Structural Design, Surface Modification of Flexible Microchannels and Applications in Vital Signs Detection of Body Surface

Author:Zhang Wei

Supervisor:wang hong zhi


Degree Year:2019





With the improvement of living standards,people pay more attention to personal health.All kinds of portable health detection devices come into people’s life.Sensors for monitoring blood pressure,body behavior and temperature are widely used in custody of older people and infants.These portable sensors should have small size,high flexibility and good wearability.Microfluidic technology often possesses high sensitivity,high efficiency,small reagent demand and low pollution,and has unique advantages in the application of portable sensors.The core of microfluidic technology is microchannels.Microchannels was originally used only to provided small space limiting fluid flow and they are mainly applied in separation devices and microreactors.Most of the microchannels are made of rigid bulk materials such as silicon wafer,glass and polymethyl methacrylate(PMMA).Due to single function,structure and poor flexibility,current microfluidic devices are difficult in application of flexible portable sensors.However,there are few researches on the structural design and functional modification of flexible microchannels in the world.Therefore,it is of great significance to combine the structural design of microchannels with the functional modification of microchannels to prepare high flexible,multi-functional and comfortable portable sensors.Author started work from the design of microfluidic devices and functional modifications of microchannels,and prepared flexible microfluidic sensors and hollow sensing fibers by lithography,wet chemical method,high speed knitting technology,electrospinning technology,microfluidic spinning.Author tested its flexibility,mechanical property,kitting properties and systematacially did analyses and researchs on sensing of pH,temperature and body behaviors.The specific research contents are listed as follows:1.A miniature Ag/AgCl reference electrode coated by polyvinyl butyral(PVB)was prepared by dip-coating.ZnO/polyaniline(PAni)micro-nanostructures array were constructed on the surface of polyethylene glycol terephthalate/indium tin oxid(PET/ITO)by wet chemical method and electrodeposition technology.ZnO/PAni composite showed high pH sensing performance and working stability and its sensitivity was up to 120 mV/pH.Temperature-sensitive poly(N-isopropyl acrylamide)/reduced graphene oxide PNIPAm/rGO hydrogel was prepared by cross-linking PNIPAm and water dispersing rGO.Temperature-sensitive PNIPAm/rGO hydrogel showed high temperature sensing performance and good cycling stability and its resistance variation was up to-3.3% /℃.These two sensors were well integrated into a polydimethylsiloxane(PDMS)microfluidic device for pH and temperature detection of fluids.2.Grass-like double-layer ZnO micro-nanostructures with the vertical height as high as 50μm were fabricated on the inner wall of silicon glass capillary via a simple wet chemical method.Obtained ZnO micro-nanostructures showed good temperature sensing performance and stability.When the temperature kept unchanged,the resistance of ZnO kept stable within 100 seconds.The sensitivity of ZnO temperature sensor measured from 23 ℃ to 60 ℃ was up to-2.4%/℃.Subsequently,surface modification of Pt solutions produced uniformly distributed catalytic Pt micro-nanostructures in a facile method.ZnO/Pt micro-nanostructures showed high catalytic efficiency in continuous reduction reaction of o-nitrophenol and degradation methylene blue.3.Cotton hose was prepared by a high speed knitting machine and a layer of single-wall carbon nanotubes(SWCNTs)/ZnO micro-nanostructures were prepared on the surface of cotton hose by using dip-coating method and wet chemical method.A polyvinylidene fluoride(PVDF)fiber film was prepared on the surface of SWCNTs/ZnO by using electrospinning technology.Final integrated microfluidic device could be used for detecting the pressure on the inner wall,pulse frequency and temperature of pulsed fluid.In addition,the microfluidic device can be used to detect limb behaviors such as pressing and bending.Even the ending angle can be distinguished according to the voltage.4.After studying the theory of double emulsions and the droplet-to-jet principle,hollow polylactic acid(PLA)fibers were prepared by a simple microfluidic device fabricated with Polytetrafluoroethylene(PTFE)tubes of different diameters.Functional hollow PLA fiber,including beaded PLA fiber and thermochromic PLA fiber,could be prepared continuously by simply adjusting compositions.These temperature-sensitive PLA fibers showed good knitting properties and temperature sensitivity,and could be produced on a large scale.Therefore,they have potential applications in intelligent color-changing textiles.