Abstract
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.
Highlights
Metal oxide semiconductor gas sensors are widely used in daily life,[1] industrial production,[2] and hazardous chemicals transport.[3]
The microdroplets stayed on each micro hotplate (MHP) and didn’t interfere with each other, thanks to the bridge structure that trapped the microdroplets in the central area and left no place for them to flow away or spread out
This result demonstrates that bridge type MHP is helpful to promote the print accuracy, especially when several microdroplets are printed on an MHP
Summary
Metal oxide semiconductor gas sensors are widely used in daily life,[1] industrial production,[2] and hazardous chemicals transport.[3]. One-dimensional, hierarchical or hollow structure metal oxides often have larger dimensions and more excellent gas sensing properties than nanoparticles because they have a larger specific surface area and more active sites.[32,33] MHP gas sensors based on these materials are highly expected, but they can hardly be printed with a high resolution by a piezoelectric printer. The printhead, which is a low-cost metallic needle, should fulfill the accuracy demand for material deposition on the MHP of 100 um × 100 um and simultaneously avoid the clogging problem. This thought was proved by the smooth printing process observed by a high-speed camera. The gas sensitivity test showed the excellent performance of the MHP gas sensor and proved the effectiveness of the EHD printing method
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