LIMPET ADHESION BIOMIMICRY AND ADHESIVE ENGINEERING
Ivan Magdaleno*, Pablo Vazquez*, Nathan Laidig†, Koshy Varghese†, Dr. Mariappan Jawaharlal†
*Citrus Community College Stem2, †California State polytechnic University, Pomona Mechanical
Engineering Department
CONCLUSION
In order to better understand the glue-like mucus produced by the
limpets, a chemical analysis was performed. A test was conducted to
measure the shear force of the dried mucus. The chemical analysis tests on
the mucus samples gave us some important results. The shear test shows
that the Limpet mucus can withstand a weight of up to 30 psi. An FTIR
(Fourier Transform Infrared Spectroscopy) test was also conducted to
determine what kind of organic bonds were present in the sample. It was
found that the pedal mucus contained the presence of water molecules and
some carbon and oxygen bonds. A T-peel test of the mucus resulted in
observed adhesive qualities.
The final test was to measure the normal and shear force required to
pry off a Limpet from the adhering surface using a force gauge. It was
determined that the Limpets in the aquarium tank needed less force
compared to the Limpets in the wild. The Limpets in the tank only required
around 11 psi, which is just shy of atmospheric pressure. However, the
Limpets in the wild were observed to need a stress of around 47 psi. Note
that at this stress the Limpets did not come off. This was the point when
our measuring system failed. The Limpets were still clamping down on the
rocks.
Introduction
Below is a chart which displays an assortment of organisms, their
functions and possible real world applications that can possibly be achieved
using Biomimicry.
Limpet Function
Description
• Chemically
 The mucopolysachirides in the pedal mucus glands and
etching and
the mantle edge have carbonic anhydrase that is capable
softening calcium
of chemically etching and softening calcium carbonate
carbonate
and rocks before being scraped away by the radula.
(Lindberg and Dryer in prep.)
• Tooth as a self The softer back side and fiber orientation keeps the front
sharpening
harder edge of the tooth sharp and thus acting as a selfdevice
sharpening device. (Runham, Thornton, Shaw and Wayte
1969)
 The radula is capped with goethite, having a hardness of
about 5 units in the Mohs scale. (Lindberg and Dryer in
prep.)
• Excavating rocks  The formidable structures of the radular teeth are
and removing
capable of excavating rocks and removing microflora in
micro flora
crevices or rock surface. (Branch 1981)
How Limpets Work
A limpet is an aquatic gastropod mollusk found almost exclusively in
the intertidal zone of the ocean. They are similar to sea snails such that a
limpet has a shell, a foot, and eats algae. The limpet is able to clamp
tightly to surfaces, using both an adhesive mucus and suction, in order to
protect its self from predators, desiccation in low tides, and prevent being
washed away by the crashing waves. By combining both functions, a limpet
is able to move across a surface. These fastening techniques are described:
• Adhesive mucus- A mucus is secreted with viscoelastic properties that
prevents separation from the rock surface. This occurs typically in low
tides in protection from shear forces such as intense wave action.
• Suction- A muscular foot found under the shell creates a pressure
differential between the bottom of the foot and the surrounding setting.
This behavior is a response to resist normal forces, predators, and
desiccation at high tides.
Due to impressive Limpet adhesion strengths, the following tests were performed
to understand more about how quality adhesion is accomplished.
Cutting
Non-dulling tools
• Adherence Test Observation Qualitatively determined the
strength of the adhesive mucus
versus suction. The through holes
served the purpose to determine if
limpets used suction as a method of
adhesion.
Digging, cutting
into strong
surfaces
 Limpets use their shell for water storage as a cooling
method. (Vermeij 1973)
Cooling methods
Water storing
• Filter feeding
 Several Limpet species feed through filtration systems.
(Newell and Kofoed 1977a)
Filtration systems
• Adhesion
 The viscoelastic nature of the mucus behaves as a solid
and a liquid when needed to establish effectiveness in
adhesion. (Grenon and Walker 1978)
Adhesion
Adhesives
• Environmental
 The limpet is able to discriminate between mucus by
chemical analysis detecting polarity within the mucus. (Cook and Cook
1975, Cook 1969, Edelstam and Palmer 1950)
Studies
Softening rocks
Breaking apart
strong surfaces
• Water storage
• Force Study- Quantifying the
threshold force limpets are able to
withstand in either a normal or
shear direction.
