Fabrication Of Microfluidic Chips Based On PCB And ITS Application In Manipulation Of Droplets

As a biochemical analysis platform, microfluidic chips have gained numerous applications, such as cell analysis, DNA analysis, drug research and so on. In the microfluidic chip system, the fabrication of microfluidic chips is a very important research topic. Traditionally, the fabrication of microfluidic chips is generally based on lithography, which requires expensive facilities, costs a lot and needs a long period to fabricate chips. Other fabrication methods such as laser etching, hot pressing are also complex and cost a lot. Some researches tried to fabricate microfluidic chips based on PCB to lower the difficulty of chip fabrication. However, high bonding cost and low bonding strength still exist in this method. Depending on this condition, this thesis succeeded in developing a cheap, fast and easy fabrication process to fabricate PDMS (Polydimethylsiloxane) microfluidic chips, which decreased the fabrication cost to 1/10 and shortened the fabrication period to 4 days compared to the lithography method. In addition, based on the fabricated microfluidic chips using the PCB method, we succeeded in achieving effective manipulation of droplets, which is significant for the droplet microfluidics. The main research work and results are as follows:1. Based on the feasibility of the PCB as mold to fabricate PDMS microfluidic chips, we designed microfluidic structure with Protel and delivered the PCB document to the factory. With PCB as mold, the structure of the copper on the PCB was transferred to the PDMS using Mold Shaping method. Then, the PDMS with structure on it was bonded with a smooth PDMS to realize the bonding of the PDMS microfluidic chips. After microanalysis of the microfluidic chips, we found that the depth of the chips was 70um and the minimum width of the chips could be 150um. Through microfluidic experiments, we found that there was no congestion or liquid leakage in the chips, which proved the strength of the chips strong enough to bear the fluidic pressure.2. Based on the PCB method, we fabricated PDMS microfluidic chips with T-junction and flow-focusing structures. Then, we carried out several microfluidic droplet generation experiments in these two chips with oil flow rate was 50ul/h,80ul/h, 100ul/h and water flow rate ranging from lOul/h to 50ul/h. We analyzed the droplet size and droplet generation frequency of the two structures under the condition that oil flow rate was 50ul/h, water flow rate was lOul/h and found that droplet size was uniform and droplet generation frequency was stable. In addition, we statisticsed the droplet size under different oil flow rate and water flow rate, finding that the droplet size was proportional to the water flow rate and inversely proportional to the oil flow rate.3. Based on the PCB method, we fabricated several PDMS microfluidic chips with different microfluidic structures on it and realized several basic manipulations of droplets including:(1) sysmetric T junction and nonsysmetric T junction were introduced into the microfluidic channels to realize the droplet splitting; (2) a chamber was introduced into the microfluidic channels to realize the droplet fusing and a Y structure behind was used to change the concentration of the surfactant around the fused droplets, which increased the surface tension and stability of the fused droplets; (3) a serpentine structure was introduced into the microfluidic channels to stretch droplets to realize the mixing in the droplets; (4) a T junction structure was introduced into the microfluidic channels to add new contents into an exsiting droplet to realize the droplet sampling; (5) two microfluidic channels with different width were introduced into a microfluidic chips with different depths to realize the droplet sorting based on the size difference.