| Microfluidics refers to the technology of manipulating small amount of fluid,thus succeeding in fluid transferring,transmitting,mixing and reaction.It has a wide application in many diverse fields by virtue of its less material consumption but fast response and high accuracy.In general,microfluidics driving is realized by field force,i.e.electricity,gas,liquid,or self-realized through preparation of surface with different surface energy.Nonetheless,they have a plenty of flaws,encompassing limited application,high accuracy of preparation and high cost.Based on two contact states of water droplets on hydrophobic surface,this thesis puts forward a self-driven approach to dynamic regulation of micro-structure on surface via infrared laser.Precisely,in view of PDMS with high thermal expansion coefficient and CNT with excellent effects of absorbing heat,this thesis prepares the micro-structure on PDMS/CNT surface and then changes its size via infrared laser,thus manipulating the contact states of water droplets and finally succeeding in self-driven droplet.Firstly,this thesis systematically analyzes the thermal performance of PDMS/CNT with different concentration proportion as well as the effects on its thermal deformation from laser power,CNT concentration and pre ptosis quantity.After exploring how processing parameters affect thermal deformation of PDMS/CNT by orthogonal experiments,it obtains the most optimal parameter combination,referring to 500 m W of laser power,0.5%wt of CNT and0.15 mm of pre ptosis quantity.Secondly,a thermal field model of laser heat source and PDMS/CNT is set up based on finite element,with which the amount of deformation is calculated in terms of the size and space of micro-structure on surface with different processing parameters.Accordingly,it concludes that the deformation of the film is mainly concentrated at the upper and lower ends of the irradiation area when the amount of pretension at both ends of the film is small,whereas at the left and right ends when large.The variation of microstructure spacing increases with the increase of laser power and CNT concentration,which keeps consistent with the experimental results.Thirdly,this thesis prepares the micro-structure on PDMS/CNT surface based on the transformation conditions of the two contact states of water droplets on hydrophobic surface and combined with the deformation law of the PDMS/CNT microstructure.The manipulation rule of each processing parameter is investigated on the surface contact angle and rolling angle of PDMS/CNT surface with micro-structure.When the droplet volume is greater than 6.5 ?l,its contact state has changed under laser irradiation.Furthermore,based on the response surface method designed by the Box-Behnken experiment,the most optimal parameter combination is found with the contact angle as the dependent variable,that is,500 m W of laser power,1%wt of CNT and 5.15 ?l of the droplet volume.Finally,the movement characteristics of water droplets on the laser-regulated surface were studied for the understanding of influence factors on the movement hereof.When the droplet moves from the non-irradiated area to the irradiated area,the interface imbalance forms a driving effect,and if conversely,a hindrance effect.Furthermore,this thesis explores how processing parameters affect movement of droplets by orthogonal experiments.The analysis shows that the CNT concentration has the most significant effect on the acceleration change of the droplet,which is followed by the laser power.Meanwhile,the laser power has the most obvious impact on the droplet deceleration change,which is followed by the CNT concentration.Nonetheless,the droplet volume has no significant effect on both two occasions aforementioned. |
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