Ray Wijewardene memorial lecture by Prof Gehan Amaratunga's lecture at IESL, Colombo - 2013 Being Ingenious at the Nanoscale

1. Being Ingenious at the Nanoscale
Gehan Amaratunga
Engineering Dept., Cambridge University
Sri Lanka Institute of Nanotechnology
Ray Wijewardane Memorial Lecture
15th November 2012

2. Ingenieur
Engineer
• Creator of things Ingenious is an Ingenieur (Engineer)
• Ray Wijewardane is a Sri Lankan Ingenieur par
excellence
Ingenious – hand held tractor
Holistic – sustainable agriculture
Socially engaged – academia,
government, commerce
• Cambridge Engineering Dept. almunus!

3. The scale of the physical world

4. NANO
NANO
Contact CE

5. Materials when taken down to the < 50nm
scale can exhibit physical and chemical
properties not seen in bulk phases:
The Carbon Nanotube is a good example of
this

6. Carbon forms tubes when sheet structure in graphite
goes to nanometer scale in one dimension
• Depends on the angle of rolling and diameter as
to whether metallic or semiconducting

7. What does the 50 nm node in electronic devices mean?
• Man made electronic structures are smaller than the size of biological
organisms
Transistor for 90 nm node (Source: Intel)
2012: 30nm node with
22nm gate length
Influenza virus (Source: CDC)

8. Continuous shrinking of transistor sizes through ‘ingenious’ methods
the source of shrinking electronic devices with increased functionality
such as mobile phones
22nm

9. Nanoscale effects in nature
http://www.youtube.com/watch?v=xdzS4-d31n8

10. Engineered Lotus Leaf Effect

11. Water drop from training slide http://youtu.be/ivcMUxCP0T0

12. Light at the nanoscale

13. Light at the nanoscale

14. Iridescence – changing of colour with direction of observationof the butterfly wing
Colours due to pigments do
not show angular variation

15. The nanostructure of the butterfly wing
Constructive interference of reflected light at
400nm gives blue colour – structural light

16. The colours of the peacock

17. Peacock feathers have
within them structures (50
-100 nm) which are
smaller than the blue
wavelength of light
(400nm).
They interact to
preferentially reflect blue
light in ‘blue’ feathers.
This is a photonic band
gap effect which was
understood in detail only
in1992 (Yabalanovich)

18. Engineering nanostructures to interact with light

19. Photonic band gap defects in c-Si NW arrays for guiding light

20. Light guiding in c-Si NW arrays
H. Butt et al
Prog. Electromag. Res, (113),
2011
60 deg angle of
incidence

21. Precisely engineered carbon nanotube arrays
through catalytic synthesis
•
•
Step 1: At 700°C (growth temp), Ni catalyst
agglomerates into catalyst clusters.
Step 2: PECVD - C2H2 is the growth gas for
CNTs, NH3 is the etching gas for unwanted a-C.

22. Very tight control of diameter (catalyst size) and
height ( growth time)
r=24.5nm
r=40.5nm
r=45nm
400nm

23. Periodic and quasi periodic arrays of carbon nanotubes

24. Optical image of an engineered carbon
nanotube butterfly wing with an ‘ingenious’
feature
White light on rotating CNT array-2
Red laser on Cambridge crest
Green laser on Cambridge crest-1
http://youtu.be/4gitbgUIkFg
http://youtu.be/W8VDXMYatGU
http://youtu.be/05mibZ4j-mg

25. In addition to normal iridescence the
engineered butterfly wing has a
holgram embedded within it. It can be
seen at a specific wavelength of light (
green in this case) in the far field when
a screen is placed: CNT holography

27. Metallic MWCNT arrays can be exploited for Plasmonic
Photonic Band Gaps (P-PBG)
a
r
E
H
Metamaterial design with heavy plasmons
Extremely low frequency plasmons in
metallic mesostructures – Pendry et
al, PRL, 1996

28. Metamaterials being designed for invisibility
cloaks
Object being
made invisible
Metamaterial cloak – it guides light around the object and reforms the
light waves without any reflection or absorption
Possible by engineering the optical characteristics of the cloak precisely
with spatial variation in the nanometer scale

30. End note
• Nanotechnology is the exploration of a new
frontier, that of the ultra-small, in our
continuous quest to be ‘ingenious’
Dedicated to Ray Wijewardane
In memorium