Research on Microfluidic Technology and Experiments of Optical Colour-changing System Based on Microfluidic Channel Structures

Author:Zhang Min

Supervisor:li song jing


Degree Year:2018





Nowadays,traditional automatic colour-changing way mainly adopts solid photochromic materials,which have different molecule/electron structures under different environment lights resulting in colouration effects.However,they have some shortcomings,such as bad controllability,bad reversibility and short lifetime.In recent years,microfluidic technology has been widely ap plied in many areas,such as biological detection,chemical analysis and medical diagnosis,the combination of microfluidic and optics is also an important research orientation.Therefore,we present a new optical colour-changing system with “self-cleaning” function based on microfluidic channel structures,which has high controllability and good reversibility.This microfluidic optical colour-changing system will have a broad application prospect in optical field.Microfluidic optical colour-changing devices with different structures are researched by using a polydimethylsiloxane(PDMS)material based on a fabrication technology of soft lithography.Through the research on “self-cleaning” mechanism of the microfluidic channels with rectangle sections,the channel corner structures are optimized.Meantime,the effects of liquid gravity on PDMS film deformation and the flow characteristics in microfluidic channels,as well as the colour-changing responding time of the system are investigated.Optical model s of the microfluidic colour-changing system with different channel structures are developed,MTF image evaluation and chroma uniformity analysis are carried out.The appearance vision performances of the colour-changing film are also discussed.A microfluidic actuator based on SMA is developed for liquids circulating of the microfluidic optical colour-changing system.The whole SMA actuator is designed and researched,dynamic model and thermodynamic model of SMA element,as well as the whole actuated system are developed.The key affecting parameters for the system performances,such as the diameter of SMA spring,the turn number of SMA spring and heating current,are studied.System energy consumption,restoring force and responding performance are taken as the optimization objects,the multi-objective optimization model is established,and the above key parameters are optimized.Experimental tests are conducted to verify the optimization results.For the fabrication of the microfluidic PDMS colour-changing film,a cost-effective and fast prototyping method for microfluidic molds making are studied based on the dry film photoresist,the key manufacturing parameters are optimized through experiments.Different surface modification methods are discussed and applied for the bonding of PDMS film and CR39 substrate,the wetting properties and bonding strengths are tested,the best bonding way and the optimal bonding parameters for microfluidic colour-changing system are approved.Due to the low hardness and poor anti-wear property of PDMS surface,we also investigate the development of an organosilicon coating method on elastic surface to enhance the hardness and anti-wear property of PDMS surface.Some experiments are also carried out to test the hardness,anti-wear property and optical performance of the coated PDMS surface.Based on the study of the microfluidic optical colour-changing system,the innovative microfluidic sunglasses,microfluidic camouflage film and microfluidic optical filter are developed,which show the advantages of simpler structures,easier fabrication and more flexible capabilities.Light intensity decreasing and anti-ultraviolet performances of the microfluidic sunglasses are researched,and human vision protections are realized by wearing the sunglasses.Depending on different experimental backgrounds,body camouflage and human face camouflage functions are realized by using microfluidic camouflage films.Gray histogram model and “Canny” boundary logic algorithm are used for camouflage effects analyzing.According to different optical filtering demands,the image clarity is improved and halo is suppressed by applying the microfluidic optical filters on digital CCD,the filtering effects are observed and analyzed.