References
[1] Mabuchi, K., Tanaka, K., Uchijima, D., Sakai, R. Frictional Coefficient Under Banana Skin (2012).
Tribology Online, Japanese
Society of Tribologists
. DOI: 10.2474/trol. Retrieved from
peel face down. The slipping scenario was then
simulated by rubbing the peel with a forward sliding
motion of the sole of a shoe upon contact. A force
transducer was secured under the linoleum plate to
measure the magnitude of the forces in the x and
y directions to determine the coefficient of friction
(µ) between the contact surface and the ground. A
lower coefficient of friction implies that the surface
is more slippery. The experiment was repeated
five times with twelve banana skins. It turns out
that the addition of a banana skin dramatically
reduced the friction between the shoe and the
surface by up to 80%, with the resulting µ to be
at about 0.066 – a value that is significantly lower
than general surfaces and comparable to well-
lubricated surfaces (0.1). To put this into perspective,
the banana peel was found to be as slippery as
skating on ice, validating the general consensus
that banana skins are indeed slippery.
The lubricating property of the banana skin
is due to its branches of follicular gel, composed
of polysaccharides and proteins, held together
by the skin. When the skin is compressed during
slippage, the cellulose membranes of the follicles
are crushed, releasing the follicle gel and creating
a homogenous solution. This solution forms a
lubricating fluid film between the shoe and the
surface that decreases friction.
While this experiment simulates the scenario
well, it does not take into account the age of the
banana skin. For instance, one is less likely to slip
when a banana skin is dried or when the surface
is rough. A dr y banana sk in has lower water
content, and hence a lower volume of follicular gel.
Furthermore, if the surface of the floor is too rough,
its irregularity disrupts the layer of the fluid film and
increases the coefficient of friction. It also does not
take into account the difference between static
and dynamic friction. The above experimental set-
up measures the dynamic friction between the
inside of the banana peel and the surface. In a
real life scenario, when someone steps on the peel,
the friction involved is static. It is known that static
friction can be larger than dynamic friction, thus
the danger of banana peels may be overestimated
in this experiment.
So there you have it. The notion of slippery
banana skins indeed holds some truth. Aside from
this being a funny shower thought though, experts
say that the research has the noble potential to
bring about new types of lubricants or provide
insight into bioengineering lubricating joints for
arthritis.
蕉皮的潤滑性歸功於所含的囊泡凝膠。凝膠由多糖和
蛋白質組成，平時鎖於蕉皮內。當蕉皮受壓時，囊泡的纖維
素膜破裂，凝膠流出成為均勻溶液，在鞋與地面之間形成一
層流體潤滑膜，減低摩擦力。
雖然這個實驗很好地模擬了踩蕉皮的情境，卻沒有考慮
到蕉皮的新舊程度。比如說，蕉皮太乾的話，囊泡多糖凝膠
的體積便會因水份不足而減少，潤滑效果自然就不明顯。此
外，若果地面過於粗糙，流體薄膜受到破壞，潤滑功能也未
必能發揮。另外，這個實驗並未考慮靜態和動態摩擦之別。
實驗量度的是蕉皮內側和接觸面之間的動態摩擦。可是在
現實中，我們踩蕉皮時所涉及的摩擦是靜態的，而靜態摩擦
是可以比動態摩擦強，因此這實驗有可能高估了踩蕉皮的
危險。
好了!現在大家明白踩到蕉皮會滑倒，是確有其道理!除
了提供趣味小知識，專家指出這研究還有更深遠的意義，可
以帶來新型的潤滑劑，亦會有助設計更潤滑的關節。
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