NFC-Powered Sweat Biosensor for Glucose and Lactate

Researchers at Northwestern University Center for Bio-Integrated Electronics are championing the development of sweat biosensors with their latest glucose and lactate sensors.

什么是汗生物传感器？

汗水生物传感器是监控一个给定的设备physiological quantity in sweat, often being worn on the arm or the back shoulder as these locations experience high sweat production compared to the rest of the body. Oftentimes, sweat biosensors are designed for analyzing biomarkers such as glucose, lactate, or sodium, providing information on glycemic content, muscle activity, or hydration.

汗水t生物传感器已经看到有了兴趣he medical device industry and in academia as they present a unique opportunity for non-invasively monitoring important biomarkers for health and fitness applications as well as for medical diagnosis and treatment.

Researchers at Northwestern University Center for Bio-Integrated Electronics, led by Professor John Rogers, are among those championing the investigation of wearable sweat biosensors. One of their recent publications titled “Battery-free, skin-interfaced microfluidic/electronic systems for simultaneous electrochemical, colorimetric, and volumetric analysis of sweat” highlights their efforts.

图显示了汗水生物传感器的不同方面，特别突出了其多层结构及其无电池操作。来自Rogers Research Group

电位计量葡萄糖和乳酸传感器的电压缓冲液

The analog front-end is fairly simple requiring only a simple voltage follower with integrated RF filters. The glucose and lactate sensors are potentiometric sensors, meaning they output a small voltage proportional to the concentration of glucose or lactate present in the sweat sample being analyzed. This same operation is the basis of common laboratory pH probes and requires fairly simple hardware, consisting of a low-noise voltage buffer, to implement.

Schematic of glucose and lactate potentiometric sensors. Each signal is buffered and filtered before digitizing to remove extraneous noise. Image content recreated from Science Advances.

研究小组在追随者电路的反馈网络中包括一个电容器，以降低带宽并降低噪声。然后通过14位类似物到数字转换器读取信号。

通过NFC的无线电源

One of the key features highlighted by the research team is the battery-less operation of their device. Instead of powering the device with a standard primary or secondary cell battery, the Rogers Research Group instead chose to employ a wireless powering scheme craftily leveraging NFC (near-field communication) for both power and communication.

该技术在消费者NFC标签中著名地用于标签和启用NFC的智能设备之间的短距离无线通信。尽管NFC并未像许多以前预测的那样完全接管消费电子行业，但NFC仍在发现使用手机和智能手表的非接触式支付中的使用越来越yabosports官网大。

NFC提供了非常适中的功率，因此有必要以极低的功率运行。他们利用Texas Instruments的RF430FRL152H传感器应答器，该仪器设计用于在小电池上操作或更有趣的是在磁场上。

The functional block diagram of the Texas Instruments RF430FRL152H. Image from theRF430FRL152H数据表。

RF430FRL152H的工作电压为1.45 V，旨在处理间歇性磁场提供的不受监管的可变功率。

The RF430FRL152H includes Texas Instruments’ popular low power MSP430 microcontroller architecture, which boasts one of the lowest operating voltages in the industry. The Rogers group mention buffering the sensor signals with the ADA4505-2, a small footprint, zero-crossover, low noise, low operating voltage amplifier. Minimal footprint is critical for ensuring the sensor remains inconspicuous when worn on the body. Zero-crossover and low noise are necessary to minimize distortion since the signals from the glucose and lactate sensors have a very small dynamic range and are not amplified (because an amplifier, rather than a unity-gain buffer, would require additional passive components).

与传统实验室技术相比，传感器的传感器葡萄糖和乳酸测量结果。来自Rogers Research Group

Some In-House Fabrication

NFC天线制造是在内部使用光刻的内部进行的，以将导电痕迹模拟在柔性印刷电路板材料（杜邦Pyralux AP8535R）上，该电路板（杜邦Pyralux AP8535R）被一层聚酰亚胺隔开，并被硅胶材料封装，以进行水上性。在内部开发NFC天线的研究小组在质量控制方面具有最大的灵活性，从而使Q出色的天线性能具有高Q，即使在适度的高弯曲半径下也是如此。

早期可行性研究

研究人员展示了他们的设备在使用启用NFC的智能手机为设备供电的同时测量不同生物标志物的能力，以及从定制设计的大型天线，用于在骑固定自行车时进行连续监视。当然，结果是初步的，但是仍然有希望。

汗水生物传感器对于基线漂移，温度变化以及由于感应元件的变化而导致的变异性臭名昭著，导致随着时间的推移随着时间的推移而导致信噪比降低的感应元件。尽管本文并未具体解决这些问题，但其他问题，例如低过敏性粘合剂和模拟前端的微型化，为汗水生物传感器面临的非常具有挑战性的问题提供了有趣的解决方案。

低功率和小型化的情况

This paper demonstrates the need for miniaturization and for more flexible powering options in order to develop advanced biomedical technology as well as the need for wafer scale integrated circuits for reducing device footprint. Miniaturization and decreased power consumption are particularly critical for wearable sensors as such sensors rely on being discreet and long-lasting. This paper also presents key opportunities for industry-academia relations that would streamline the development of new medical technology by leveraging each partner’s particular specialties.

Semiconductor companies can provide chipsets with advanced feature sets and low power, fabrication houses can provide academics tape out space for turning their prototypes into custom integrated circuits, and academia can provide the testing centers for the high-risk work that companies would like to explore.