Biomedical Engineering Reference
In-Depth Information
TABLE 9.1
Comparison of the Properties of IPMNCs, SMAs, and EACs
Property
IPMNC
SMA
EAC
Actuation displacement
> 8%
< 6% short fatigue life
0.1-0.3%
Force (MPa)
10-30
about 700
30-40
Reaction speed
µsec to sec
sec to min
µsec to sec
Density
1-2.5 g/cc
5-6 g/cc
6-8 g/cc
Drive voltage
0.1-7 V
NA
50-800 V
Fracture toughness
Resilient, elastic
Elastic
Fragile
When electroactive ceramics or SMAs are applied to micromanipulation, a
variety of creative approaches have been taken to compensate for each actuator's
limitations. For example, many creative systems have been proposed, including
nonlinear, high-ratio transmission systems made with a piezoelectric actuator and
micromanipulation using SMAs and the use of temperature change to modify the
pressure inside microholes on the surface of the end-effector.
The current state of the art in MEMS technologies in connection with robotic
micromanipulation and assembly, as well as sensing and actuation, is that small
micron-size components can be made by traditional micromachining in the semi-
conductor industry. Sensors, valves, pumps, manipulators, filters, probes, and con-
nectors are just a few examples of MEMS-based devices. Fabrication processes
involve silicon surface micromachining, silicon bulk micromachining and wafer
bonding, LIGA, EDM (electrodischarge machining), and single-point diamond
machining. MEMS are the integration of mechanical elements, sensors, actuators,
and electronics on a common silicon substrate through the utilization of the preceding
microfabrication technology. Since MEMS devices are manufactured using batch
fabrication techniques, similar to ICs, unprecedented levels of functionality, reliabil-
ity, and sophistication can be placed on a small silicon chip at a relatively low cost.
IPMNC sensors and actuators can be naturally integrated with the current MEMS
technology because they can be easily batch processed and manufactured and they
can be made as small as desired and in any desired geometry, as we have proven.
IPMNC-MEMS technology will definitely become an enabling new technology to
help in biotechnology as well. Technologies such as the polymerase chain reaction
(PCR), microsystems for DNA amplification and identification, the micromachined
scanning tunneling microscopes (STMs), biochips for detection of hazardous chem-
ical and biological agents, and microsystems for high-throughput drug screening and
selection will particularly benefit from IPMNC-MEMS integration. IPMNC-MEMS
can also easily integrate into high-output dynamic sensing systems such as acceler-
ometers and dynamic motion and force sensors as well.
Although MEMS devices are extremely small, MEMS technology is not about
size. Furthermore, MEMS is not about making things out of silicon but is a manu-
facturing technology: a new way of making complex electromechanical systems
