Biomimetics: Its Practice and Theory

Abstract

Biomimetics, a name coined by Otto Schmitt in the 1950s for the transfer of ideas and analogues from biology to technology, has produced some significant and successful devices and concepts in the past 50 years, but is still empirical. We show that TRIZ, the Russian system of problem solving, can be adapted to illuminate and manipulate this process of transfer. Analysis using TRIZ shows that there is only 12% similarity between biology and technology in the principles which solutions to problems illustrate, and while technology solves problems largely by manipulating usage of energy, biology uses information and structure, two factors largely ignored by technology.

Full text

REVIEW
Biomimetics: its practice and theory
Julian F. V. Vincent*, Olga A. Bogatyreva, Nikolaj R. Bogatyrev,
Adrian Bowyer and Anja-Karina Pahl
Department of Mechanical Engineering, Centre for Biomi metic and Natural Technologies,
University of Bath, Bath BA2 7AY, UK
Biomimetics, a name coined by Otto Schmitt in the 1950s for the transfer of ideas and
analogues from biology to technology, has produced some significant and successful devices
and concepts in the past 50 years, but is still empirical. We show that TRIZ, the Russian
system of problem solving, can be adapted to illuminate and manipulate this process of
transfer. Analysis using TRIZ shows that there is only 12% similarity between biology and
technology in the principles which solutions to problems illustrate, and while technology
solves problems largely by manipulating usage of energy, biology uses information and
structure, two factors largely ignored by technology.
Keywords: biomimetics; bionics; TRIZ; technology transfer; conflict; inventive principle
1. INTRODUCTION
Otto Schmitt was a polymath, whose doctoral research
was an attempt to produce a physical device that
explicitly mimicked the electrical action of a nerve. By
1957, he had come to perceive what he would later label
biomimetics as a disregarded—but highly significant—
converse of the standard view of biophysics:
Biophysics is not so much a subject matter as it is a point
of view. It is an approach to problems of biological science
utilizing the theory and technology of the physical
sciences. Conversely, biophysics is also a biologist’s
approach to problems of physical science and engineering,
although this aspect has largely been neglected.
(Harkness 2001)
The word bionics was coined by Jack Steele of the US
Air Force in 1960 at a meeting at Wright-Patterson Air
Force Base in Dayton, Ohio. He defined it as the science
of systems which have some function copied from
nature, or which represent characteristics of natural
systems or their analogues. At another meeting at
Dayton in 1963, Schmitt said
Let us consider what bioni cs ha s come to mean
operationally and what it or some word l ike it
(I prefer biomimetics) ought to mean in order to make
good use of the technical skills of scientists specializing,
or rather, I should say, despecializing into this area of
research. Presumably our common interest is in
examining biological phenomenology in the hope of
gaining insight and inspiration for developing physical
or composite bio-physical systems in the image of life.
(Harkness 2001)
Later, Schmitt used the word biomimetics in the
title of a paper (Schmitt 1969); the word made its first
public appearance in Webster’s Dictionary in 1974,
accompanied by the following definition:
The study of the formation, structure, or function of
biologicall y produced substances and materials (as
enzymes or silk) and biological mechanisms and processes
(as protein synthesis or photosynthesis) especially for the
purpose of synthesizing similar products by artificial
mechanisms which mimic natural ones.
(Harkness 2001)
Biomimetics (which we here mean to be synonymous
with ‘biomimesis’, ‘biomimicry’, ‘bionics’, ‘biognosis’,
‘biologically inspired design’ and similar words and
phrases implying copying or adaptation or derivation
from biology) is thus a relatively young study embracing
the practical use of mechanisms and functions of
biological science in engineering, design, chemistry,
electronics, and so on. However, people have looked to
nature for inspiration for more than 3000 years (since the
Chinese first tried to make an artificial silk). Historically,
we have:
— Leonardo da Vinci studied birds flying and designed
some machines, but never made any.
— In Swift’s satire of the Royal Society:
There was a most ingenious architect who had contrived
a new method for building houses, by beginning at
J. R. Soc. Interface (2006) 3, 471–482
doi:10.1098/rsif.2006.0127
Published online 18 April 2006
The electronic supplementary material is available at http://dx.doi.
org/10.1098/rsif.2006.0127 or via http://www.journals.royalsoc.ac.
uk.
*Author for correspondence (j.f.v.vincent@bath.ac.uk).
Received 21 December 2005
Accepted 27 March 2006
471 q 2006 The Royal Society

the roof, and working downwards to the foundation;
which he justified to me by the like practice of those two
prudent insects the bee and the spider.
(Swift 1726)
— Henry Mitchell of the American Coast Survey
invented a pile
so cut that the lower portion of it, of a space of six or eight
feet, presents the appearance of a number of inverted
frustums of cones, placed one above the other.
When this sways under the action of waves it sinks
deeper into the sea bed, a design
borrowed from nature .certain seed vessels, by virtue of
their forms, bury themselves in the earth when agitated
by wind or water.
(from H. D. Thoreau’s Journal (1859); thanks to
Prof. Kalman Schulgasser for the information)
— Pettigrew had some pithy comments to make
about people’s failure to produce a usable flying
machine, saying that
It has been cultivated, on the one hand, by profound
thinkers, especially mathematicians, who have worked
out innumerable theorems, but have never submitted
them to the test of experiment; and on the other, by
uneducated charlatans who, despising the abstractions
of science, have made the most ridiculous attempts at a
practical solution to the problem.
Interestingly, he also pointed out that the invention of
the hot air and hydrogen balloons had misled
research, causing people
to look for a solution. by the aid of a machine lighter
than air, and which has no analogue in nature.
(Pettigrew 1873, p. 209)
Pettigrew thus missed the analogy of a balloon in air
and a neutrally buoyant organism in water.
— Clement Ader designed and built several steam-
powered aircraft (Eole) using the wing design of a
bat. He attained a flight of 300 m or so, but could
not gain control with such a compliant wing
(Coineau & Kresling 1987).
The following list is by no means complete; the
Internet is a large and unreliable source of further
examples. We have chosen examples which are conten-
tious, interesting or iconic.
— The stable wing designed by Ignaz and Igo Etrich in
1904 was derived from the large (15 cm span)
winged seed of Alsomitra macrocarpa, a liana which
grows on islands in the Pacific (Coineau & Kresling
1987). The seed with its outgrowths functions as a
flying wing and can glide for significant distances.
