Drop‐on‐demand inkjet printing of highly viscous fluids represents a highly attractive emerging technology for advanced material deposition. The jetting of viscous inks, such as concentrated polymer solutions and nanoparticle suspensions, is a key enabling technology for many industrial applications, ranging from microelectronics to biomedicine and ceramics manufacturing. Currently available standard inkjet printers typically operate in a relatively narrow viscosity range (up to 16 mPa s), and alternative drop‐on‐demand printing techniques (such as laser‐induced forward transfer) present limited industrial applicability. In this context, the development of a piezoelectric‐driven printhead capable of jetting high‐viscosity fluids is of great interest. Herein, a prototype of such a device is presented and its performance is evaluated using model fluids at increasing viscosities. Specifically, the dependence of emitted droplets’ properties on jetting parameters is evaluated and linked to the physical characteristics of the system. In optimal conditions, piezoelectric jetting of solutions characterized by viscosities in excess of 200 cP is achieved. Finally, as an applicative example, the jetting of functional inks is attempted. A ZnO suspension and a poly(3,4‐ethylenedioxythiophene) (PEDOT) based solution are successfully jetted to demonstrate the applicability of the developed printhead to the deposition of ceramic suspensions and concentrated polymer solutions.
We report developing a SnO2 thick-film gas sensor deposited by screen printing onto a micromachined dielectric stacked membrane equipped with an embedded polysilicon microheater and two resistors for temperature measurement. The microheaters were designed to enable an operating temperature of 400 °C at about 30 mW power consumption. A newly developed scheme for temperature measurement was adopted for on-line adjustment of the film temperature through a conventional low-power feedback circuit. The electrical response of the prototypes to CO and CH4 is discussed, and their performance is compared to traditional devices fabricated via thick-film methods.
We report on the design, fabrication, and characterisation of a microheater module for chemoresistive, metal-oxide semiconductor gas sensors, consisting of a dielectric stacked membrane, micromachined from bulk silicon and with an embedded polysilicon resistor heater. Fabricated structures exhibit excellent heating efficiency, requiring only 30 mW to achieve a temperature of 500 C. Measured electrothermal characteristics are in good agreement with the outcomes of 3D numerical simulations.
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