A Flexible Pressure Sensor Consisting Of Polydimethylsiloxane And Thin Film Transistor

As a basic flexible electronic component,flexible pressure sensors can convert the pressure to electric signals,which have a wide range of potential applications in the fields of human-computer interaction,medical diagnosis and intelligent display.Therefore,it has received extensive attention from both academia and industry.According to different working mechanisms,flexible pressure sensors can be divided into several types,such as piezoresistive,capacitive,piezoelectric and so on.The capacitive flexible pressure sensor has been extensively studied due to the advantages of temperature stability and sensitivity to low static pressure.However,capacitive pressure sensors convert the pressures to capacitance,which is inconvenient to be integrated into the circuit systems,where the complexity of peripheral modules will be significantly increased.The large-area array manufacturing of the capacitive pressure sensor is another challenge.This thesis presents a novel pressure sensor based on polydimethylsiloxane(PDMS)and amorphous indium gallium zinc oxide thin film transistor(a-IGZO TFT).A series of investigation and optimization of integrated flexible pressure sensor are carried out focusing on three key factors: sensitivity,flexibility and large-area fabrication accordingly.These researches have been detailed as following:(1)Scheme design and analysis of integrated flexible pressure sensor.The circuit and structure of the integrated flexible pressure sensor are designed initially.Then,combining the mechanism of the capacitive pressure sensor and the electrical characteristics of the thin film transistor,the integrated flexible pressure sensor is analyzed from the functional and principle aspect respectively.(2)Characterization and optimization of the pressure sensitive property of PDMS.Firstly,the fabrication process of PDMS film is designed,followed by the investigation of the impact of curing temperature to the pressure sensitivity of PDMSfilm.At the same time,the pressure test system is set up successfully.The optimum curing temperature in the range of 80-200? is confirmed by a series of pressure sensitivity tests at different curing temperatures.Subsequently,the microstructure is experimentally proved to be correlated to the pressure-sensitive properties of PDMS films.The microstructured molds are fabricated using photoresist by photolithography and development techniques.The microstructured PDMS films is successfully assembled,which further improves the pressure sensitivity of PDMS film.(3)Preparation and analysis of integrated flexible pressure sensor.The layout of the integrated flexible pressure sensor is designed initially.Then,the fabrication process of the flexible thin film transistor on the PI substrate is explored,and the integrated flexible pressure sensor is successfully fabricated.These thin film transistors have different channels with respective width-to-length ratios,which is confirmed to be correlated to the performance of the thin film transistor.Additionally,plasma treatments with various parameters have been conducted to the thin film transistor leading to the threshold voltage modulation.The performance of the integrated flexible pressure sensor is improved based on above studies.The pressure sensitivity of the integrated flexible pressure sensor is tested in the subthreshold region and the linear region finally.With the confirmation of the stability,this pressure sensing device is proved to be integrated and applied as an array.