Research by UC Berkeley engineers unravels why shoelaces get untied

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Research conducted by a team of mechanical engineers at UC Berkeley has unveiled why shoelaces become untied.

According to the research paper, failure of the knot happens “in a matter of seconds.” Slow-motion footage revealed that the repeated impact of the shoe on the floor serves to loosen the knot, while the whipping motions at the free ends of the laces produce the slipping of the laces.

Titled “The roles of impact and inertia in the failure of a shoelace knot,” the self-funded research was co-authored by Oliver O’Reilly, campus professor of mechanical engineering, and campus graduate students Christopher Daily-Diamond and Christine Gregg.

According to Gregg, the main motivation behind the study was scientific curiosity. Daily-Diamond said his interest in the study was sparked when Gregg showed O’Reilly a TED talk titled “How to tie your shoes.”

“My co-author’s … and I were all plagued by untied shoelaces,” Gregg said in an email. “Specifically, Oliver was intrigued after teaching his daughter to tie her shoes, and realizing that he didn’t want hers to always come undone like his do.”

To conduct research, the team made use of a high-speed camera and a treadmill in the Recreational Sports Facility to film Gregg running. The researchers were able to watch in “great detail how the knot failed,” according to Gregg, and subsequently form a hypothesis. They tested their hypothesis using a pendulum to simulate walking. The pendulum test was done in the lab of Gregg’s adviser, Paul Wright, in Etcheverry Hall.

According to O’Reilly, he and his team conducted research for this study in their spare time over a period of three years, using equipment and space provided by both the department of mechanical engineering and the RSF.

Tarek Zohdi, a campus professor of mechanical engineering not affiliated with the study, said in an email that the study is “in depth,” “useful” and “highlights the wide-ranging interests of (campus) faculty.” Zohdi added that he believes the research can be used to design better sporting equipment and reduce accidents.

Although the full implications of this research are still unknown, having a basic understanding of the dynamics of tying laces and knots can be useful, according to Daily-Diamond. Additionally, the research can have implications in DNA folding and surgery sutures, according to Gregg.

Gregg also said in an email that although this is the first study of its kind, the reason behind why “certain knots are better than others from a structural perspective” is still an open question. Gregg added that she hopes the research serves as a stepping stone for further investigation in this area.

According to O’Reilly, the team is overwhelmed by the amount of attention their work has generated from both the public and the media.

“The three of us are immensely grateful to UCB for giving us the freedom and opportunity to explore the mystery of why your shoelaces can untie while walking,” O’Reilly said in an email.

Contact Azwar Shakeel at [email protected] and follow him on Twitter at @azwarshakeel12.