人体医疗植入设备也能无线充电了！

经过长达6年的毫米级医疗植入物研究，美国斯坦福大学(Stanford University)电子工程系助理教授Ada Poon终于取得符合安全兼容性实验室的验证报告，并证实她的这项研究具有商用化潜力。 Poon兴奋地解释，这项研究主要利用活体动物组织作为媒介，可在大约5公分以上的距离透过“中场”(mid-field)无线电源提供超过200微瓦的功率。 “我们确定模拟过程相当安全，”Poon指出，”我们使输出功率保持在500mW，这和手机是一样的，接着我们进行测量，检查温度的上升。我们进行一切的验证，最终才真的确定与证明这项技术是安全的，然后我们才送交第三方测试。” Poon和其他研究人员们针对这项主题为“医疗植入设备的中场无线电源研究”提交了一份论文至国家科学院(National Academy of Sciences)，内容描述一种可穿透约5cm皮肤组织为植入于兔子心脏中的2mm微型刺激器供电的方式。 这种电流感应耦合方法取决于植入设备与外部设备之间的近场耦合──在植入设备与外部设备之间无非就是一层薄薄的皮肤。Poon的团队采取了一种不同的方法，经由生物组织拥抱1.6GHz的信号传输，而非采取试图避开的作法。 斯坦福大学的研究人员们称这种方式为“中场”(mid-field)无线。斯坦福大学研究生John Ho解释，基本上是将“近场”转换为“远场”(far-field)电磁波，这种传输方式较安全但远离讯号源后快速衰减，但已能将能量传送到更远的距离。 该技术可传送超过200mW功率，远远超过当今起搏器所需的8mW功耗。Poon以及其他研究人员们预见到有一天将出现一种仅有米粒大小的微型刺激器，它可能比当今所用的植入设备或药物更加高效。 “我们的供电方式适用于更广泛的设备类型，如植入式诊断传感器或局部药物递送工具，”Ho说，“这些设备未能商业化开发出来的部份原因可能是现有植入设备尺寸太大。” “一个有趣的应用是在一种俗称‘电药’(electroceutical)的新兴药物治疗方式，这种直接安装在人体内部进行调节的微型设备，在某些疾病的治疗上可能比用药物更有效。在这方面还需要更多的研究，才能了解疾病的神经基础以及开发电子治疗方法，但无论如何，所有的这一类途径都需要安全传送电力的方式。”

斯坦福大学开发的微型刺激器植入设备尺寸约2mm，大约是一颗米粒的大小。
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本文授权编译自EE Times，版权所有，谢绝转载 本文下一页：从物理到医学，从理论到手术

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• 大势所趋，医疗制造专有技术正快速向中国转移
• [图文报道]飞思卡尔技术论坛（FTF2014）聚焦深圳
• 无线充电标准比拼，市场期待大一统i5zesmc

{pagination} 从理论到手术 为了使植入式设备最小化，许多微型刺激器并未加装电池。当使用者想产生脉冲以减轻疼痛或读取嵌入式传感器的数据时，他们通常都必须在患处放置一个如信用卡大小的充电器。其他的刺激或传感器可能内建微型电池，从而实现自动化作业。但用户仍必须经由外部设备为植入式设备进行充电。 而在未来的12个月内，预计Poon的研究团队就能首次在人体内植入这种新式微型刺激器，可能用于治疗外围神经疼痛。不过，在这项产品获准用于医疗用途以前，大约还要经过几年的时间进行测试。

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Poon 所开发的设备比目前由Medtronic与St. Jude Medical等公司开发约几公分大小的起搏器更小几个数量级。这些较大型设备的问题是必须抗拒更大的力量，才能保持与身体组织之间的恒定。此 外，Poon也有兴趣探索这种电磁能量究竟可达到多远的距离限制。

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“我所受的训练主要是在信息论方面，”她说，“这是在电子工程学中最密集使用数学的部份，我们总是问这样的问题：通过一定信道的最高数据速率是多少？” 她的职业生涯一开始是在英特尔(Intel)公司从事可重配置射频方面的工作，目前在于制造出更高灵敏度的基带芯片。后来，她还曾经任职SiBeam，该公司是60GHz CMOS 芯片先驱，为消费电子设备提供高解析的无线视频。 “当我开始研究生物组织的电磁学时，我对于这方面所存在的限制也感到好奇。每个人都在用电感耦合，但什么是最佳解决方案却一直没有答案。” 在经过长达6年的追寻后，这个问题仍然开放各种解答，未来，也还有更多年的路要走。她说，“这是一段漫长的旅程。” “这项研究的一个有趣之处在于它所涵盖的范围是如此地广泛，从物理到医学，”Ho说，“有一段时间我还同时展开数学研究与动物实验──这真的很令人振奋！” 微型刺激器可经由导管插入体内。 本文授权编译自EE Times，版权所有，谢绝转载 编译：Susan Hong 参考英文原文：Implant Gets Power Through Flesh，by Rick Merritt

