High-performance H2 sensors with selectively hydrophobic micro-plate for self-aligned upload of Pd nanodots modified mesoporous In2O3 sensing-material

Miniaturization technology is of great importance in the research field of gas sensors. By using MEMS (micro-electro-mechanical system) technology, various micro-sensors have been developed. To fabricate chemiresistive type micro-sensors, one of the critical technologies lies in that the sensing material is needed to precisely load onto the designated micro-region, which is still a difficult task up to now. Herein, patterned self-assembly monolayer (SAM) with super-hydrophobic characteristic, which is prior grown onto the non-sensing region of the micro-chip, is used to guide the sensing material spontaneously flow onto the hydrophilic sensing area. As a proof of concept, Pd nanodots modified mesoporous-In2O3 is successfully loaded onto the desired micro-sensing area of a micro heating-plate sensor. The fabricated sensor shows ultra-high response to H2 gas with concentrations in the range of 0.5-100 ppm. Without SAM, some special instruments such as micro-manipulator are needed to deposit the sensing material onto the micro-sensing region. Our experiments indicate that the patterned SAM not only simplify the process of material loading, but also facilitates to improve the sensing performance (i.e. reduce the noise coming from sensing material dispersion and electric leakage). Our technology is suitable for various sensing materials precisely loading onto micro sensors without the aid of special instruments.