Biomedical Engineering Reference
In-Depth Information
using batch fabrication techniques similar to the way in which integrated circuits
are made and making these electromechanical elements along with electronics. It is
in this spirit that ionic polymer-metal composite (IPMNC) sensors and actuators
can easily be integrated into MEMS technologies and manufacturing techniques.
These new manufacturing technologies will have several distinct advantages.
First, MEMS is an extremely diverse technology that potentially could have a signif-
icant impact on every category of commercial and military products. MEMSs are
currently used for everything from indwelling blood pressure monitoring to active
suspension systems for automobiles to airbag accelerometers. Historically, sensors
and actuators are the most costly and unreliable parts of a macroscale sensory-actuator
electronics system. In comparison, MEMS technology allows these complex electro-
mechanical systems to be manufactured using batch fabrication methods. In this
context, the use of IPMNCs to make large MEMS-based microarrays of sensors and
actuators for distributed types of applications is quite promising. Examples of these
applications are distributed microactuator arrays for photonic optical fiber switching
and tactile biosensing. These new applications will allow the cost and reliability of
the sensors and actuators to be put into parity with those of integrated circuits.
IPMNC-based MEMS switches have the potential to form low-cost, high-
performance, ultrabroadband, quasioptical control elements for advanced defense
and commercial applications. IPMNC-based MEMS quasioptical switches offer
numerous advantages over conventional switches. Another potential application will
be in military and commercial microwave systems requiring monolithic solutions
for the realization of low-cost, compact systems. The IPMNC-actuated microma-
chined switch has great potential for microwave applications due to its extremely
high power-handling capability and compatibility with other state-of-the-art fabri-
cation technologies for higher level integrated circuits or systems.
The developments in state-of-the-art MEMS technology have made possible the
design and fabrication of micromachined control devices suitable for switching
microwave signals. IPMNC-MEMS switches will have low parasitics at microwave
frequencies (due to their small size) and will be amenable to achieving low resistive
switching or high capacitive (on-capacitance) switching. Also, in MEMS technolo-
gies, micromanipulation has always been the most difficult problem.
The first and most obvious way to make a microgripper is to miniaturize an
industrial size gripper. Unfortunately, this does not take into account the physics of
changing the scale of the problem. Normally, gravity is the predominant force, and
when a gripper opens (and sometimes sooner) the carried object falls to the floor.
In the microworld, gravity is no longer the predominant force. Adhesive forces, such
as electrostatic, van der Waals, and surface tension forces, dominate in the small
scale. It has been shown that, at a 10-
m object radius, the attractive forces between
a sphere and a plane show 10
-10
, 10
-10
, 10
-8
, and 10
-5
N for gravity, electrostatic,
van der Waals, and surface tension forces, respectively.
Given the challenges to micromanipulation, it is not surprising to find a wide
variety of approaches to the problem. Recent approaches to fabricate microgrippers
have attempted to use
µ
