Executive Summary
Introduction
To improve personalized medical care, a rapid inexpensive method for determining a patient’s genetic predisposition for potential drug interactions or diseases is needed. Current technology is expensive and can take up to two weeks to return results. A microfluidic device made of glass has been developed that allows for genetic characteristic identification from a small sample of DNA. To obtain accurate results, the DNA is amplified to allow for better detection. The amplification process requires the DNA to be thermocycled between two temperatures. The current method to produce thermocycling takes up to one hour of set up time before testing can begin. For this product to be viable for market, a more precise and faster thermocycling device must be developed.
A fluid handling system is also necessary for the product to be viable in the marketplace. Currently, the fluid containing the DNA is pumped into the lab on a chip device using a syringe and syringe pump. With this method it takes approximately 30 minutes to run one sample of DNA and the cleaning protocol. This method is time consuming and wasteful of DNA, due to the large volume of fluid necessary to run the syringe pump. A system is needed that can facilitate this process and allow for different samples of DNA to be run in sequence.
Design Subsystems
Thermocycler
The thermocycler system will need to create a thermal gradient on a 25mm x 75 mm glass substrate. Amplification of the DNA will occur as a fluid sample containing DNA is repeatedly channeled across the temperature gradient. The gradient will be created by heating both ends of the glass slides at different temperatures. The temperature at each ends of the glass slide should be variable and controlled by the user for different types of DNA samples. A user interface along with a control system will be implemented to insure accurate temperature control at each side of the glass substrate. The control system will be fitted with a microcontroller to keep the system self contained.
Fluid Delivery
The fluid processes for the insertion of the DNA sample and follow-up cleaning of the glass slide have set drastic limitations on the length of time required for the completion of one DNA test cycle. Following the DNA testing of one sample in the test slide, three wash steps are required in preparation for the testing of a new sample. These steps include injecting cleaner through the micro channels of the slide, rinsing the slide by flushing it with distilled water, and drying the channels by blowing air through them. The efficiency of these three processes will be improved by implementing a repeatable fluids maintenance interface between the fluid pump and the microfluidic channel imbedded in the glass device.
Design Approach
Thermocycler
Design of the thermocycler will be divided into four phases. The first phase will consist of finalizing design specifications, research, benchmarking, and brainstorming. The second phase will entail developing a prototype of the thermocycler and determining the open loop characteristics of the system. The third phase will include final design decisions of the thermocycler and implementing the closed loop control system. The forth, and final phase, will consist of product and customer testing.
Fluid Delivery
The development of the fluids delivery system will likewise undergo a series of phases in the design process. Initially, time will be spent doing research activities. Topics of research include: time and cost effective methods, characteristics of microfluidic channels, types of fluid pumps and their interfaces, and benchmarking. The second phase will include calculations to ensure that all design parameters for the fluid flow in the slide are met and selecting an improved method for fluid delivery. Upon selection of an improved method, a prototype will be built. Finally, the improved design will be tested and undergo further implementation to confirm an effective and time efficient fluid delivery system.
Conclusion
The successful completion of the thermocycler and fluid delivery system will increase the efficiency and marketability of the DNA analysis device. This device will provide an inexpensive and fast way for medical personal to determine patients genetic characteristics. With this knowledge, personal medical care will improve by allowing doctors to determine potential drug interactions and by determining genetic diseases while the patients are in the doctor’s office.