| With the rapid development of Integrated Circuits and Sensors Industry, new generation of sensors with simple manufacturing process, low cost, light weight, high flexibility are on stage. Flexible sensors have a wide range of application in environmental monitoring, food transport and storage, comfort detection and so on. The design of flexible sensors on organic polyimide substrates includes lots of topics like the metallization realization, the stability during the bending process, the compatabilty of process, and so on. In our work, in combination of the inkjet printing, the patterned metallization on polyimide is realized via the surface modification and ion exchange. To simplify the process steps further and optimize the sensing performance, the double-side metallization structure is first proposed. The large-area array of temperature, humidity and gas sensors are batch-fabricated. The capacitive sensors with the integrated heaters located on two sides can be used for both in-situ sensitive material synthesis and high temperature reset and testing application. The main work is as following:First, in combination of the ink-jet printing and ion exchange technologies, the patterned Ag film was formed on PI via the low-temperature solution method. The PI surface modification was first conducted by KOH soaking, following by the ion-exchange process and ink-jet printing masking process, Ag patterns were obtained. The properties of surface morphological, electrical and mechanical are studied. The results indicated that the fabricated Ag/PI offers the properties like the highly conductive and highly flexible, which can meet the flexible sensor requirements.Secondly, the flexible resistive sensors for human body temperature detection wre fabricated. The sensors with different shapes were designed and fabrication and the corresponding electrical and mechanical properties were studied. The results indicated that the sensitivity, i.e., the temperature coefficient of sensor, can be adjusted by the process. For the snake-shaped sensors, the maximum sensivity obtained was (2.638±0.024) ×10-3/℃ in the range of -20～+120℃.Thirdly, with the innovative double-sided metallization technique, the humidity sensor integrated with heater is designed, which can realize in situ material synthesis and enhance the sensor performance. In combination of drop coating and in-situ heating process, the nano-leaf sized zinc oxide films were perpared. The humidity sensing performances of different sensitive layer such as PI, PAA, ZnO on the flexible substrate are studied. By introducing the heater, the properties such as the hysteresis and the desorption rate can be obviously improved.Fourthly, the capacitive ZnO gas sensors with the integrated heaters were fabricated. With the in situ synthized ZnO as sensing materials, the sensor responses toward to alcohol, acetone and ammonia were measured. The results indicated that the developed had the good performance. With the integrated heater, the reponse time, the sensitivity of the flexible gas sensor had been improved remarkably.Lastly, in view of the above flexible capacitive sensors, an interface circuit based on switching capacitor mechanism is presented. One important potential application of capacitive multi-sensors is the concept of flexible tag, and a LC structure based on PI substrate is prepared.The technology developed in this research has important guiding significance for the future research of flexible electronic devices and flexible gas sensors. |
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