— Velcro is an invention derived from the action of
the hooked seeds of the burdock plant which
caught in the coat of George de Mestral’s dog when
they were out on a walk (Velcro 1955). The first
use he wanted to put the concept to was a novel
type of zip fastener.
— Jeronimidis analysed the main tougheni ng mech-
anism of wood in tension and decided it was due to
the orientation of cellulose in the walls of the wood
cells, which is commonly at 158 to the long axis of
the cells in softwoods. He made assemblages of
tubes with various orientations of glass fibre in a
resin matrix and showed that this indeed produces
the toughest material (Gordon & Jeronim idis
1980). In another series of tests he showed that
this structure is, weight-for-weight, about five
times tougher than anything else in impact
(Chaplin et al. 1983 ).
— The observation that the leaves of the lotus are
always clean, despite growing in muddy and
stagnant water, led to the production of Lotusan,
a paint for self-cleaning surfaces (Barthlott &
Neinhuis 1997). Similar surface textures are used
to repel dirt or make it easily removed (e.g. a honey
spoon which drains completely), and have been
observed in many other plants and in other
systems, such as insect wings (Wagner et al.
1996). The same surface properties are now being
developed on metals.
— Antireflective surfaces have been discovered sev-
eral times on insect eyes (Bernhard et al. 1965;
Parker et al. 1998), wings of insects (Stoddart et al.
2006) and leaves of plants in the understorey of
tropical forests (Lee 1986). This has now been
manufactured on polythene sheet, which is
adhered to the glass surface of a solar panel
(using glue which matches the refractive indices),
resulting in a 10% improvement in capture of light.
— Soft Kill Option (a finite-element model by
Mattheck (1989) developed from his studies on
stress-relieving shapes in the adaptive growth of
trees) was used to design the chassis of the
DaimlerChrysler Bionic Car based on the shape
of the boxfish (Ostracion meleagris), which has the
unusual combination of a large volume within a
small wheelbase (Anon 2005 ). It is possible that
this design is based on original obser vations by
Daniel Weihs and others (Bartol et al. 2005 ), but
this is not acknowledged by DaimlerChrysler in
their promotional literature.
— Dry adhesive tape has been made using the
adhesive mechanism of gecko feet. A single gecko
foot hair (seta) adheres equally well to hydro-
phobic and hydrophilic surfaces, generating van
der Waals forces of 10 MPa, showing that the
adhesive properties of gecko setae are a result of
the size and shape of the tips, which conform to the
local surface topography, and are not strongly
affected by surface chemistry (Autumn et al. 2001;
Geim et al. 2003).
— A micro-air vehicle has been made with oscillating
wings inspired (in part) by birds (Jones & Platzer
2002), especially those flying low over water
making use of the ground effect. This is particu-
larly interesting because it also illustrates the
472 Biomimetics: its practice and theory J. F. V. Vincent and others
J. R. Soc. Interface (2006)

limitations which observation of nature can
impose. Although the Jones & Platzer design
uses up-and-down motion of wings, it is technically
plunging rather than flapping since the whole
aerofoil is moved up and down by the same amount
along its span (Lai & Platzer 2001), which is
anatomically impossible for an animal which has
the wing attached to the body at one end. The
plunging aerofoils have a changing angle of
incidence since they move on an arc, but thei r
(summed) net angle is zero. They therefore provide
mainly thrust; lift and control are provided by a
separate fixed wing. Yet the design is inspired by
nature. The problem has always been stated as ‘how
can we implement flapping flight?’ rather than ‘how
can we oscillate one or more aerofoils so as to
produce thrust?’ The effect is identical if the
aerofoils are mounted vertically rather than hori-
zontally, which could be a mechanism which seals
use to generate thrust with their hind limbs.
— Robotic control systems inspired by natural neural
circuits, especially those of insects, prove to be
exceptionally robust and simple (Reeve & Webb
2001).
— By clever design of its ‘ear’ drums and associated
nervous system, a fly (Ormia ochracea) increases
the time difference between the two ears in response
to a noise and can detect the source of the sound
highly accurately (Mason et al.2001).
— Camouflage, especially during the Second World
War, was biomimetic under the direction of Hugh
Cott. More recently, motion camouflage has been
described and will be implemented (Anderson &
McOwan 2003). An example is given by the
dragonfly which, as it approaches its prey on the
wing, endeavours to occupy the same part of
the prey’s visual field, thus appearing not to move
and therefore not to be a threat. It is difficult to
detect an object moving towards you if all it does is
increase in size.
— The surfaces of earth-moving machinery (ploughs,
bulldozers) can be made more effective when
modelled on surfaces of soil-moving animals which
have geometrically optimized ridges and bumps.
This reduces the degree of interaction of the earth-
moving surface with the soil, reducing friction and
improving separation of the soil from the plough
(Li et al.2004).
— The vortices induced by ridges on shark skin can cut
down friction drag significantly. This is being used
on the hulls of sailing boats (and outlawed in
competition, so it is obviously very successful!) and
the lining of pipes carrying liquid. The same system
has been used on aircraft, showing drag reduction of
5–10% (Bechert et al.2000). (See also swimwear
below.)
— The divided wing tip of birds with wings of low
aspect ratio (buzzard, vulture, eagle) reduces tip
drag (Tucker 1993) and can be abstracted into a
loop that reduces drag in aircraft wings and
underwater propellers (Stache 2004).
— The fins offishes are much more efficient propulsors
than conventional propellers and have been
implemented (as ‘nektors’) in small submersibles
by Nekton, Inc. These vessels, with four nektors,
have all six degrees of freedom of movement. An
early example of the concept is the Twiddlefish
(McHenry et al.1995).
— The body shape of a penguin has extremely low drag
and has been used to design low-drag dirigibles
(Bannasch 1993).
— The bumpy surface of the elytra of beetles from the
Namibian desert encourages the formation of
droplets of water from damp air at the dew point
(Parker & Lawrence 2001). This mechanism is
being implemented by Q
INETIQ.
— Many architects use biology as an inspiration.
