声表面波爆炸物传感的质-热双重敏感机制研究

The conventional SAW gas sensors are based on mass sensitive effect in the adsorption state either with specific coatings or without any film at all. The sensors with coatings have poor long term stability and slow response, while those with non-film are relied on low temperature condensation thus suffered from very poor selectivity. In this project, mass/heat double effects in the desorption state are proposed as a new sensing mechanism for SAW gas sensors to detect explosive particles. Through non-film condensation at low temperature and subsequently heating the sensor, the sudden changes of the SAW signal are expected to be detectable at the fixed melt points of each explosive based on two fold mechnisms. On the one hand, the evaporation rate of a particle will undergo a sudden change at the particle melting progress, therefore induces a sudden change of the SAW signal according to the mass effect. On the other hand, the small amount of heat adsorbed in the melting progress will also resulted in a sudden change of the SAW signal according to the temperature effect. The two mechnisms can be mutually enhanced and contributes a larger signal. Tht project aims at establishing a new recognition method for explosives which utilize the sudden signal changes at the melt points as a new criterion. The new method can realize qualitative identification and quantitative determination of a chemical sensor with no interferece, not only have the advantages of high sensitivity and high selectivity, but also inherently posses small size and long-term stability. The technical scheme of this project is original and can promote the self-innovation ability, and is of great importance for homeland security and anti-terrorism.

现有的SAW气体传感器大多工作于吸附时的质量敏感效应，有敏感膜的响应慢、长期稳定性差，无膜冷凝式的存在着基本没有选择性的问题。本项目提出基于脱附时的质量/温度双重敏感效应的SAW气体传感新机制，通过无膜冷凝吸附爆炸物微粒后测量加热解吸谱，利用微粒熔点固定的特征，一方面基于SAW传感器的质量敏感效应，测量微粒在熔化前后由于蒸发速度的突变所导致的SAW频率突变；另一方面基于SAW传感器的温度敏感效应，测量微粒在熔化时吸热所导致的频率突变，研究质/热双重效应的叠加与复合机制，建立以熔点处的频率突变为判据的爆炸物识别方法。该方法引入了温度这一新的维度，能实现化学传感器的定性识别和定量检测两个基本功能的独立工作而互不干扰，不仅兼顾高灵敏和高选择，同时还具有体积小、长期稳定性好等内在优势。本项目的技术方案具有原创性，可提高我国相关领域的基础研究水平和自主创新能力，对于国土防卫及反恐安防具有重要意义。

不同于常规的SAW传感器，本项目完全不使用敏感膜，突破了敏感膜所带来的传感器仅具有半选择性、响应慢、长期稳定性差等固有缺点。同时本项目的检测对象也不是气体分子，而是爆炸物微粒，不仅规避了气相检测对灵敏度高达10-6ppb的严苛要求，还利用微粒具有固定熔点的特性，通过一个内置有铂膜加热器的兰姆波器件，建立了以熔点处的频率突变为判据的爆炸物识别方法。微粒在熔化阶段的频率突变一方面源于SAW传感器的质量敏感效应，由熔化前后蒸发速度的突变所导致；另一方面源于SAW传感器的温度敏感效应，由微粒在熔化时吸热所导致。通过采用负温度系数的兰姆波器件，实现了质量突变信号和温度突变信号的叠加增强，发展了SAW传感器的质/热双重敏感新机制。该新机制引入了温度这一新的维度，如同色谱中的时间维度和质谱中的空间维度一样，实现了仅用一个检测器就能对多种物质的进行识别，大幅度地提高了传感器的选择性，进而实现了化学传感器的定性识别（根据突变信号对应的温度）和定量检测（根据突变信号的大小）两个基本功能的独立工作而互不干扰。.项目已经完成的兰姆波器件为全膜片结构，该种器件在一次温度扫描中正确识别出DNT和TNT两种物质，最小检测限为250ng，发展了一种兼顾高灵敏、高选择、高稳定的SAW气体传感器新技术，完成了项目的既定研究目标。