Biomedical Engineering Reference
In-Depth Information
piezoresistive strain gauges (Hexsil process) for tactile feedback or the assem-
bly of precision optical and magnetic components
a vacuum system with Lithographic Galvanoformung Abformung (LIGA)
fabrication
temperature change causing a change in pressure
SMAs (i.e., rotary microjoint)
laser trapping
dielectrophoresis effects
The technologies that have been applied to micromanipulation do not satisfy all
of the requirements necessary for an economically viable approach. One would
expect a material that is flexible rather than brittle, has long life rather than short
life, reacts quickly rather than slowly, and is simple rather than complex. IPMNCs
are believed to satisfy such requirements of MEMS microactuation technologies.
Since these muscles can be cut as small as desired, they present a tremendous
potential to MEMS sensing and actuation applications. Figure 9.32 displays a
micron-sized array of IPMNC muscles cut in a laser microscope work station.
A variety of MEMSs can be made by packaging and fabricating IPMNCs in
small, miniature, and micro sizes. Some examples include micropropulsion engines
for material transport in liquid media and biomedical applications such as active
microsurgical tools. Other applications involve micropumps, microvalves, and
microactuators. Flagella and cilia type IPMNC actuators fall under this category.
Figure 9.32 shows a manufactured IPMNC in a thickness of 25
m. Note that an
effective way of manufacturing such microsized IPMNCs is to incorporate solution-
recasting techniques.
As noted, IPMNCs have shown remarkable displacement under a relatively low
voltage drive, using a very low power. However, these ionomers have demonstrated
a relatively low force actuation capability. Since the IPMNCs are made of a relatively
strong material with a large displacement capability, we investigated their application
to emulate fingers. As seen in figure 9.33, a gripper is shown that uses IPMNC
fingers in the form of an end-effector of a miniature low-mass robotic arm. The
fingers are shown as vertical gray bars. Upon electrical activation, this wiring con-
figuration allows the fingers to bend inward or outward, similarly to the operation
of a hand, and thus close or open the gripper fingers as desired. The hooks at the
ends of the fingers represent the concept of nails and allow securing the gripped
object encircled by the fingers.
A two-dimensional schematic of the microgripper is provided in figure 9.33.
The gripper would normally be attached to a gross manipulation device (e.g., a small
robot) and the artificial muscles are actuated under voltage control. When actuated,
the muscles will move together and grip the object in a compliant manner. By
increasing the control voltage, the amount of gripping force is increased, and a firmer
grasp is achieved. Since the artificial muscle also can act as a sensor, gluing muscles
together provides an interesting mechanism to explore how closed-loop controlled
microgripping is best achieved. It is envisaged using the sensing capabilities of the
µ