Some, such as Frei Otto, make direct and useful
reference and so produce efficient lightweight
tensile structures taking direct inspiration from
spider webs (Coineau & Kresling 1987). Architects
commonly use biology as a library of shapes. As
decoration (Art Nouveau, Jungendstil, and the
like), this is obviously acceptable, but the client still
has to be able to afford it. Unfortunately, biology is
also used ineptly as a structural rationale, and Frei
Otto was as guilty of this as anyone, with his
notorious ‘pneu’ studies, where he claimed that all
biology is the product of inflatable structures,
totally missing the point that the shape of a soap
bubble is necessitated by the inability of a soap film
to resist shear; therefore, the skin of an object
shaped like a soap bubble will also be shear-free and
thus lighter and more efficient.
Some systems may be apocryphal in their derivation,
have the status of urban myth, or be the product of over-
enthusiasm:
— It is uncertain whether Joseph Paxton got his ideas
for the Crystal Palace from the leaves of a giant
water lily: he used a leaf as an illustration during a
talk at the Royal Society of the Arts in London,
showing how to support a roof-like structure, and
the myth may have grown out of over-enthusiastic
reportage (Vogel 1998). Certainly there is little
similarity between the design of the water lily leaf
(which uses support of radial tapering beams) and
the design of the roof of the Crystal Palace (which,
with its corrugations, more resembles other types
of leaf, such as beech or hornbeam).
— There are stories that Eiffel’s tower was based on
the structure of trabecular struts in the head of the
human femur, or the taper of a tulip stem. In fact,
it was constructed to resist wind loading, a topic in
which Eiffel was an early expert. In the construc-
tion of the tower, the curve of the base pylons was
calculated, so that the wind loads were resisted
related to their force and the moment exerted with
height. Thus, even in the strongest winds the tower
sways no more than 12 cm.
— Swim-suits whose surface structure is modelled on
sharkskin (see above) do not reduce drag signifi-
cantly when their performance is examined objec-
tively (Stager et al.2000). They probably support
the muscles to some extent.
Biomimetics: its practice and theory J. F. V. Vincent and others 473
J. R. Soc. Interface (2006)

— Polar bears are supposed to have a dark skin to
prote ct them from UV, but have hairs that
transmit radiation down to the skin. However, it
appears impossible for the hairs to act as light
guides since they are largely hollow, and the air
spaces which will reflect and disperse radiation
rather than transmitting it. There is no referred
study published about this supposed phenomenon.
2. A FRAMEWORK FOR BIOMIMETICS
No general approach has been developed for biomi-
metics, although a number of people are currently
developing methods for searching biological literature
for functional analogies to implement. We think that this
is only part of the required framework. Although it is
well known that design and engineering are rendered
much easier with use of theory, in biomimetics, every
time we need to design a new technical system we have
to start afresh, trying and testing various biological
systems as potential prototypes and striving to make
some adapted engineered version of the biomimetic
device which we are trying to create. Additionally, the
transfer of a concept or mechanism from living to non-
living systems is not trivial. A simple and direct replica
of the biological prototype is rarely successful, even if it
is possible with current technology. Some form or
procedure of interpretation or translation from biology
to technology is required. More often than not, the
technical abstraction is possible only because a biologist
has pointed out an interesting or unusual phenomenon
and has uncovered the general principles behind its
functioning (e.g. the self-cleaning lotus effect). Only then
does the biological principle become available outside
biology for biomimetic use. The result is often unex-
pected (e.g. self-cleaning buildings) and the final
product—in this instance, a paint containing par-
ticles—seldom resembles the biological prototype. We
present here a logical framework that we believe exposes
some important underlying patterns.
Approximately 50 years ago in Russia, a particularly
successful problem-solving system began to be
developed. It was named TRIZ, the acronym of Teorija
Reshenija Izobretatel’skih Zadach (loosely translated as
‘Theory of Inventive Problem Solving’).TRIZ is well
known for its successful transfer of various inventions
and solutions from one field of engineering to another.
Since the main thrust of biomimetics is also to transfer
functions, mechanisms and principles from one field to
another, TRIZ seems the ideal starting point (Bogatyrev
2000; Vincent & Mann 2002). We also use TRIZ as a
functional summary and definition of engineering
methodology, a novel use of the system. We know of
no other strategy or system which is so powerful and so
general. Since TRIZ is not very well known to Western
science and technology, a short description is necessary,
outlining its normal use by problem solvers.
TRIZ is a collection of tools and techniques,
developed by Genrich Altshuller and Rafik Shapiro
(Altshuller 1999) that ensures accurate definition of a
problem at a functional level and then provides strong
indicators tow ards s uccessf ul and of ten highly
innovative solutions. At the definition stage, a number
of techniques are used to ensure that the problem is
placed properly within its context (simply changing the
context may solve the problem.) and the available
resources listed. In the most popular (though probably
not the best) technique for solution, the problem is then
characterized by a pair of opposing or conflicting
characteristics (typically ‘what do I want’ and ‘what is
stopping me getting it’, but Hegel’s thesis and antithesis
will do as well, suggesting that it is a form of dialectic
process), which can be compared with pairs of charac-
teristics derived from other, solved, problems derived
from the examination and analysis of more than three
million significant patents.
In order to standardize the process, each of the
conflicting characteristics has to be assigned to a term
contained in a definitive list of 39 contradiction features
(Domb 1998; Altshuller 1999). The solved problems
whose conflict pairs match most closely those of the
problem under examination are then used as analogues
1
of the solution that is being sought, and thus provide the
synthesis to complete the dialectic of thesis–antithesis.
In order to make this matching process easier, the
inventive principles derived from existing patents are
entered into a matrix with the antithetic features along
the top, and the desired features arranged along the
vertical axis. This contradiction matrix then serves as a
look-uptable.Hence,theproblemisresolved.Crucially,
this method al lows the problem, and its derived
analogue(s), to be separated from their immediate
context, so that solutions to any problem can be drawn
from a very wide range of science and technology. Hence,
TRIZ should become a suitable vehicle for identifying
functions and transferring them from nature to engin-
eering. In passing, one of the characteristics of this
metho d, which points to something much deeper,
presumably soluble only by some philosophical argu-
ment, is that the more apparently incompatible the
contradiction features are, the stronger the solution
which will be revealed. This has to mean that the nature
of the problem is better defined, or perhaps even
identified, by a thesis–antithesis pair that is as conflict-
ing as possible. Therefore, a robust definition assists the
identification of a more robust synthesis to the dialectic.
