Li Nan, Lowe Christopher R, Stevenson Adrian C
Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, CB3 0AS, UK.
Cambridge Academy of Therapeutic Sciences, University of Cambridge, 17 Mill Lane, Cambridge, CB2 1RX, UK.
Ultrasonics. 2019 Apr;94:376-381. doi: 10.1016/j.ultras.2018.07.001. Epub 2018 Jul 7.
A versatile system to construct bulk polymeric phononic crystals by using acoustic waves is described. In order to fabricate this material, a customised cavity device fitted with a ∼2 MHz acoustic transducer and an acoustic reflector is employed for the acoustic standing wave creation in the device chamber. The polymer crystal is formed when the standing waves are created during the polymerisation process. The resulting crystals are reproduced into the shape of the tunable device cavity with a unique periodic feature. The separation is related to the applied acoustic wave frequency during the fabrication process and each unit cell composition was found to be made up to two material phases. To assess the acoustic properties of the polymer crystals their average acoustic velocity is measured relative to monomer solutions of different concentrations. It is demonstrated that one of the signature characteristics of phononic crystal, the slow wave effect, was expressed by this polymer. Furthermore the thickness of a unit cell is analysed from images obtained with microscope. By knowing the thickness the average acoustic velocity is calculated to be 1538 m/s when the monomer/cross-linker concentration is 1.5 M. This numerical calculation closely agrees with the predicted value for this monomer/cross-linker concentration of 1536 m/s. This work provides a methodology for rapid accessing a new type of adaptable phononic crystal based on flexible polymers.
描述了一种利用声波构建块状聚合物声子晶体的通用系统。为了制造这种材料，采用了一种配备有~2 MHz声换能器和声学反射器的定制腔室装置，用于在装置腔室内产生驻波。当在聚合过程中产生驻波时，聚合物晶体形成。所得晶体被复制成具有独特周期性特征的可调谐装置腔室的形状。间距与制造过程中施加的声波频率有关，并且发现每个晶胞组成由两个材料相组成。为了评估聚合物晶体的声学特性，相对于不同浓度的单体溶液测量了它们的平均声速。结果表明，这种聚合物表现出声子晶体的一个标志性特征——慢波效应。此外，从显微镜获得的图像分析了晶胞的厚度。当单体/交联剂浓度为1.5 M时，通过知道厚度计算出平均声速为1538 m/s。该数值计算与该单体/交联剂浓度的预测值1536 m/s非常吻合。这项工作提供了一种快速获取基于柔性聚合物的新型可适应声子晶体的方法。
