Diatom Nanotechnology

1
Diatom Nanotechnology
By Susan J. Crawford-Young Electrical Computer
Engineering, University of Manitoba, 2003,
mudworks_at_access.cici.mb.ca
Diatoms are unicellular algae that form intricate
shells of silica. Diatom nanotechnology is the
study of how to use diatoms or their silica
forming processes to make nanodevices.
2
Diatoms are three dimensional. A scanning
electron microscope is needed to see this.
Frustule
Frustules are made like two overlapping boxes.
epitheca
Septum
hypotheca
Diatoms range in size from 1 to 500 µm the ones
in this picture are approx 20 µm
3
Diatoms come in many shapes and forms. There are
approximately 105 species of diatom each with a
different shape.
10µm
4
There are two types of diatoms
Pinnate Most species of this type of diatom can
move.
Centric
The colors of the diatoms are partially due to
the refraction of light in the silicon shells and
partly due to their brown pigmentation. Diatoms
are small refraction gratings and are good at
collecting light.
5
Diatoms often collect in shaped colonies. This
type of self assembly might be of use in building
a nano device.
A star made of pennatae diatoms
Zipper Diatom
Licmophora colony
6
Why Use Diatoms ?

• Diatoms have nanometer features that are not
  reproducible by current technology
• Diatoms grow themselves as long as there is
  light, heat and the correct nutrients available.
• Grow at ambient temperatures and pressures.

Problems with using Diatoms

• Have to grow diatoms of one type or species to
  use in a specific application.
• There is no automated way to place diatoms into
  a MEMS device. They have to be arranged by hand
  or persuaded to grow in the right place.

7
Growing the right Diatom
Growth media with antibiotic
Laser guided by a vision recognition system
Genetically altered diatom antibiotic resistant
Dead diatom
Dead diatom
Using Biotechnology
Using a Compustat
8
Using diatoms as a template
Kovacs, G.T.A. Micromachined Transducers
Sourcebook 1998 page 137
9
Diatom Size Change
Micrograph courtesy of M. B. Edlund
Frustules of the diatom Stephandiscus niagarae
Ehrenb., viewed in a scanning electron
microscope. Larger frustule is complete, and is
near maximum size range for this taxon. In the
smaller frustule, which is near the minimum size
range for the species, the valves are separated,
and the interior of one valve is visible.
10
Diatom Growth
Frustules divide (asexually reproduce) by
separating and then each part produces another
half. The bottom diatom will be slightly smaller.
This causes a size range in diatoms.
epitheca
Septum
hypotheca
11

• Silica Starvation
• - is a method of growing diatoms so that they are
  at the same stage.
• Partially grown diatom shells could be made
  using this method.
• The diatoms are grown in a Teflon container so
  that they do not have any silica available to use
  for growth. The diatoms then reproduce and grow
  only when silica is added. This is because DNA
  synthesis is silica dependent In diatoms.

Teflon
Diatoms in nutrients and light, without silica
12
Growing Diatoms on a Comb
1.
2.
Make a silicone comb by etching
Dip the comb is Teflon
Diatoms
3.
4.
Dip in silicon starved diatom mix. The diatoms
will attach themselves to the silica via
hydrophilic mucilage.
Polish off the Teflon on the tips of the comb
13
Using silica starvation to grow a diatom comb
Acknowledgement Dr. R. Gordon
Partly grown diatom
Diatoms grow in several different ways. Pennate
diatoms grow like this.
New diatom shells grow inside the diatom cells in
synchrony when silica is added to a silica
starved diatom culture. If the diatoms are killed
all at the same time, and at the right stage,
there will be diatom combs in the mixture of
shells.
80µm
Partially grown diatoms are fragile so further
processing might be necessary.
A fully grown diatom like this starts off as a
comb shape.
14
Diatom Diffraction Grating
One way to create diffraction gratings using
diatoms would be to align them, secure them in
place, and then copy them with a molding
technique. The molding technique has to be able
to reproduce fine nanometer scale features.
The ribs and diffraction gratings also form
structural members.
15
Biosilicon

• Biosilicon is the material that diatom shells
  are made of.
• It is made of silicon silaffins, frustulins and
  polyamines.
• It is made by precipitation SiO2 using
  polypeptides (silaffins, frustulins)
• and polyamines.
• comes in differing hardness in diatoms and
  therefore could be made
• with varying hardness levels.

16
Structure of Silaffin 1A from C.fusiformis
H2NSSKKSGSYSGSKGSKCOOH

OH
N
N
N
N
H
H3C
CH3
H3C
CH3
H
CH3
N
N
H
H
n4-9
n4-9
N
N
CH3
CH3
N
N
CH3
H3C
CH3
H3C
17
Structure of Polyamines from N. angularis
A family of 25 amines is generated by variation
of the chain length and the degree of
methylation. Additional variation is achieved by
exchange of the butylamine (left) for a
propylamine unit.
R
N
N
N
N
R
n
CH3
CH3
R
R CH3, H n 7-11
Pohnert G., Angew Chem. Int. Ed. 2002, 41, No. 17
18
Silica precipitates induced by N angularis
polyamides. Scale bars 500 nm (A and B) and 1 µm
(C to F)

• Polyamine molecular masses 1,000 to 1,200 Da used
• (B) Polyamine molecular masses 600 to 750 Da used
• (C - F) Polyamine molecular masses 600 to 1,250
  Da used
• (C) pH 5.4
• (D) pH 6.3
• (E) pH 7.2
• (F) pH 8.3

19

• Effect on silica morphology of combining N.
  angularis polyamines and silaffins.
• Enriched silaffins used for precipitation.
• (B) Mixture of silaffins and polyamines used for
  precipitation.
• Scale bars 500 nm and 1µm insets

Kroger et al (1997) (26) 14133
20
Magnesium Diatom Shells
Diatom shells were placed in an atmosphere of
magnesium at 900o C for four hours. The overall
frustule shape and meso/nanoscale features were
retained.
View of open end (other end closed)
Other ceramic materials could be made using this
technique.
Research by Dr. Kenneth Sandhage
Longitudinal view revealing fine ( 102 nm
diameter Pores )
21
Radiolaria
Another type of marine life form that has a
silica shell.
www.microscopy-uk.org.uk
22
Making microscopic art with diatoms.
The End
Reference web sites www.bgsu.edu www.calacademy.or
g hjs.geol.uib.no www.indiana.edu www.microscopy-u
k.org.uk Canadian Museum of Nature