That such a system of definition and solution of a
problem should emerge from Russia is not surprising
when it is realized that similar philosophical arguments
and teaching are (or were) given to Russian children
while still in school.
3. SOLVING PROBLEMS IN BIOLOGY AND
TECHNOLOGY
The nature and organization of biology and engineering
are very different: organisms develop through a process
of evolution and natural selection; biology is largely
descriptive and creates classifications, whereas engin-
eering is a result of decision-making; it is prescriptive
and generates rules and regularities. Types of
1
In TRIZ these are called inventive principles, of which there are
about 40. Appendix 1 of the electronic supplementary material lists
both technical and biological examples of the principles.
474 Biomimetics: its practice and theory J. F. V. Vincent and others
J. R. Soc. Interface (2006)

classification can be hierarchical (e.g. phylogenetic),
parametric (e.g. cladistic, or like the Periodic Table) or
combinatorial. However, the driver for change in biology
and engineering may well be the same: the resolution of
technical conflict.
We present a case study based on a relatively simple
natural fibrous composite material—the outer covering
or cuticle of arthropods. This layer of material, produced
by a single layer of epithelial cells, is called upon to
provide a large number of functions, such as shape,
structure, hinges, barrier, filter and similar functions
(Neville 1975). Some of these functions are intrinsically
and profoundly conflicting, although obviously since
they coexist some form of compromise must have been
evolved, so that the cuticle can be multifunctional. A list
of these functions and the associated characteristics of
cuticle was generated partly by reference to literature
(such as Neville 1975) and partly from experience with
insects and insect cuticle over the years.
Consider, then, the function of the cuticle in providing
a stiff support or exoskeleton for the insect, attachment
for muscles, mechanical protection and control of shape
(Vincent 2005). A uniformly stiff skeleton does not
permit movement, so hinged areas are needed. In the
insect, this has been achieved by making the cuticle
softer along the hinge line. This appears to be the same
as TRIZ inventive principle (IP) 3: Control of local
quality, which is characterized by the following state-
ments: use gradients instead of uniformity (change an
object’s structure, or its environment, from homo- to
heterogeneous); compartmentalize (make each part of an
object more adapted to its own purpose); introduce
multifunctionality (make each part of an object fulfil a
different function like a pencil with an eraser; a hammer
with a nail-puller; or a Swiss army knife). Translated
into cuticular structure, the hinge areas have different
amounts and orientation of chitin (the fibrous com-
ponent), and the matrix proteins are chemically different
from the stiff areas and so more hydrated and softer; the
geometry of the hinge can be linear (for an interseg-
mental membrane) or circular (for a hair socket).
Second, stiffness requires extensive cross-linking of the
matrix protein, which militates against the use of the
cuticle as a labile, resorbable chemical energy store
(important for insects which feed only intermittently,
such as Rhodnius prolixus, a blood-sucking bug). The
resolution of this conflict is achieved by processes
described by IP 2: Extraction—extract, isolate or
remove an interfering or necessary part or property
from an object. Its cuticular translation is to have a
minimum of two layers of cuticle, the inner one being
only partially stabilized and available for resorption.
Since this layer is more likely to take loads in tension, its
ability to resist compression is less important. Third, an
external skeleton is a barrier to transmission of sensory
information about the external environment, a function
provided by sensory hairs and holes (the functional basis
of the campaniform sensillum and slit sense organ). Note
that translucent cuticle, needed over photoreceptors
(IP 3), can still be cross-linked and stiff. Resolution here
is achieved by the morphology of IP 31 Porous materials,
make an object porous; use the pores to introduce a
useful substance or function. Last, the animal will gain
advantage if it recycles as much of the old cuticle as
possible when synthesizing the new one at the moult,
which stiffness will compromise since it requires exten-
sive cross-linking. Larval and nymphal cuticles tend to
be less cross-linked than adult cuticles, probably for this
reason. Resolution is achieved in soft-bodied larvae by
prestressing the material in tension to allow the
structure to take compressive forces (i.e. a hydrostatic
skeleton), which provides protection before the challenge
and is described in IP 9 Prior counteraction.
In order to compare these biological resolutions of a
design conflict with those which technology would use, it
is necessary to convert the functions identified in the
cuticle into the conflict topics that TRIZ recognizes. For
instance, the functions change stiffness, protection, soft
cuticle and stiff skeleton are all reduced to conflict
number 11, which is defined as stress or pressure
(com pression, tension or bending). Simila rly, keep
poison out, self cleaning, surface properties and water-
proof all become conflict number 30, which is external
harm affects the object. The conflicting functions are
similarly classified into the standard TRIZ features,
which now allow the conflicts to be treated in the
standard TRIZ system (Vincent & Mann 2002)anda
direct comparison to be made between technical and
biological solutions to the same problem.
One outcome of this study is that biology and
technology solve problems in design in rather different
ways. Apart from similarities in spectral filtering which
allow the cuticle t o let visible light through to
photoreceptors, yet resist damaging UV radia tion
(a resolution which we would resolve in the same way
that the insect does), most of the functions of cuticle are
provided by detailed control of properties over a very
short distance at a chemical and morphological level,
summarized in IP 3. The TRIZ matrix derived from
technology reveals that we tend to use a rather blunter,
more global approach. This is illustrated by the fact
that IP 35 is the commonest resolution in the TRIZ
matrix, which involves changing a parameter, such as
temperature.
TRIZ was conceived in and derived from the
environment of things artificial, non-living, technical
and engineering. But biomimetics operates across the
border between living and non-living systems. And since
the reason for looking to nature for solutions is to
enhance technical functions, it is necessarily true that
TRIZ does not contain many of these functions, and
probably does not have the means of deriving them.
Despite the fact that TRIZ is the most promising system
for biomimetics, we still have a mismatch. This is
conflated by a number of factors that are currently not
normally observed in a technical system. For instance,
the more closely an artificial system is modelled on a
living prototype, which is typically complex and
hierarchical, the more frequently we have emergent
effects, which are unpredictable, th erefore mostly
unexpected and often harmful. Furthermore, one of the
basic features of living systems is the appearance of
autonomy or independence of action, with a degree of
unexpectedness directly related to the complexity of the
living system. This gives living systems great adapta-
bility and versatility, but at the expense of the
Biomimetics: its practice and theory J. F. V. Vincent and others 475
J. R. Soc. Interface (2006)

predictability of the system’s behaviour by an external
observer. In general, we do not accept unpredictability in
technical systems; indeed, we avoid it. But we need to
consider this even in our current technology, since nearly
every technical system is actually a combination of a
technical system in the narrow sense, and a living
(usually human) system which is the operator of this
technical system. This immediately suggests a broader
and more general definition of the term technical
system—a biological system, part of the functions of
which is delegated to a device that is mostly artificial
and/or non-living. This definition includes agriculture.
