Benjamin Franklin, Philadelphia's Favorite Son, was a Membrane Biophysicist


Biophysical Journal Volume 104 January 2013 287–291 287
Benjamin Franklin, Philadelphia’s Favorite Son, was a Membrane
Biophysicist
Da-Neng Wang,†‡* Heather Stieglitz,† Jennifer Marden,† and Lukas K. Tamm§{*
†The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine and ‡Department of Cell
Biology, New York University School of Medicine, New York, New York; and §Center for Membrane Biology and {Department of Molecular
Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
ABSTRACT Benjamin Franklin, mostly known for his participation in writing The Declaration of Independence and work on
electricity, was also one of the first scientists to seek to understand the properties of oil monolayers on water surfaces. During
one of his many voyages across the Atlantic Ocean, Franklin observed that oil had a calming effect on waves when poured into
rough ocean waters. Though at first taking a backseat to many of his other scientific and political endeavors, Franklin went on to
experiment with oil, spreading monomolecular films on various bodies of water, and ultimately devised a concept of particle
repulsion that is indirectly related to the hydrophobic effect. His early observations inspired others to measure the dimensions
of oil monolayers, which eventually led to the formulation of the contemporary lipid bilayer model of the cell membrane.
As a Founding Father of the United States of America,
statesman, philosopher, diplomat, inventor, and scientist,
Benjamin Franklin (1706–1790) had an amazing life (1,2).
Born in Boston, Franklin moved to Philadelphia at the age
of 17 and began working in local print houses. He was
soon heralded as a favorite son of Philadelphia because of
his literacy, devotion to learning, community service, and
leadership (Fig. 1). His experiments on the electric proper-
ties of lightning are much renowned; however, less well
known are his studies involving oil monolayers on water
surfaces and hydrophobic forces. As told in the book
Ben Franklin Stilled Waves: An Informal History of Pouring
Oil on Water with Reflections on the Ups and Downs of
Scientific Life in General by the late Charles Tanford (3),
a former president of the Biophysical Society (1979–
1980), Franklin’s experiments on oil monolayers were the
first of their kind and eventually led to the formulation of
the lipid bilayer model of the biological membrane.
OIL ON THE SEA

In 1757, Franklin was sent by the American House of
Assembly of Philadelphia to Great Britain to petition King
George II against the policies and activity of the Penn
family, the proprietors of Pennsylvania. Soon after leaving
New York harbor, the fleet of 96 ships encountered windy
weather, sending them ferociously rocking over the waves.
Franklin noticed that two of the ships in the fleet were
sailing much more smoothly than the rest and inquired
from the Captain a reason for the anomalous smooth sailing
Submitted November 8, 2012, and accepted for publication December 10,

2012.

*Correspondence: wang@saturn.med.nyu.edu or lkt2e@virginia.edu

Note: This article is published on the occasion of the 57th Annual Meeting

of the Biophysical Society, held February 2–6, 2013 in Philadelphia.

Editor: Brian Salzberg.

� 2013 by the Biophysical Society
0006-3495/13/01/0287/5 $2.00
(4). ‘‘The cooks . have, I suppose, been just emptying their
greasy water through the scuppers, which has greased the
sides of those ships a little,’’ the captain told him in
a matter-of-fact tone. (Apparently, pouring olive oil on
rough water was known since the Classical Era to have
a calming effect and was a common way for seamen to
weather storms (5), although the practise was connected
with magic and fanciful explanations. Plutarch attributed
to Aristotle that ‘‘the oil produces calm by smoothing the
water surface so that the wind can slip over it without
making an impression’’ (6).) The incident piqued Franklin’s
curiosity, perhaps partially because it reminded him of the
wax he played with as a 10-year-old apprentice in his
father’s soap-making shop. However, he did not quite agree
with the captain’s rationale that ship-greasing was the cause
of the water-calming effect, but was unable at the time to
think of another explanation.

During later trips he observed the phenomenon again and
again and like any good scientist, Franklin performed a liter-
ature search to find anything he could about the phenom-
enon and its underlying cause (4): ‘‘I at times revolved in
my mind, and wondered to find no mention of them in our
books of experimental philosophy.’’ Therefore, Franklin
‘‘resolved to make some experiment of the effect of oil on
water, when I should have opportunity.’’
MONOLAYER OF OIL ON A LAKE

Over the next decade, Franklin continued his distinguished
work on lightning for which he was eventually awarded
the Copley Medal, a first for any scientific work carried
out in North America. Previous winners of this most presti-
gious honor from the Royal Society included Franklin’s
long-time hero, Isaac Newton. Possibly because he was
encouraged by his recent successes or the opportunity
finally arose, in 1769, the same year Franklin published
his book, Experiments and Observations on Electricity,
made at Philadelphia in America, he decided to revisit his
http://dx.doi.org/10.1016/j.bpj.2012.12.028

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FIGURE 1 Benjamin Franklin of Philadelphia, L.L.D., F.R.S., in

between 1763 and 1785, during the period when he carried out his experi-

ments of oil on water (by Edward Fisher, 1730–ca.1785). Print shows

Benjamin Franklin, three-quarter-length portrait, seated at desk, looking

to his right at an electrical device; in his left hand are papers upon which

he is taking notes, and visible through a window to his left is lightning

striking a building (Courtesy of the Library of Congress, Washington, DC).

