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High Frequency Sonoprocessing: A New Field of Cavitation‐Free Acoustic Materials Synthesis, Processing, and Manipulation
Advanced Science ( IF 15.1 ) Pub Date : 2020-11-23 , DOI: 10.1002/advs.202001983
Amgad R Rezk 1 , Heba Ahmed 1 , Shwathy Ramesan 1 , Leslie Y Yeo 1
Affiliation  

Ultrasound constitutes a powerful means for materials processing. Similarly, a new field has emerged demonstrating the possibility for harnessing sound energy sources at considerably higher frequencies (10 MHz to 1 GHz) compared to conventional ultrasound (⩽3 MHz) for synthesizing and manipulating a variety of bulk, nanoscale, and biological materials. At these frequencies and the typical acoustic intensities employed, cavitation—which underpins most sonochemical or, more broadly, ultrasound‐mediated processes—is largely absent, suggesting that altogether fundamentally different mechanisms are at play. Examples include the crystallization of novel morphologies or highly oriented structures; exfoliation of 2D quantum dots and nanosheets; polymer nanoparticle synthesis and encapsulation; and the possibility for manipulating the bandgap of 2D semiconducting materials or the lipid structure that makes up the cell membrane, the latter resulting in the ability to enhance intracellular molecular uptake. These fascinating examples reveal how the highly nonlinear electromechanical coupling associated with such high‐frequency surface vibration gives rise to a variety of static and dynamic charge generation and transfer effects, in addition to molecular ordering, polarization, and assembly—remarkably, given the vast dimensional separation between the acoustic wavelength and characteristic molecular length scales, or between the MHz‐order excitation frequencies and typical THz‐order molecular vibration frequencies.

中文翻译:

高频声处理:无空化声学材料合成、加工和操作的新领域

超声波是材料加工的有力手段。同样,一个新领域的出现证明了利用比传统超声波(⩽3 MHz)更高频率(10 MHz 至 1 GHz)的声能源来合成和操纵各种块状、纳米级和生物材料的可能性。在这些频率和所采用的典型声强度下,空化现象(支撑大多数声化学或更广泛的超声介导过程)基本上不存在,这表明完全不同的机制在发挥作用。例子包括新颖形态或高度定向结构的结晶;二维量子点和纳米片的剥离;聚合物纳米颗粒的合成和封装;以及操纵二维半导体材料的带隙或构成细胞膜的脂质结构的可能性,后者导致增强细胞内分子摄取的能力。这些引人入胜的例子揭示了与这种高频表面振动相关的高度非线性机电耦合如何产生各种静态和动态电荷生成和转移效应,以及分子排序、极化和组装——值得注意的是,考虑到巨大的维度声波波长和特征分子长度尺度之间的分离,或者MHz级激发频率和典型THz级分子振动频率之间的分离。
更新日期:2021-01-07
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