Technology developed by Carville allows blocks of pre-machined acrylic to be bonded together to form complex yet compact manifolds, offering great prospects for analytical instruments
The technology of diffusion bonding has been central to the
development of a new range of portable instruments for real-time
field analysis of water quality, industrial effluent,
pharmaceutical processes, and even blood.
They are due to enter
commercial production as soon as strategic partnerships have been
established to market the products.
The modular instruments,
which are PC-controlled by LabView software running under
Windows, are the culmination of the so-called Hisant (high speed
analysis on-line using new technology) project, part funded by
the UK Department of Trade and Industry.
are Cardiff and Luton Universities, Ingenion Design, Biotech
Instruments, and Thames Water, London Hospital, and SmithKline
Beecham which have provided test facilities.
Heralding a new era
of powerful, on-site monitoring of anything from environmental
pollutants to blood sugar, the helium gas-driven flow injection
analysers comprise an array of interconnected modules.
include an ultrasonic device for separating particles down to
below five microns from a pre-filtered, low volume fluid sample,
and a bespoke, diffusion-bonded, acrylic manifold produced by
The latter has built-in miniature solenoid valves
supplied by Lee Products in a number of reagent blocks together
with incubation, mixing, refrigeration and holding chambers; and
finally a flow-through detection cell with a fibre optic link to
a spectrophotometer sensitive to the UV or visible spectrum.
analysing the change in colour of the fluid sample after addition
of reagents, the concentration of the analyte under investigation
The manifold can be configured for each of the
main application areas - water, medical, pharmaceutical - and
instead of having one channel for analysis, it could be
manufactured to sample and test multiple analytes.
Dyke, a director of Cambridgeshire-based Ingenion Design,
"The advantage with diffusion-bonding is that it gives us
the flexibility to configure the manifold for various uses.
started trying to machine a single plastic block and attach
standard Teflon tubing, but there were problems with the fine
drilling operations and in any case we could only produce right
"The beauty of the Carville system is that it
is possible to insert components where they are needed and
machine passageways and chambers of any shape before joining the
blocks, so curved channels for smooth flow can be created and
dead spaces within the manifold are minimised.
there is no swarf or debris inside the block, as these are
removed before bonding.
The overall result is a more compact and
reliable unit that may be reproduced exactly every time during
manufacture." As the flowpaths are sealed in
diffusion-bonded blocks that are clamped together, reliability is
superior to designs that rely on discrete components connected by
Additionally, by making the passageways very
fine, smaller test samples may be taken to minimise the use of
The other major benefit of diffusion bonding
is that there is no adhesive between layers to corrupt the
Owing to its chemical inertness, acrylic is generally
chosen for applications like the Hisant project.
still at its prototype stage, shows good correlation with results
obtained in laboratories.
Key to its performance is the
efficiency of the ultrasonic filter at the front end, the best
reported clearance (separation efficiency) being 10,000-fold
based on a suspension of yeast cells.
have been made of water and sewage samples; and for the clinical
device, 99.98 clearance was achieved with whole blood without
significant potassium leakage from the red cells, leaving about
30% by volume of clear plasma for sampling.
In view of these
successes, commercial prospects are high as the market for the
products in their respective sectors is enormous.
In 1998 there
were over two million official water quality determinations in
the UK, the majority carried out in analytical laboratories.
Europe-wide, Frost and Sullivan in January 2000 reported the
water pollution monitoring instrument market as £198 million,
rising to £277 million by 2005.
In clinical care, the diabetes
market alone accounts for 1.25 million adults in the UK suffering
from non-insulin dependent diabetes, with a further 350,000 known
On-line analysis of fermentation broths in
pharmaceutical processes provides another significant marketing