This consideration is commonly omitted; technical
systems are often considered in isolation, neglecting
any broader context despite the fact that engineering is
really a subset of human behaviour. At best this can lead
to reduced effectiveness, at worst it produces techno-
logical catastrophes and/or social tension and unrest.
Another TRIZ concept of which we make much use is
the System Operator or ‘9 Windows’. It is commonly
depicted as nine squares arranged 3!3, horizontally
representing time (‘before’, ‘now’ and ‘after’) and
vertically representing size or hierarchy. This allows us
to regularize levels of hierarchy above and below almost
any object being studied that can be in a different
condition (growth, death, attainment of a goal and so
on) before and after the time at which they are currently
being considered. In biology, the hierarchical levels are
organelle, cell, tissue, organ, organism, population,
ecosystem; the hierarchical level of the object under
scrutiny is always referred to as the System. The super-
System represents the assemblage of which the System is
apart (for a cell it is the tissue; for an organism it is the
population) and the sub-System represents one of the
components of the System (for a cell it is an organelle; for
an organism it is an organ).
Increasingly, we are finding that this classification—
which in TRIZ is usually regarded simply as a way of
expanding the conceptual approach to a problem—is an
integral part not only of understanding the problem but
of divining where the solution to the problem might lie.
This is because the System Operator, especially in
biology, defines the context of the System. The
implication is that context is less important in engin-
eering, which, in turn, implies that integration between
hierarchies (insofar as they exist in engineering) is less
good. To some extent this is true, since we find,
empirically, that the solution to a problem where
hierarchy is less important (as in engineering) usually
lies at the same level within the hierarchy (this is
probably obvious), whereas the solution to a problem
where hierarchy is integral usually lies at a level above
(or occasionally below) the current level of the System
(figure 1). This result is not obvious. It is apparent,
though, that we should take into account the relation-
ship of the sub-System and super-System to a given
System. Therefore, we also consider the hierarchy
(which regulates resources, energy distribution and the
capacity of the System in space and time) and the
inertia, (which affects the likelihood of an effect
being expressed on a different level of the hierarchy).
The further the super-System is from the effector in
terms of hierarchical levels, the less the likelihood that
the effect will be expressed at the remote level. This
causes cumulative properties of biological effects which
appear as emergent effects. An effect has influence in the
super-System, and the super-System tries to compensate
for the actions/effects of its sub-Systems. But the only
System that ‘wants’ to change is that which has a goal.
The inherent inertia (homeostasis) in biological systems,
due to negative feedback, opposes change. That is why
an active effect is always coercive at the levels of the
super-System and environment, a fact emphasized by
the few positive-feedback systems in nature, for example
the pheromonal/behavioural induction of swarming in
locusts. If the organism is considered as the System
(figure 1), then super-System is the environment or
ecosystem and sub-System is the organ within the
organism. Such classification is to some degree arbitrary,
but the general rules are that the super-System ‘wants’
to maximize input and use the System as a resource,
while the System ‘wants’ to minimize effort and wants its
resource from the super-System.
4. TRIZ AND BIOLOGY: THE SYNTHESIS
We have analysed some 500 biological phenomena,
covering over 270 functions, at least three times each at
different levels of hierarchy. In total, we have analysed
about 2500 conflicts and their resolutions in biology,
sorted by levels of complexity (Vincent et al.2005). Even
so, this is less than a thousandth of the data contributing
to the engineering TRIZ system. To enable us to process
this huge amount of information, we established a logical
framework (Bogatyreva et al.2004) captured by the
mantra: things do things somewhere. This establishes six
fields of operation in which all actions with any object
can be executed: things (substance, structure) includes
hierarchically structured material, i.e. the progression
sub-system–system–super-system; do things (requiring
energy and information) implies also that energy needs
to be regulated; somewhere (space, time). These six
operational fields re-organize and condense the TRIZ
classification both of the features used to generate the
conflict statements and the inventive principles (appen-
dix 2—electronic supplementary material). Although
this generalization blunts the contradictions tool of
TRIZ, it actually makes other processes easier (e.g. the
implementation of functional analysis in TRIZ, com-
monly called the Substance–Field system) and is
considerably more logical and easier to use than the 39
system
supersystem
subsystem
Figure 1. The System Operator hierarchy for biological
systems.
476 Biomimetics: its practice and theory J. F. V. Vincent and others
J. R. Soc. Interface (2006)

contradictions system. Moreover, it is more complete, in
that the conflict matrix that is constructed from these
fields has all the cells occupied. This more general TRIZ
matrix (which we name PRIZM—Pravila Reshenija
Izobretatel’skih Zadach Modernizirovannye—translated
as ‘The Rules of Inventive Problem Solving, Moder-
nized’) is now used to place the inventive principles of
TRIZ into a new order that more closely reflects the
biological route to the resolution of conflicts. We call this
new matrix BioTRIZ.
We can now compare the types of solution to
particular pairs of conflicts which are arrived at in
technology via classical TRIZ, and in biology. Although
the problems commonly are very similar, the inventive
principles that nature and technologies use to solve
problems can be very different (tables 1 and 2).
In fact, the similarity between the TRIZ and BioTRIZ
matrices is only 0.12, where identity is represented by 1.
Only the principles of spatial composition are signifi-
cantly similar (0.73) in biology and technology. The
differences are in large part to do with the pervasive
presence of hierarchy in biological structure s and
systems. But they are also to do with the degree of
detail it is possible to incorporate into a structure which,
like an organism, is self-assembled and even designed by
the forces of molecular interaction (Vincent 1999, 2005).
