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

生物医学植入物有望极大地改善健康和福祉，例如，使人们能够通过实时跟踪体内化学物质(如pH、葡萄糖、乳酸、组织氧)来主动监测健康状况，通过靶向和量身定制的药物输送治疗疾病，通过神经假体治疗神经疾病等。然而，只有当植入物变得更小、寿命更长时，这种愿景才是可能的。目前集成电路和微型传感器设计和制造的最先进水平可以实现立方毫米尺寸的植入物，这将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，成为植入物小型化的障碍。非常小的电池会很快耗尽，然后整个植入物将不得不通过手术更换。该项目的目标是通过使用容易穿透人体的低频磁场向生物医学植入物无线传输电力来克服这一电力问题。这些磁场将激发磁电接收器，该接收器将成为植入物的一部分。磁电接收器会将磁场转换成电流，然后对其进行适当的调节，为植入物提供动力。首席调查员(PI)及其附属研究人员将探索两种相互竞争的磁电设备类型，并对它们进行表征，特别是在与植入物和相关功率接收器的位置和对准相关的不确定性方面。将开发新的制造工艺，使微型磁电设备能够产生更多电力，从而使生物医学植入物进一步微型化。除了实现植入物的小型化外，该项目完成的工作还可以在传感和无线能量传输方面为最先进的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和磁电功率接收器来向生物医学植入物传输电力。目标是安全地提供每立方毫米100微瓦的电力，这将使广泛植入的传感器和治疗设备成为可能。低频磁场之所以吸引人，是因为它在人体组织和封装结构中的吸收率很低。将研究两类磁电器件：磁致伸缩材料和压电材料的叠层，以及永磁体/压电结构的联合制造。考虑到对齐和定位的不确定性以及与人体组织相互作用相关的问题，将对这两种方法进行比较。具体地说，研究人员将表征周围组织在降低共振式磁电接收器的品质因数方面所起的作用。阐明了该方法发电的关键关系和性能极限，并进行了实验验证，为系统设计提供了依据。将开发一种新的微制造工艺，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，将开发和验证一个系统来控制植入物从外部发射器使用的直流电压，以消除与传统电力电子相关的大型机载无源组件的需要。外部控制方法的有效性将充分体现在直流电压的稳定性和对系统不确定性的鲁棒性方面。这项研究的结果将通过克服以足够的密度输送电力的问题，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.