Research On The Preparation And Performances Of Flexible Carbon Nanocomposite Pressure Sensors

Flexible sensors have been widely used in recent years in the manufacture of smart wearable devices,which can monitor mechanical deformation,and then convert the mechanical deformation into electrical signals（voltage,resistance,capacitance,etc.）that can be recognized by electronic devices,and the flexible wearable devices made of them can be used for human motion monitoring,health detection and other fields.But with the progress of society and the expansion of the scope of application of flexible sensors,its function gradually to multi-functional development.As the core component of flexible sensors conductive hydrogel,conductive hydrogel is also put forward higher requirements,conductive hydrogel needs to have both self-recovery,fatigue stability,large strain,high sensitivity and other characteristics.Therefore,the preparation of multi-functional conductive hydrogels has become a research hotspot,and then the flexible sensors prepared from conductive hydrogels as core devices can be widely used in wearable electronic devices,artificial intelligence and soft robotics.Based on this,three composite carbon-based conductive hydrogels were prepared in the thesis.The main research contents and conclusions are as follows.（1）Preparation and performance analysis of S-CNTs/PVA conductive hydrogelsA composite conductive hydrogel（S-CNTs/PVA conductive hydrogel）was prepared using silane-modified multi-walled carbon nanotubes（S-CNTs）,polyvinyl alcohol（PVA）,glycerol（Gly）,and the organic solvent dimethyl sulfoxide（DMSO）.The results showed that the addition of S-CNTs could improve the mechanical properties of the hydrogel,and the tensile strength and elastic modulus could be increased by 1 and 0.6 times,respectively;the internal network of the hydrogel has multiple reversible hydrogen bonds,so it has good self-recovery performance and cyclic stability,and it also has a high sensitivity（GF=5.7 100%-140%）;in addition,the S-CNTs/PVA conductive hydrogel can be fixed on human skin.gel can be fixed on human skin,presenting different resistances according to the bending angle of the knuckles and showing stable sensing performance,which can be repeatedly monitored for strain and deformation in real time,providing a feasible method for constructing conductive hydrogel sensors.（2）Preparation and performance analysis of CNC/GO/Na Cl/PVA conductive hydrogelsCellulose nanocrystals（CNC）were added to aqueous dimethyl sulfoxide（DMSO）solution,followed by the introduction of the conductive ion Na⁺,then polyvinyl alcohol（PVA）/graphene oxide（GO）/glycerol（Gly）was added to obtain the composite solution by a simple one-pot method,and finally CNC/GO/Na Cl/PVA conductive hydrogels were prepared.The results showed that the introduction of CNC solved the problem of GO and Na⁺dispersion in the solvent,and the prepared CNC/GO/Na Cl/PVA conductive hydrogels showed high tensile strength（320 k Pa）and stretchability（317.89%）;dynamic hydrogen bonding and ionic coordination bonding interactions gave CNC/GO/Na Cl/PVA conductive hydrogels good self-recovery and cyclic stability;the hydrogel also has a high sensitivity（GF=6.08,150%-200%）.The CNC/GO/Na Cl/PVA conductive hydrogel-based sensor can be used as a wearable device to monitor the activity of different body parts at room temperature.This CNC/GO/Na Cl/PVA conductive hydrogel has promising applications in electronic skin and wearable devices.（3）Preparation and performance analysis of CNC/GO/CNTs/PVA/SA-Ca²⁺conductive hydrogelsThe CNC/GO/CNTs/PVA/SA-Ca²⁺composite solution was prepared by the one-pot method using the solid-phase esterification reaction of polyvinyl alcohol（PVA）and succinic acid（SA）,and then the CNC/GO/CNTs/PVA/SA-Ca²⁺conductive hydrogels were prepared by the freeze-thaw method.The results showed that:the chemical cross-linking between polyvinyl alcohol and succinic acid improved the tensile strength of the hydrogel（0.2 MPa;226%）;with the addition of SA,the hydrogel showed a more dense three-dimensional network structure;ionic coordination bonds were formed inside the hydrogel after the introduction of Ca²⁺,and the sensitivity（GF=4.55,0-200%）and cycling stability were improved;the hydrogel-based wearable strain sensors can be applied to human motion monitoring.