The uniqueness of X-ray microscopy
It is the
complexity of analytical techniques that makes
modern X-ray microscopy unique due to the
specific interaction of X-rays with atoms in any
kind of solid, liquid or gaseous matter. Shorter
wavelength allow higher optical resolution
compared to visible light microscopy. High X-ray
penetration power gives 'deeper' insight into
the specimen and avoids in many cases slicing as
required for electron microscopies. The
electronic structure of atoms provides each
element a specific finger print that allows
X-ray microscopy to identify the elemental
distribution. X-ray analytical techniques are
even sensitive to slight modification in the
electronic structure of an atom by its
neighboring atoms, which can provide in addition
a wealth of information on the chemical
speciation of your specimen. The object
field of the human cell image on top is 20
micron, which is less than half the diameter of
a human hair.
"It would be a big improvement on microscopes using light or electrons, for X-rays combine short wavelengths, giving fine resolution, and penetration" (Paul Kirkpatrick in 1948).
Twinmic, the twin soft X-ray transmission and emission microscope
European
scientists with highest expertise in X-ray
microscopy, diffractive X-ray optics, X-ray
contrast technologies and detection, started in
2001 to integrate the advantages of
complementary scanning and full-field imaging
modes into a single instrument,
which they named 'TwinMic'. The microscope
station has been designed as highly modular in
its optical configuration and specimen
environment, and scientists, engineers and
technicians continuously improve the instruments
performance and versatility to suit your
experimenter's requirements. One of the recent
milestone implementations is low-energy X-ray
fluorescence analysis. Chemical sensitivity down to parts per million by different microanalytics
One of the most
attractive features in the complexity of X-ray
microscopy analysis is elemental and chemical
speciation. X-ray near absorption spectroscopy
identifies the chemical chemical and oxidation
state of elements in your specimen. TwinMic is
the first instrument worldwide that offers
low-energy X-ray fluorescence specially
optimized for the analysis of light elements
as they typically occur in life sciences
applications.
From conventional specimen environments to
functional specimen cells
Space for mounting extended specimen
environments is very limited in soft X-ray
microscopy due to short distances to optical
elements in the millimeter range or below.
Anyhow, we at TwinMic have foreseen the
possibility to operate the specimen
environment in vacuum, in air or in inert gas
atmosphere. The in-vacuum operation of the
specimen environment is the standard
mode. We strongly encourage experimenters
to develop and implement functional
specimen environments that allow in-situ
controlling the electromagnetic bias, temperature or in-situ chemical reactions.
The sketch illustrates a prototype electrochemical reaction cell based Si3N4 membranes simulating in-situ the electro-corrosion of electrodes in fuel cell applications. Collaboration with B. Bozzini, Uni Salento, I.
Morphological analysis with lateral resolutions down to the sub-100nm range
TwinMic offers transmission X-ray microscopy
that has up to 10 times higher optical
resolution than conventional visible
microscopy, combined with a natural
contrast between organic matter and water that
allows imaging of specimen in their natural
liquid environment without staining. Specimen
can due to the higher penetration power
thicker than in electron microscopy and can
provide valuable 'bulk' information. Highest
lateral resolution can be achieved with the
full-field imaging mode, which is currently
about 20 nm using special objective lenses.
Other imaging modes as a compromise of X-ray
intensity to chemical sensitivity can offer
much less lateral resolution, in some cases up
to 1 micron.
Versatile contrast technologies for various research and applications
Although X-rays interact strongly with any
kind of matter, pure absorption imaging may in
many cases not be sufficient to provide you
with crisp and detail-rich images. Therefore
we implemented in TwinMic a versatility of
different phase-sensitive techniques. Among
those are Zernike phase contrast, differential
phase and interference contrast. It is worth
noting that some of the EC TwinMic project
partners were the first to realize
differential interference contrast.
X-ray micrograph: Brightfield or absorption image of a 3T3 mouse fibroblast cell. Specimen preparation by P. Marmorato (EC JRC Ispra, I).