Our aim is to develop an inexpensive lab-on-a-chip device for the point-of-care (POC) monitoring of HIV/AIDS in the resource limited settings of the world. CD4+ T cell (a type of white blood cell) count in human whole blood has been used conventionally as the metric for proliferation of HIV in an infected individual and its progression into AIDS. We are working towards developing a biochip (microfluidic device) which can perform CD4+ T-cell counting for HIV/AIDS monitoring.
We have developed a cell trapping biochip for capturing human white blood cells (WBCs). Our preliminary findings indicate that this biochip with a novel 3D trapping architecture enables to obtain a high (> 90%) trapping efficiency of WBCs. Our design for a compact point-of-care device for HIV/AIDS monitoring incorporates integration of the above biochip with an on-chip microcscopy technique, hence eliminating the need for bulky and expensive external microscopy setup. Towards this end, we have developed a high numerical aperture (NA) microlens array for on-chip imaging of micron sized objects. Employing these microlenses, we have demonstrated for the first time, use of microlenses for direct image formation on an inexpensive imaging sensor without the use of any intermediate optics. High NA (~0.5) microlenses were able to resolve 1µm resolution patterns comparable to the performance of conventional microscope objectives.
After their development and performance characterization, the biochip will be integrated with the on-chip microscopy module comprising the microlens array, laser for excitation and charged coupled device (CCD) sensor for image capture and analysis. This will form the first prototype of a standalone device for CD4+ T-cell counting.