288 Wang et al.
questions on the water-calming effect of oil that he had been
pondering for over a decade.

While staying in the Clapham Common area in south
London during another trip to Great Britain, he and his
merchant friend Christopher Baldwin went to lake Mount
Pond, located near Baldwin’s home (7). There they started
the experiment that is best described by Franklin’s own
words (4):

‘‘At the length being at Clapham where there is, on the
common, a large pond, which I observed to be one
day very rough with the wind, I fetched out a cruet
of oil, and dropt a little of it on the water. I saw it spread
itself with surprising swiftness upon the surface .
and there the oil, though not more than a teaspoonful,
produced an instant calm over a space several
yards square, which spread amazingly, and extended
itself gradually till it reached the lee side, making all
that quarter of the pond, perhaps half an acre, as
smooth as a looking-glass. . [The oil layer was]
Biophysical Journal 104(2) 287–291
so thin as to produce the prismatic colors, for a con-
siderable space, and beyond them so much thinner
as to be invisible, except in its effect of smoothing
the waves at a much greater distance.’’

Franklin had actually discovered a layer of oil that was
a single-molecule-thick!

As a good experimentalist, Franklin did not forget to
repeat his experiment at other locations and under different
conditions, and was able to reproduce his results (4). ‘‘After
this, I contrived to take with me, whenever I went into the
country, a little oil in the upper hollow joint of my bamboo
cane, with which I might repeat the experiment as opportu-
nity should offer; and I found it constantly to succeed.’’
THE HYDROPHOBIC FORCE

Franklin actually considered the underlying forces that
caused the oil to spread on the water surface (4):

‘‘In these experiments, one circumstance struck me with
particular surprise. This was the sudden, wide, and
forcible spreading of a drop of oil on the face of water,
which I do not know that anybody has hitherto consid-
ered. If a drop of oil is put on a polished marble table,
or on a looking-glass that lies horizontally; the drop
remains in its place, spreading very little.’’

In contrast, on a water surface, Franklin observed something
totally different:

‘‘If there be a mutual repulsion between the particles of
oil, and no attraction between oil and water, oil dropt
on water will not be held together by adhesion to the
spot whereon it falls; .it will be at liberty to expand
itself; and it will spread on a surface that, besides
being smooth to the most perfect degree of polish,
prevents, perhaps by repelling the oil, all immediate
contact, keeping it at a minute distance from itself;
and the expansion will continue, till the mutual repul-
sion between the particles of the oil is weakened and
reduced to nothing by their distance.’’

Importantly, Franklin further observed, ‘‘there seems to
be no natural repulsion between water and air, such as to
keep them from coming into contact with each other.’’

Clearly, Franklin understood that oil ‘‘particles’’ could
move freely at the interface between water and air and
that they reduced the tension between the two bulk phases.
The concept of molecules, which among others was
promoted by John Dalton in the early 1800s, was of course
not yet known during Franklin’s times and even the ideal gas
law attributed to Emile Clapeyron based on Amedeo Avoga-
dro’s law of 1811 was only formulated in 1834. What
Franklin actually observed was a monomolecular layer of
oil, which eventually expanded into a two-dimensional gas
of oil molecules at the air-water interface. When expanded



Franklin’s Oil Monolayer 289
into the more condensed liquid monolayer state, Franklin
observed a reduction of surface tension, which caused
the oil’s wave-calming effect and which is at the source of
the hydrophobic forces or hydrophobic effect as they were
realized later. Therefore, Franklin’s experiment may well
be the first experiment on the nature of the hydrophobic
effect!