相关阅读：
• 大势所趋，医疗制造专有技术正快速向中国转移
• [图文报道]飞思卡尔技术论坛（FTF2014）聚焦深圳
• 无线充电标准比拼，市场期待大一统i5zesmc

{pagination} Implant Gets Power Through Flesh Rick Merritt SAN JOSE, Calif. — Ada Poon still recalls the day she read the report from the safety compliance lab. The Stanford assistant professor had gotten validation for her six years of research on millimeter-scale medical implants that were now shown to have commercial potential. "I was quite excited," says Poon of her work exploiting living animal tissue as a medium to deliver more than 200 microwatts of power over a distance of 5 centimeters or more. "We knew it was safe in simulation," Poon tells us. "We kept the output power to 500 mW, which is the same as a cellphone, and we did measurements to check the temperature rise. We did all this validation, but in the end to be really sure and articulate our point that our technique was safe, I said let's do third-party testing." Today Poon and colleagues submitted a paper to the National Academy of Sciences on their work in so-called midfield wireless power for a medical implant. It describes a way to deliver power through nearly 5 cm of tissue to a 2 mm microstimulator implanted on a rabbit's heart. Current inductive coupling methods rely on near-field coupling between an implant and an external device with nothing more than a thin layer of skin in between. Poon's team took a different approach, embracing propagation of the 1.6 GHz signal through biological tissue rather than trying to avoid it. The Stanford researchers call their approach "mid-field" wireless. Essentially, they converted "electromagnetic waves from the 'evanescent' or 'near-field' type, which are safe but decay rapidly away from the source, to the 'propagating' or 'far-field' type, which carry energy away with much farther reach," explains John Ho, a Stanford graduate student and co-author of the paper The more than 200 microwatts the technique delivers far exceeds the 8 mW consumed by today's pacemakers. Poon and others foresee the advent of a class of microstimulators the size of a grain of rice that may someday be more effective for some ailments than today's implants or drugs. "Our powering method could be applicable to a broader class of devices that have yet to be developed, such as implantable diagnostic sensors or localized drug delivery tools," says Ho. "Part of the reason they are not commercially used today may be because of the bulkiness of existing implants. "One intriguing application is in an emerging class of medicines called 'electroceuticals.' Tiny devices that directly modulate neural activity in the body may provide more effective treatments for some disorders than drugs. Much more research is required to understand the neural basis for diseases and develop electronic treatments, but all such approaches will require ways to safely transfer power." The Stanford microstimulator implant measures 2mm across, about the size of a grain of rice. To keep the implants small, many microstimulators will have no battery. When users want to generate pulses to relieve pain or read data from an embedded sensor, they will place over the affected area a credit-card sized charger, such as the thin 6x6 cm device the Stanford team used. Other stimulators or sensors may have tiny batteries so they can work automatically. Users will charge the implants with the external device. Within the next 12 months, Poon's team hopes to implant its microstimulator in a human for the first time, probably on peripheral nerves for pain therapy. It could take several years of tests before such products are approved for medical use. Poon's device is an order of magnitude smaller than today's centimeter-sized pacemakers from Medtronic and St. Jude Medical. The larger devices must resist greater forces to stay anchored to tissues amid the flow of body fluids. Poon is interested in exploring the limits of what electromagnetic energy can deliver over how great a distance. "My training is in information theory," she says. "It's one of the most mathematically intensive branches in electrical engineering. We always ask the question: What's the highest data rate through a given channel?" Her career started with work on reconfigurable radio at Intel, trying to make baseband chips as agile as possible. She later worked at SiBeam, which pioneered 60 GHz chips in CMOS, delivering wireless, high-definition video for consumer electronics gear. "When I started work on electromagnetics in biological tissue, I applied the same curiosity about what's the limit. Everyone was using inductive coupling, but what was the optimal solution was not answered." The question remains an open one she has now been pursuing six years, with several more years of work ahead. "It's a long journey," says Poon. "One interesting thing about this work was that it was incredibly broad, ranging from physics to medicine," says Ho. "There were times where I performed mathematical studies and animal experiments on the same day -- as primarily a theorist by training, this was exhilarating/" The microstimulator could be inserted via a catheter.