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24 Biomimetics: Biologically Inspired Technologies

cells to the scale of the full body. Imitated processes, including artificial synthesis of certain
vitamins and antibiotics, have been in use for many years. More recently, biomimetics have been
used to design navigational systems, data converters, mathematical algorithms (Chapters 4
and 5), and diffusion processes. The neural network (part of the field of AI that was covered
earlier) is a hypothetical biomimetic computer that works by making associations and guesses, and
that can learn from its own mistakes. Examples of biomimetic processes are described throughout
this book.

1.7 BIO-SENSORS

Living creatures are equipped with a sensory system, which provides input to the central nervous
system about the environment around and within their body and the muscles are commanded to
action after analysis of the received information (Hughes, 1999). Biological sensory systems are
extremely sensitive and limited only by quantum effects (Chapter 11; Bill Bialek, 1987). This
sensory network is increasingly imitated, where we find our surroundings filled with sensors. Such
sensors are monitoring our property to protect it from intruders; releasing soap and water when
washing our hands; releasing hot air or paper towels to dry our hands; tracking our driving speed;
observing our driving through intersections that are monitored by traffic lights; as well as
performing many other tasks that we accept as part of our day-to-day lives. Our cars sense
when we close the doors, whether there is sufficient air in the tires, charge in the battery and oil in
the engine, and if all the key functions are operating properly. Sensors also control the flow of
gasoline to the ignition system in our cars to optimize gas consumption. Similar to the ability of
our body to monitor the temperature and keep it within healthy acceptable limits, our habitats,
working, and shopping areas have environment control to provide us with comfortable temper-
atures. These examples are only a small number of the types of sensors that are used in our
surroundings and in the instruments that we use today. Pressure, temperature, optical, and
acoustical sensors are widely in use and efforts are continuously made to improve their sensing
capability and reduce their size and required power while mimicking ideas from biology. These
include adapting principles from the eyes to camera, from the whiskers of rodents to sensors for
collision avoidance, and from bats to acoustic detectors that imitate their sonar. Specific examples
of biomimicked sensors are described below.

1.7.1 Miniature Sensors in Biomimetic Robots

The integration of sensors into mobile systems is critical for their operation, as it is necessary to
provide closed-loop feedback to accomplish mobility tasks and other dynamic functions. Emulat-
ing the dimensions, density, integration, and distribution of sensors in the human finger will
require significant advancements in such fields as MEMS and nano-electro-mechanical systems
(NEMS). While currently the packing density of sensors per unit surface using MEMS tech-
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nology is about 1 to 10 sensors/mm there is still a long way to go before reaching the density
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level of hundreds of sensors/mm of the skin area of the fingertips. Combining the equivalence of
soft skin and integrated sensors is a desired biomimetic development goal. An array of multiple
types of sensors will need to be used to provide critical, detailed data about the environment and
the performance of the various elements of mobile system. It is also highly desirable to see the
development of miniature vision and sound receivers with real-time image and voice recognition
allowing rapid response to the environment in a manner akin to living creatures. Moreover, there
is increasing need for soft sensors that can support the development of electroactive polymers
(EAP) as artificial muscles (Chapter 10). These materials have functional similarities to biological
muscles and the use of such sensors as strain gauges is not effective because of the constraining
effect that results from the rigidity of the widely used gauges.