This document discusses nanopillars, which are pillar-shaped nanostructures approximately 10 nanometers in diameter. It describes various properties and fabrication methods of nanopillars, including their increased surface area, mechanical stability, optical characteristics, and biocompatibility. Case studies are presented on the synthesis of nanopillars using top-down lithography approaches as well as bottom-up growth techniques. Applications of nanopillars in areas such as antibacterial coatings, optics, energy, and biosensing are explored through additional case studies. The document concludes by stating that nanopillars provide many advantages for applications in biomedical, energy, and agricultural fields due to their vertically aligned nature and ability to be easily fabricated.

1. Dr. A. Lakshmanan
The Professor & Head, DNST
TNAU, Coimbatore
M.S.Kumuthan
Ph.D Scholar
TNAU, Coimbatore
NANOPILLARS
M. Latha
Ph.D Scholar
TNAU, Coimbatore

2. INTRODUCTION

3. • Nanopillars is an emerging technology within the
field of nanostructures.
• Nanopillars are pillar shaped nanostructures
approximately 10 nanometers in diameter.
• It is a type of metamaterial, mostly artificial designed
structures and not their natural properties.
• Each nanopillar has a pillar shape at the bottom and
a tapered pointy end on top.
• Nanopillars have many applications including
efficient solar panels, high resolution analysis,
antibacterial surfaces and medicine.

4. Properties of nanopillars

5. • The presence of many vertically aligned nanopillars on a flat
surface significantly increases the surface area without
changing the overall dimensions of the original substrate.
• The surface area of a nanopillared surface (S) can be
calculated from the following equation:
S = S0 + n(2rl)
S0 - Area of the original flat surface
r - Radius of each nanopillar
l - Height of the nanopillars
n - Number of nanopillars on the flat surface
• The increased surface area has various bio applications such
as biosensing.
• A sensor based on this surface can interact with more target
analytes, with higher sensitivity.
Surface area

6. Mechanical Stability
• Smaller is stronger.
• Compression testing -nanoindenter
apparatus.
• Elastic properties increased.
• Plastic deformation reduced.
Scanning electron micrographs - Au nanopillar in an
instrumented nanoindenter (a) prior to, and (b), post compression

7. Optical Characteristics
• Surface-plasmon resonance - the electrons at the surface oscillate collectively in response to incident light.
• The control over surface-plasmon interaction may be replicated by patterning gold with nanopillars of
various diameters.
• Gold nanopillar surfaces are suitable for forming surface-plasmon traps
Surface-plasmon resonance

8. Biocompatibility
• Nanopillars also possess a unique geometry that
strengthens their interaction with cells.
• Creates “pinning” effect
• The placement of nanopillars in an ordered array
encourages cells to position themselves in
between pillars while wrapping the ends of their
membranes around the pillars for increased
support.
• Nanopillars improve cell growth and proliferation
Tight adhesion of cells to gold nanopillars. (a) cell-
nanopillar interface. (b) cell membrane protruding into the
inter-pillar regions

9. • Thermoelectric efficiency is high.
• Short length of the nanopillars leads to
ballistic phonon transport.
• Thermal conductance of nanopillars are
smaller than bulk material.
• Phonon transport only through the pillars.
Electrical property
Electric field distributions in a) planar and b) nanopillar
devices indicating that carriers generated deeper. Trap
occupation (c and d) and Shockley-Read-Hall (SRH)
recombination (e and f)

10. FABRICATION OF NANOPILLARS

11. Bottom-up growth techniques
i) Chemical vapor deposition (CVD),
ii) Physical vapor deposition (PVD),
iii) Template synthesis
Top-down approaches
i) Lithography and etching

12. TOP- DOWN APPROACHES

13. (a) Patterning by single
exposure,
(b) patterning by layer-by-layer
coating and exposure,
(c) tilted patterning by single
inclined exposure,
(d) patterning by double
inclined exposure,
(e) tapered patterns by rotating
tilted exposure.
Photolithographic methods using masked irradiation and a negative
photoresist material

14. (a) Injection molding,
(b) Hot embossing,
(c) UV exposure,
(d) Soft lithography,
(e) Solvent assisted molding.
Other lithographic methods

