Yinfang Zhu

Cantilever array sensor for multiple liver cancer biomarkers detection

A novel microcantilever biosensor was batch-fabricated with IC compatible MEMS technology for joint detection of liver cancer biomarkers with high sensitivity, high throughput, high specification, and good precision. A micro-cavity was designed in the free end of the cantilever for local antibody-immobilization using micro printing system, which can dramatically reduce the effect of adsorption-induced k variation. A linear relationship between the resonance frequency shift and the antigen concentration was observed for three liver cancer biomarkers, AFP, GGT-2, and HGF. In addition, the presented immunosensing method has little cross-reactivity to different antigen, paving the way to a highly specific technique. These approaches will promote clinical application of the cantilever sensors in cancer early diagnosis.

Ultrasensitive Detection of Infrared Photon Using Microcantilever: Theoretical Analysis

We present a new method for detecting near-infrared, mid-infrared, and far-infrared photons with an ultra-high sensitivity. The infrared photon detection was carried out by monitoring the displacement change of a vibrating microcantilever under light pressure using a laser Doppler vibrometer. Ultrathin silicon cantilevers with high sensitivity were produced using micro/nano-fabrication technology. The photon detection system was set up. The response of the microcantilever to the photon illumination is theoretically estimated, and a nanowatt resolution for the infrared photon detection is expected at room temperature with this method.

A High-Throughput Cantilever Array Sensor for Multiple Liver Cancer Biomarkers Detection

A novel microcantilever biosensor was batch-fabricated with integrated circuit compatible micro-electro-mechanical system technology for joint detection of liver cancer biomarkers with high sensitivity, high throughput, high specification, and good precision. A micro-cavity was designed in the free end of the cantilever for local antibody-immobilization using micro-printing system, which can dramatically reduce the effect of adsorption-induced stiffness coefficient k variation. A linear relationship between the resonance frequency shift and the antigen concentration was observed for three liver cancer biomarkers, alpha-fetoprotein, γ - glutamyl transpeptidase II, and hepatocyte growth factor. In addition, the presented immunosensing method has little cross reactivity to different antigens, paving the way to a highly specific technique. These approaches will promote clinical application of the cantilever sensors in early cancer diagnosis.

Stability of Mechanical Properties for Submicrometer Single-Crystal Silicon Cantilever Under Cyclic Load

The stability of mechanical properties of submicrometer-thick cantilevers was systematically investigated under different conditions: driving force, vacuum, humidity, and temperature. For the submicrometer-thick cantilever, the cyclic test did not lead to failure but resulted in distinguish resonant frequency shift. The frequency shift is caused by fatigue stress, adsorption/desorption, and temperature-induced lever softening effect. At a vacuum of 10-3 Pa, the stress change makes a dominant contribution to the frequency shift, and the desorption induced lever softening is a secondary factor. The resonant fre quency continuously goes down with the cycles, and this frequency shift increases with the driving force of the lever. At a vacuum of 1 Pa, the resonant frequency is nearly unchanged until 109 cycles. Humid air accelerates water adsorption and dramatically enhances the lever stiffness, resulting in frequency increase. At room temperature, the Q factors of the lever change a little with the cycles in spite of the frequency decrease. At elevated temperature (100°C and 200°C), the frequency and Q factors increase with the cycles due to the dominant desorption.

Development of Microcantilever Sensors for Liver Cancer Detection

Recently, microcantilever-based technologies are playing more and more important roles in early diagnosis of cancer due to their high sensitivity, fast response, low cost, small reagent consumption, portability, real-time, labelfree detection, and so on. However, in conventional cantilever sensors working on mass-loading principle, the change of stiffness coefficient k is neglected. This results in distinct error for mass detection. Some researchers tried a local immobilization method to eliminate the undesired effect of k. But the change of k in this method still brings unexpected error. An accurate theoretical model is needed to take the effect of k change into account in the local immobilization approach. A micro-cavity was designed in the free end of the cantilever for local antibodyimmobilization in our work, thus the adsorption-induced variation of k can be dramatically reduced compared to that caused by adsorption of the whole lever. In addition, an analytical model has been established to eliminate the effect of adsorption-induced lever stiffness change and has been applied to precise mass detection of cancer biomarker AFP, the detected AFP antigen mass (7.6 pg/ml) is close to the calculated one (5.5 pg/ml), two orders of magnitude better than the value by the fully antibody-immobilized cantilever sensor. These approaches will promote clinical application of the cantilever sensors in early diagnosis of cancer.