All-printed low-power metal oxide gas sensors on polymeric substrates

Abstract This paper presents a novel approach for the fabrication of miniaturized and fully printed metal-oxide (MOX) gas sensors on a polyimide (PI) substrate by using digital manufacturing of the functional layers, namely aerosol jet and inkjet printing technologies. We are reporting a stacking approach for all-printed MOX sensors for the first time. High resolution (∼20 μ m) printing of metallic patterns is enabled by aerosol jet of gold nanoparticles in solution, which leads to printed resistive thermal transducers with a reduced size of 500 × 500 μ m 2 . The wide area printing feature of the aerosol jet is also applied for printing a thin (∼2 μ m) inter-dielectric PI layer in between the heater and gold electrodes. The gas sensing layer, i.e. Pd-doped tin oxide (SnO 2 ) nanoparticles, is deposited through drop on demand inkjet printing. Proper operation of the printed sensors is evaluated in both dry and humid conditions under reducing and oxidizing gases i.e. CO and NO 2 , respectively. All the tests are performed at 250 °C, produced by the integrated micro-hotplate at a low power consumption of ∼78 mW. The chemo-resistive responses of the sensors towards both the gases are found to be in the acceptable range as compared to conventional metal-oxide gas sensor responses. These results are very promising for future integration of MOX gas sensors notably in smart printed electronics, disposable systems and wearables.