Fiber Gas Sensors Integrated Smart Face Mask For Room-temperature Distinguishing Target Gases

Gas sensors with wide range of use in many fields,including environmental monitoring,industrial process control,clean energy deployment,and medical diagnosis have been obtained widely interest in recent years.Furthermore,gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high temperature operation,and hence simplifies the fabrication of sensor devices and reduces the operating cost.Various materials have been employed to make room temperature gas sensors such as metal oxide,[1-3] organic semiconductors[4-8],carbon nanotubes and graphene,which promote the development of wearable gas sensors[9-12].Compared with conventional room temperature gas sensors,wearable gas sensors have a large number of advantages including excellent drapability,pliability,durability,a light weight,and low cost.Recently,a variety of wearable gas sensors have been extensively studied.For example,Yun et al.reported a wearable gas sensor by electrostatic self-assembly wrapped reduced graphene oxides on the yarn which exhibited chemical durability,mechanical stability,and a high response to NO2 gas[13].The thread-based gas sensor based on poly partial isobutyl/methyl mixed ester and multi-walled carbon nanotube have also been studied by Kerdcharoen et al.,which could be applied to detect NH3.[14] In addition,some other researchers fabricated wearable gas sensors for human safety and health monition[15-16].However,an important problem of the above fiber based gas sensors is that the gas species may not be distinguished in complex gas conditions.In order to develop a high-performance wearable gas sensor for distinguishing gas,researchers tried to “One key to one lock” proving it a promising solution to realize wearable gas sensors to distinguish between gases[17].Herein,in this work,we describe three kinds of gas sensors based on conductive fibers to detect different poisonous gases.Nylon rope is acted as the flexible substrate and the surface of nylon rope is wrapped with single walled carbon nanotube(SWCNT),multi walled carbon nanotube(MWCNT)and the ZnO quantum dots recombined with SWCNT(SWCNT@ZnO),respectively.The as-fabricated gas sensors possess good sensitivity,good reversibility,excellent selectivity towards to formaldehyde,ammonia and ethanol.The gas sensors also show no gas properties degradation under bending states and after many washing times which demonstrate the gas sensors can be used as flexible wearable devices.We present a multi-functional face mask based on these wearable fiber gas sensors.Each gas sensor corresponds to an independent LED with different color of red,green and blue,respectively.When the multi-functional mask did not encounter the target gases in a seal cover,the resistance of the sensors will not change and the indicator LED lights are in the unlit state.While the target gases injected in the seal cover,the resistance of the certain gas sensor will increase and the LED will switch to alight state.The face mask can distinguish different gases through different selectivity of three types of fiber gas sensors.