Franklin was eager to understand such forces (4). ‘‘The
quantity of this force, and the distance to which it will
operate, I have not yet ascertained; but I think it a curious
inquiry and I wish to understand whence it arises.’’ Of
course, the underlying molecular nature of the hydrophobic
effect was, understandably, to remain unclear for another
150 years (8,9).
FIGURE 2 Structure of a major component of olive oil, triolein (1,2,3-

(9Z-octadecenoyl)-glycerol). Three oleate chains are ester-linked to a

glycerol moiety at the bottom, which contacts the water surface when

spread as a monolayer. (A) Chemical structure. (B) Space-filling model.
MEASUREMENTS OF MONOLAYER THICKNESS

Franklin did not go on to calculate the thickness of the oil
monolayer, although he did mention ‘‘particles spreading
on the water surface’’ (4). Had he done this he would have
predated the first measurement of the physical dimensions
of a molecule by over 100 years. The fact that he did not
attempt the calculation is a bit puzzling, however, for
Franklin must have had the conceptual computational
knowledge required. In Philadelphia, he once calculated
the audience size for a popular priest, who had a clear and
very loud voice, by measuring the furthermost distance
one could hear his voice and by estimating the surface
area that one person occupies (1). Franklin found that
he could still distinctly hear the preacher’s voice up to
a distance of 200 feet. He then determined that by
‘‘imagining then a semi-circle, of which my distance should
be the radius, and that it were fill’d with auditors, to each
of whom I allow’d two square feet, I computed that he
might well be heard by more than thirty thousand.’’ Both
calculations are the same type of close-packing problems
that occur on a two-dimensional flat surface. However, the
actual experimental measurements of a molecule’s dimen-
sions would have to wait until a British Lord and a German
amateur scientist entered the scene (3,7,10).

Lord Rayleigh (1842–1919), then Professor of Natural
Science at the Royal Institute in London, was a physicist
with many interests who made contributions to multiple
areas of science, from optics and electromagnetism, to
photography and liquid capillarity. He found the question
of oil spreading on a water surface to be ‘‘of great interest
which attaches to the determination of molecular magni-
tudes, [and] the matter seemed well worthy of investiga-
tion’’ (11). In March, 1890 he published his experiments
on the thickness of an olive oil monolayer performed in
a round sponge-bath (Fig. 2). He found that 0.81 mg of olive
oil was just enough to cover the entire surface area of
the bath with a diameter of 84 cm. Using a density of
0.9 g/mL, Lord Rayleigh obtained 16.3 Å as the thickness
of the olive oil monolayer (5,11).
The accuracy of Rayleigh’s measurements improved
significantly when a self-taught scientist, Agnes Pockels
(1862–1935), approached Lord Rayleigh when she saw his
1890 paper in the Royal Proceedings. Pockels was born in
Venice but grew up in Lower Saxony, Germany. Even
though she had no formal training and suffered various
health problems during her life, Pockels developed a strong
interest in surface chemistry and physics (3,10). Working
totally on her own, at the age of 20 she invented a tin trough
with a sliding barrier that was used to measure surface
tension by means of the force required to pull a small disk
(a button) from contact with the surface. This trough is
considered to be a precursor of the more famous Langmuir
trough of 1917, as also acknowledged by Langmuir himself.
When Pockels sent to Lord Rayleigh her experimental
results that she obtained independently and literally at her
kitchen bench, he immediately arranged for their publica-
tion in the journal Nature (12,13). Pockels’ original experi-
ments were actually carried out between 1882 and 1890, i.e.,
they predated Lord Rayleigh’s experiments (10). Pockels
measured the first pressure-area diagrams of lipid mono-
layers with her device. By identifying the drop in surface
tension when a specified amount of oil was applied, she
calculated the thickness of the oil film to be 13 Å. Guided
by Agnes Pockels’ findings, Lord Rayleigh subsequently
improved his own measurements of molecules in surface
films (14). These accomplishments by the famous future
Nobel Laureate Lord Rayleigh and Miss Pockels, a self-
educated scientist who as a woman was denied higher
Biophysical Journal 104(2) 287–291



290 Wang et al.
education and never held any academic position, using very
simple techniques, were extraordinarily ahead of their time.
They measured sizes of molecules even before the discovery
of x-rays, which would be used decades later to accurately
measure molecular dimensions of lipid films as well as
many other molecules. (Agnes Pockels’ accomplishments
were recognized by the German academic establishment
only much later. In 1932, shortly before her 70th birthday,
she was awarded her well deserved if belated honorary
doctorate from the University of Braunschweig in her home-
town (10).)

Then entered on the scene the great American chemist and
physicist and future Nobel Laureate, Irving Langmuir
(1881–1957). Langmuir was working at the General Electric
Research Laboratory in Schenectady, New York, where he
initially worked on the improvement of light bulbs by filling
them with gases. His work on the surface chemistry of gas
adsorption to metals (motivated by understanding the proper-
ties of tungsten wires in gas-filled light bulbs) and his famous
experimental and theoretical work on the physical chemistry
of adsorption also piqued his interest in the chemistry of oil
films. By inventing the Langmuir trough of similar design to
that of Miss Pockels with the addition of a pressure-
measuring device attached to a fixed barrier, he was able to
accurately measure the effect of various compounds on
water’s surface tension (15,16). This in turn provided
a way to investigate both the water-oil interaction and the
properties of oil monolayers at the air-water interface,
including the monolayer thickness and cross-sectional areas
of many amphiphilic molecules including membrane lipids.
CALMING WATER WAVES

