Barauskas Dovydas, Pelenis Donatas, Dzikaras Mindaugas, Mikolajunas Marius, Vanagas Gailius, Virzonis Darius
Panevezys Faculty of Technology and Business, Kaunas University of Technology, 44249 Kaunas, Lithuania.
Sensors (Basel). 2022 Mar 16;22(6):2288. doi: 10.3390/s22062288.
The trade-off between the functionalization shift of the informative parameters and sensitivity of capacitive micromachined ultrasound transducers (CMUT)-based CO sensors is addressed, and the CMUT surface modification process by thin inkjet-printed polyethyleneimine (PEI) films is optimized. It was shown that by the proper preparation of the active CMUT surface and properly diluted PEI solution, it is possible to minimize the functionalization shift of the resonance frequency and the quality of the resonance and preserve the sensitivity potential. So, after optimization, we demonstrated 23.2 kHz frequency shift readings of the sensor with 16 MHz nominal frequency while in the gas chamber and switching between pure N and CO. After testing the sensors with different PEI film thickness, it was confirmed that a 200 nm average thickness of a PEI film is an optimum, because this is the practical limit of CO absorption depth at given conditions. Additionally, we note that modification of the hydrophilic/hydrophobic properties of the CMUT surface allows changing the nanoscale surface roughness of the printed PEI film and controlling the area resolution of the inkjet functionalization by reducing the diameter of a single dot down to 150 μm by a commercially available printer cartridge.
研究了基于电容式微机械超声换能器（CMUT）的一氧化碳（CO）传感器信息参数功能化转变与灵敏度之间的权衡，并对通过喷墨打印薄聚乙烯亚胺（PEI）薄膜进行的CMUT表面改性工艺进行了优化。结果表明，通过适当制备有源CMUT表面和适当稀释PEI溶液，可以最小化共振频率的功能化转变和共振品质，并保留灵敏度潜力。因此，优化后，我们展示了在气室中且在纯氮气和一氧化碳之间切换时，标称频率为16 MHz的传感器的频移读数为23.2 kHz。在测试了具有不同PEI薄膜厚度的传感器后，证实PEI薄膜的平均厚度为200 nm是最佳值，因为这是给定条件下CO吸收深度的实际极限。此外，我们注意到，CMUT表面亲水/疏水特性的改性允许改变印刷PEI薄膜的纳米级表面粗糙度，并通过使用市售墨盒将单个墨滴的直径减小至150μm来控制喷墨功能化的面积分辨率。
