Why is spider silk so strong? It's all thanks to this little trick of the spider →

Stills from the movie Spider-Man 2

You may have marveled at the magical spider silk shot by Peter Parker in the Spider-Man movie - it can pull up a runaway train, weave into a protective net tougher than steel, and even allow superheroes to swing freely between city skylines.

In nature, spiders are definitely low-key "material masters". They use tiny spider silk that is invisible to the naked eye to weave webs that are tougher than bulletproof vests. This seemingly fragile silk thread hides a secret that has fascinated scientists for a century.

Recently, a team from Northwestern University in the United States finally cracked the "spider silk code". In fact, the action of the spider gently pulling with its hind legs when spinning silk is actually a precise forging at the molecular level.

Spiders: Natural masters of fiber design

Spider silk is a filamentous substance made of spider silk proteins and auxiliary proteins secreted by the spinning apparatus at the end of the spider's abdomen. It solidifies and polymerizes when exposed to air and is used to weave webs or build other structures.

Spider silk can be used as a sticky trap to catch prey, to entangle and restrain prey before the spider hunts, to transmit tactile information, or as a nest or cocoon to protect offspring.

Spiders can use silk to suspend themselves from great heights, float through the air, or glide to avoid predators. Most spiders vary the thickness and stickiness of their silk, depending on its purpose.

Scientists have long been interested in spider silk research because of its excellent performance: its strength exceeds that of steel of the same diameter, its toughness is better than that of Kevlar fiber, and its elasticity is comparable to that of rubber. Spider silk is the "hexagonal warrior" in the material world. Spider silk is the strongest organic fiber, and its biodegradable properties make it an ideal material for medical use.

For example, it can be used as surgical sutures or wound closure adhesives, and these materials can then be harmlessly degraded naturally in the body. However, obtaining natural spider silk by breeding spiders is expensive, energy-intensive, and difficult to operate. Therefore, artificial synthesis of spider silk materials in the laboratory has become a research focus.

Over the years, researchers have successfully transformed microorganisms to produce spider silk proteins, and have produced artificial fibers comparable to spider silk by manually stretching engineered spider silk. Although we have mastered the "recipe" of spider silk, how the spinning process changes the fiber structure and strength remains a mystery.

Strengthening mechanism of spider silk: stretch-induced molecular ordering

Simulated stretched silk fiber diagram

The Northwestern University research team used molecular dynamics simulations to study how stretching changes the order of proteins, the connections between proteins, and the movement of molecules within the fiber. The study found that the stretching action of the spider's hind limbs during the spinning process essentially "aligns" the proteins, thereby increasing the overall strength of the fiber.

They also found that stretching increases the number of hydrogen bonds, which act as bridges between the protein chains that make up the fiber, contributing to the fiber's overall strength, toughness and elasticity. Compared to freshly produced silk, silk stretched to six times its initial length was significantly stronger.

This research not only cracked the mechanical code of spider silk, but also demonstrated the powerful vitality of interdisciplinary research. From gene editing in molecular biology, to spinning technology in fluid mechanics, to performance optimization in materials science, the integration of knowledge in multiple fields has led to revolutionary technological breakthroughs.

In the future, spider silk will be involved in all aspects of our lives, from seamless sutures in operating rooms to lightweight building materials for bases on Mars. This silk thread derived from spider spinners is weaving a tougher and more sustainable future.

When we marvel at the performance of spider silk, we should ponder the natural wisdom behind it. Spiders are not objects waiting to be imitated, but mentors spanning billions of years of time and space. What spins in their spinning organs is not just silk threads, but a set of survival strategies tempered by natural selection - using the least resources to obtain the greatest benefits, coexisting harmoniously with the ecosystem while meeting functional needs, which is the ultimate goal pursued by human engineering.

Humans may not need to imagine alien technology or anti-gravity engines. The code base written by life on Earth over 3.8 billion years contains countless technical codes to be solved. As the truth revealed by spider silk research, the greatest innovations often begin with humble observations of nature.

References:

[1]https://scitechdaily.com/stronger-than-steel-tougher-than-kevlar-spider-silks-secret-finally-revealed/

[2]https://www.sciencedaily.com/releases/2025/03/250307144702.htm

[3]https://www.science.org/doi/10.1126/sciadv.adr3833

[4]https://en.wikipedia.org/wiki/Spider_silk

Compiled by: Yang Yuxin

Planning: Liu Ying, Zhang Chao, Li Peiyuan, Yang Liu

Reviewer: Wang Chuanqi, Director of Science and Technology of the National Museum of Zoology