- Published in the world-renowned academic journal "Proceedings of the National Academy of Sciences of the United States of America" (PNAS)

- Revealing the secrets of swallow nests from an engineering perspective, a key clue to advancing 3D printing

▲ (From left) Dr. Jeong Yeonsu from Seoul National University,
Professor Kim Wonjeong from Sogang University, Professor Kim Hoyoung from Seoul National University

 

The scientific secrets of mud-made swallow nests, which can withstand over 100 times the weight of a swallow, have been revealed through an engineering approach.

A joint research team from the Department of Mechanical Engineering at Seoul National University (Dr. Jeong Yeonsu, PhD candidate Jeong Sohyun, Professor Kim Hoyoung), the Department of Mechanical Engineering at Sogang University (Professor Kim Wonjeong), and the Daegu Gyeongbuk Institute of Science and Technology (Professor Lee Sangim) uncovered the scientific secrets of swallow nests.

Every summer, the migratory bird swallow returns to its mud nest under the eaves. This nest shows that swallows are great builders but is often overlooked by people. From an engineering perspective, a swallow's nest is a masterpiece that optimally designs and construction using the most readily available materials. Birds that build houses securely attached to vertical walls, like swallow nests, are estimated to account for less than 5% of all bird species.

In order for the nest to adhere to a wall, it must withstand the downward force exerted by its weight and mud is naturally weak against pulling forces. The research team discovered that after a swallow mixes saliva and mud pellets, the saliva's polymer material acts as an adhesive, bonding the mud pellets together and greatly resisting pulling forces. Additionally, swallows reinforce the part of the nest that receives the most force. Thus, nests built in this way can withstand over 100 times the weight of the bird.

Besides, the way swallows build their nests is similar to 3D printing. 3D printing construction has recently been in the spotlight as a technology to quickly build buildings in places such as disaster sites. When swallows return for breeding and cannot reuse their nests, they must quickly build new ones. Similar to 3D printing, swallows rapidly construct nests by stacking materials (mud) layer by layer. This design is inherent to the swallow's instincts. Swallows are estimated to have been building nests for about ten million years, making them worthy mentors of 3D printing.

In "The Origin of Species", Darwin expressed surprise at the swallow’s nest-building instinct, speculating that “species of swallows that build nests using a mixture of mud and saliva may have gradually evolved through natural selection into species that build nests using only saliva.”. The engineering solution to the amazement and questions Darwin had 160 years ago has now been provided.

Research leader Professor Kim Hoyoung said, "Through the fusion of 3D printing technology mimicking the swallow's nesting technique, mathematical modeling, and biology, we have uncovered the scientific secrets of the familiar swallow's nest." and added, "This research will contribute to the advancement of bio-mimetic 3D printing technology using environmentally friendly materials."

The research findings were published in the prestigious international journal "Proceedings of the National Academy of Sciences of the United States of America" on January 12th.

 

■ Image Description

▲ A swallow nesting under a canopy in Suwon, Gyeonggi-do. The swallow's architectural skills, which allows it to nest anywhere,
has made coexistence with humans possible.

▲ An artificial nest 3D-printed in the same proportions as a swallow's nest.