Hierarchy is exceedingly important in the solution of
problems (see above); this is not obvious because our
current technologies are either not significantly hier-
archical, or ignore any hierarchical structure. However, a
strictly scalar approach is difficult since many basic
biological functions occur in organisms over a very wide
range of sizes. Thus, the basic processes of cellular
metabolism are more or less invariant from protista to
large mammals; complexity and added functionality are
achieved by adding levels of hierarchy which can be
quantified quasistatically by considering the number of
cell types in an organism (Bonner 1965), or in a more
dynamic way by considering the provision of infrastruc-
ture (West & Brown 2005).Thehierarchicalapproachis
also difficult to use, since in engineering (taken here to
represent the entire spectrum of effects which people
impose on the world in an attempt to make it more
habitable) hierarchy is not as well developed as in
biology. The definition of cause and effect needs
clarification: in physical terms, ambient pressure
(cause) dictates the temperature of the boiling point of
pure water (effect); in biological terms, an effect is a
problem to be solved by the organism and the cause is
the method of solution. Changing the boiling tempera-
ture invokes the operation field energy as does changing
pressure. These are at the substance level of hierarchy.
At the molecular level of hierarchy we would say, ‘the
speed at which molecules move in a liquid (operation
field is time) depends on the pressure (operation field is
energy) and temperature (energy) which we apply to
them.’ Appendix 3 of the electronic supplementary
material illustrates our classification of effects.
We can now comment quantitatively on the differ-
ences between biology and technology (figures 2 and 3)
At size levels of up to 1 m, where most technology is
sited, the most important variable for the solution of a
problem is manipulation of energy usage (up to 60% of
the time), closely followed by use of material (figure 2).
Thus, faced with an engineering problem, our tendency
is to achieve a solution by changing the amount or type
of the material or changing (usually increasing) the
energy requirement. But in biology the most important
variables for the solution of problems at these scales are
information and space (figure 3). This can be illustrated
by comparing the functionality of biological and man-
made polymers, proteins and polysaccharides. People
have produced over 300 polymers, but none of them is as
versatile or responsive as these two biological polymers.
For example, at the primary level, proteins are
remarkably similar in the energy required for their
synthesis since the peptide bond is the pervasive motif.
However, there is a wide range varying from inert fibrous
(such as collagen or silk) to responsive fibrous (such as
muscle) and from inert globular (such as skeletal
Table 1. PRIZM matrix derived from standard TRIZ matrix.
fields substance structure space time energy information
substance 6 10 26 27 31 40 27 14 15 29 40 3 27 38 10 12 18 19 31 3 15 22 27 29
structure 15 18 26 1 13 27 28 19 36 1 23 24
space 8 14 15 29 39 40 1 30 4 5 7–9 14 17 4 14 6 8 15 36 37 1 15–17 30
time 3 38 4 28 5 14 30 34 10 20 38 19 35 36 38 22 24 28 34
energy 8 9 18 19 31 36–38 32 12 15 19 30 36–38 6 19 35–37 14 19 21 25 36–38 2 19 22
information 3 11 22 25 28 35 30 1 4 16 17 39 9 22 25 28 34 2 6 19 22 32 2 11 12 21–23 27 33 34
Table 2. PRIZM matrix derived from biological effects: BioTRIZ.
fields substance structure space time energy information
substance 13 15 17 20 31 40 1–3 15 24 26 1 5 13 15 31 15 19 27 29 30 3 6 9 25 31 35 3 25 26
structure 1 10 15 19 1 15 19 24 34 10 1 2 4 1 2 4 1 3 4 15 19 24 25 35
space 3 14 15 25 2–5 10 15 19 4 5 36 14 17 1 19 29 1 3 4 15 19 3 15 21 24
time 1 3 15 20 25 38 1–4 6 15 17 19 1–4 7 38 2 3 11 20 26 3 9 15 20 22 25 1–3 10 19 23
energy 1 3 13 14 17 25 31 1 3 5 6 25 35 36 40 1 3 4 15 25 3 10 23 25 35 3 5 9 22 25 32 37 1 3 4 15 16 25
information 1 6 22 136182224323440 320222533 2391722 1362232 310162325
Biomimetics: its practice and theory J. F. V. Vincent and others 477
J. R. Soc. Interface (2006)

proteins in insects) to responsive globular (such as
enzymes). The difference between these proteins is less to
do with the energy required for their synthesis than the
complement and order of the amino acids, which is a
derivation of information stored in the DNA of the
nucleus or elsewhere. Space is also relevant, since the
shape of the protein is an essential part of its function.
The same story pertains when considering biological
hard tissues. Calcium, and less commonly silicon,
derivatives are commonest, and carbonates and phos-
phates are predominant. This limited range of chemicals
(with the occasional addition of iron, zinc or manganese)
suffices for nearly all biological hard materials. In insect
cuticle, the main variety of function is achieved by
making complex composites with anything up to 10
constituents and a range of properties (like Young’s
modulus), thus covering several orders of magnitude
with a single material (Vincent & Wegst 2004).
This comparison between the few materials of
biology and the many materials of technology has
been made commonly, but never explained functionally.
We can now do this. It appears that biological systems
have developed relatively few synthetic processes at low
size at which the contribution of energy is significant;
but the main variety of fu nction is achieved by
manipulations of shape and combinations of materials
at larger sizes achieved by high levels of hierarchy,
where energy is not an issue. This is a very subtle
biomimetic lesson. Instead of developing new materials
each time we want new functionality, we should be
adapting and combining the materials we already have.
Obviously, we are doing this to an extent, but it is
unclear whether we recognize this as a significant route
rather than a route of convenience.
In order to approach this, we note that engineering
materials can be mapped with property dimensions, such
as mechanical, thermal, electrical, optical and cost.
These maps show significant gaps in property space,
which can sometimes be filled with hybrids of two or
more materials (A, B) or of material and space (ZAC
BC shapeCscale; Ashby & Brechet 2003). Particulate
and fibrous composites are examples of one type of
hybrid, but there are also sandwich structures, foams,
lattice structures and others. The structural variables
expand the design space of homogeneous materials,
allowing the creation of new materials with specific
property profiles. Although it can be difficult and
expensive to make a successf ul hybrid, so is the
alternative of developing a new material. Both routes
involve exploration of property space; the hybrid will be
more likely to deliver the required properties, but the
quality may be compromised by factors, such as
chemical incompatibility of the components. We already
have some tools to short-circuit this process: for
instance, a database of composites, of reinforcing fibres,
chemistries and choice of structure; these methods allow
promising hybrids to be identified. To go further, we
should attenuate a significant number of our materials
synthesis systems, concentrating on those with the least
energy requirement and the greatest initial variability,
and generate the required functionality by closer control
of the information content (e.g. monomer sequence). We
can also realize the potential of nanotechnology, which is
to escape from the nano approach as soon as possible,
and progress to making larger structures which can
self-assemble in a programmed manner using the
information captured as, for instance, the type and
arrangement of monomers along the polymer chain.
