State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China.
Nanotechnology. 2010 Jul 2;21(26):265501. doi: 10.1088/0957-4484/21/26/265501. Epub 2010 Jun 10.
This paper presents a novel sensing layer modification technique for static micro-cantilever sensors that detect trace explosives by measuring specific adsorption-induced surface stress. For the first time, a method of directly modifying a siloxane sensing bilayer on an SiO(2) surface is proposed to replace the conventional self-assembled monolayers (SAMs) of thiols on Au to avoid the trouble from long-term unstable Au-S bonds. For modifying the long-term reliable sensing bilayer on the piezoresistor-integrated micro-cantilevers, a siloxane-head bottom layer is self-assembled directly on the SiO(2) cantilever surface, which is followed by grafting another explosive-sensing-group functionalized molecule layer on top of the siloxane layer. The siloxane-modified sensor has experimentally exhibited a highly resoluble response to 0.1 ppb TNT vapor. More importantly, the repeated detection results after 140 days show no obvious attenuation in sensing signal. Also observed experimentally, the specific adsorption of the siloxane sensing bilayer to TNT molecules causes a tensile surface stress on the cantilever. Herein the measured tensile surface stress is in contrast to the compressive surface stress normally measured from conventional cantilever sensors where the sensitive thiol-SAMs are modified on an Au surface. The reason for this newly observed phenomenon is discussed and preliminarily analyzed.
本文提出了一种新颖的传感层修饰技术，用于通过测量特定的吸附诱导表面应力来检测痕量爆炸物的静态微悬臂传感器。本文首次提出了一种直接修饰在 SiO2 表面上的硅氧烷传感双层的方法，以替代传统的 Au 上的硫醇自组装单层（SAMs），从而避免长期不稳定的 Au-S 键带来的麻烦。为了修饰集成在压阻式微悬臂梁上的长期可靠的传感双层，硅氧烷头底层直接自组装在 SiO2 悬臂梁表面上，然后在硅氧烷层的顶部接枝另一个爆炸物传感基团功能化分子层。实验表明，经过硅氧烷修饰的传感器对 0.1 ppb TNT 蒸气具有高度可分辨的响应。更重要的是，在 140 天后的重复检测结果显示传感信号没有明显衰减。实验还观察到，硅氧烷传感双层对 TNT 分子的特异性吸附会在悬臂梁上产生拉伸表面应力。与通常在 Au 表面上修饰敏感硫醇-SAMs 的传统悬臂梁传感器所测量的压缩表面应力相反，本文测量到了拉伸表面应力。讨论并初步分析了这一新观察到的现象的原因。
