CAREER: Powering Micro Scale Biomedical Implants through Controlled Low Frequency Magnetic Fields and Multiferroic Transducers

生物医学植入物有望显著改善健康和福祉，例如，通过实时跟踪身体内部化学（例如pH值、葡萄糖、乳酸、组织氧），使人们能够主动监测健康状况，通过有针对性和量身定制的药物输送治疗疾病，通过神经假体治疗神经紊乱等。然而，只有当植入物变得更小、寿命更长时，这一愿景才有可能实现。集成电路和微传感器设计和制造的最新技术可以使立方毫米大小的植入物大大减少对患者的创伤，并改善持续的健康监测。然而，电力系统已经落后并成为植入小型化的障碍。非常小的电池很快就会耗尽，然后整个植入物就必须通过手术更换。这个项目的目标是通过无线传输能量到生物医学植入物，使用低频磁场，很容易穿透人体，来克服这个电力问题。这些磁场会激发一个磁电能量接收器，它将成为植入物的一部分。磁电接收器将把磁场转化为电能，然后适当地调节为植入物提供动力。首席研究员（PI）和附属研究人员将探索两种相互竞争的磁电装置，并对它们进行表征，特别是与植入物和相关功率接收器的位置和对齐相关的不确定性。将开发新的制造工艺，使微尺度磁电器件产生更多的功率，从而使生物医学植入物进一步小型化。除了使植入物小型化之外，该项目所完成的工作可以为传感和无线电力传输的最新技术带来更广泛的好处。该项目的目标是探索使用低频磁场与磁电功率接收器相结合，向生物医学植入物传输能量。目标是安全地提供每立方毫米100微瓦，这将使广泛的植入传感器和治疗设备成为可能。低频磁场因其在人体组织和封装结构中的吸收率极低而具有吸引力。两类磁电器件将被研究：磁致伸缩和压电材料的层压板，以及联合制造的永磁/压电结构。这两种方法将比较给定的对齐和取向的不确定性和问题与人体组织的相互作用。具体来说，研究人员将描述周围组织在降低谐振磁电功率接收器质量因子中的作用。本文将阐明该方法发电的关键关系以及性能限制，并通过实验验证，这将作为系统设计的基础。将开发一种新的微加工工艺，通过使用更厚的活性材料（即压电和磁致伸缩）来实现高功率换能器。最后，将开发并验证一种控制植入物使用的直流电压的系统，以消除对与传统电力电子相关的大型板载无源元件的需求。外部控制方法的有效性将在直流电压的稳定性和对系统不确定性的鲁棒性方面得到充分表征。这项研究的结果将通过克服在足够密度下传输能量的问题，为更小、更普遍的生物医学植入物奠定基础。

Biomedical implants hold the promise of dramatically improving health and well-being by, for example, enabling people to pro-actively monitor health through real-time tracking of internal body chemistry (e.g. pH, glucose, lactate, tissue oxygen), treat diseases through targeted and tailored drug delivery, treat neural disorders through neural prostheses, etc. However, this vision is only possible if implants become much smaller with longer lifetimes. The current state of the art in integrated circuit and micro-sensor design and manufacturing could enable cubic millimeter sized implants that would greatly reduce trauma to the patient and improve continuous health monitoring. However, power systems have lagged behind and become a barrier to implant miniaturization. Very small batteries would quickly become depleted and then the entire implant would have to be surgically replaced. The goal of this project is to overcome this power problem by wirelessly transmitting power to the biomedical implants using low frequency magnetic fields that easily penetrate the human body. These magnetic fields will excite a magnetoelectric power receiver that will be part of the implant. The magnetoelectric receiver will convert the magnetic fields to electricity which will then be properly conditioned to power the implant. The Principle Investigator (PI) and affiliated researchers will explore two competing types of magnetoelectric devices and characterize them especially in terms of uncertainties related to the position and alignment of the implant and associated power receiver. New fabrication processes will be developed that enable micro-scale magnetoelectric devices to generate more power, thus enabling further miniaturization for biomedical implants. In addition to enabling the miniaturization of implants, the work to be accomplished by this project could have broader benefits for the state of the art in both sensing and wireless power transfer.The goal of this project is to explore the use of low frequency magnetic fields coupled with magnetoelectric power receivers to transmit power to biomedical implants. The target goal is to safely supply 100 microwatts per cubic millimeter, which would enable a wide range of implanted sensors and therapeutic devices. Low frequency magnetic fields are attractive because of their very low absorption in human tissue and encapsulating structures. Two classes of magnetoelectric devices will be investigated: laminates of magnetostrictive and piezoelectric material, and jointly fabricated permanent magnet / piezoelectric structures. The two approaches will be compared given alignment and orientation uncertainties and issues associated with human tissue interaction. Specifically, researchers will characterize the surrounding tissue's role in degrading the quality factor of the resonant magnetoelectric power receivers. The key relationships for power generation by this method as well as performance limits will be elucidated and experimentally validated, which will serve as a basis for system design. A new microfabrication process will be developed to enable high power transducers through the use of much thicker active materials (i.e. piezoelectric and magnetostrictive). Finally, a system to control the DC voltage used by the implant from the external transmitter will be developed and validated to remove the need for large onboard passive components associated with traditional power electronics. The efficacy of the external control method will be fully characterized with respect to stability of the DC voltage and robustness to system uncertainties. The results of this research will establish the basis for much smaller, more ubiquitous biomedical implants by overcoming the issue of delivering power at sufficient densities.