PZT-hydrogel integrated active non-Hermitian complementary acoustic metamaterials with real time modulations through feedback control circuits

这笔赠款将支持将产生关于PZT水凝胶基活性互补声学超材料的动力学和声学特性的新的基础知识的研究。这种声学超材料将使高频能量能够通过声屏障传输，包括那些具有强烈内在损失的声屏障，如用于脑成像和脑机接口的头骨。经颅超声(即通过头骨的超声传播)有许多应用，包括非侵入性手术和药物输送。然而，目前的经颅超声技术都是基于频率相对较低、空间分辨率较差的声波，即使是这样的低频声波，通过有耗颅骨的能量传输也很低。脑成像和脑机接口需要更高的空间分辨率，这可以通过通过头骨传输高频超声波来实现，这是现有技术无法实现的。有源非厄米互补声学超材料(NHCMM)是一种很有前途的补偿介质，可以弥补高频声波在颅骨中的强传播损失。本项目探索了PZT-水凝胶复合材料的声学和材料性能，并结合反馈控制电路，实现了NHCMM的实验实现，该NHCMM可以补偿高频超声通过真实头骨的传播损失。这一实验实现将为高分辨率超声脑成像和脑机接口奠定基础。这项研究将通过满足对高性能脑成像和脑机接口的迫切需求，在科学、国防、工业和一般社会产生更广泛的影响。此外，这项研究还将促进基础声学、软物质物理和超材料的发展。这项多学科的研究将扩大未被充分代表的群体在科学和工程领域的参与，并对STEM教育产生积极的影响。本研究的目标是通过集成PZT元件、水凝胶和反馈控制电路来设计、制造和实验表征有源NHCMM，这些电路可以用于补充声屏障，包括那些具有较强固有损失的声屏障，以实现脑成像和脑机接口的最佳能量传输。NHCMM具有有效密度和体模，但势垒的有效密度和体模为负值，以抑制强阻抗失配和平衡势垒本征损耗的材料增益。NHCMM将通过将压电元件和水凝胶与电路元件相结合来实现。集成反馈控制电路将主动调制超材料的有效声学特性，以实现NHCMM的预期参数，同时补偿阻抗失配和损耗。这一基础研究项目将为实现无创超声脑成像、高强度聚焦超声治疗、脑刺激和脑机接口铺平道路。为了实现拟议的目标，两家PI将利用他们在声学、超材料和软物质方面的互补专业知识来完成下列研究任务：1)确定不同类型水凝胶在宽带内的动态特性；2)设计和制造具有反馈电路控制的压电元件的水凝胶基活性NHCMMs，以实现任何所需的有效密度和体积弹性模量以及声学增益；3)表征和优化NHCMMs，以增强通过有损头骨进行的声能传输，用于脑成像和脑机接口。该奖项反映了NSF的法定使命，并通过利用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This grant will support research that will generate new fundamental knowledge on the dynamic and acoustic properties of a PZT-hydrogel based active complementary acoustic metamaterial. Such acoustic metamaterials will enable high energy transmission at high frequency through sound barriers, including those with strong intrinsic loss like skull for brain imaging and brain-machine interface. Transcranial ultrasound (i.e. ultrasound transmission through skull) has many applications including noninvasive surgeries and drug delivery. However, current transcranial ultrasound techniques are all based on sound waves with relatively low frequency and poor spatial resolution, and the energy transmission through the lossy skull is low even for such low frequency sound waves. Brain imaging and brain-machine interfaces require better spatial resolution, which can be realzied by enabling transmission of high frequency ultrasound through skulls, which is not achievable with existing technologies. Active non-Hermitian complementary acoustic metamaterials (NHCMM) are promising compensation media to complement with the strong transmission loss through skull for high frequency acoustic waves. This project explores the acoustic and material properties of PZT-hydrogel composites integrated with feedback control circuits for the experimental realization of NHCMM that can compensate the high frequency ultrasound transmission loss through a real skull. This experimental realization will set the foundation for high resolution ultrasound brain imaging and brain-machine interface. This research will have broader impacts in science, defense, industry and general society by satisfying the critical need for high performance brain imaging and brain-machine interface. In addition, this research will promote the progress of fundamental acoustics, soft matter physics, and metamaterials. This multi-disciplinary research will broaden the participation of underrepresented groups in science and engineering and positively impact STEM education.The objective of this research is to design, fabricate, and experimentally characterize an active NHCMM by integrating PZT elements, hydrogel, and feedback control circuits that can be used to complement sound barriers, including those with strong intrinsic loss such as skull, to achieve optimal energy transmission for brain imaging and brain-machine interface. The NHCMM has effective density and bulk modulus with negative values of that of the barrier to suppress the strong impedance mismatch and material gain that balances the intrinsic loss in the barrier. The NHCMM will be realized by integrating piezoelectric elements and hydrogel with electrical circuit components. The integrated feedback control circuit will actively modulate the effective acoustic properties of the metamaterials to realize the desired parameters of NHCMM and compensate impedance mismatch and loss simultaneously. This fundamental research project will pave the road for the realization of noninvasive ultrasonic brain imaging, high intensity focused ultrasound treatments, brain stimulation, and brain-machine interface. To achieve the proposed objective, the two PIs will utilize their complemented expertise in acoustics, metamaterials, and soft matter to accomplish the following research tasks: 1) Identify the dynamic properties of different types of hydrogels in a wide ultrasonic frequency band; 2) Design and fabricate hydrogel-based active NHCMMs with feedback-circuit-controlled piezoelectric elements to realize any desired effective density and bulk modulus with acoustic gain; 3) Characterize and optimize NHCMMs to enhance acoustic energy transmission through lossy skull for brain imaging and brain-machine interface.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.