyk A, Schreiber R, Fan Z, Pardatcher G, Roller E-M, Hogele A, Simmel FC, Govorov AO and Liedl T (2012) Assembly of DNA origami gold nanoparticle helices and principle of circular dichroism. Nature, 483, 311-314

• Fabrication: One pot reaction. Annealing buffer.


• The Buffer solution encourages base pair annealing and protects DNA during annealing.

• Initial Denaturation occurs at around 90 degrees celsius. This temperature is then gradually lowered as part of a controlled and design specific annealling cycle.

Fabrication Protocols


Nanolight

• Measuring the diffusion of particles under Brownian motion, with the Stokes-Einstein relationship to determine size distribution of particles

50nm 100nm

Size nm Size nm

Nu

mb

er

Nu

mb

er


SEM

• Imaging under SEM on silica did not present clear images at this stage.

• Issues are being addressed and the next phase of imaging will begin shortly.

500nm (x100000 maginification)


AFM

• Imaging under AFM showed high levels of aggregation of SRR structures.

• Silica was shown to be a poor substrate under these conditions and further imaging will be conducted on mica with specific fixing protocols.

• AFM went Bang on last use.


What next…

• Lattice construction will be attempted by the attachment of complementing sequences.

• Protocols for high yield both in terms of fabrication and functionalisation will be refined.

• Imaging of structures on mica will be pursued.

• Characterisation of material under specific EM frequencies of interest will take place.


We would like to thank the AFOSR and the EPSRC for there support

Bio-inspired Metamaterials - University of New...

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