Flexible Miniaturized Nickel Oxide Thermistor Arrays via Inkjet Printing Technology

In this study, an inkjet printing process was developed to produce thermistor arrays for temperature sensing applications. First, a formulation process was carefully performed to generate a stable nanoparticle ink for nickel oxide, a material with a large temperature coefficient of resistance. The thermistor was then fabricated by printing a square NiO thin film in between two parallel silver conductive tracks on either glass plates or polyimide films. The printed thermistor, which has an adjustable dimension with a sub-millimeter scale, can operate over a wide range from room temperature to 200 degrees C with great sensitivity (B values similar to 4300 K) without hysteretic effects. When printed on polyimide films, the thermistors can also be bent or attached to curved surfaces to provide accurate and reliable temperature measurements. Moreover, the thermistor responds quickly to small temperature changes and provides an effective tool for transient temperature measurements. Finally, a thermistor array was fabricated to show the flexibility of this inkjet printing process and to demonstrate the applicability of the printed devices for temperature sensing applications.