Department of Engineering, Reykjavik University, Menntavegur 1, 107 Reykjavik, Iceland.
Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik, Iceland.
Sensors (Basel). 2023 Dec 18;23(24):9901. doi: 10.3390/s23249901.
Accurate and fast breath monitoring is of great importance for various healthcare applications, for example, medical diagnoses, studying sleep apnea, and early detection of physiological disorders. Devices meant for such applications tend to be uncomfortable for the subject (patient) and pricey. Therefore, there is a need for a cost-effective, lightweight, small-dimensional, and non-invasive device whose presence does not interfere with the observed signals. This paper reports on the fabrication of a highly sensitive human respiratory sensor based on silicon nanowires (SiNWs) fabricated by a top-down method of metal-assisted chemical-etching (MACE). Besides other important factors, reducing the final cost of the sensor is of paramount importance. One of the factors that increases the final price of the sensors is using gold (Au) electrodes. Herein, we investigate the sensor's response using aluminum (Al) electrodes as a cost-effective alternative, considering the fact that the electrode's work function is crucial in electronic device design, impacting device electronic properties and electron transport efficiency at the electrode-semiconductor interface. Therefore a comparison is made between SiNWs breath sensors made from both p-type and n-type silicon to investigate the effect of the dopant and electrode type on the SiNWs respiratory sensing functionality. A distinct directional variation was observed in the sample's response with Au and Al electrodes. Finally, performing a qualitative study revealed that the electrical resistance across the SiNWs renders greater sensitivity to breath than to dry air pressure. No definitive research demonstrating the mechanism behind these effects exists, thus prompting our study to investigate the underlying process.
准确和快速的呼吸监测对于各种医疗保健应用非常重要，例如医学诊断、研究睡眠呼吸暂停和生理紊乱的早期检测。用于此类应用的设备往往会使受测者（患者）感到不适且价格昂贵。因此，需要一种具有成本效益、重量轻、尺寸小且非侵入性的设备，其存在不会干扰所观察到的信号。本文报道了一种基于硅纳米线（SiNWs）的高度敏感人体呼吸传感器的制造，该传感器是通过自上而下的金属辅助化学蚀刻（MACE）方法制造的。除了其他重要因素外，降低传感器的最终成本至关重要。增加传感器最终价格的一个因素是使用金（Au）电极。在这里，我们研究了使用铝（Al）电极作为具有成本效益的替代方案的传感器响应，因为电极的功函数在电子器件设计中至关重要，会影响器件的电子特性和电极-半导体界面处的电子传输效率。因此，我们比较了由 p 型和 n 型硅制成的 SiNWs 呼吸传感器，以研究掺杂剂和电极类型对 SiNWs 呼吸传感功能的影响。我们观察到在 Au 和 Al 电极下，样品的响应存在明显的方向变化。最后，进行定性研究表明，SiNWs 上的电阻对呼吸的敏感性大于对干燥空气压力的敏感性。目前还没有明确的研究证明这些效应背后的机制，因此我们的研究旨在调查潜在的过程。
