In-situ Fabrication And Sensing Properties Of Copper-based Micro-nano Sensors In Microchannels

Microfluidics is an interdisciplinary subject developed on the basis of the microfabrication,chemical synthesis,fluidic dynamic,biological Engineering.It is widely used in biochemical detection,cell separation,sensor monitoring and other fields.The integration of functional micro-nano materials or structures and microfluidic devices will promote the multi-functionality and wide application of the certain devices.The positioning and preparation process of the micro-nano structure in the microchannel is limited by the size of the microchannels.While the electrical interconnects,as an important part of sensing and detecting,is also limited by the fluid properties and microchannel fabrication processes.In this work,the liquid-liquid two-phase interface reaction system in the microchannel is controlled,and the integration of synthesis,interconnection and sensing application of micro-nano structures take place together in the microfluidic device with the electrical part.Firstly,the products,mass transfer process as well as macro-interfacial reaction mechanism were studied by liquid-liquid immiscible two-phase macro-interface reaction,The mass transfer process of the interface reaction system is affected by the interface.Under the combined effects of reactant transport,interface solute partitioning and chemical reaction,sub-diffusion,diffusion,and super-diffusion occur in different reaction stages.The competition of the above processes during the reaction determines the size,morphology and properties of the products.It can also guide the control and applications of the liquid-liquid two-phase immiscible interfacial reaction system.The in-situ controllable synthesis of copper-based micro-nanowires with an aspect ratio of at least 1000 was achieved by controlling the immiscible two-phase parallel flow in the microchannel.The interface reaction mechanism and module in the microchannels were studied by the observation of reaction process as well as the morphology,size of the in-situ synthesized products.The Reynolds number of the two-phase parallel flow in the microchannel is smaller than 0.1,which is a typical laminar flow.In microchannels,the mass transfer along the vertical interface direction(lateral direction)is mainly controlled by diffusion.The interface reaction process and the ultimate morphology as well as size of the products were determined by the lateral diffusion under dimensional constraints.The in-situ synthesis of copper-based micro-nanowires and their electrical interconnects were successfully achieved by pre-integrating the thin film electrodes on the substrate and then performing the in-situ interfacial reaction.Finally,the sensing properties of in-situ copper-based micro-nanowire with main component of copper oxide were studied.The current response signal in methanol and ethanol liquid environments was increased by 2?3 orders of magnitude compared to nitrogen and liquid n-hexane environments.Under different illumination conditions,the maximum sensitivity of the sensor in methanol and ethanol solutions reached 70% and 40%,respectively.The adsorption,desorption and redox processes of the hydroxyl-reactive groups contained in the alcohol on the surface of cuprous oxide change the carrier distribution on the surface and inside of the copper-based product,leading to different electrical properties under different light conditions.And the detection properties of hydroxyl can be achieved.The copper-based micro-nano sensor provides a new method for the detection of hydroxyl-containing substances in the certain liquid environment.