用於感測介電常數的CMOS微波生醫感測器

Abstract

近年來越來越多研究將先進的互補式金屬氧化物半導體(CMOS)技術應用於感測器。相較於常規以微機構技術製成的感測器，基於CMOS技術的感測器具有微小化、造價便宜及數位訊號處理的優點，並可以實現可攜式、植入式……等功能，而本研究目的在於使用CMOS技術應用於生醫感測器上，實現一個可攜式、低功耗與低成本的感測器，以取代龐大且昂貴的實驗室儀器。 本研究提出了以CMOS技術應用於生醫量測的介電常數感測器，透過設計具有特定功能的積體電路晶片，將介電常數的實部與虛部的相關數值數位化並讀出，最後再經由外部微控制器控制晶片訊號，以及將相關數值傳送到電腦運算。本研究量測不同濃度的甲醇及乙醇的介電常數，並與商用向量網路分析儀量測到的介電常數進行比較，其中量測甲醇的百分比誤差為0.1%到17.8%。因為我們的感測平台具有低檢測極限和基於物理的感測機制，且其具有微小化及高靈敏度的特性，所以可以針對各種應用進行調整和整合，我們相信這樣的感測平台將為未來的生醫應用找到更多新的機會。本文中的主要電路包含了LC振盪器、數位類比轉換器、比較器、除頻器。

In recent years, more and more researches have adopted advanced complementary metal-oxide-semiconductor (CMOS) technology for sensors. In comparison with conventional micro-mechanism sensors, CMOS sensors have the advantages of miniaturization, low manufacturing cost and signal digitization, thus realizing state of the art technologies such as portable, wearable, and implantable devices. The purpose of this research is to apply CMOS technology to realize a portable, low-power and low-cost biomedical sensor to replace bulky and expensive laboratory instruments. In this study, we proposed a CMOS permittivity sensor for biomedical measurements. By designing an integrated circuit chip with specialized functions, the readouts of the real and imaginary parts of permittivity are digitized. The chip signal is controlled by an external microcontroller unit, which transmits the digitized data to a computer for calculation. In the evaluation, the permittivity of various concentrations of methanol and ethanol were measured using the proposed CMOS sensor, and compared to the measurements of a benchmark commercial vector network analyzer. The percent error for methanol ranged from 0.1% to 17.8%. In conclusion, the proposed sensing platform has a low limit of detection, physics-based sensing mechanism, miniaturization and high sensitivity, thus can be adapted and integrated to a wide range of applications. We believe that such a sensing platform will create new opportunities for biomedical applications in the future. The main circuit in this article includes LC oscillator, digital to analog converter, comparator, and frequency divider.