Design,Manufacture And Application Of Flexible Sensor Based On Interface Cross-linking Intensified Electroless Deposition

In the era of Artificial Intelligence?AI?of the Internet of Everything?IoE?led by 5G technology,sensors,big data,machine learning and intelligent robots are connected with each other to form a system of mutual support and mutual promotion,which constantly promotes the progress of science and technology.However,the most of AI behaviours and applications need to be realized by sensors.As the hardware foundation for the development of AI technology,sensors have become the necessary conditions for the AI of the IoE.As an importantbranch of sensors,flexible sensors play an important role in the fields of wearable devices,flexible electronic skin,disease diagnosis,and intelligent robots.Among them,flexible electrodes,flexible strain sensors and flexible pressure sensors have received the most extensive attention and research in the capture of human physiological signals.However,there are still many problems in the testing,design and manufacturing of these flexible devices:?1?In terms of test equipment,there are no commercial special test equipment for flexible electronic devices,such as the test equipment that realizes uniaxial and circumferential stretching,bending and torsion of flexible devices,and the equipment that realizes sensor array measurement,etc.?2?In terms of materials,it is necessary to improve the binding force between sensitive materials and flexible substrates,so as to ensure that the signals of flexible devices will not be unstable due to material peeling during long-term use.?3?In terms of devices,reasonable structural design is crucial to obtain large measuring range,high tensile limit and high sensitivity,etc.Based on the above requirements for test equipments,sensitive materials and structures of device,the full text of the research is as follows.Firstly,a uniaxial stretching,compression and torsion test platform for flexible devices has designed and manufactured.The stretching and compression distance of the device ranges from 0.01 to 400 mm,and the repeated positioning accuracy is±0.01mm/m.In addition,the torsion angle of the device is no less than 0.01 rad,and the repeated positioning accuracy is±0.05 rad/r.The circumferential tensile test platform for flexible devices was designed and and manufactured.The variation range of circumferential stretching distance is 0.01-400mm,and the repeated positioning accuracy is±0.01mm/m.The high-throughput resistance test platform was designed and and manufactured with a sampling frequency of 50 Hz and 24 single-ended signal acquisition.Secondly,an electroless deposition?ELD?process based on cross-linking enhancement of dopamine?DA?and functionalized silane is proposed to prepare flexible electrodes with a strong binding?3.1 MPa?between the Ag layer and the flexible substrate.In this process,flexible substrate,DA,functionalized silane and metal are bonded layer by layer to ensure that the conductive metal film is firmly bound to the flexible substrate.Since the adsorption of catechol groups in dopamine is suitable for many substrates,the amino groups in functionalized silanes can complex with many metal ions,this process is highly versatile and can produce different metal films on different substrates.The completed cross-linking ELD-Ag flexible electrode can stably capture the surface electromyogram?SEMG?signals with high signal-to-noise ratio?26.3?and small error bar?±1.8?.Thirdly,a hierarchical pressure-peak structure?HPPS?is proposed to make flexible pressure sensor with a wide pressure test range?0.04⁶00 kPa?and a high sensitivity(11.60 kpa^-11608.75 kpa^-1),and the pressure-peak effect?PPE?of the pressure peak structure?PPS?is explored thoroughly.Using a metal plate with regular pyramid protrusions on the surface as the template,Polydimethylsiloxane?PDMS?film with micro pyramids on the surface is fabricated by the two-step soft lithography process.The Polyvinyl Pyrrolidone?PVP?nanowire mesh with adjustable pore size is prepared on the plate electrode by electrospinning.During the compression contact of the flexible pressure sensor,the contact area change between the micro pyramids and the entire plate electrode form the first-stage PPS,and the changes between the sensitive material and the electrode in the PVP nanowire mesh form the second-stage PPS.This HPPS can effectively slow down the decreasing rate of the change of resistance in compression deformation,thereby improving the pressure test range while ensuring test sensitivity.In the PPE of PPS,the change of contact area is the main reason for the change of the resistance of piezoresistive flexible pressure sensor.In the compression contact process,the fewer the number of peaks,the thinner the sensitive material,the slower the resistance decline rate,and the wider the pressure range can be detected.As application,the cross-linking enhanced ELD-Ag HPPS flexible pressure sensor can steadily and rapidly capture pressure changes,such as the detection of physiological stress in human body and the detection of the clamping force in the fixture of Da Vinci surgical robot.Finally,a microporous structure is proposed to make flexible strain sensor with large uniaxial tensile limit?60%?,and the current-bridge effect?CBE?of the microporous structure is explored thoroughly.By applying lotus leaf as the template,PDMS films with microporous structure on the surface were prepared by one-step lithography process.The microporous structure can change the strain distribution of the conductive layer during tensile strain,and make the conductive layer form micro-mesh cracks with micropores as nodes.Throughout the conductive path,the micropores act as the current bridges,ensuring a stable change in current under tensile strain andas the use of the strain sensor.In the CBE of the microporous structure,the deeper the micropore is and the smaller the spacing of micropores is,the better the effect of strain range lifting.The lifting effect was not significant after the micropore depth is greater than the micropore diameter and the micropore spacing is zero.For the prepared cross-linking enhanced ELD-Ag microporous structure flexible strain sensor,it can stably and quickly capture strain changes,such as finger bending.