超薄燃料电池利用人体自身糖分发电

葡萄糖是人们从食物中吸收的糖分，它是为人体每个细胞提供动力的“燃料”。那么葡萄糖是否也能为医疗植入物提供动力？美国麻省理工学院和德国慕尼黑工业大学的工程师给出了肯定答案。他们设计了一种新型葡萄糖燃料电池，可将葡萄糖直接转化为电能。

带有30个独立葡萄糖微型燃料电池的硅芯片。图片来源：《先进材料》

该装置厚度仅400纳米，约为人类头发直径的1/100。该含糖电源每平方厘米产生约43微瓦的电力，实现了迄今为止葡萄糖燃料电池的最高功率密度。

近日发表在《先进材料》上的论文指出，新电池能承受高达600℃的温度。如果嵌入医疗植入物中，燃料电池可在植入设备所需的高温灭菌过程中保持稳定。该电池的核心由陶瓷制成，这种材料即使在高温和微型尺度下也能保持其电化学特性。研究人员设想，新设计可制成超薄膜或涂层，并包裹在植入物周围，利用人体丰富的葡萄糖被动地为电子设备供电。

在新研究中，研究人员设计了一种葡萄糖燃料电池，其电解质由二氧化铈制成，二氧化铈是一种具有高离子电导率的陶瓷材料，机械强度高，因此被广泛用作氢燃料电池的电解质，其已被证明是生物相容的。

研究团队将电解质与由铂制成的阳极和阴极夹在中间，铂是一种容易与葡萄糖反应的稳定材料。他们在一个芯片上制造了150个单独的葡萄糖燃料电池，每个约400纳米薄，300微米宽（大约30根人类头发的宽度）。团队将电池图案摹刻到硅晶片上，实验表明电池可与常见的半导体材料配对。随后他们测量了电池在定制测试站中将葡萄糖溶液流过每个晶片时产生的电流。

团队发现，许多电池产生的峰值电压约为80毫伏。鉴于每个电池的尺寸很小，该输出已是任何现有葡萄糖燃料电池设计中最高的功率密度。

研究人员表示：“这是第一次将电陶瓷材料中的质子传导用于葡萄糖到能量的转换，定义了一种新型的电化学。它将材料从氢燃料电池扩展到新的、令人兴奋的葡萄糖转换模式。” 新电池使用的陶瓷无毒、便宜，而且对体内条件和植入前的灭菌条件都呈惰性，因此为植入传感器和其他功能的微型电源开辟了一条新途径。

Silicon chip with 30 independent glucose micro fuel cells. Photo Source: advanced Materials

The device is only 400 nanometers thick, which is about 100 times the diameter of human hair. The sugary power supply produces about 43 microwatts per square centimeter, achieving the highest power density of glucose fuel cells so far.

A recent paper published in Advanced Materials points out that the new battery can withstand temperatures as high as 600 ℃. If embedded in a medical implant, the fuel cell can remain stable during the high temperature sterilization process required for the implanted device. The core of the battery is made of ceramic, which can maintain its electrochemical properties even at high temperature and micro-scale. The researchers envision that the new design could be made into an ultrathin film or coating and wrapped around the implant, using the body's rich glucose to passively power electronic devices.

In the new study, the researchers designed a glucose fuel cell whose electrolyte is made of cerium dioxide, a ceramic material with high ionic conductivity and high mechanical strength, so it is widely used as an electrolyte for hydrogen fuel cells. it has been proved to be biocompatible.

The team sandwiched the electrolyte to anodes and cathodes made of platinum, a stable material that reacts easily with glucose. They built 150 individual glucose fuel cells on a chip, each about 400 nanometers thin and 300 microns wide (about the width of 30 human hairs). The team imitates the battery pattern on a silicon wafer, and experiments show that the battery can be paired with common semiconductor materials. They then measured the current generated by the battery as it flowed glucose solution through each chip at a custom test station.

The team found that many batteries produce a peak voltage of about 80 millivolts. Given the small size of each cell, the output is already the highest power density in any existing glucose fuel cell design.

"this is the first time that proton conduction in electroceramics has been used for glucose-to-energy conversion, defining a new type of electrochemistry," the researchers said. It extends the material from hydrogen fuel cells to new and exciting glucose conversion modes. " The ceramic used in the new battery is non-toxic, cheap, and inert to in vivo conditions and pre-implantation sterilization conditions, thus opening up a new way for micro-power sources for implanted sensors and other functions.