An area-variant type MEMS capacitive sensor based on a novel bionic swallow structure for high sensitive nano-indentation measurement

In this paper, a high sensitive area-variant type MEMS capacitive sensor was proposed for nano-indentation measurement. The proposed bionic swallow structure processed a high mechanical sensitivity without influences from the load coupling effect. Six comb arrays were optimized and integrated into the proposed sensor with a novel comb sensing configuration for eliminating electrostatic interferences resulting from multiple combs and maintaining compact chip size. Based on the proposed micro-machined process, comb arrays have been fabricated with great consistency, which exhibited a static differential output of 0.0554 pF. The fabricated sensor has been characterized with rigid glass cube and AFM cantilevers, and the measured force sensitivity can reach 98.54 aF/nN for a larger measurement range of 142 µN with a linearity of 0.9996. The fabricated sensor also exhibited a high resolution of 0.9819 nN, indicating its great feasibility in nano-indentation measurement at the sub-nano-Newton level.