Development of Precise and Fast Heating and Cooling System of a Thermal Cycler

Project Title

Project Area of Specialization

Mechanical Engineering

Project Summary

Traditional thermal cyclers are expensive and have a large size. One of the major contributors to this size and price is the heating element. With research being conducted on thermal cyclers constantly, this project uses a new heating element to increase the efficiency and decrease the size of thermal cyclers. We are using a graphene-induced layer on a tape which is responsible for the heating of the thermal block. The thermal block is designed in such a way that the graphene tape is directly in contact with the thermal block at all sides to provide uniform and efficient heating. The thermal block has been designed to house 8 samples which is the minimum mark to have the product commercially ready. The cooling is done using standard fans which are connected to a power source. The thermal cycler along with the heating element and cooling elements will be controlled using a microcontroller. Using standard and simple components will help us decrease the overall cost of the device.

Project Objectives

The aim of this project is to manufacture a thermal cycler for the use of PCR testing. This thermal cycler would not only be cost-efficient but would be efficient as compared to conventional thermal cyclers. In order to achieve this aim certain objectives were laid down which are as follows:

1. A 10° per second temperature gradient.

2. Reducing the size of a traditional PCR testing machine.

3. Efficient Circuitry design.

Project Implementation Method

A thermal cycle process requires three major steps. First, there is Denaturation, this process is the separation of strands of DNA and is carried out at 95°C. second, there is annealing in which primers are added to the strands to form separate DNA strands which is carried out at 68°C. finally, there is the Elongation step which is responsible for the replication of DNA which is carried out by synthesis or the DNA strands formed in the Annealing phase which is carried out at 72°C. this contributes to a single cycle which should be completed in 30 seconds to a minute. Having this high demand of temperature variation is the major challenge in thermal cyclers. For a diagnostic test, there should be around 30-40 cycles for formation of billions of strands which are needed for the diagnostic test. As the conventional thermal cycler uses Peltier or a heating tube for heating, this project will utilize graphene tape. Graphene is one of the best conductors out there, this means that it will be able to dissipate heat easily which will help us in heating the samples as soon as possible. This project also uses an unorthodox thermal block which is designed to be in direct contact with this thermal tape which will provide it uniform heating from all sides.

Benefits of the Project

Over the past couple of years with the outbreak of COVID, diagnostic tests have seen a surge in their application. For any diagnostic test, a thermal cycler is one of the most integral components. It is not entirely new technology, but one which has come into use recently. Even after various research and experimentation, this diagnostic is a tedious and expensive process. When the outbreak of COVID occurred in 2020, one of the biggest problems every county faced was a lack of COVID testing machines, which lead to a delay in testing and resulted in loss of countless lives. 2 years after the outbreak, it is still a varying disease which is infecting people by each passing day. The need for diagnostic machines is prevalent as it was. With the cost and importance of these machines in mind, we hope to create a thermal cycler which is more efficient, fast and cheaper than the currently used model. For any diagnostic, the most important part is the amplification of DNA. This starts with a polymerase chain reaction which is carried out in the thermal cycler. A thermal cycler is a machine that first, denatures the DNA strands, then annealing occurs in which the DNA samples are replicated, and finally elongation occurs in which the whole DNA is replicated. These processes require a sudden increase and decrease in the temperature which is carried out in a thermal cycler. We hope to implement a new heating method by using graphene-induced tapes which will provide us large temperature increase in a short period of time. By having this new technology implemented we can increase the efficiency of thermal cyclers and decrease their cost by replacing the prevalent Peltier or other forms of heating. This will make thermal cyclers more accessible for further research and ease of use in rural areas, as the cost of the thermal cycler will be low as compared to the conventional one.

Technical Details of Final Deliverable

PCR tests require fast cooling and heating of the sample to perform DNA amplification. Conventional PCR thermal devices are very expensive and large in size which makes them inconvenient for mobility, especially for resource-limited areas where small sample sizes are needed for testing. Hence, we are working on reducing the size of the thermal cycler whilst keeping sufficient cooling and heating rates. Moreover, a novel heating element known as graphene by laser induction of polyimide tape is used which will be powered by a variable power supply. By increasing the voltage, we can increase the temperature rise of the thermal cycler and control it precisely using a microcontroller. The results indicate a temperature rise of 10 degrees per second per volt. The thermal block which will encompass the samples is designed in such a way that it will be surrounded by the tape to provide uniform and efficient heating. For the cooling of the samples, conventional cooling fans were used to keep the cost of the system within a reasonable budget. We are confident in maintaining a high level of efficiency for our thermal cycler while keeping the cost low to compete with the conventional brands in the market.