Modification and functionalization of MEMS resonator for heavy metal ion detection

Abstract

The concern over heavy metal ion pollutants and their profound impact on the environment and human health demands the development of robust detection systems. Heavy metal ions pose a significant threat due to their potential imbalance for ecological and adverse health effects. Common detection methods often fall short in terms of sensitivity and selectivity, emphasizing the need for innovative sensing technologies. The proposed Micro-Electro-Mechanical System (MEMS) resonator utilizes its mass-sensitive properties to provide a highly accurate and reliable platform for heavy metal ion detection. To enhance the sensing capabilities and specificity of the MEMS resonator, an approach involving gold modification and functionalization within the microchannel has been employed. The closed and narrow structure of the microchannel, a common feature in microchannel resonators, presented challenges for conventional gold deposition methods. Overcoming this limitation, electroless deposition emerges as a viable technique for gold coating within the microchannel, hence amplifying the sensor's performance.

In this thesis, the MEMS resonator has been modified and functionalized to optimize mass sensing for heavy metal ions. The electroless gold deposition method was utilized and characterized to ensure gold deposition, contributing to the sensor's sensitivity and selectivity. Experimental results and characterization showcase the modified resonator detecting four heavy metal ions: mercury, lead, copper, and chromium. The resonance measurement was conducted for mercury adsorption, both in step-wise measurement and real-time measurement. The research findings not only contribute to a promising solution to address the challenges associated with heavy metal ion pollution in water environments but also offer an advancement of MEMS-based sensors in terms of internal modification and functionalization. Furthermore, specific functionalization was done to introduce the recognition element to enhance the sensing performances. Surface morphology, chemical characteristics, and mechanical resonance measurements were done to characterize and determine the system's sensing ability. The modified and functionalized devices were able to detect mercury up to 0.1 ppm of concentration. Further development of the sensing platform in terms of dimension and confined structure is expected to enhance the system's sensing ability.