Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305, United States.
Anal Chem. 2011 Dec 15;83(24):9314-20. doi: 10.1021/ac201626b. Epub 2011 Nov 29.
Distributed sensing of gas-phase chemicals using highly sensitive and inexpensive sensors is of great interest for many defense and consumer applications. In this paper we present ppb-level detection of dimethyl methylphosphonate (DMMP), a common simulant for sarin gas, with a ppt-level resolution using an improved capacitive micromachined ultrasonic transducer (CMUT) as a resonant chemical sensor. The improved CMUT operates at a higher resonant frequency of 47.7 MHz and offers an improved mass sensitivity of 48.8 zg/Hz/μm(2) by a factor of 2.7 compared to the previous CMUT sensors developed. A low-noise oscillator using the CMUT resonant sensor as the frequency-selective device was developed for real-time sensing, which exhibits an Allan deviation of 1.65 Hz (3σ) in the presence of a gas flow; this translates into a mass resolution of 80.5 zg/μm(2). The CMUT resonant sensor is functionalized with a 50-nm thick DKAP polymer developed at Sandia National Laboratory for dimethyl methylphosphonate (DMMP) detection. To demonstrate ppb-level detection of the improved chemical sensor system, the sensor performance was tested at a certified lab (MIT Lincoln Laboratory), which is equipped with an experimental chemical setup that reliably and accurately delivers a wide range of low concentrations down to 10 ppb. We report a high volume sensitivity of 34.5 ± 0.79 pptv/Hz to DMMP and a good selectivity of the polymer to DMMP with respect to dodecane and 1-octanol.
利用高灵敏度和低成本传感器对气相化学物质进行分布式感测，对于许多国防和消费应用来说具有重要意义。在本文中，我们使用改进的电容式微机械超声换能器（CMUT）作为谐振化学传感器，实现了对二甲氧基甲基膦酸酯（DMMP）的 ppb 级检测，分辨率达到 ppt 级，DMMP 是沙林毒气的常见模拟物。改进后的 CMUT 工作在 47.7 MHz 的更高谐振频率下，与之前开发的 CMUT 传感器相比，其质量灵敏度提高了 2.7 倍，达到 48.8 zg/Hz/μm²。为了进行实时感测，开发了一种使用 CMUT 谐振传感器作为频率选择器件的低噪声振荡器，在存在气流的情况下，它的 Allan 偏差为 1.65 Hz（3σ）；这相当于质量分辨率为 80.5 zg/μm²。CMUT 谐振传感器采用桑迪亚国家实验室（Sandia National Laboratory）开发的 50nm 厚的 DKAP 聚合物进行功能化，用于检测二甲氧基甲基膦酸酯（DMMP）。为了演示改进后的化学传感器系统的 ppb 级检测能力，在配备有实验化学设备的认证实验室（MIT Lincoln Laboratory）中对传感器性能进行了测试，该设备能够可靠、准确地提供广泛的低浓度范围，低至 10 ppb。我们报告了对 DMMP 的高体积灵敏度为 34.5 ± 0.79 pptv/Hz，以及聚合物对 DMMP 的良好选择性，相对于十二烷和 1-辛醇。
