Biomedical Engineering Reference
In-Depth Information
[
3
,
17
,
30
,
31
], neurophysiology [
3
], and so on. There are projects with the aim
of developing mobile microrobots [
32
-
34
] and producing them using microme-
chanics technologies. Peripheral Research Corp., Santa Barbara, Calif. estimated
the micromechanical devices market to grow to $11 billion in 2005 from between
$3.7 billion and $3.8 billion in 2001, even as average sensor prices declined
sharply in 2005 to $1 from $10 in 2001 [
35
].
At present, the base technology for micromechanical device production is
lithography [
3
,
36
]. Up to 99% of commercial MEMS production uses this technol-
ogy [
3
], but lithography makes it possible to produce only two-dimensional (2D)
shape details. The production of three-dimensional (3D) shape details has many
problems, which is why many researchers try to use conventional methods for the
mechanical treatment of materials to produce microdevices [
3
,
36
-
40
]. For this
purpose, they use precise and ultra-precise machine tools because tolerances of
microdetails must be very small. The preciseness of machine tools may be deter-
mined as a relation of the machine tool's size to the minimal tolerances it ensures.
To increase the preciseness of machine tools for microdetail manufacture, it is
necessary to miniaturize them. Two main reasons for miniaturization of machine
tools have been given [
36
]. The first is a decrease of heat deformation of machine
tools with a decrease in their sizes. The second is a decrease of material consump-
tion for machine tool production; in this case, more expensive materials with better
properties can be used for machine tool manufacture.
There are also other reasons for miniaturization of machine tools, one being that
the vibration amplitudes of small machine tools are lower than those of large ones
because the inertial forces decrease as the fourth power of the scaling factor, and the
elastic forces decrease as the second power of the scaling factor [
41
]. Moreover,
smaller machine tools demand less space and lower energy consumption.
Microequipment technology is also advantageous because it preserves conven-
tional mechanical technology methods in small-scale device manufacturing, which
can lead to decreasing not only the cost of the products but also the time it takes for
products to reach the market. In contrast, almost all MEMS-produced microdevices
demand new mechanical designs. To invent and to develop a new device design
requires a great deal of time. Special kinds of materials, which are used in MEMS
technology, demand additional investigations of the microdevice properties and the
resolution of many problems (such as wearing, lubrication, etc.), which are solved
in macromechanics for traditional materials. In comparison with MEMS, micro-
equipment technology permits us to make minimal changes in the design and
production methods of microdevices.
A special project for microfactory creation based on miniature micromachine
tools has been initiated in Japan [
42
]. The Mechanical Engineering Laboratory has
developed a desktop machining microfactory [
7
,
43
] consisting of machine tools
such as a lathe, a milling machine, a press machine, and assembly machines such as
a transfer arm and a two-fingered hand. This portable microfactory has external
dimensions of 625 x 490 x 380 mm
3
and weighs 34 kg (its main body weight is
23 kg). It uses three miniature CCD cameras mounted on each machine tool, which
display the image of a machined section on a 5.8-inch LCD monitor. This factory
