Fabrication Of Microfluidic Device Based On Low Precision Milling For Droplet Microfluidic Application

Microfluidics,to manipulate fluids on microscale level,has displayed many advantages such as low consumption,high efficiency and portability.However,the conventional techniques including soft-lithography for the fabrication of prototype microfluidic devices remain expensive,and require many facilities including high-precision equipments;These make challenges for the low-cost,speedly,high-efficiency preparation of future microfluidic devices.This thesis would research the way of constuction of prototype microfluidic devices based on the processing ability of common low-precision CNC mini-engraving machine equipment(positioning accuracy of ±0.05mm),and discussed its possibility to apply on some testing cases requiring high resolution.The main work is as follows:(1)Developing a new technical method to construct PDMS prototype microfluidic device based on the combination of two following measures: PMMA positive master fabricated with a ―clamping(meaning of ?from two opposite sides‘)‖ milling strategy via the CNC mini-engraving machine,and untouched moulding.The results showed that the width of the microchannel as low as 0.035 mm could be fabricated out when applying the conventional precision CNC engraving machine equipped with an end mill(φ=0.4mm).Moreover,the bottom surface of cured PDMS chip could provide good sealing thanks to adpotion of untouched moulding.(2)Typical microfluidic droplet-generators were constructed using the above method,and the experimental results showed that such prototype microfluidic devices having the microchannels with rough side-inner walls could still successfully generate droplets.(3)The effects of surface roughness of the innner wall of thus-fabricated microchannel devices on the droplet formation behavior were investigated.The characteristic parameters of the generated microdroplets,including the sizes,the movement rates along X-axis,the deformation rate,and the generation frequency,which were tested and analyzed with DMV,a microdroplet analysis.The results showed that the droplet generation behavior in thus-fabricated of microdroplet generators was significantly different from that of the conventional soft-lithographical fabricating device with almost equal geometrical configuration to the former.(4)To further test the applicability of thus-fabricated microdroplet generator in analytic cases with the requirement of high resolution,the experiments were performed in the devices,including microdroplet generation,the encapsulation of small moleculars and the fluorescence detection,using the signal amplification reactions among short-nucleotide probes and aptamers as an example.The results showed that the fluorescence response time could be significantly speeding,15 s fast compared with the contrast device.In summary,this paper demonstates a novel fabrication technique for the construction of prototype microfluidic device,with features of low-cost,more simple,and in particular the applicability to be utilized into some high-resolution analytic cases,this may be a step closer towards the future requirements of low-cost,speedly,high-efficiency preparation of microfluidic devices.