At NanoDotTek we do our homework ...
Nothing comes easy: the transformation of theoretical ideas, and experimental evidence into an established body of knowledge is a laborious process that requires extensive research. To complicate matters further, the ever-changing industrial environment demanding optimized quality, and new products makes it challenging to decide which parameters enter the competition, and what concepts are relevant for their investigation.
Nanoscale events in a material ultimately have macroscopic effects. Conversely, observations of material characteristics on a macroscopic scale allow inferences to be made about material properties on a nanoscale. Therefore, at NanoDotTek we believe that the rigorous consideration of these truths will lead to improved methods of nondestructive testing, materials fabrication or characterization, and prototype development.
So, let us tell you what we do...
New insights are obtained through ongoing work on a nanoscale
Confinement effects in nanostructures give rise to new and intriguing properties that can be exploited for a variety of applications ranging from semiconductor electronics to medical diagnostics. Overcoming challenges in fabrication at such a tiny scale holds great promise for building big from small and defining the future of nanotechnology.
a few examples of ... NANOFABRICATION
· Nanoetching
Alumina masks can be self-assembled through a simple anodization process.
The alumina membrane displays throughout its thickness a hexagonal array of
nanopores similar to a honeycomb structure.
SEM image of regular alumina nanopores.
Substrates can be etched on a nanoscale using reactive ion etching and an
alumina mask that has been appropriately thinned.
SEM image of a cross section of a
thinned alumina mask.
The regular hexagonal nanopattern of the alumina mask can be etched onto
a GaN substrate.
SEM image of duplicated honeycomb nanopattern
on GaN.
· Nanodots
If an electron beam of a heated material hits the nanopores of an alumina
membrane, it will deposit minute quantities of that particular material, if the
membrane is thin enough to allow the beam to go through the pores. The membrane
which serves as a mask is removed after the evaporation and an array of
nanodots is obtained on the substrate on which the mask had been placed.
SEM image of quasi-ordered nanodots obtained
by e-beam evaporation through a self-assembled alumina mask.
· Nanowires
The alumina membrane can be used to selectively electrodeposit under ac
or dc conditions metals, semiconductors or organic materials into the
nanopores. As a result, an array of nanowires can be fabricated in templates
that are subsequently removed.
TEM image of electrodeposited nanowires.
By fine tuning the fabrication process on a nanoscale, interesting
properties can be obtained for these nanostructures, and ultimately new devices
can be developed. However, knowledge is built gradually through a variety of
projects.
Expertise has been acquired through previous projects
The ability to engineer properties down to small dimensions originates
in the interdisciplinary effort spent on earlier work leading the pathway for
new technologies.
BIOMEDICAL DEVICES
· Development
of Microchip-Based Optical Device for Single Cell Diagnostics
A prototype for a medical diagnostic instrument was built based on the light
scattering properties of single biological cells. These cells are manipulated
on a microchip using microfluidic methods, and
this involves avoiding damage to the cells themselves. The intensity levels of
the scattered light have a large dynamic range that can be equalized using a
thin-film optical interference filter. A commercial shortwave-pass filter
proves to be an appropriate choice. The filter is incorporated into the
instrument to preferentially attenuate scattering peaks. Low and high angles of
scattering can be imaged simultaneously in one test. This feature has the
potential to automate data collection by allowing detection over a wide angular
range. The data collected contains important information about nanoscale
biological cell features useful in diagnosing disease conditions at the
cellular level.
MATERIALS CHARACTERIZATION AND NONDESTRUCTIVE TESTING
· Microyielding
Phenomena in Mild Steel Detected Using Magnetic Barkhausen Noise
This work revealed novel observations on the influence of microyielding
on magnetic behaviour. Experiments focused on magnetic
Barkhausen noise response to progressive deformation below the macroscopic
elastic limit of mild steel specimens. Subtle changes in signal were attributed
to redistribution of strain around and within grains affected non-uniformly by
stress. Results indicated that the magnetic Barkhausen noise technique can
detect microyielding.
· Analysis
of Magnetic Behaviour of Plastically Deformed Mild Steel
The purpose of this work was to differentiate the effects of elastic
and plastic deformation on magnetic Barkhausen noise signals. It was
determined that the dissimilarity in response is in fact due to different
mechanisms governing elastic and plastic strain. Elastic strain significantly
alters the magnetic anisotropy in the sample, leaving the isotropic signal
almost unchanged. Plastic deformation has a smaller, but apparently opposite
effect, in that it appears to change the isotropic background, with little
influence on magnetic anisotropy.
· Cold
Rolling Effects on Magnetic Anisotropy of Nuclear Reactor Pressure Vessel Steel
This study has attempted to further investigate what is termed 'roll magnetic anisotropy'. The latter is likely to be
influenced by different factors accompanying cold rolling - crystallographic
texture development, the formation of a significant (and possibly anisotropic)
dislocation structure, and residual stresses on both a micro and macro scale.
An initial axial magnetic easy axis, likely due to crystallographic
texture present in the undeformed samples, is destroyed in the early stages of
cold rolling. It is replaced at intermediate reduction ratios by a transverse
easy axis resulting after unloading from macroscopic axial compressive
stresses. With further rolling the influence of the compressive macroscopic
residual stress appears to diminish, and a strong axial easy axis develops.
· Scanning
Electron Microscopy Surface Analysis of Fractured Components
Sometimes an independent assessment for the reasons of failure of engineering
components is required. A scanning electron microscope is
employed to study the appearance of fracture surfaces and analyze the mechanisms that led to failure. Results of the
investigation are usually combined with an energy dispersive X-ray analysis
that allows identification of the nature of inclusions present along the
fractured surfaces. Some projects require a quality
assessment of certain products such as steel wool or copper wires.
FABRICATION IN HIGH VACUUM
· Development
of a Pyranometer Based on Thermopiles
A prototype instrument was built for measuring the global solar radiation which
consists of both the approximately parallel radiation transmitted directly
through the atmosphere and the diffuse radiation from the sky. The
thermocouples composing the transducer of
the new instrument were obtained by thermal evaporation of Bi and Sb. The manufacturing
process was more economical than obtaining junctions through a local melt of
constantan (60 % Cu, 40 % Ni) and manganin (84 % Cu, 12 % Mn, 4 % Ni) as in the
old instrument.