Another implication of this argument is that we should
have a database of the engineering properties and
hybridization potential of both technical and biological
materials. The database of technical materials is
comparatively well known; that of biological materials
isduealmostentirelytotheeffortsofWegst(Wegst &
Ashby 2004) and is as yet unavailable generally.
5. THE EXPANSION OF TRIZ
In order to develop TRIZ as a framework for biomimetics,
we first have to make biological information available
within its structure by cataloguing and classifying the
effects of the actions, and mechanisms of functioning, of
biological systems, and perhaps modify and expand
TRIZ, so that it can cope with the extra varieties of
input information. For this task, we need the framework
to be suitable for describing and classifying both
engineering and biological data. In general, we have to:
— find patterns in the solution of problems in
technology (the original TRIZ system);
— find patterns in the solution of problems in biology
(develop a modified, BioTRIZ, system);
— make these patterns compatible within a new
general Biomimetic TRIZ.
The data from technology and biology present a
continuum of variables and contradictions at different
1.0
0.8
0.6
0.4
0.2
0
nm µm mm
size
problem resolutions
mkm
information
energy
time
space
structure
substance
Figure 2. Engineering TRIZ solutions arranged according to
size/hierarchy.
1.0
0.8
0.6
0.4
0.2
0
problem resolutions
nm µm mm
size
mkm
information
energy
time
space
structure
substance
Figure 3. Biological effects arranged according to
size/hierarchy.
478 Biomimetics: its practice and theory J. F. V. Vincent and others
J. R. Soc. Interface (2006)

levels of complexity—from a cellular organelle to an
ecosystem, from a single transistor in a microcontroller
to a fleet of aircraft. The biological data have to be
structured into a framework that is compatible with
technology to operate with this large amount of very
varied information. Initially, we designed auxiliary
conflict matrices for biological structures and environ-
ments, and for causes and limits of actions. These allow
us to break natural data into engineering-like chunks of
information and cover the primary TRIZ components of
‘function’, ‘effect’ and ‘conflict’. The matrix we have
developed takes account of:
— an object and its parts (which are accounted for
in the TRIZ contradiction matrix);
— the environment in which the object operates;
— the limits and causes of action;
— the ultimate purpose of action;
— the resources and auxiliary systems involved.
It incorporates the ideas of several TRIZ tools within
a single context, and is thus not only a database of
physical effects, but also a database of intention and
motivation. This is needed because biological systems
are teleological. Their goal is a condition that enhances
the reproduction of the individual. Thus, no biological
system can be described as having only emergent
behaviour. Although a computer model can describe
the behaviour of ants or termites in the apparent absence
of a target state, the goal h as been set by the
experimenter. In real life, the goal is set implicitly by
the individual organism or by its forbears, and the
function of a biological system is the action needed to
achieve a useful or desired condition. In technical
systems, the achievement of the goal is delegated to a
technical device, but the goal remains the same: the
future condition of the system. So, the function of a
technical system is the action needed to achieve a useful
or desired condition with the help of a technical device.
The technical effect is equivalent to the use of tools, a
phenomenon observed in many mammals, birds and
insects. Technology is not uniquely human. An isolated
technical system cannot set its own goals, although a
machine with embedded logic functions could transgress
this differentiation (Vincent et al.2005).
6. BIOMIMETICS USING TRIZ
We need to show that the introduction of biology into
TRIZ does not compromise its ability to solve engineer-
ing problems and yet makes it compatible with the
natural solutions to various problems from biology. This
is best shown with a case study. The sequence of solving
the problem is:
(i) define the problem in the most general, yet
precise way. It is essential to avoid specific
directions of thought or premature solution of
the problem. One should also avoid special
terminology, because it inevitably confines the
thinking space to the existing (i.e. conventional)
sphere. Then list the desirable and undesirable
properties and functions;
(ii) analyse and understand the problem and so
uncover the main conflicts or contradictions.
The technical conflicts are then identified in the
TRIZ matrix
2
and listed. Find the functional
analogy in biology (look into the PRIZM) or go to
the biological conflict matrix (table 2);
(iii) compare the solutions recommended by biology
and TRIZ. Find the common solutions for
biological and engineering fields. List the techni-
cal and biological principles thus recommended;
(iv) based on these common solutions, build a bridge
from natural to technical design. To make the
technical and biological systems compatible,
make a list of their general recommended
compositions;
(v) to create a completely new technology, add to the
basic TRIZ principles some pure technical or pure
biological ones (e.g. those listed in appendix 1—
electronic supplementary material).
6.1. Case study: the cat’s claw wheel
In many areas, the winter temperatures go below 0 8C,
leading to dangerously icy road conditions. But the
spikes or chains often attached to wheels for the whole
winter damage ice-free roads. It is inconvenient to be
changing continually between special winter and sum-
mer tyres or putting chains on and off the wheels. It
would be better to have an instantly changing tyre,which
would be a conventional rubber tyre on an ice-free road
and able to generate high friction on an icy surface.
Thus, we have a typical TRIZ conflict, with require-
ments to be soft and smooth and to be solid, hard and
sharp. It is also possible to formulate our problem as: ‘we
need adequate friction between a wheel and a road under
variable road surface conditions.’ The friction must also
vary without the weight of the vehicle changing. Now
follow the steps above and try to find a biomimetic
solution. How can we maximize the grip of the tyre to the
road surface under all driving conditions? How can we
change the gripping mode instantly when the type of
surface changes? A relevant functional biological proto-
type would be a cat’s paw with claws that can be
withdrawn, allowing the soft pad to contact the ground.
Figure 4. The ‘cat-paw’ wheel, (a) inflated and (b) ready for
icy surfaces.
2
The classical TRIZ contradiction matrix, at 39!39 elements, is
much larger than the PRIZM matrix, more detailed and more difficult
to use. It is available from many sources (e.g. TRIZ Journal on the
Internet) and so is not provided here.
