Colloidal gels, where nanoscale particles aggregate into an elastic yet fragile network, are at the heart of materials that combine specific optical, electrical and mechanical properties. Tailoring the viscoelastic features of colloidal gels in real-time thanks to an external stimulus currently appears as a major challenge in the design of "smart" soft materials. Here we present rheo-acoustic gels a new class of materials that are ultrasound sensitive. By using a combination of rheological and structural characterization, we evidence and quantify a strong softening in three widely different colloidal gels submitted to ultrasonic vibrations (with submicron amplitude and frequency 20–500~kHz). This softening is attributed to the fragmentation of the gel network into large clusters that may or may not fully re-aggregate once ultrasound is turned off depending on the acoustic intensity. Ultrasound is further shown to dramatically decrease the gel yield stress and accelerate shear-induced fluidization, thus opening the way to a full control of elastic and flow properties by ultrasonic vibrations.

中文翻译：

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流变声学凝胶：通过超声振动调整胶体凝胶的力学和流动性能

胶体凝胶是纳米级粒子聚集到一个弹性而又脆弱的网络中的胶体，是结合了特定光学，电学和机械性能的材料的核心。由于“外部”刺激，实时定制胶体凝胶的粘弹性特征目前似乎是“智能”软材料设计中的主要挑战。在这里，我们介绍了流变声学凝胶，它是一类对超声波敏感的新型材料。通过结合流变学和结构表征，我们证明并量化了三种不同的，经受超声振动（亚微米振幅和频率20-500〜kHz）的胶体凝胶的强软化作用。这种软化归因于凝胶网络破碎成大簇，一旦关闭超声，取决于声强，大簇可能会或可能不会完全重新聚集。进一步显示，超声可以显着降低凝胶的屈服应力并加速剪切诱导的流化，从而为通过超声振动完全控制弹性和流动性质开辟了道路。