Following Franklin’s experiments, thoughts about the
underlying reasons for the calming effect of oil on water
waves progressed in the late 19th century. A Scottish mete-
orologist named John Aitken expanded on Franklin’s obser-
vation and proposed that it is ‘‘not the bite, grip or friction of
the air on the surface’’ that was reduced when oil was poured
on water as had been believed by many of his predecessors,
but that it is the surface tension on the water surface, or the
lack of it upon the spreading of oil, that accounts for the oil’s
wave-calming effect (17,18). This is best explained by Lord
Rayleigh (5):

‘‘Let us consider small waves as propagated over the
surface of clean water; as the waves advance, the
surface of the water has to submit to periodic exten-
sions and contractions. At the crest of the wave the
surface is compressed, while at the trough it is
extended. As long as the water is pure there is no force
to oppose that, and the wave can be propagated
without difficulty; but if the surface be contaminated,
the contamination strongly resists the alternating
stretching and contraction. It tends always, on the
Biophysical Journal 104(2) 287–291
contrary, to spread itself uniformly; and the result is
that the water refuses to lend itself to the motion
which is required of it. The film of oil may be
compared to an inextensible membrane floating on
the surface of the water, and hampering its motion;
and under these conditions it is not possible for the
waves to be generated, unless the forces are very
much greater than usual.’’
FROM MONOLAYER TO BILAYER AND BEYOND

Initially, Langmuir’s work attracted little attention from biol-
ogists, but one Dutch pediatrician, Evert Gorter, saw the
important implications for Biology almost immediately
(3,19). In 1925, he and his graduate student François Grendel
published a short paper describing their measurements of the
total area of lipids extracted from red blood cells by
spreading the lipids as a monolayer on water (20). They
compared this to the total surface area of the red blood cell
membrane and obtained a ratio of two. This seminal work
provided the first evidence that the cell membrane may
consist of a phospholipid bilayer. Although their conclusions
were correct, Gorter and Grendel were lucky. Due to tech-
nical limitations and the limited knowledge of biological
membranes at the time, they made a few ‘‘mistakes,’’ which
however canceled each other out (21). Contemporary lipid
extraction procedures allowed them to quantitatively extract
only about half of all lipids present in the red cell membrane.
This underestimate was compensated by the chosen film
balance surface pressure, which we now know was much
too low to simulate the area/lipid in a bilayer. Aditionally,
an underestimate of the red blood cell surface was counter-
acted by the fact that a substantial fraction of the total area
of cell membranes is occupied by membrane proteins.
Despite these shortcomings, the ratio of two is still true
and the concept of the lipid bilayer was born.

In the 1940s, the newly-invented electron microscope
provided the first picture of a cell at a magnification and
resolution high enough that its membrane could be visual-
ized. Improved resolution allowed researchers to discover
the ‘‘tri-laminar’’ ultrastructure of membranes in the late
1950s, which however was initially incorrectly interpreted
in terms of lipid and protein arrangements (22). In the
1960s, a wealth of classical x-ray diffraction experiments
on lipids in excess water by Vittorio Luzzati firmly estab-
lished that the lipids in biological membranes are organized
in bilayer structures with liquid acyl chains (23). Based on
a multitude of biochemical and functional experiments
and additional electron microscopy, x-ray diffraction, and
thermodynamic and spectroscopic data, the fluid mosaic
model of the cell membrane eventually became widely
accepted (24).

With the development of new concepts and novel technol-
ogies, our understanding of biological membranes is making



Franklin’s Oil Monolayer 291
rapid progress (25). But it is with the same curiosity that
Benjamin Franklin displayed at sea and on a lake 250 years
ago that the advance of science today is driven. Research on
membrane biophysics, pioneered by Mr. Franklin, has gone
a long way in answering fundamental questions in biology
and medicine and, yet, still more discoveries lay ahead.

D.-N.W.’s work is supported by National Institutes of Health grants No.

R01 DK073973, No. R01 GM093825, No. R01 MH083840, No. R01

DA019676, and No. U54 GM075026. L.K.T.’s work is supported by

National Institutes of Health grants No. R01 GM51329, No. R01

AI30577, and No. P01 GM72694.
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Biophysical Journal 104(2) 287–291


	Benjamin Franklin, Philadelphia’s Favorite Son, was a Membrane Biophysicist
	Oil on the Sea
	Monolayer of Oil on a Lake
	The Hydrophobic Force
	Measurements of Monolayer Thickness
	Calming Water Waves
	From Monolayer to Bilayer and Beyond
	References