Biomimetics: its practice and theory J. F. V. Vincent and others 479
J. R. Soc. Interface (2006)

Let us compare the suggestions from the conventional
39!39 TRIZ matrix with our 6!6 PRIZM TRIZ and
biological matrices (tables 2 and 3).
The conflict is that force in contact with the road
should increase (feature 10) but not by increasing the
weight of the vehicle (feature 1), which would be the
usual way to increase the normal force, with the TRIZ
matrix suggesting IP 1 Segmentation;IP8Anti-weight;
IP 18 Mechanical vibration and IP 37 Thermal expan-
sion. The solutions suggested by nature from the Bio-
TRIZ matrix are:
—IP1Segmentation: the cat’s paw is segmented into
several pads and claws;
—IP 3 Local quality: the paw is not sharp in its
entirety, but only at some points—at the operating
zones of the claws;
—IP 14 Spheroidality or curvature: the pads are
spheroidal, the claws are curved;
—IP 15 Dynamics: the claws can be deployed or
retracted at will;
—IP 17 A nother dimension: giving the contact
surface a third dimension, i.e. the soft paw pad
with the retracted claws is quasi-planar; when the
claws are deployed the paw moves into the third
plane.
Alternatively, we can reduce the contact area to
maximize ground contact stress (feature 5) without
changing the weight of the vehicle (feature 1): how to
minimize contact surface area without losing weight of
the object—the field 5/1 in the TRIZ matrix. In this
case, TRIZ r ecommends IP 2 Taking out;IP4
Asymmetry;IP17Another dimension and IP 29
Pneumatics and hydraulics. Solutions from the Bio-
TRIZ matrix repeat those above:
—IP3Local quality;
—IP15Dynamics;
—IP17Another dimension.
These again suggest versatile claws, which can be
retracted and protracted according to necessity.
The third conflict can be formulated as: how can the
wheel possess the quality sharpness only under icy
conditions and/or how to grip the road surface, or how
to reduce t he ground contact area without losing
adaptability and composition stability. This points to
fields 5/35 and 5/13 in the TRIZ conflict matrix, and IP
2 Taking out;IP11Prior cushioning;IP13The other
way round;IP15Dynamics;IP30Flexible shells and
thin films and IP 39 Inert atmosphere. The Bio-TRIZ
matrix recommends
—IP1Segmentation;
—IP17Another dimension;
—IP19Periodic action.
Overall, the principles held in common between the
three conflict pairs are IP 1, IP 15 and IP 17. This
suggests that sharp and soft parts should be segmented
and/or alternately structured (arranged in space),
perhaps as multiple claws and pads. These alternating
units should be alternated in time as well, in other
words, soft and sharp modes of operation of the wheel
should be switched on and off in time. And eventually,
IP 17 clearly indicates the necessity to design some
spikes (claws, serrations, teeth and so on) to provide
adequate grip for the wheel. All this shows that we
should design the wheel/tyre with spikes, which will
operate like cat’s claws—dynamically, according to the
prevailing road conditions. The wheel and tyre already
possesses IP 29 Pneumatics and hydraulics and IP 30
Flexible shells and thin films—the flexible pneumatic
rubber tyre. IP 2 Taking out should be also employed as
already recommended above. It means that the alter-
nated segmented parts due to their dynamics should
perform the ‘soft’ and ‘sharp’ modes due to the taking
out principle. And the last (but not least) point is that
one should pay attention to IP 13 The other way round.
It means that the supposed wheel with the retractable/
protractible claws is much easier to design vice versa—
the rigidly mounted claws are combined with the
inflatable/deflatable soft part, the pneumatic tyre.
Technically, it is much more convenient to inflate and
deflate a tyre than to make sophisticated actuating
protraction and retraction mechanism for numerous
spikes. Eventually, the wheel would look like figure 4.
6.2. Other TRIZ tools in biomimetics
We have described the relevance of only one of the TRIZ
tools, the contradiction matrix, and related it to the
System Operator and hierarchy. TRIZ offers more
similarities between biology and engineering, notably
in its Evolutionary Trends series, where the tendency of
technical systems is to evolve towards increased
functional complexity and versatility, often with associ-
ated structural simplicity (Pahl & Vincent 2002). In
both technology and biology, control systems tend
towards decentralized feedback; skeletal structures tend
towards compliance and flexibility (although obviously
gravity exerts a constraint on this tendency). We have
Table 3. The degree of similarity in the inventive principles between technology and biology.
fields of operation substance structure space time energy information
substance 0.18 0 0.22 0.2 0 0
structure 0.36 0 0.73 0.25 0.29 0.28
space 0.18 0.17 0 0.25 0 0
time 0 0 0.2 0.22 0.18 0
energy 0.22 00000.36
information 000000
480 Biomimetics: its practice and theory J. F. V. Vincent and others
J. R. Soc. Interface (2006)

merely observed these remarkable parallels without
attempting analysis of any sort. It would be a fruitful
area for palaeontological comparisons and predictions,
and could either highlight constraints in biology that
had been overlooked, or could suggest evolutionary
trends in technology which biology has been able to
exploit more effectively or which technology has
ignored. A combination of functional analysis and the
identific ation of inventive principles gives a more
sophisticated method called Substance–Field (or Su-
Field or S-Field) analysis.
Other TRIZ tools are methods mostly to help sharpen
the definition of a problem and to ensure that the problem
is not wrongly named or identified, which could lead to
the adoption of a wrong or inappropriate solution.
7. CONCLUSION
Biomimetics is not a new way of adapting ideas from
biology, but it is currently empirical in its approach. If it
is to build on current successes, and to be able to serve
our technological society, then it needs some sort of
regularizing, best introduced as a set of common
principles. Such principles exist in TRIZ, and it is in
this area that there seems to be the most promise for
establishing a transparent method for technologists to
access biology, which they otherwise view as an arcane
and complex world. This is because while TRIZ was
developed as a systems approach for engineering,
biology is, itself, a system. The benefits to be gained
from biomimetics are not yet totally obvious, other than
to deepen the human race’s box of technical tricks.
However if, as our study (and indeed many other
studies) suggests, biological functions and processes are
less reliant on energy, then the implications could be
very significant. That this change in our approach to
technology and engineering could be achieved by
developing nanotechnology (see above) would surely
please Richard Feynman (1959).
We thank the EPSRC for funding this project.
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