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Design and Fabrication of a Microfluidic Droplet Digital PCR System Based on Plasmonic Heating

jalili, Abbas | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58086 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Amir Shamloo; Akbari, Javad
  7. Abstract:
  8. Polymerase Chain Reaction (PCR) is a process in which a special piece of a gene is amplified millions of times over a short period. The advancement of gene amplification devices over the past years and attention to droplet-based methods have led to the development of droplet digital PCR. This method is very accurate in the diagnosis of diseases, so it can identify several different types of defective genes at the same time. In the present study, a microfluidic droplet-based chip was designed and fabricated for digital PCR amplification. The chip consists of microchannels for droplet formation as well as a reservoir to store droplets. Droplet formation was carried out by the flow-focusing method to take advantage of this method in producing droplets of equal size. Placing the reservoir to store droplets during the thermal cycle protects the sample fluid from possible contamination caused by droplet outflow. On-chip thermal cycling, along with its benefits, imposes problems such as evaporation of sample fluid during heating as well as the formation of air bubbles in the system. To prevent the evaporation of the droplets during the thermal cycles, the chip is saturated by mineral oil. Also, to prevent air bubbles forming inside the chip, the chip is bonded to the substrate by a thermal method instead of a conventional methods such as plasma. The results of the experiments indicate the success of the project's approaches in performing the on-chip PCR reaction without any problems. Conventional and commercial PCR systems generally use thermoelectric effect for thermal cycling. In this project, the optical heating method using a gold layer with a 120-nanometer thickness and cooling with a high-speed fan was used for thermal cycling. Also, the problem of poor adhesion of the chip (PDMS) to gold on optical heating was solved by using transparent double-sided scotch tape. The results show that the thermal cycles in the commercial device take 90 min, while this time in the built-in device is reduced to less than 60 min and it indicates that our device is 30% more efficient than the commercial device
  9. Keywords:
  10. Microfluidic System ; Lab-on-a-Chip ; Polymerase Chain Reaction (PCR) ; Photothermal Material ; Polydimethylsiloxane ; Thermal Fusion Bonding

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