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

该基金将支持有关pzt -水凝胶活性互补声学超材料的动态和声学特性的新基础知识的研究。这种声学超材料将使高能在高频率下通过音障进行传输，包括那些具有强内在损失的音障，如用于脑成像的头骨和脑机接口。经颅超声（即通过颅骨的超声传输）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，通过有损耗的颅骨的能量传输也很低。脑成像和脑机接口需要更好的空间分辨率，这可以通过使高频超声通过颅骨传输来实现，这是现有技术无法实现的。有源非厄米互补声超材料（NHCMM）是一种很有前途的补偿介质，可以弥补高频声波通过颅骨的强传输损耗。本项目研究了pzt -水凝胶复合材料与反馈控制电路集成的声学和材料性能，用于实验实现补偿高频超声通过真实颅骨传输损失的NHCMM。该实验的实现将为高分辨率超声脑成像和脑机接口奠定基础。该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，本研究将促进基础声学、软物质物理和超材料的发展。这项多学科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教育产生积极影响。本研究的目的是通过集成PZT元件，水凝胶和反馈控制电路来设计，制造和实验表征一个有源NHCMM，可以用于补充声障，包括具有强内在损失的声障，如头骨，以实现脑成像和脑机接口的最佳能量传输。NHCMM的有效密度和体积模量均为势垒的负值，以抑制强阻抗失配和平衡势垒内固有损耗的材料增益。NHCMM将通过将压电元件和水凝胶与电路元件集成来实现。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所需的参数，同时补偿阻抗失配和损耗。该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、脑机接口等奠定基础。为了实现上述目标，双方将利用各自在声学、超材料和软物质方面的互补专业知识，完成以下研究任务：1)确定不同类型水凝胶在宽超声频带内的动态特性；2)设计和制造基于反馈电路控制的压电元件的水凝胶有源nhcmm，以实现任何期望的有效密度和体积模量与声增益；3)表征和优化nhcmm，增强声能通过有损颅骨的传输，用于脑成像和脑机接口。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.