Abstract
This work focuses on an inkjet-fabricated sensor based on copper oxide nanostructured particles on polymer flexible substrate for the sensing of alcohol vapours and humidity at room temperature. Nanoparticles were prepared by a microwave-assisted solvothermal sealed vessel synthesis method. The ink composition was developed on the basis of viscosity and surface tension optimization by the addition of polymeric steric surfactant and dispersant. The printing process was optimized with the help of non-dimensional criteria. Silver nanoink was used for the printing of an interdigitated pattern on a PET substrate which was overprinted by the copper oxide ink, thus obtaining a flexible flat sensor. Material design and all fabrication steps of the sensor respected the temperature limitation given by the thermal stability of the polymer substrate. Printed layers and motifs were characterized microscopically and by resistance measurement. The effectiveness of the prepared sensor was demonstrated and studied by measuring the response to saturated vapours at room temperature. The sensing layer showed the opposite resistance response to stimuli than expected for the well-known p-type sensing mechanism of CuO sensors operated at high temperatures. In addition to vapour sorption, condensation and desorption influencing electron, proton and ionic conductivity, manifestation of another mechanism was observed and an explanation suggested in terms of the electrochemical mechanism.
Highlights
Inkjet printing is a well-known technology which has been originally focused to transfer electronic graphical data onto substrates, like paper and flexible polymer sheets
We demonstrate the preparation of a fully inkjet-printed gas humidity and volatile organic compounds (VOC)
We show that CuO imparts a more complicated sensing mechanism at room temperature, different from the common p-type semiconductor mechanism applied in high-temperature operating CuO-based sensors
Summary
Inkjet printing is a well-known technology which has been originally focused to transfer electronic graphical data onto substrates, like paper and flexible polymer sheets. Inkjet printing is an additive manufacturing non-contact technique which enables transfer of graphical data to a target substrate by digitally-controlled deposition of droplets of ink. This method can be used for graphics or text printing but it can be used more generally to deposit materials onto any flat surface. A plethora of inorganic solid compounds can be deposited by this non-contact digital technique if they are prepared in the form of a fluid nanosuspension Among such nanomaterials, copper(II) oxide (CuO) is an important p-type semiconductor metal oxide. Among the studies of transition metal oxides (MOs) CuO has become a hot topic due to its interesting properties It is a p-type semiconductor material with a relatively narrow
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