Vacuum-assisted, phaseguide-assisted blood typing device for point-of-care (POC) diagnostics
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With every advancement in the technology today, there is more focus on developing fast and minimally invasive procedures for diagnostics. As a result, the point-of-care (POC) diagnostics have been in the spotlight for a long time now and the researchers are experimenting with a lot of parameters like the volume of the sample, the time span and simple user-friendly detection to formulate the best combination to improve the quality, accuracy and simplicity of medical tests. In our attempt to develop a point-of-care diagnostic device we have chosen a blood-based immunoassay to determine a person's blood type. The device is made on polydimethylsiloxane (PDMS) and works with 6ul of whole blood obtained by a finger prick method. The other samples needed are 2ul each of Anti-A, B and D serums and the result is obtained in less than 10 minutes. The test is based on the reaction between the whole blood and anti-seras. If the antigen in the sample binds with the specific antibody, it will result in an agglutination reaction. The blood type can be determined by the presence of agglutinants in the detection chamber. The device works on negative pressure created by the vacuum chamber that utilizes the gas permeability of polydimethylsiloxane (PDMS). The device consists of one inlet for blood and three inlets for Anti-A, B and D seras, a mixing channel with phase-guide structures that control the flow by pinning the liquid until it develops the pressure to overcome the pinning and overflow at the point, a vacuum chamber to create the pressure difference and three detection chambers to determine the respective blood type. Another important factor here is the difference in viscosity of the whole blood and Anti-seras. The different viscosities can be an issue because the dynamic pressure to initiate the flow will be different for fluids with different viscosities (typically high for high viscosity fluids) and here the phase-guide structures come in handy to facilitate the mixing of liquids with different viscosities. The syringe is connected to the vacuum chamber by a tube. After the whole blood and anti-seras are added the syringe is pulled out and a spacer is used to keep it in place to create the micro-pumping.