15. CASE STUDY FOR TOP DOWN APPROACH
SYNTHESIS OF NANOPILLARS

16. Fabrication of nanopillars by nanosphere lithography
Cheung et al., 2006
Step 1: spin coat a hexagonally close packed
monolayer of polystyrene beads on substrates.
Step 2: tailor the size of the beads’ “resist” by oxygen
plasma etching.
Step 3: etch the exposed semiconductor areas by
deep reactive ion etching
SEM image of Silicon nanopillars

17. Fabrication of Nanopillars based on Silicon Oxide Nanopatterns
Synthesized in Oxygen Plasma Removal of Photoresist
Mao et al., 2006
Creating nanopillar or nanoneedle structures SEM images of nanoresidueson different substrates

18. Spatioselective fuctionalization of gold nanopillar arrays
SEM images :
(A) Top of the nanopillars grafted
with a thiolactone copolymer
layer
(B) surface entirely grafted with a
thiolactone copolymer
(C)surface entirely functionalized
with a SAM.
Chattaway et al., 2019

19. BOTTOM-UP GROWTH TECHNIQUES

20. Imprinting for nanopillar
CVD
PVD

21. CASE STUDY FOR BOTTOM UP APPROACH
SYNTHESIS OF NANOPILLARS

22. (a)Si-on-diamond template with 9*9 array of 400 nm holes
produced by FIB
(b)enlarged image of one of the holes.
Growth of diamond nanopillar with imbedded SiV colour
centers
SEM images of diamond nanopillars grown
through the holes for deposition time of 6 min (a)
before and (b)after Si mask removal.
Sovyk et al., 2016

23. Zinc phthalocyanine (ZnPc) nanopillars initiated
from pencil-drawn graphite.
• After the templating layer is prepared, physical
vapor transport (PVT) is used to evaporate the
organic material.
• Single crystals of ZnPc stack in a semi-vertical
orientation with the substrate at a 61° angle.
Gecko-Inspired Biocidal Organic Nanocrystals Initiated
from a Pencil-Drawn Graphite Template
Arellano et al., 2018

24. Micrographs of nanopillars initiated from pencil-drawn graphite as a function of evaporation time. (a) ZnPc
film deposited on Si wafer (no nanopillars). (b–f) Cross-sectional micrographs of ZnPc nanopillars initiated
from pencil-drawn graphite grown as a function of evaporation time, from 3.0 min to 5.0 min. All scale bars
are 1 µm.
Arellano et al., 2018

25. Fabrication of cylindrical and multibranched nanopillars surfaces
(a) cylindrical nanopillar surfaces (CNS) and (b) multibranched
nanopillared surfaces (MNS) film formation from anodized
alumina molds (AAMs) having cylindrical and multibranched
columnar structures, respectively. Polycarbonate was drop casted
on the nanoporous molds.
(a) the standard anodized alumina mold (AAM),
(b) the resultant cylindrical nanopillar surface
films.
Altuntas et al., 2017

26. APPLICATIONS OF
NANOPILLARS

27. Optics
Solar panelAntibacterial coating
Biosensors Medicine

28. ANTIBACTERIAL COATING AND IT’S
CASE STUDY

29. Why Dragonfly Wings Kill Bacteria?

30. CASE STUDY: Bactericidal activity of black silicon
Ivanova et al., 2013
Characterization of black silicon and D. bipunctata wings
Non-viable bacterial cells and spores were stained
with propidium iodide (red), whereas the living
cells were stained with SYTO 9 (green).

31. CASE STUDY: ZnO Nanopillar Coated Surfaces with Substrate-Dependent
Superbactericidal Property
Yi et al., 2018
E. coli bacteria destroyed by the
anti-bacterial coating made from
zinc oxide nanopillars
Zinc oxide nanopillars Fluorescent imaging of E. coli

32. NANOPILLAR IN OPTICS AND IT’S
CASE STUDY

33. Development of superhydrophilic and transparent optical devices

34. CASE STUDY: Superhydrophilic nanopillar structured quartz
surfaces for the prevention of biofilm formation of optical devices
SEM images of nanopillarFabrication process
Han et al., 2017

