Biomedical Engineering Reference
In-Depth Information
10.5
Design of the System
Despite architectural differences, the tasks involved in designing the systems have certain
standard objectives. These objectives establish the foundation of knowledge and capabilities
required to build the specific system. They include: (a) understanding the cellular and
molecular biology of the skin-environment interface, that is, the epidermal barrier; and (b)
developing tools, techniques, and protocols to nonintrusively or semiintrusively collect rel-
evant physiological information using an array of micro/nanoprobes, sensors, and analysis
protocols. For a global-level system, it includes: (c) using distributed computing, imaging,
and wireless communication to analyze, correlate, and understand the response of the skin
at various body sites to a single-controlled stimulus and across a group of sensors at a pop-
ulation level. Fluid transfer systems entail: (d) developing models to understand microflu-
idic coupling between SC and MEMS-based tools and on-chip immunoassays and sensors.
Therapeutic systems include: (e) developing therapeutic application methodologies and
protocols to deliver required medication based upon computational algorithms.
Each of the objectives mentioned above encompasses numerous tasks, which comprise
varied undertakings in biology, medicine, chemistry, information technology, and
microtechnology. The first task includes interface testing on various surfaces, such as bio-
engineered cellular films, bioengineered skin, excised human skin, and the intact human
body. Relevant target measurements such as bioimpedance, immunoassay, and analyte
detection would have to be conducted. This would assist in identifying key analytes to be
monitored, and determining the baseline and deviation standards. Information/models and
images would be used to enable extrapolation of data from the tissue-level microenviron-
ment, to an understanding of meaningful physiological responses at the level of the organ-
ism. For reagent analysis systems, immunoassays and analyte detection protocols have to be
developed. Sensor/analyzer designs have to be built accordingly by the MEMS designers.
Deciding upon the physical design and establishing fabrication procedures of the individual
micro/nanostructures would form the most vital component of system development. The
biggest challenge would lie in integration of the various microdevices (such as the elec-
trodes, sensors, microchromatographs, and fluidic components). To ease the development
process, the microinterface systems can be expected to have a modular design, that is each
subsystem would be functionally independent. However, subsystem development cannot
be independent of other tasks, and continuous collaboration between MEMS and biotech-
nology/information technology groups would have to be a standard feature of the design
process. The information technology tasks could include development of data processing
capability and a data transfer interface. Depending upon whether the skin-interface unit is
a stand-alone node or part of a global sensing system, the tasks would include creation of
low-power wireless communication protocols within multiple nodes, distributed comput-
ing algorithms and protocols at these nodes, and transmission of raw or significant data col-
lected from individual nodes. Data management tasks would comprise signal conditioning,
post processing, sensor fusion, and feedback control to manage and optimize the
device/skin interface. Data depiction front-ends would have to be created to facilitate easier
data interpretation, for example providing the data as a 3-D image composite.
10.6
Significance of Skin-Interface Systems
Bioengineered systems would comprise application-specific MEMS devices coupled to
the skin via microelectrodes or microneedles. Systems may incorporate elements such as
 
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