Research On Fabrication Of Flexible Functional Devices And Integrated Systems

With the rapid development of lightweight,miniaturized and flexible wearable electronic devices,flexible integrated systems with supercapacitors as energy storage units have been paid much attention,because integration systems are different from the traditional systems which are supplied by independent external power and have complex connection between units.However,these studies just stay in the laboratory stage,and they can not be applied in practice.In the commercialization process,it is urgent to explore low-cost,large-scale manufacturing technology to fabricate multi-functional integrated microsystems.The dissertation mainly focuses on the fabrication of the flexible integrated micro system with micro supercapacitors as energy storage units.Based on the study on storage units and functional units,low-cost and large-scale technology have been explored to fabricate high-performance units,and to prepare the integrated microsystem.The specific research work is summarized as follows:Firstly,taking supercapacitor as the energy storage unit,the electrode fabrication method and high-performance electrode materials fabrication technology are studied.?1?A low-cost and large-scale printing method is proposed to prepare thin-film carbon electrodes for supercapacitors.Activated carbon slurry is prepared,and carbon film electrodes are printed on flexible carbon paper.Pseudocapacitive material are electrochemically deposited on carbon film electrodes to obtain positive electrodes,and a device is assembled.The electrochemical performance and reliability of flexible devices are carried out.?2?A low-cost,scalable method is proposed to fabricate high-performance carbon material for supercapacitors.The mass of potassium hydroxide is used to tune the porosity of the carbon electrode.75.9%capacitance retention is obtained when current density increased to 50 A g^-1,showing high rate capability.This method provides a low-cost and large-scale route for fabricating high-performance activated carbon materials.Secondly,taking the sensing unit as the research object,flexible pressure sensor and glucose sensor are fabricated.?1?A low-cost and large-scale method is proposed to fabricate porous graphene paper for pressure sensors.Two reduction methods including hydrazine vapor reduction and hydroiodic acid reduction methods are used to fabricate graphene paper.The effect of reduction methods on the structure and morphology are investigated.The results show that the graphene paper with gas-phase reduction method has larger deformation under external force,suggesting higher sensitivity.The sensitivity,response time and reliability of the device are tested,and its applications in human pulse detection,muscle and joint motion detection and speech recognition are also explored.?2?Three different copper oxide/carbon fiber structures are fabricated for glucose sensing.The sensitivity and response time of the three structures are tested.The reproducibility test,stability test,interference test and glucose dectection of calf serumsample are also carried out.The effect of the different nanostructures on the performance of the device is also analyzed.It turns out the glucose sensors based on the CuO nanostructures show high sensitivity,rapid response and high sensitivity.Finally,to fabricate a flexible integrated system,a micro supercapacitor as the energy storage unit and a photodetector serving as the functional unit are integrated on the same plane.A flexible solid-state symmetric hybrid microsupercapacitor is prepared through laser processing,electrochemical expansion and electrochemical deposition MnO₂.The capacitance,rate capability and cycle life is tested.At the same time,the cycling testing under bending states is carried out to testify its reliability.The result shows that four energy storage devices in series can light up the LED and successfully drive the electronic clock for 40 min.Then perovskite material serves as a photosensitive layer on the microelectrode to fabricate a photodetector.Finally,the microsupercapacitors and photodetectors are integrated on the same PET substrate to fabricate a flexible microsystem.It turns out that the microsupercapacitor can drive the photodetector successfully,and the signal is almost consistent with the external power supply,confirming the feasibility of the integrated flexible microsystem.