Biomedical Engineering Reference
In-Depth Information
limit at the nanometer scale (30,31). Yet, naturally occurring molecular devices found in
living organisms seem to thrive on the nanometer scale, where “cross-talks” of devices are
the normal mode of device operations.
Perhaps the nanometer-scale interactions are essential for the manifestation of intelli-
gence. Size and densities matter but perhaps miniaturization alone is insufficient for true
intelligence to arise. Perhaps there is something more in biology than that which meets the
eyes. The nanometer-scale interactions in biology are nothing but the familiar biochemical
interactions. Since biochemistry is ubiquitous in the living world, biochemical reactions may
be responsible in part for intelligence. In addition, the almost exclusive use of carbon-based,
organic materials as construction materials in the living world suggests that organic materi-
als are more suitable than silicon-based materials for building intelligent devices, presum-
ably because of the inherently diverse variety of organic compounds and the rich repertoire
of biochemical reactions. The prominent role played by proteins in living systems suggests
that proteins are more amenable to subtle and gradual changes of functions (26).
Comparison of various living organisms on the evolutionary scale further suggests that
the emergence of intelligence might have something to do with the increasing complexity
of “device architectures” (26,32). As compared to digital computer architectures, it is
apparent that the device architectures in living organisms allow for massively parallel, dis-
tributed information processing—a feature that digital computers strive to emulate with
limited success. These features provide a road map; device intelligence lies in exploiting
both physical and chemical interactions of component materials, in the use of organic
materials as building blocks, and in the configuration of life-like architectures. However,
this road map does not prescribe detailed implementations. Numerous obstacles need to
be overcome. Thus, the design goal is clear but what ought to be the optimal direction
needs to be determined. From the very outset, molecular electronics research has been con-
troversial and the approaches have frequently been disputed. For this reason, we should
ask whether reverse-engineering biology is a viable approach.
The wisdom of reverse-engineering Nature has frequently been questioned. The skepti-
cism was not totally unfounded. One of the best-known attempts to imitate Nature was
Leonardo da Vinci's idea of designing a flying machine by imitating how a bird flies (33).
As the history of technology transpires, all designs based on flapping wings failed.
However, the argument against this particular example had an inherent flaw. A closer look
at the history of science and technology reveals a sufficient number of successful examples
of imitating Nature to warrant a second thought. It is important to remind ourselves that
even the case of flying machines could be reinterpreted to favor reverse engineering, if one
examines the case from a different angle.
Indeed, an important aspect of aircraft designs was a consequence of imitating Nature.
Most, if not all, aircrafts, which glide in mid-air, have a wing profile similar to that of a
bird: the curvature of the top surface is greater than that of the bottom surface, thus giv-
ing rise to a longer path of air flow on the top than on the bottom surface. It is well known
that such a feature gives rise to a force of floatation (lifting) in air (Bernoulli principle). The
departure from a “verbatim” imitation of birds was reflected in completely different
designs of the propulsion mechanism. Birds use wings for both floatation and propulsion
whereas using the wings for propulsion is ill conceived because moving parts, made of
conventional materials, are usually the first to break. But then who said that both the
propulsion and the floatation mechanisms must be implemented with a single device?
Human ingenuity allowed past inventers to see through this superficial and imagined
restriction by seeking separate devices for floatation and propulsion. The obvious lesson
to learn is that imitation need not be performed at a superficial or “verbatim” level but
rather at a deeper, more fundamental level of principles. To be able to do so requires some
basic understanding. This is why basic research is important for technological endeavors.
