Design and Implementation of Reference-Free Drift-Cancelling CMOS Magnetic Sensors for Biosensing Applications
Design and Implementation of Reference-Free Drift-Cancelling CMOS Magnetic Sensors for Biosensing Applications
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DOI：
10.1109/jssc.2018.2865480
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发表时间：
2018-11-01
影响因子：
5.4
通讯作者：
Hajimiri, Ali
中科院分区：
文献类型：
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作者：
Sideris, Constantine;Khial, Parham P.;Hajimiri, Ali
磁性成像仪，利用磁性纳米颗粒作为标签来实现生物检测分析，在使用点部署具有重要的前景。基于共振位移的传感器可以在标准CMOS工艺中实现，无需后处理修改，并且以低价格提供高灵敏度。不幸的是，CMOS谐振位移磁传感器在信噪比和长期稳定性方面受到严重的影响，这是由于片上电感质量因素低以及有源器件和热变化带来的显著噪声。这使得基于共振位移的标准成像仪不适合用于低信号生物检测分析。此外，最重要的是，由于缓慢变化的噪声源和温度变化导致的显著的长期漂移使得这些传感器不适合生物实验，因为生物实验可能需要数小时才能完成。在本文中，我们提出了一种基于变压器的方法，该方法可以在不需要任何热补偿的情况下检测百万分之一（PPM）的信号。该方法是自引用的，通过消除对复制参考单元的需要，大大节省了芯片面积。通过与原二阶系统的比较，分析了基于变压器的电路的性能，证明了其在抑制系统噪声方面的优越性。提出了一种基于2 × 2 CMOS变压器的全集成磁传感器阵列的概念验证设计，该阵列实现了无参考、亚ppm的磁信号检测。该系统可以完全通过笔记本电脑的USB接口供电和操作，每个传感单元可以消耗不到3兆瓦的直流功率。最后，我们展示了初始DNA生物检测实验的结果，该实验证实了传感器可用于现实生物分析的能力。
Magnetic imagers, which utilize magnetic nanoparticles as labels to realize biodetection assays, hold significant promise for deployment at the point-of-use. Resonance-shift-based sensors can be realized in standard CMOS processes without post-process modifications and offer great sensitivity at low price tags. Unfortunately, CMOS resonant-shift magnetic sensors suffer significant degradation in SNR and long-term stability due to low on-chip inductor quality factors and significant noise introduced from active devices and thermal variations. This makes standard resonant-shift-based imagers undesirable for use in low-signal biodetection assays. Furthermore, and most importantly, the significant long-term drift due to slow-varying noise sources and temperature changes makes these sensors inadequate for bioexperiments which may take timescales on the order of hours to reach completion. In this paper, we propose a transformer-based approach which enables sub-parts-per-million (PPM) signal detection without the need for any thermal compensation. The approach is self-referencing, leading to significant savings in chip area by removing the need for replica reference cells. We analyze the performance of the transformer-based circuit compared to the original second-order system and demonstrate its superiority for rejecting system noise. A proof-of-concept design of a fully integrated 2 x 2 CMOS transformer-based magnetic sensor array is presented which achieves reference-free, sub-PPM detection of magnetic signals. The system can be powered and operated completely from a laptop USB interface and each sensing cell can consume less than 3 mW of DC power. Finally, we show the results of an initial DNA biodetection experiment which confirms the capability of the sensor to be used for realistic bioassays.