Interaction of high-intensity focused ultrasound with polymers at the atomistic scale
Interaction of high-intensity focused ultrasound with polymers at the atomistic scale
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DOI：
10.1088/1361-6528/abbfd2
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发表时间：
2021-01-22
期刊：
影响因子：
3.5
通讯作者：
Mirzaeifar, Reza
中科院分区：
文献类型：
--
作者：
Peng, Kaiyuan;Shahab, Shima;Mirzaeifar, Reza
实验表明，高强度聚焦超声(HIFU)是一种具有多种优越和独特的能力的刺激，可以无创地在聚合物中诱导局部加热和实现时间和空间热效应。当聚合物受到HIFU时，与直接受到热源的情况相比，它们的加热方式不同；然而，这种差异的来源仍然完全未知。我们假设，聚合物在HIFU作用下的宏观响应的差异强烈地取决于聚合物的链、组成和结构，即结晶或非晶态。在这项工作中，这一假设被分子动力学研究在原子水平上进行了研究，并在宏观水平上得到了实验的验证。结果表明，由应力-应变位相滞后测量的粘弹性、链的回转运动以及由均方根涨落量化的振动诱导的局部迁移率是造成HIFU热效应差异的主要原因。这揭开了HIFU刺激聚合物背后的未知机制，并为在未来的应用中使用这种方法铺平了道路。
Experiments show that high-intensity focused ultrasound (HIFU) is a promising stimulus with multiple superior and unique capabilities to induce localized heating and achieve temporal and spatial thermal effects in the polymers, noninvasively. When polymers are subjected to HIFU, they heat up differently compared to the case they are subjected to heat sources directly; however, the origins of this difference are still entirely unknown. We hypothesize that the difference in the macroscale response of polymers subjected to HIFU strongly depends on the polymer chains, composition, and structure, i.e. being crystalline or amorphous. In this work, this hypothesis is investigated by molecular dynamics studies at the atomistic level and verified by experiments at the macroscopic scale. The results show that the viscoelasticity, measured by stress-strain phase lag, the reptation motion of the chains, and the vibration-induced local mobility quantified by the root mean square fluctuation contribute to the observed difference in the HIFU-induced thermal effects. This unravels the unknown mechanisms behind stimulating the polymers by HIFU, and paves the way in front of using this method in future applications.