• T-Peel test - A peak stress value of the mucus can be recorded and thus having
an idea of the limpet mucus strength
Neural Network
for
environmental
readings
• Shear test- Alternate method of quantifying peak stress values of the limpet
mucus in a shear resistive direction.
RESULTS
T-peel
Specimen 1
18
Through Hole (1/4 in)
Lost all suction. Still capable
of holding on because of
pedal mucus.
Specimen 4
Still has suction and
is still pretty firm.
Specimen 5
Lost suction the
Suction lost immediately.
moment it went over
the blind hole.
Specimen 3
15.6
16
Initially lost suction
and regained suction
as it covered the
hole.
Initially suction lost.
Regained suction as
it went over the
hole.
Lost suction initially.
Specimen 2
•Performing T-peel tests of limpet mucus exhibits
the peak force of adherence possible.
•6 T-peel tests were conducted
•two test with suction mucus.
•three tests with adhesive mucus.
•one test without any mucus.
•The suction mucus adds in strength to the
masking tape by about 34%.
•The adhesive mucus adds about 7.4%.
•The increase in strength of the tape strips can
strongly be justified by the addition of limpet
mucus, and thus proposing some strength in
adhesion.
T- Peel Mucus Peak Resistance Force
Adherence Test Observation
Limpet Specimens Blind Hole (1/4 in)
The imitation and replication of the functions found in nature does
not entirely capture the science that is Biomimetics. Biomimetics, or
Biomimicry, is a fairly new science which draws inspiration from designs
which are found in nature and used to solve human problems. Organisms
found throughout the earth have managed to do what we as humans do
without polluting or exhausting fossil fuels. Nature is the perfect model to
use in order to begin to address many modern problems through an
engineering perspective. One particular area of engineering that could
benefit from an analysis of nature is adhesion, since many commonly used
adhesives don’t break down completely after a useful life. A solution to this
problem can be achieved through the study of biomimicry on limpets.
Biomimicry
Application Ideas
Percent
pedal mucus
40%
14.75
14
Percent
Suction
60%
12.5
12.5
11.25
12
11.25
10
8
6
4
2
0
Suction lost immediately.
30%
70%
Suction lost immediately.
30%
70%
Just came off easily.
25%
75%
30%
70%
limpet,
suction
limpet,
suction
limpet,
adhesive
limpet,
adhesive
limpet,
adhesive
none
Mucus type
•Qualitatively determined that the strength of the adhesive mucus is less than suction.
•In response to through holes, limpets were observed to use suction as a method of adhesion.
Surface Area vs Stress of Limpet Failure
Stress vs area
40
30
Shear Test
37.7
33.9
35
•Shear and normal force tests were conducted in
23
25
Limpet natural habitat.
21
20
•9 detached limpets quantified the threshold force
15.6 15.3
14.3
15
of detachment.
10.9
10
7.57
•3 limpets were detached by an opposing shear
5
force
0
•6 limpets were detached by an opposing
0.00
0.10
0.20
0.30
0.40
normal force.
Surface Area (in2)
•The data in this category suggests the increasing relationship of foot surface
area to adherence stress.
•12 out of the 21 tested limpets were unable to be detached from the substratum
they adhered to.
•The testing methods utilized to detach limpets proved insufficient for these.
•Loctite used in our testing methods failed at higher foot surface area.
•A perverted quadratic polynomial relationship was produced due to failure in
testing methods
•The data trend suggests the linear relationship if better testing methods were
utilized.
Shear Test
Shear Stress
y = 489.7x2 - 347.4x + 67.853
R² = 1
Normal Stress
y = -323.82x2 + 154.14x + 0.1379
R² = 0.2098
0.50
Inspiring innovation by nature is the basis of Biomimicry. Nature is engineering’s
unexpected solutions. There is still much to uncover about limpet adhesion and
learning from that technology to incorporate possible applications in the
commercial and industrial world. The ideal situation would be developing a
completely biodegradable and wasteless recyclable product that doesn’t cost too
much. This would be a great stride toward integrating nature’s efficient perfection.
