Fabrication,Packaging And Glucose Detection Of Chitosan Electric Double Layer IGZO Thin Film Transistor

Biochemical sensors have important applications in the area of homeland security,medical and environmental monitoring,bioscience research and also food safety.Nowadays,the effect-field transistor?FET?biosensor has been widely used in the biochemical molecular detection due to rapid electrical detection,portability,inexpensive mass production,and the possibility of on-chip integration of both sensor and measurement systems.Compared to all kinds of thin film transistors?TFTs?,oxides TFTs,especially indium gallium zinc oxide?IGZO?TFTs,have attracted considerable attention due to their simplified structure,cost-effective,fast response,high sensitivity,and superior electrical properties.Nevertheless,TFTs based on conventional gate dielectrics normally operate at a large voltage,which is undesirable from the standpoint of energy consumption.In this paper,we employ a simple method for the large scare fabrication of transparent IGZO TFTs with Chitosan?CS?gate dielectric on a pilot line.By examining devices with different channel structures,the optimal channel structure is determined.Then,the CS-based IGZO TFTs are sealed in different ways,and the sealing effects of different packaging technologies are compared.Based on the above research,the IGZO TFTs with CS gate dielectric are used to detect glucose and the fluid passage is fabricated.The works of this paper are as follow:?1?The characteristics of the CS gate dielectric and the IGZO thin films are studied.The results indicate that the CS gate dielectric has a large capacitance and electric double layer characteristics.Furthermore,the IGZO thin films are amorphous,and the thin films have a very smooth and compact surface.Meanwhile,the performance of the TFTs with different channel structures is tested.Besides,by establishing the capacitance equivalent model and the channel geometry model,the influence of channel geometry on TFTs performance is explained.The results show that the TFTs with L=100 ?m,W=100 ?m and D=100 ?m have a high on/off current ratio? 10⁶?,a low subthreshold swing(0.24 V.dec^-1),and a low threshold voltage?0.20 V?.?2?The Al₂O₃ thin film packaging,PDMS packaging,and laser packaging are employed to encapsulate devices.Comparing the effects of different Al₂O₃ thicknesses on devices,it is found that the threshold voltage and subthreshold swing enhance with the increase of the Al₂O₃ thin film thickness.This may be caused by cracks generated after Al₂O₃ deposition.Moreover,the advantages and disadvantages of the PDMS and laser packaging methods are discussed,and the performance of the devices with different sealing methods are studied.As a result,it is found that the performance of the CS-based IGZO TFTs with PDMS packaging is reduced remarkably after stored under the air environment for three months.Compare to the devices with PDMS packaging,the devices with laser packaging exhibit better long-term stability.And the laser packaging process is easy to realize larger scale industrial production.?3?In order to make the CS-based IGZO TFTs with sensitivity to glucose,the glucose oxidase is drop-cased on the CS gate dielectric surfaces.It is found that this sensor can detect glucose in the concentration range between 0.5 m M and 30 m M,covering typical glucose concentrations in the human body?normal range is 3.9-6.1 m M?.Moreover,compared with a remarkable response to the change of glucose concentration in the blood range,exposure of the sensors to uric acid?UA?and ascorbic acid?AA?have little response irrespective of the concentration of AA and UA,which implies that the concentration of UA and AA have no effect on the detective sensitivity of glucose.In addition,in order to detect samples with convenience,the fluid passage is successfully made.