The "Janus" feature/structure inspired by the ancient Roman double-sided protector is prominent in the field of materials science due to its unique "asymmetric" concept and flexible and adjustable characteristics. The emergence of numerous biomaterials based on Janus properties/structures provides a different approach to material design for complex biomedical scenarios. Gel materials with excellent water absorption, flexibility and biocompatibility in various biomedical applications have greatly increased, and the structural design and functional integration of gels have reached some bottleneck. The Janus properties/structures completely subvert the traditional concept of "homogeneous gel" and break the limitation of "two-sided consistency" in biomedical gels. The concept of "two-sided asymmetry" led by "Adhesion-antiadhesion properties" and "hydrophilic-hydrophobic properties" has emerged and expanded the broad biomedical application prospects of Janus gels. In this review, we first summarize the various structural characteristics of Janus gel materials and the preparation technology of these gels, and explore the secret behind Janus structures from the raw materials and design concepts. Secondly, different kinds of asymmetries, including “hydrophilic-hydrophobic properties”, “Adhesion-antiadhesion properties”, structural heterogeneity and other unusual asymmetry, are discussed to show the relationship between Janus characteristics and structure. The applications of advanced Janus gels in biomedical fields such as tissue repair, anti-adhesion, substance delivery, hemostasis and human activity sensing are emphatically reviewed. In addition, the latest challenges and possible future direction of Janus gel are proposed.

中文翻译：

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用于生物医学应用的 Janus 凝胶：进展和未来展望


受古罗马双面保护器启发的“Janus”特征/结构因其独特的“不对称”概念和灵活可调的特性而在材料科学领域中脱颖而出。大量基于 Janus 特性/结构的生物材料的出现为复杂的生物医学场景的材料设计提供了不同的方法。具有优异吸水性、柔韧性和生物相容性的凝胶材料在各种生物医学应用中大大增加，凝胶的结构设计和功能集成已达到一定的瓶颈。 Janus的性质/结构完全颠覆了“均质凝胶”的传统概念，突破了生物医学凝胶“双面一致性”的限制。以“粘附-抗粘附性能”和“亲水-疏水性能”为主导的“两侧不对称”概念的出现，拓展了Janus凝胶广阔的生物医学应用前景。在这篇综述中，我们首先总结了Janus凝胶材料的各种结构特征以及这些凝胶的制备技术，并从原材料和设计理念上探讨了Janus结构背后的秘密。其次，讨论了不同类型的不对称性，包括“亲水性-疏水性”、“粘附-抗粘附性”、结构异质性和其他不寻常的不对称性，以显示Janus特性与结构之间的关系。重点综述了先进的Janus凝胶在组织修复、抗粘连、物质输送、止血和人体活动传感等生物医学领域的应用。此外，还提出了Janus gel面临的最新挑战和未来可能的发展方向。