• Adherence Test Observation
•Limpets used suction and adhesive mucus as a method of adhesion.
•Suction adhesion mechanism of limpets is stronger than adhesive adhesion
mechanism in.
•Force Tests
•Better testing methods would enable more limpet detachment.
•The data trend suggests a possible increasing surface area to stress relationship
if better testing methods were utilized.
•The data of the 9 limpets that were able to be detached implied an increasing
relationship of foot surface area to adherence stress.
•T-peel
•The suction mucus adds in strength to the masking tape by about 34% and the
adhesive mucus adds about 7.4%.
•The T-peel tests propose some strength in adhesion qualities of Limpet mucus.
•More T-peel tests will allow ability to support mucus strength qualities.
•Shear Tests
•Results proved encouraging
•Use of an Instrom machine would allow constant pull force applied parallel to
the substratums.
• Various data can be obtained throughout the duration of the test.
•Coauthors, Nathan and Koshi, achieved peak readings of about 38 psi and 18
psi.
•The extremely tedious and time consuming characteristics of this endeavor labels
Limpet Biomimicry as a continuing project:
•Perform enhanced Force Tests and Shear tests
•Perform more T-peel, Shear, and Force tests
•During the course of our research several labs around the country and the globe
were contacted to have a chemical analysis done on a sample of limpet mucus. We
hoped for a better foundation of information to use in the development of an
adhesive. Numerous labs were unable to perform such a test. One response went on
to detail us why such a test would prove difficult and that determining the
chemical structure of limpet mucus would be a good “doctoral dissertation.”
Acknowledgements :
California State polytechnic University, Pomona Mechanical Engineering
Department
Nathan Laidig, Koshy Varghese, Dr. Mariappan Jawaharlal, Dr.
Cabrillo Marine Aquarium
Dr Kiersten Darrow and Staff
Citrus Community College RACE to STEM Program
Lucia Riderer, Dr. Marianne Smith, and Staff
References:
0.60
0.70
20
19
18
16
Peak Stress (psi)
The first experiment conducted was an adherence test to determine
the adhesion methods used by limpets. It was observed from our
experiment, that the Limpets used both suction and glue like pedal mucus
to adhere to the surface. It was qualitatively determined that the force of
adhesion due to the limpet mucus was less than the force due to suction.
The reason for performing the studies is to gain insight on the
mechanisms limpets use to successfully adhere to a substrate against opposing
forces. The information gained from these studies in limpet “technology” is
crucial for determining the strength of possible biodegradable adhesives
alternatives. This is one future direction of limpet Biomimicry.
Peak Force (N)
Biomimicry is the study of nature’s solutions and applying these to
human problems. The purpose of this project is to study adhesive
characteristics of limpets and possibly create an application for engineering
purposes using this data. We have been researching general information
about these creatures as well as technical papers on an assortment of
limpet characteristics. Tests to determine adhesion characteristics were
performed at Cabrillo Marine Aquarium. The tests performed were suction
and adhesive tests, chemical analyses of the pedal mucus, and different
directional force tests of limpet adhesion to a substratum. With this data,
we hope to design a unique prototype that utilizes limpet characteristics for
a biodegradable adhesive with quality performance and application.
Limpets inspiring Engineering
Stress (psi)
Abstract
Reason for Studies
14.8
14
12
10
8
6
4.04
4
2.25
2
0
1
2
3
Shear Test #
4
•The peak force reading was recorded when
the two adhered wood strips detached
•8 shear tests were performed
•4 shear tests could not be completed
due to failure of preserving adherence
•2 shear tests resulted in quality
readings
•2 shear tests resulted in erratic
readings
•Quality shear tests gave readings of 14.8
psi and 19 psi.
•Promising adhesion qualities are
observed
•Erratic shear tests gave readings of 4.04 psi
and 2.25.
•Contamination and a variety of factors
contributed to the failure and
perversion of these last tests.
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