A research team led by Professor Hezhou Liu and Professor Yujie Chen from the School of Materials Science and Engineering at Shanghai Jiao Tong University, in collaboration with Professor Ximin He's team at the University of California, Los Angeles (UCLA), has made significant progress in the preparation and synthesis of damping hydrogels. The team proposed a novel strategy combining dense entanglement domains with steric hindrance, enabling the development of high-performance damping hydrogels with excellent impact protection and vibration suppression capabilities. The findings were published in Nature Communications, a leading international interdisciplinary journal, under the title: "Amplified Friction via a Cooperative Entanglement Domains and Steric Hindrance for Damping Hydrogels." The first co-authors are Ph.D. students Zimo Pang and Sijia Li. The corresponding authors are Researcher Yujie Chen, Professor Ximin He, and Professor Hezhou Liu.

Hydrogel materials, known for their tunable modulus and high extensibility, hold broad application potential in fields such as soft robotics, electronic skin, and biomedical engineering. The damping performance of hydrogels—critical for absorbing vibrational and impact energy and ensuring device longevity—has drawn increasing research attention. By leveraging ionic interactions or solvent–polymer network interactions, researchers have developed numerous ionogels and organogels with excellent energy dissipation properties. However, the practical application of ionic liquids and organic solvents is hindered by their significant environmental and biological toxicity, as well as the high cost of ionic liquids. In contrast, hydrogels offer advantages in environmental friendliness and lower cost. Yet, the inherent lubricating effect of water molecules within the polymer network weakens intermolecular interactions, making the development of high-damping hydrogels a persistent challenge.

To address this issue, the team proposed a friction amplification strategy based on cooperative entanglement domains and steric hindrance. This approach simultaneously increases frictional resistance during chain sliding, expands the friction interface, and enhances interchain interactions. In this design, entanglement domains act as amplifiers, significantly raising the energy barrier for chain sliding imposed by steric hindrance. Unlike conventional strategies that rely solely on increasing the density of binary entanglement points—which offer limited energy dissipation—this new strategy achieves an order-of-magnitude increase in damping capacity (a 610-fold improvement), while maintaining high damping efficiency (96.3%) and a substantial loss factor. The team further demonstrated that this strategy significantly improves the mechanical properties of hydrogels, exhibits broad generalizability, and holds promising potential for impact protection and vibration suppression applications.

Fig. 1 | Concept of friction amplification strategy for hydrogels.

Fig. 2 | Preparation process of friction-reinforced and comparative hydrogels.

Fig. 3 | Friction-reinforced PMOTAC hydrogel and its comparative hydrogel.

Fig. 4 | Toughening mechanism of the friction-reinforced PMOTAC hydrogel.

Fig. 5 | Impact protection and vibration damping capabilities of PMOTAC.

Fig. 6 | Universality of the reinforced-friction strategy.

Specifically, the team developed a friction amplification strategy that geometrically amplifies interchain friction, thereby significantly enhancing the damping performance of hydrogels. This strategy relies on the synergy between dense entanglement domains and steric hindrance. The team emphasizes that both elements are indispensable for achieving the desirable combination of high damping efficiency and high damping capacity. Through this synergy, frictional dissipation enables an order‑of‑magnitude increase in damping capacity. Moreover, the domain-based structure plays a critical role in enhancing mechanical properties and releasing stored chain segments to alleviate stress concentration, endowing the hydrogels with exceptional toughness, high modulus, crack propagation resistance, and puncture resistance. These characteristics make the hydrogels highly suitable for load‑bearing structural components. Impact and vibration tests conducted under various scenarios demonstrate that the material can effectively attenuate impact forces, protect fragile objects, and rapidly suppress vibrations. The generalizability of this strategy has been validated. Future work will focus on more systematic studies exploring the integration of this structure with other hydrogel composites and investigating the corresponding mechanical properties. The combined advantages of these properties offer broad prospects for the development of ultra‑strong damping hydrogels.

In addition, recognizing the rapid development of the damping gel field yet the lack of systematic reviews—particularly insufficient summarization of fundamental characterization methods for damping gel design and damping testing—the team has systematically summarized the major advances and key challenges in the current damping gel field from the perspectives of characterization methods, energy dissipation design strategies, and application scenarios. These findings were published in the leading international materials journal Advanced Functional Materials under the title: "Advances in Damping Gel Materials: From Characterization and Design to Applications." Ph.D. student Zimo Pang is the first author, and Professor Yujie Chen and Professor Hezhou Liu are the corresponding authors.

Fig. 7 | Overview of the design strategy, testing method, and application of damping gels.