Electrohydrodynamic inkjet printing of Pd loaded SnO2 nanofibers on a CMOS micro hotplate for low power H2 detection

A high-performance low-power micro hotplate (MHP) hydrogen sensor was fabricated through electrohydrodynamic (EHD) inkjet printing technique. Electrospun Pd loaded SnO2 nanofibers with lengths of 250-850 nm were precisely printed on the suspended central part of an MHP with an area of 100 um × 100 um. The printhead in the printing system was a low-cost metallic needle with an inner diameter of 110 um, which was large enough to prevent clogging by the nanofibers. The printing process was observed by a high-speed camera. Small droplets with diameters of 50-80 um were produced at each ejection by providing a high voltage to the metallic needle. It was found that the bridge-type MHPs used in our experiment can promote the positioning precision due to its bound effect to the droplet. In the gas sensing measurement, the Pd loaded SnO2 MHP gas sensor showed a remarkable response to H2 with a low power of only 9.1 mW. The experiment results demonstrate the excellent adequacy of EHD inkjet printing technique to realize effective mass fabrication of MHP gas sensors or sensor arrays.