Study On Polyelectrolyte Humidity Sensor And Its Application In Respiration Monitoring

Humidity is an important environmental parameter related to people's daily life.Humidity control and detection play an important role in the fields of agriculture,industry,aerospace and goods storage.With the accelerating development of the Internet of Things?IoT?,the intelligent society sets higher requirements for the properties of humidity sensors.In recent years,the humidity sensor has broken through the application in the traditional field,and gradually emerged in the field of human respiration monitoring.Nowadays,the methods of respiration monitoring?detection?in clinical medicine is mainly based on the spirometer,the polysomnography monitor and the end-tidal CO₂ detection monitor.These methods can obtaind various parameters of lung function and respiration pattern accurately.However,the cost and threshold is high,medical examination process is complicated,the guidance of professionals is required and portable examination is limited.In order to meet the needs?high humidity stability and fast response/recovery speed?of respiration monitoring,researchers have designed and prepared humidity sensors based on various advanced functional materials.However,it's difficult to record the breath signal accurately from multiple dimensions and perform effective analysis and modeling.The thesis focuses on the study about the synthesis of humidity sensitive materials and the preparation technology of humidity sensors for fabricating respiration monitoring platform.This paper mainly focuses on following research:1.The method of loading humidity sensitive salt has been widely used in fabrication of high-performance humidity sensor.However,the‘two-step'method?loading active groups after framework synthesis?will lead to inexact loading amount and maldistribution of active sites.In this chapter,different kinds of lithium salts?LiCl and PAALi?were introduced into the 3D crosslinked network via in-situ loading technology and click chemistry.The polyelectrolytes 8%LiCl/PETMP-DVB and 3%PAALi/MPOSS-DVB with better humidity sensing properties were obtained.The sensor 8%LiCl/PETMP-DVB shows about 2 orders of magnitude impedance variation,the hysteresis is 1.5%RH and the response/recovery time is 3.5 s/63 s.The sensitivity of the sensor 3%PAALi/MPOSS-DVB is over 2 orders of magnitude,the hysteresis is2.2%RH and the response/recovery time is 1.2 s/0.6 s.2.In-situ loading is still a kind of physical method,which easily leads to the loss of hydrophilic groups under the high humidity atmosphere or moisture condensation.On the basis of previous work,this part presents that the active groups were introduced into skeleton via chemical decoration method and the stable polyelectrolyte MPOSS-DVB-SSS was obtained.When the molar ratio of raw materials is 1:3:2,the P2 sensor showed the widest sensing range and excellent sensing properties.At operating frequency 500 Hz,the sensitivity is 634.7?11%-95%RH?,the hysteresis is 4.5%RH and the response/recovery time is 5.5 s/23.7 s?11%-95%RH?.The P2 sensor with good water-resisitant ability guarantees its excellent stability.3.Based on the chemical decoration and in-situ preparation technology,this part illustrates the preparation of ultrafast-response and stable humidity sensors for respiration monitoring.The hydrophobic framework and hydrophilic salt were crosslinked via thiol-ene chick chemistry and amphipathic ionogels?MPOSS-DVB-SSS and MPOSS-PIL?were obtained.The sensitivity of MPOSS-DVB-SSS sensor with the sensing range 54%-95%RH is about 2 orders of magnitude,the hysteresis is2.6%RH and the response/recovery time is 0.75 s/0.48 s?33%-95%RH?.The sensitivity of MPOSS-PIL sensor with the sensing range 33%-95%RH is over 2 orders of magnitude and the response/recovery time is 0.19 s/0.30 s?33%-95%RH?.The ultrafast humidity response mechanism was explored fully through the QCM technology and complex impedance spectrum.Different breath patterns of different subjects were well recorded and monitored by these two ultrafast-response humidity sensor.4.Chapter five provided an efficient way to fabricate the 3D porous polyelectrolyte humidity sensitive materials aiming at solving the problem of complicated porous polymer fabrication.The 3D porous P4VP film was fabricated by the breath figure method.And then the porous polyelectrolyte was synthesized via the gaseous quaternization between the obtained porous film and chloralkane.The humidity sensor was prepared after printing interdigital electrodes with the aid of silk-screen printing technology.