IEEE Trans Ultrason Ferroelectr Freq Control. 2022 Oct;69(10):2756-2765. doi: 10.1109/TUFFC.2022.3197705. Epub 2022 Sep 27.
Millimeter-scale implants using ultrasound (US) for power and communication have been proposed for a range of deep-tissue applications, including neural recording and stimulation. However, published implementations have shown high sensitivity to misalignment with the external US transducer. Ultrasonic beamforming using a phased array to these implants can improve tolerance to misalignment, reduce implant volume, and allow multiple implants to be operated simultaneously in different locations. This article details the design of a custom planar phased array US system, which is capable of steering and focusing US power within a 3-D volume. Analysis and simulation is performed to determine the choice of array element pitch, with special attention given to maximizing the power available at the implant while meeting FDA limits for diagnostic US. Time reversal (TR) is proposed as a computationally simple approach to beamforming that is robust despite scattering and inhomogeneity of the acoustic medium. This technique is demonstrated both in active drive and pulse-echo modes, and it is experimentally compared with other beamforming techniques by measuring energy transfer efficiency. Simultaneous power delivery to multiple implants is also demonstrated.
毫米级植入物使用超声（US）进行功率和通信已被提出用于各种深层组织应用，包括神经记录和刺激。然而，已发表的实现方案表明，它们对外置 US 换能器的对准具有很高的敏感性。使用相控阵对这些植入物进行超声成束可以提高对准容限、减小植入物体积，并允许在不同位置同时操作多个植入物。本文详细介绍了一种定制的平面相控阵 US 系统的设计，该系统能够在 3D 体积内引导和聚焦 US 功率。进行了分析和模拟以确定阵列元件间距的选择，特别关注在满足 FDA 对诊断 US 的限制的同时最大化植入物可用的功率。时间反转（TR）被提议作为一种计算简单的波束形成方法，它具有鲁棒性，尽管声学介质存在散射和非均质性。该技术在主动驱动和脉冲回波模式下均得到了演示，并通过测量能量传递效率与其他波束形成技术进行了实验比较。还演示了对多个植入物的同时功率传输。
