Preparation And Properties Of Fabric Humidity Sensor Based On Graphene Oxide

Humidity monitoring plays a vital role in the sphere of medical treatment,environmental monitoring,food storage,industry and agriculture and so on.Compared with polymers and paper based flexible humidity sensor,fabric based humidity sensors have the advantages of ventilation,comfort and direct integration into clothes,and have received wide-ranging attention and research recently.In our work,accroading to the human respiration,fabric humidity sensor based on functional graphene oxide with sandwich structure and arachnoid nanofiber membrane are designed to explore their applications in humidity sensing and respiratory monitoring,so as to provide the possibility of wearable fabric based humidity sensor in the field of human health monitoring.The composite of amino modified graphene oxide and mesoporous silica nanospheres was dispersed in WPU and screen printed on polyester fabric.XPS results showed that after amino modification,N accounted for 8.31%in GO-NH₂,which was basically corresponding to the weight loss of-NH₂ in TGA.The combination of GO-NH₂ and mSiO₂ not only expanded the inter-distance of GO-NH₂ layers,but also maked up for some defects on the surface of GO-NH₂.In addition,the influence of the ratio of GO-NH₂ to mSiO₂ on the sensing performance was explored.It showed that when the ratio is 1:3,the humidity sensor has the widest humidity monitoring range（23-97%RH）,the fastest response and recovery speed（12.6 s/58.5 s）,the lowest hysteresis（2.71%RH）.GO-NH₂/mSiO₂/WPU was then screen printed on the medical mask,which can significantly distinguish human respiratory rate,mouth and nose breathing,cough and finger proximity,which could be applied to the filed of human health monitoring and non-contact sensing.In order to further develop the properties of humidity sensor and improve the sensing performance,dopamine modified graphene oxide and chitosan modified mesoporous silica nanoparticles were combined with a ratio of 1:3 and dispersed in WPU and screen-printed on cotton fabric.Under the synergistic action of graphene oxide partially reduced by dopamine and chitosan coated silicon nanospheres,the fabric coating obtained excellent UV protective properties（UPF value up to 454.44）and good antibacterial properties（E.coli 91.97%,S.aureus93.56%）.The effects of the mass fraction of GO-PDA on the sensing performance were inveatigated.And the results showed that the humidity detection scope and the response speed of the fabric humidity are positively correlated with the amount of GO-PDA,but when the amount of GO-PDA was 4 wt%,the sensor obtained the lowest hysteresis（9.71%RH）.In addition,the humidity sensor could also be applied to monitor human respiratory rate,apnea,palm coverage and water drop proximity,which is of great significant to human health protection.In order to visually observe the relative humidity level,nanofibrous membranes with cobweb structure were prepared by electrospinning with wet chemically treated NiI₂,GO-NH₂and thermoplastic polyurethane masterbatch.From the microstructure of the nanofiber membrane,it can be seen that the nanofiber membrane presented a staggered cobweb structure,and NiI₂ was evenly distributed on each fiber.According to analysis of the FTIR spectrum of the nanofibers membrances after heating,the discoloration principle of the nanofibers membrances is based on the absorption and desorption of Ni I₂ crystal water.After wet chemical treatment of Ni I₂,the preferred orientation of the crystal occured,the surface activity and hydrophilicity were improved,and the humidity sensitivity was enhanced.When TPU/GO-NH₂/mSiO₂ nanofiber membrane changed from low humidity to high humidity,a color change from black to tangerine and then to chartreuse occured,and remained stable in 20 cycles.The nanofiber film performed fast response and recovery speed（0.9 s/6.3 s）,low hysteresis（6.37%RH）and excellent linearity（R²=0.9630）in the range of 0-97%RH.Fitting it on the medical mask can distinguish human respiratory rate,mouth and nose breathing and finger movement,which could be applied to human health monitoring and humidity visualization.