基于微悬臂梁高次谐波的微小质量检测技术研究

Ultra-small mass detection based on a higher harmonics microcantilever in liquid

针对微悬臂梁动态检测方式无法应用于液体环境,提出了一种利用微悬臂梁的高次谐振进行微小质量检测的方法。对于相同的被测量质量变化量,微悬臂梁的谐振级次越高,其频率偏移就越大,从而达到较高的灵敏度。以表面修饰了三乙基氢硫基十二基铵层(敏感层)的微悬臂梁为传感元件,以CrO42-为被测物,在原子力显微镜(AFM)上检测了敏感层吸附CrO24-前后微悬臂梁的5次、6次、7次和8次谐振频率的变化。结果证明,谐振级次越高,灵敏度越高,在8次谐振时的检测灵敏度能够达到2.50Hz/pg。

A microcantilever working on dynamic mode is usually used for ultra-small mass detection by measuring its resonation frequency shift before and after mass adsorption. However,when operating in liquid,the heavy hydrodynamic damping effect often disables the application of a microcantilever resonating at its fundamental frequency because of its very low detection sensitivity. To solve this problem, a detection method of using higher harmonics of a microcantilever is suggested and described in this paper. For the same amount of mass change,the higher the harmonics is,the bigger the frequency shift of the microeantilever vibration will be. Experiments with CrO4^2- as target molecules,and triethyl-12-mercaptododecylammonium immobilized on a microcantilver as the detection probe, were conducted on an atomic force microscope（AFM）. The results showed that higher harmonics give higher detection sensitivity,and at the 8^th harmonic,a detection sensitivity of 2. 50 Hz/pg was achieved.