Biomedical Engineering Reference
In-Depth Information
The cutter positions relative to the pin axis were also measured. It is difficult to
verify these positions directly, so in order to evaluate correctness, we produced
extremely fine pins. If the cutter does not have the correct position, it is impossible
to obtain a small diameter pin. We have made pins with a diameter as small as
50
m
m. An example of such a pin is given in Fig.
8.35
8.9 Possible Applications of Micromachine Tools
Many applications of micromachine tools can be considered as a consequence of
low cost, small space, and low energy consumption of such tools, and of the mass
parallel automatic production process. The preferable area of application is the
production of devices that contain huge numbers of micromechanical details of
arbitrary 3D shapes. We suppose that many types of new products will appear due
to the low cost of such devices. As examples, we can mention large flat screens with
mechanically driven image cells, mechanically driven random access memory, and
microbar assembly materials. Here we consider one such application: microfilters
for fine filtration of liquids and gases.
This problem relates to different branches of technological processes and envi-
ronmental protection. Fine filtration of air is needed for “clean rooms” used in
microelectronics, medicine, and other applications. Filtration of gases is needed for
environmental protection from pollution by power plants, transport vehicles, and
other devices that use fossil fuel. Fine filters have many applications in the food and
chemical industries, microbiology, and so on.
8.9.1 The Problem of Liquid and Gas Fine Filtration
Existing filters do not always solve filtration problems efficiently. Some of them do
not perform properly; others do not give sufficiently fine filtration or cannot be used
in all environmental conditions. Paper filters are often used for filtration of liquids
and gases, and their main advantages are low cost and relatively high relation of
throughput to pressure drops. At present, there are technologies for manufacturing
filter papers with parallel fibres. Such filters permit the filtration of particles down to
0.2
m
m, but they have some disadvantages, including the following:
l
paper filters demand relatively large space;
l
the paper cannot be used in some environmental conditions (e.g., high-temperature
gases, liquids);
l
paper filters for liquids do not permit filtration of particles smaller than 0.2
m
m.
m, membrane filters are used, but such filters
have very low throughput and high pressure drops [
57
].
To filter particles smaller than 0.2
m