35. SEM images of E.coli on nanopillar structured quartz surface
Antifogging property
Han et al., 2017

36. CASE STUDY: Super hydrophobic/Super hydrophilic Transparent
Nanostructured Glass Fabricated by Wet Etching
Kumar et al., 2014
Self-cleaning property by using hydrophilic and hydrophobic
property of glass

37. NANOPILLARS IN ENERGY

38. Solar panels
Light-trapping geometries for thin
film solar cells.
Metal nanoparticles
placed on top of a solar
cell
Metal nanoparticles
embedded in
semiconductor
Nanostructures on
backsurface of solar
cell

39. CASE STUDY:Decreasing reflection through the
mutually positive effects of nanograss and nanopillars
Lin et al., 2014
(a) Single-layer nanopillar
(b) Double-layer nanograss-on-
nanopillar nanostructures
(a) Schematic representation of the geometries of the
simulated structures.
(b) Simulated total reflectance spectra of the single-layer
nanopillar and double-layer nanograss-on-nanopillar
nanostructures

40. A new twist for nanopillar light collectors
• Germanium nanopillar array embedded in an
alumina foil membrane.
• Cross-sectional SEM images of a blank alumina
membrane with dual-diameter pores.
Javey et al., 2020

41. NANOPILLARS IN BIOSENSING AND
MEDICINE

42. Stem cell culturing
DNA separation Neuronal growth and pinning
Enhance the efficacy of drug delivery systems

43. Signal enhancement in biosensors

44. CASE STUDY: Fine-Tuning the Degree of Stem Cell Alignment on Ordered
Arrays of High-Aspect-Ratio Nanopillars
Bucaro et al., 2012
(A) Cells grown on high-aspect-ratio Si NPs (r = 100 nm, h =
10μm, p =2μm),
(B) Cells grown on Si NPs (r = 200 nm, h =5μm, p =2μm),
(C) Cells grown on an polymer micropillar array (r = 750 nm, h =
10μm, p = 3.5 μm)
(D) Cells grown on a silicon micropost array
NP arrays in controlling the morphology
and alignment of stem cells

45. CASE STUDY: Biofunctionalized 3D Nanopillar Arrays Fostering Cell
Guidance and Promoting Synapse Stability and Neuronal Activity in
Networks
(A) Cell body are guided by the geometrical pattern of NPs.
(B) Close-up image
(C) Bundle of neuronal axons is precisely guided on PDLO/NPs.
(D) Neuronal axons are guided along a complex circular like
pattern of NPs functionalized with PDLO.
Amin et al., 2018

46. CASE STUDY: Nanopillar array structures for
enhancing biosensing performance
Gold nanopillar array structures developed using
electrodeposition: immediately after deposition (a) and after
the water droplet test and several electrochemical test runs
(b).
Amperometric responses (a) of gold nanostructured and flat
electrodes in an electrolyte containing various concentrations of
K4Fe(CN)6 in Na2SO4. Calibration curve (b) of steady state
current versus the concentration of K4Fe(CN)6.
(Anandan et al., 2006)

47. CASE STUDY: Separation of Long DNA Molecules by Quartz
Nanopillar Chips under a Direct Current Electric Field
Kaji et al., 2004
Nanopillar structures fabricated on a
quartz glass plate before
Schematic representation of a microchannel
equipped with nanopillars for a large DNA
separation

48. CASE STUDY: Flexible nanopillar-based electrochemical sensors
for genetic detection of foodborne pathogens
a. Schematic illustration of NPE fabrication processes.
b. Scheme and photographic image of NPE.
c. bending and twisting status of NPE.
d. confirmation of USB connection.
e. SEM images of top and side view of NPE. Park et al., 2018

49. CASE STUDY: Enhanced Humidity Sensitivity
with Silicon Nanopillar Array by UV Light
Li et al., 2018
AFM image of Si nanopillars
Humidity sensor stability

50. FUTURE GOALS OF
NANOPILLARS IN THE FIELD OF
AGRICULTURE

51. NOKIA MORPH

52. • The vertically aligned nature of nanopillars offer significantly greater advantages
than regular, planar surfaces.
• Nanopillars provide many applications in biomedical, energy and agriculture field.
• Fabrication of nanopillars is easy by simple methods.
• High sensitivity and accuracy in detection due to their optical and electrical
properties.
Conclusion

53. References
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55. Thank you…