Construction And Performance Of Microfluidic Channel Based On Colloidal Photonic Crystals

The microfluidic channel as the core analysis equipment is expected to replace the traditional biochemical analysis equipment in biotechnology,drug detection,environmental analysis and many other fields because of its portability,low power consumption,automation,low sample and reagent consumption and so on.Biochemical sensors based on photonic crystal and metal plasmon characteristics are favored by more and more researchers because of their high sensitivity,fast response and real-time monitoring of biochemical samples.In this paper,focusing on the colloid-based photonic crystal structure which can be constructed under the microflow channel,the PDMS microflow channel with polystyrene microsphere photonic crystal structure,conformal coated photonic crystal structure or silver inverse opal structure was successfully constructed,and its optical properties and refractive index response behavior were studied.The main research contents include:(1)The photonic crystal structure,conformal coated photonic crystal structure and silver inverse opal structure of polystyrene microspheres were prepared under PDMS microchannel.Polydimethylsiloxane(PDMS)polymer material combined with vacuum casting method was used to prepare PDMS microfluidic channel.Based on the pipe geometry of PDMS microfluidic channel,the photonic crystal structure of polystyrene microspheres suitable for microfluidic channel was prepared by colloidal crystal vertical deposition self-assembly technique.in this process,the photonic crystal structures suitable for specific geometric shapes under microfluidic channels were prepared by physical geometry restriction method,mechanical stripping method and micro-zone solution cleaning method,respectively.Compared with the optical properties of photonic crystal-based microfluidic channels prepared by three methods,the optical properties of photonic crystal-based microfluidic channels can be successfully demonstrated by mechanical stripping method.Conformal coated photonic crystals suitable for microfluidic channels were prepared by atomic force deposition((ALD))method,and silver inverse opal photonic crystals suitable for microfluidic channels were prepared by electrochemical deposition and electrochemical polishing methods.The three kinds of photonic crystal structures in the PDMS microflow channel can effectively realize the microscopic detection of the liquid to be detected.(2)The spectral properties of photonic crystal structure,conformal coated photonic crystal structure and silver inverse opal structure of polystyrene microspheres under PDMS microchannel were studied.The spectral characteristics of photonic crystal structure under PDMS microflow channel under different microscope magnification are explored.Through the comparative analysis of the reflection spectrum of the structure under 20 x objective lens with different magnification,it is clear that the 20 x microscope objective lens is suitable for the microflow channel with 3mm width,and the characteristic peak and valley of reflection spectrum is clear.The half-wave width of photonic crystal structure with particle size 238 nm is 50 nm at 563 nm,and the reflectivity is 65%.The half-wave width of the coated photonic crystal structure at522.13 nm is 38 nm,and the reflectivity is about 15%.Thus,a microspectral scheme is developed to match the spectral characteristics of the photonic crystal structure under the microflow channel,which is suitable for subsequent responsivity testing experiments.The spectral characteristics of silver inverse opal structure with the decrease of metal filling rate were studied.In the 500～1100 nm band,the reflectance decreased sharply and then decreased slowly,the transmittance increased gradually,and the cut-off frequency of metal was red-shifted.The cutoff frequency of silver inverse opal structure with 238 nm particle size was red-shifted from 500 nm wavelength to 650 nm wavelength.With the increase of polishing period,the Bragg second-order diffraction peak of the structure also has a red shift.The Bragg second-order diffraction peak of the silver inverse opal structure with 300 nm particle size shifts from the 400 nm wavelength to the 500 nm wavelength,and the half-wave width decreases accordingly,from the original 103 nm to 45 nm.(3)The responsivity characteristics of photonic crystal-based PDMS microchannels in different refractive index environments are studied by experiment and simulation.The responsiveness of polystyrene photonic crystal structure,conformal coated photonic crystal structure and silver inverse opal structure to different ethanol ratios in PDMS microchannel are studied,which shows that the photonic crystal-based PDMS microchannel sensor has a certain responsiveness to the change of environmental refractive index.The sensitivity characteristics of polystyrene microsphere photonic crystals with different particle sizes in PDMS microchannel are simulated and compared.the results show that the photonic bandgap reflection peaks of the structures are red-shifted with the increase of refractive index.The sensitivity characteristics of silver inverse opal structures with different periodic constants and different polishes are simulated and analyzed,and the characteristic peak of the structure is redshifted regularly with the increase of refractive index.In the experiment,the responsivity of photonic crystal structure with 238 nm particle size in PDMS microchannel was investigated with the help of microinjection pump system.When entering the aqueous solution,the photonic band gap reflection peak located at 528 nm was red shifted to 536 nm,and when the proportion of ethanol was increased to 20%,the reflection peak moved to 567 nm,moved 31 nm,and when the proportion of ethanol continued to increase to 60%,80%,100%,the reflection peak moved to 567 nm,569 nm and 572 nm respectively.When the proportion of ethanol increased from 0% to 100%,the reflection peak shifted regularly and shifted 36 nm.The responsivity characteristics of conformal coated metal platinum photonic crystal structure under PDMS microfluidic channel are investigated.The characteristic peak of the structure is red-shifted from the 530 nm wavelength when the ethanol content is 0% to the 535 nm wavelength when the ethanol content is 100%,The total shift is 5 nm,and the refractive index changes by 0.028 in the process.The responsiveness characteristics of silver inverse opal photonic crystal structure under PDMS microchannel were investigated.when the proportion of ethanol increased from 0% to 100%,the surface plasmon valley was red-shifted and the Bragg diffraction peak was blue-shifted,but the blue shift was not obvious and moved about 1nm.