Photoacoustic Emission Efficiency of Polymer Matrix Nanocomposites for Use in Epiretinal Prosthetics*

When used as photoacoustic transmitters, the design of polymer matrix nanocomposites can significantly impact the efficiency of the photon-to-acoustic conversion process. This efficiency is critical in applications using these transmitters as epiretinal prosthetic devices where delicate tissues can be damaged by excess energy if it is not effectively dissipated by naturally occurring biological processes. In these prosthetic devices, pulsed laser excitation of the nanocomposite produces acoustic wave emission that neuromodulates cells contained in the retina. For the nanocomposite materials studied in this work, the matrix is highly transparent at the excitation wavelengths of interest while the nanoparticles distributed in the bulk of the material serve as optical absorbers that photothermally heat the matrix when excited by laser pulses. Matrix thermal expansion launches ultrasonic waves that ultimately reach the retina and produce the desired neuromodulation. In this work, the efficiency of the photoacoustic process in these nanocomposites is analyzed with the aim of identifying critical laser and material parameters that affect the performance of these materials as epiretinal prosthetics.

当用作光声发射器时，聚合物基体纳米复合材料的设计会显著影响光子 - 声子转换过程的效率。在将这些发射器用作视网膜前假体装置的应用中，这种效率至关重要，因为如果多余的能量不能通过自然发生的生物过程有效消散，脆弱的组织可能会受到损伤。在这些假体装置中，纳米复合材料的脉冲激光激发会产生声波发射，从而对视网膜中的细胞进行神经调节。对于本研究中所研究的纳米复合材料，基体在感兴趣的激发波长下具有高度透明性，而分布在材料主体中的纳米粒子则作为光吸收剂，在受到激光脉冲激发时会对基体进行光热加热。基体的热膨胀会产生超声波，最终到达视网膜并产生所需的神经调节作用。在这项工作中，对这些纳米复合材料中的光声过程效率进行了分析，目的是确定影响这些材料作为视网膜前假体性能的关键激光和材料参数。