标题： 凝胶喷射：软微凝胶网络稳定并延长无喷嘴水射流 显示英文标题

标题： Jetting with gels: Soft microgel networks stabilize and extend nozzle-free water jets

摘要： 高速液体射流的稳定性对于从精密打印到无针药物输送的应用至关重要，然而它本质上受到毛细管驱动破裂的限制。 稳定射流的一种常见策略是使用表面活性剂来降低表面张力。 然而，在由表面声波（SAWs）驱动的无喷嘴喷射中，极端的变形速率会导致常规表面活性剂脱附，因此需要替代策略来稳定射流。 特别是，我们发现调整PNIPAM微凝胶的纳米尺度柔软度提供了一种强大且生物相容的策略来克服这一限制。 柔软、低交联密度的微凝胶在气-水界面形成弹性界面网络，抑制表面张力恢复，延迟雷利-普拉特勒不稳定性，并将SAW驱动的射流长度延长高达44%。 相比之下，更硬的微凝胶在受力下失去网络凝聚力，导致射流迅速破裂。 为了获得分子级的见解，我们进行了耗散粒子动力学模拟，结果表明，在软微凝胶中，聚合物桥在拉伸过程中保持纠缠，维持较低的有效表面张力。 最后，一种简单的标度分析，平衡了SAW驱动传递给液滴的动能与形成射流所需的表面能，定量预测了观察到的长度增强。 这种无表面活性剂、生物相容的方法为长寿命射流奠定了基础，使无针药物输送、高速打印和其他高应变界面流动应用成为可能。 显示英文摘要

摘要： The stability of high-speed liquid jets is crucial for applications ranging from precision printing to needle-free drug delivery, yet it is fundamentally limited by capillary-driven breakup. A common strategy to stabilize jets is to use surfactants to lower surface tension. However, in nozzle-free jetting driven by surface acoustic waves (SAWs), extreme deformation rates cause conventional surfactants to desorb, calling for alternative strategies to stabilize jets. In particular, we find that tuning the nanoscale softness of PNIPAM microgels provides a robust, biocompatible strategy to overcome this limitation. Soft, low-cross-linker-density microgels form elastic interfacial networks at the air-water interface that suppress surface tension recovery, delay Rayleigh-Plateau instabilities, and extend SAW-driven jet lengths by up to 44%. In contrast, stiffer microgels lose network cohesion under strain, leading to rapid jet breakup. To gain molecular-level insights, we perform dissipative particle dynamics simulations, which reveal that polymer bridges in soft microgels remain entangled during elongation, maintaining a reduced effective surface tension. Finally, a simple scaling analysis, balancing the SAW-driven kinetic energy imparted to the droplet against the surface energy required to form a jet, quantitatively predicts the observed length enhancement. This surfactant-free, biocompatible approach lays the foundation for long-lived jets, enabling precision needle-free drug delivery, high-speed printing, and other high-strain interfacial flow applications.