Cut electricity consumption with automation - Watt Now Magazine

The Texas instrument digital micro-mirror
device consists of more than 500 000
individually movable 20 μm square mirrors,
each representing one pixel of a projected
image. Electrostatic forces deflect the beam
which supports the mirror about one of its
diagonals at rates of more than 100 kHz
current flows between the two anchor points, both limbs of the device
experience resistive heating. Because of the very large difference in
cross-section however, the temperature rise in the narrower element
is much greater than that in the broader, which results in differential
thermal expansion and motion of the linked tips. When the current
is removed the actuator returns elastically to its rest state. At the
MEMS scale, the actuators can reciprocate at the rate of kilohertz.
Williams’ paper — which addressed friction, wear and lubrication
challenges facing micro-systems technology — speaks volumes about
just how established this technology is. He introduced his paper
by stating: “The component masses and inertias (of miniaturised
machines) rapidly become small as size decreases, whereas surface and
tribological effects, which often depend on area, become increasingly
important.”
In South Africa, the CSIR has established a micro-manufacturing
capability within the Material Science and Manufacturing unit, with
a key focus on the field of micro-fluidics — the science of designing,
manufacturing and formulating MEMS devices that deal with
volumes of fluid in the order of nanolitres or picolitres. “A nanolitre
is 10-9 litres — it is the volume contained in a cube with sides of
100 microns, a tenth of a millimetre,” says Kevin Land — senior
researcher in digital and micro-manufacturing at the CSIR.
Land’s research aims to put a whole biochemical laboratory on
a single chip — lab-on-chip — for HIV/AIDS diagnosis or malaria
detection, for example. The CSIR’s micro-manufacturing laboratory
is used mostly to model, design and fabricate the biochips, working
closely with CSIR’s biosciences research teams who specify each labon-chip
test.
Other applications of micro-fluidics include high throughput
biomedical screening and compound profiling such as DNA analysis,
and lab automation; clinical diagnostics and point-of-care testing;
inkjet printing and printer applications such as biochip production,
flat panel displays and printable electronics; chemical analysis and
synthesis; medical applications such as drug delivery and blood cell
separation; proteomics and chromatography; micro-sensors for
the automatic detection of viruses, bacteria and toxic chemicals;
dispensing; and environmental management such as temperature
control, water quality monitoring, fire detection and the stabilisation
July 2008
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